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/uni0061/uni006D/uni0065/uni0072/uni0069/uni0063/uni0061/uni006E/uni0061 /uni0020/uni0050/uni006C/uni0061/uni006E/uni0074/uni0073/uni0020/uni0066/uni006F/uni0072/uni0020/uni0050/uni006C/uni0061/uni006E/uni0074/uni0069/uni006E/uni0067  
 
 
 
 
 
ISBN No: [number]  (online) 
 
 
Version 1.0 
 
 
June 2022
Disclaimer 
While every effort has been made to ensure the info rmation in this publication is accurate, the Minist ry 
for Primary Industries does not accept any responsi bility or liability for error of fact, omission, 
interpretation or opinion that may be present, nor for the consequences of any decisions based on this  
information. 
The material and information contained in the impor t risk analysis is preliminary and will be updated 
based on any feedback received during consultation on any related import health standards or any 
further feedback that may be provided by internal o r external experts. 
 
 
 
 
 
 
 
 
 
 
Recommended citation: 
MPI (2022) Import Risk Analysis: Persea americana  Plants for Planting. Version 1.0. June 2022. 
Ministry for Primary Industries, New Zealand. 
 
 
Ministry for Primary Industries 
PO Box 2526 
WELLINGTON 6140 
Email: brand@mpi.govt.nz  
Telephone: 0800 00 83 33 
Facsimile: 04-894 0300 
This publication is also available on the Ministry for Primary Industries website at 
http://www.mpi.govt.nz/news-and-resources/publicati ons/   
 
© Crown Copyright - Ministry for Primary Industries  
 
  
3 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand  
 
 
Import risk analysis: Persea americana  plants for planting 
 
Version 1.0 
 
June 2022 
 
 
Approved for general release 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
© Crown Copyright - Ministry for Primary Industries  
  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 4 Version information 
Version No.  Comments Approved by Date of approval 
1.0 For external release Enrico Perotti 28 June 202 2 
    
    
New Zealand is a member of the World Trade Organisa tion and a signatory to the Agreement on the 
Application of Sanitary and Phytosanitary Measures (“The Agreement”). Under The Agreement, 
countries must base their measures on an Internatio nal Standard or an assessment of the biological 
risks to plant, animal or human health.  
This document provides a scientific analysis of the  risks associated with the importation of Persea 
americana  plants for planting. It assesses the introduction of pests and pathogens associated with 
Persea americana budwood  imported from around the world, and assesses the po tential impacts of 
those organisms should they enter and establish in New Zealand. The document has been internally 
and externally reviewed and is now released publicl y for feedback. Any significant new science 
information received that may alter the level of as sessed risk will be included in a review, and an 
updated version released.  
   
5 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Import Risk Analysis 
Table of Contents 
1.  Background 6 
2.  Objectives 6 
3.  IRA Scope 6 
4.  IRA methodology 7 
4.1  Hazard identification 7 
4.2  Pest risk assessment 8 
4.3  Management considerations 8 
5.  Summary of IRA conclusions 9 
6.  Summary of Pest Risk Assessments 9 
6.1  Bacteria 9 
6.1.1  Phytoplasmas on avocado ........................... ................................................... ................ 9  
6.1.2  Xanthomonas campestris  and X. axonopodis  avocado pathovars ...............................1 1  
6.1.3  Xylella fastidiosa  (bacterial leaf scorch) .......................... ..............................................12  
6.2  Fungi 14  
6.2.1  Akaropeltopsis  sp. (sooty blotch of avocado) .................... ............................................14  
6.2.2  Ambrosia fungi of the Ambrosia Fusarium  Clade (AFC), Graphium  spp. and 
Paracremonium  spp. vectored by beetles of the Euwallacea fornicatus  species complex ...........14  
6.2.3  Colletotrichum  spp. ............................................. ................................................... ........15  
6.2.4  Clonostachys pseudochroleuca  (avocado branch dieback and wilting) ............. ...........16  
6.2.5  Cophinforma tumefaciens  .................................................. ............................................17  
6.2.6  Diaporthe perseae  .................................................. ................................................... ....17  
6.2.7 Diaporthe sterilis  .................................................. ................................................... .......19  
6.2.8  Dothiorella aromatica  .................................................. ................................................... 20  
6.2.9  Elsinoe perseae – avocado scab .................................... ...............................................21  
6.2.10  Gliocladiopsis forsbergii , Gliocladiopsis peggii  and Gliocladiopsis whileyi  ...................21  
6.2.11  Grovesinia moricola  (zonate leaf spot) ............................... ...........................................22  
6.2.12  Lasiodiplodia pseudotheobromae  .................................................. ................................23  
6.2.13  Mycosphaerella perseae  .................................................. .............................................24  
6.2.14  Neocosmospora perseae  .................................................. ............................................25  
6.2.15  Neofusicoccum nonquaesitum  .................................................. ....................................26  
6.2.16  Pestalotiopsis longiseta  .................................................. ...............................................27  
6.2.17  Phyllachora gratissima  (tar spot) ....................................... ............................................28  
6.2.18  Phyllosticta perseae  (leaf spot disease) .............................. ..........................................28  
6.2.19  Pleiocarpon algeriense  and Cylindrocladiella peruviana  ...............................................29  
6.2.20  Podosphaera perseae-americanae  .................................................. .............................30  
6.2.21  Pseudocercospora purpurea  .................................................. .......................................31  
6.2.22  Pseudoidium perseae-americanae (powdery mildew of avocado) ....................... .........32  
6.2.23  Pyrrhoderma noxium  (brown root rot).................................. ..........................................33  
6.2.24  Raffaelea  spp. (laurel wilt disease)........................ ................................................... .....33  
6.2.25  Rhizoctonia noxia  (thread blight) .................................. .................................................34  
6.2.26  Rhizoctonia theobromae  (vascular-streak dieback) ........................ ..............................35  
6.2.27  Scolecobasidium musae  (sooty blotch and flyspeck (SBFS)) ............... ........................35  
6.2.28  Sooty moulds ...................................... ................................................... ........................36  
6.3  Oomycetes 36  
6.3.1  Phytophthora mengei  (Phytophthora trunk canker) ...................... .................................36  
6.3.2  Phytophthora palmivora  (bud rot of palms) ............................... ....................................38  
6.4  Viroids 39  
6.4.1  Avocado sunblotch viroid .......................... ................................................... ..................39  
6.4.2  Potato spindle tuber viroid ....................... ................................................... ...................40  
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 6 1. Background 
This import risk analysis (IRA) has been developed in response to a request to develop a new Import 
Health Standard (IHS) for the importation of avocad o ( Persea americana ) plants for planting.  
Pathways and commodities covered in this IRA are pr ovided in Table 1-1. 
Table 1-1: List of pathways and commodities assesse d in this IRA 
Commodity type Pathway description 
Persea americana plants for planting  Sea or air cargo from countries that have commercia l 
avocado orchards and publish their research in 
English or Spanish languages. 
2. Objectives 
Biosecurity New Zealand’s objectives in developing an IRA are to: 
1. Identify which pests and diseases present a level o f risk to New Zealand on the 
commodity(ies) and pathway(s) included in the scope , and 
2. Evaluate the effect of risk management measures on the level of that identified risk, 
in order to ensure that the risk managers have the information they need to recommend appropriately 
effective risk management measures. 
3. IRA Scope 
The scope of the IRA considers the following key qu estions: 
• What are the detailed commodity and pathway descri ptions? 
• Are there any additional risk management questions ? 
Detailed commodity description 
Purpose The commodity description defines the form of the c ommodity that is covered by this IRA, 
e.g. the commodity species and form under considera tion. The commodity description may 
also include commercial production and/or grading r equirements or other commodity quality 
specifications, and any actions taken that may remo ve or treat pests or diseases. 
Commodity 
Description • Budwood/ leafless cuttings 1 of Persea americana  and all its varieties and cultivars, 
brought into level 3A post-entry quarantine (3A PEQ ) for a period of active growth 
with a minimum of three distinct phenological growi ng events (referred to as ‘shoot 
flush’).  
• Budwood/ leafless cuttings are cuttings taken from mother plants. The cuttings do 
not have leaves, roots or soil attached to them, on ly buds.  
• Budwood/ leafless cuttings are dipped in 1% w/v sod ium hypochlorite for 2 minutes 
upon entry into the quarantine facility. 
• The PEQ period involves visual inspection of plants  for the presence of pests and 
symptoms. Visual inspections by an MPI inspector ar e usually carried out during 
active growing seasons - for other plants for plant ing there are two inspections in 
the spring, two in the summer and one during the sl ower growth periods. A similar 
regime will be designed for avocados. Inspections b y a facility operator are carried 
out at least twice a week. 
 
1 As Persea americana  is an evergreen species, the frequently used commo dity type in the IHS of ‘budwood/dormant cuttings’ 
will be changed to ‘budwood/leafless cuttings’ to a cknowledge the non-dormancy of the species.  
7 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Detailed commodity description 
All imported plants for planting must comply with b asic conditions as set out in Ministry for 
Primary Industries  (MPI) import health standard 155.02.06 “Importatio n of Nursery Stock” 
(IHS 155.02.06). In addition to a period of PEQ, th ese include: 
• Clean (including free from soil), inert/ synthetic materials for protection, packaging, 
and shipping. 
• Phytosanitary certification stating that the export ing country has inspected the 
commodity and found it free of visually detectable regulated pests. 
• Pesticide treatments for insects and mites. 
• Please note: measures for specific pests listed und er the “Basic Conditions” section 
of IHS 155.02.06 are not counted as basic measures but are specified measures. 
 
Detailed pathway description 
Purpose The pathway description defines the countries and m ethods the commodity will be sourced 
from and travel to New Zealand. The pathway descrip tion may also include commercial-
specific pathway requirements. 
Pathway 
Description Sea or air cargo from countries that have commercia l avocado orchards and publish their 
research in English or Spanish languages. 
 
Risk management questions 
Purpose Specific questions that the risk manager needs answ ered in order to make a decision. They 
are based on the scope of the overall project. 
Description PRAs will include information on the following risk  management questions. 
What factors influence the likelihood of the pest o r disease being detected during the 
growing period (a period of active growth with a mi nimum of three distinct phenological 
growing events referred to as ‘shoot flush’) in 3A PEQ? 
• What symptoms will the pest or disease exhibit? 
• What are the known environmental conditions conduci ve to symptom expression?  
What are the limitations to taking samples for pote ntial testing? 
• What plant part should be tested? 
• What is the optimum season for conducting detection  testing? 
4. IRA methodology 
The IRA process involves three principal stages: 
1. Hazard identification 
2. Pest risk assessment 
3. Evaluating risk management options 
The IRA methodology used by Biosecurity New Zealand  (BNZ) is described in more detail in the BNZ 
Guidelines for Undertaking an Import Risk Analysis Version 1.0 . 
4.1  Hazard identification 
A hazard is a pest or disease that: 
• is not present in New Zealand (or is present but s till represents a biosecurity risk, e.g. is 
capable of vectoring pathogens not present in New Z ealand); 
• is associated with imported risk goods and import pathways; and 
• has the ability to establish and cause harm in New  Zealand. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 8 Hazard identification (hazard ID) is the process wh ere a list of pests and diseases potentially 
associated with the commodity is compiled and then assessed against specified risk evaluation 
criteria, in order to determine which potential haz ards require further assessment.  
The results of the hazard ID provide the following:  
• Pests and diseases identified as potentially meeti ng the criteria to be quarantine pests 2 and 
diseases, associated with the commodity, and potent ially not being managed by compliance 
with the commodity description and therefore requir ing further assessment are listed in the 
Annex (Chapter 9). 
• Groups (e.g. genera or families) and high-profile pests and diseases that did not meet the 
criteria to require pest risk assessment are listed  in Appendix 1, along with the rationale for 
excluding them. 
• Given the scope of the IRA (Chapter 3), only patho gens (i.e. bacteria, fungi, nematodes, 
viroids and viruses), or diseases were considered. 
4.2  Pest risk assessment 
The purpose of risk assessment is to determine the level of risk that hazard pests and diseases 
(identified at the hazard ID stage as requiring fur ther assessment) pose to New Zealand. Specifically,  
the pest risk assessment (PRA) concludes whether th e pest or disease meets the risk evaluation 
criteria for requiring additional measures over and  above the commodity description. 
For this import risk analysis, pests and diseases t hat could potentially be associated with the 
commodity on entry into New Zealand and meet the cr iteria to be considered for additional measures 
are those that: 
• cannot be contained in a Level 3A PEQ facility and /or 
• cannot be detected during a period of active growt h with a minimum of three distinct 
phenological growing events (‘spring-flush’) in Lev el 3A PEQ. 
The PRA addresses the following: 
• Likelihood of entry: 
o The likelihood of entry into New Zealand given the  commodity and pathway 
descriptions 
• Likelihood of exposure and establishment: 
o The ability of the pest or disease to move from th e commdity into a suitable 
environment to allow establishment (exposure) 
o The suitability of the New Zealand environment for  the pest or disease (including 
climate, host plants and vectors) 
• The potential impacts in New Zealand: 
o Economic impacts: on economically important plants  (symptoms on individual plants, 
crop yield, costs of management practices, trade re strictions, rate of spread, etc.) 
o Environmental impacts: on native plants/taonga and  ecologies/ hauropi  
o Human health, sociocultural impacts: on people/tan gata whenua 
4.3  Management considerations 
For those pests or diseases for which a PRA conclud ed that the criteria to be considered for additiona l 
measures have been met on at least one pathway, inf ormation relevant to management options, 
where available in the literature, have been evalua ted. This information pertains to such options as: 
• Post entry quarantine Level 3B 
• Specified environmental conditions 
• Diagnostic tests 
 
2 In the context of this risk assessment a quarantine  pest is an organism that is not present in New Zea land (or is present but 
still represents a biosecurity risk, e.g. is capabl e of vectoring pathogens not present in New Zealand ) and is capable of 
establishing and causing harm in New Zealand.  
9 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5. Summary of IRA conclusions 
A summary of the pest and diseases that meet the cr iteria to be considered for additional measures 
are listed in Table 5-1. 
Table 5-1: Pests and diseases that meet the criteri a to be considered for additional measures. 
Pest/disease 
group  Species meeting the criteria to be considered 
for additional measures PRA conclusions  
Level of Risk Level of uncertainty 
Bacteria Phytoplasmas (i.e. Candidatus  Phytoplasma solani 
)that have a vector in New Zealand Moderate High 
Xanthomonas campestris and X. axonopodis  Moderate  High  
Xylella fastidiosa  High  Moderate  
Fungi Colletotrichum spp. Moderate  Moderate  
Diaporthe perse ae  Low  Moderate  
Diaporthe sterilis  Very low  Moderate  
Dothiorella aromatica  Low  Low  
Gliocladiopsis spp. Very low  Moderate  
Lasiodiplodia pseudotheobromae  Moderate – High  Moderate  
Neocosmospora perseae Low Moderate 
Neofusicoccum nonquaesitum  Moder ate  Moderate  
Pestalotiopsis longiseta  Low  Moderate  
Pleiocarpon algeriense and Cylindrocladiella 
peruviana Moderate Moderate 
Podosphaera perseae -americanae  Very low  Low  
Pseudoidium perseae -americanae  Very low  Low  
Oomycetes Phytophthora mengei  Moder ate  Moderate  
Phytophthora palmivora  Moderate  Moderate  
Viroids Avocado sunblotch viroid  Moderate  Low  
Potato spindle tuber viroid Moderate Low 
6. Summary of Pest Risk Assessments 
The following sections provide a summary of the pes t risk assessments described in detail within the 
Annex to this IRA. 
6.1  Bacteria 
6.1.1  Phytoplasmas on avocado 
Phytoplasmas are bacteria that lack cell walls. The y colonise the phloem of their plant hosts as well as 
various parts of their insect vectors. Phytoplasma infection is associated with a wide range of 
symptoms affecting all plant parts and can be fatal  to the plant.  Phytoplasmas belonging to the 
stolbur group (16SrXII), likely ‘ Candidatus  Phytoplasma solani’, (16SrXII-A) have been identif ied in Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 10 symptomatic avocado trees in Spain, and an unidenti fied phytoplasma has been identified in 
symptomatic avocado trees in Chile. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• The avocado-infecting phytoplasmas meet the criter ia to be hazards on imported Persea 
americana  budwood imported to New Zealand because they: 
o Are not known to be present in New Zealand, and 
o have the potential to enter New Zealand on Persea americana  budwood (as described in 
the commodity description), and 
o have the potential to establish in New Zealand and  cause harm to New Zealand. 
• The avocado-infecting phytoplasmas pose an overall  moderate risk on Persea americana  
budwood imported to New Zealand if there is a compe tent 3 vector in New Zealand, and negligible 
risk if there is no competent vector because they: 
o have a very low likelihood of entering New Zealand  on Persea americana  budwood (with 
moderate uncertainty) because: 
 Persea americana  is a known host of “stolbur” (likely ‘ Ca. P. solani’), and the 
phytoplasma found in Chile; 
 It is unlikely that avocado budwood will be taken from phytoplasma infected trees, 
since infections appear to be uncommon; 
 There is only a low volume of budwood entering Pos t Entry Quarantine (PEQ), 
which lowers the likelihood that infected budwood w ould enter PEQ even further; 
 Phytoplasmas would occur in association with budwo od, as they are systemic 
through the plant phloem sieve tube elements and su rface sterilisation of budwood 
would not affect them;  
 Plants will be held in PEQ for long enough to go t hrough 3 flush growth periods (at 
least 12 months), so any avocado plants with phytop lasma infection are likely to 
show symptoms, and if so, diagnostic tests will det ect phytoplasma.  
 However, some phytoplasma infections are asymptoma tic and these would not be 
detected in PEQ which would result in infected plan ts being released into New 
Zealand.   
 3A and 3B PEQ do not automatically include pre-det ermined phytoplasma PCR 
testing.  
o have a high likelihood of transferring from Persea americana  budwood to a suitable host in 
New Zealand (with low uncertainty) because: 
 Avocado plants derived from budwood will be plante d and nurtured to survive in 
New Zealand and used to propagate new plants for pl anting.  
 If the plants are infected with avocado-infecting phytoplasmas at the time of their 
release from PEQ they will have the infection when they are multiplied and planted.  
o have a moderate likelihood (with high uncertainty)  of establishing in New Zealand if there is 
a competent vector here, and a low likelihood of es tablishing in New Zealand (with high 
uncertainty) with no competent vector because: 
 Asymptomatic infected avocado plants released from  PEQ will be used for grafting. 
Avocado trees originating from these are likely to be infected; 
 However if phytoplasma symptoms appear in avocado trees in New Zealand the 
avocado industry and nurseries will likely start te sting for phytoplasma and only use 
clean stock;  
 It is uncertain whether there will be a competent vector in New Zealand. Known ‘Ca. 
P. solani’ vectors are not known to be present, but  insects in the same family are 
present. 
 Two insects with the potential to be vectors have been reported on avocado in 
New Zealand; 
 Climate is not likely to be a barrier to the estab lishment of these avocado-infecting 
phytoplasmas in New Zealand; 
o may cause moderate overall impact on New Zealand i f there is a competent vector present 
here (with high uncertainty), and very low overall impact (with low uncertainty) on New 
Zealand if there is no competent vector here becaus e: 
 
3 Vector competence is defined as “the ability of a v ector to transmit a disease”. It normally comprises  the capacity of a vector to 
be infected, maintain and transmit an infectious ag ent.  
11 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand  If there is no competent vector in New Zealand, th e plants infected would likely be 
limited to avocado trees grafted from infected plan ts from PEQ and their offspring, 
and possibly industry would stop grafting from infe cted plants. Phytoplasmas are not 
transmitted mechanically. 
 If there is a competent vector in New Zealand, oth er crop plants may be affected but 
it is difficult to know which without knowing the p hytoplasma or vector. Some 
phytoplasmas such as ‘ Ca. P. solani’ can have major impacts on many crop plan ts 
including reduced crop yield and plant decline and death. 
 Other phytoplasma species have caused harm to nati ve plants in New Zealand but it 
is not known if avocado-infecting phytoplasmas will . Environmental impacts are 
likely to be low (with high uncertainty) with a com petent vector and negligible (with 
low uncertainty) without a competent vector. 
 Human health impacts are likely to be negligible ( with low uncertainty) as this is a 
plant pathogen limited to plants and insects. 
 There is a very low likelihood that avocado-infect ing phytoplasmas will affect 
amenity trees, home gardens, taonga species to tang ata whenua, so sociocultural 
impacts are likely to be low (with high uncertainty ) with a competent vector present, 
and negligible (with low uncertainty) without a com petent vector. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Very low Moderate 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low 
The likelihood of establishing in the New Zealand e nvironment Moderate (vector) High 
Low (no vector) High 
Impact on the New Zealand economy, environment, hea lth and society Low (vector) High 
Very low (no vector) Low 
Overall level of assessed risk to New Zealand Moderate (vector) High 
Negligible (no vector)  Low 
Likelihood of there being a competent vector in New  Zealand Moderate High 
6.1.2  Xanthomonas campestris  and X. axonopodis  avocado pathovars 
Xanthomonas species are gram-negative bacteria that infect a wi de range of crops and wild plants. 
Two pathovars (strains that cause the same disease on the same host range) of Xanthomonas 
associated with disease in avocado ( Persea americana ) have been reported in the literature: 
X. campestris causing bacterial canker in California; and X. axonopodis  causing bacterial leaf spot in 
the Seychelles.  
Because there is very little information associated  with Xanthomonas  on avocado, information for the 
genus will be used where information for the pathov ars is lacking.  
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• The Xanthomonas campestris and  X. axonopodis  avocado pathovars meet the criteria to be 
hazards on Persea americana  budwood imported to New Zealand because they: 
o are not known to be present in New Zealand, 
o have the potential to enter New Zealand on P. americana  budwood (as described in 
the commodity description) and, 
o have the potential to establish in New Zealand, an d cause harm to New Zealand. 
• The X. campestris and  X. axonopodis  avocado pathovars pose an overall moderate risk on  
P.  americana  budwood imported to New Zealand because they: 
o have a very low likelihood of entering New Zealand  on P. americana  budwood (with 
high uncertainty) because: 
 they could survive as epiphytes on avocado budwood  in PEQ without causing 
symptoms for the entire PEQ period, but Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 12  in the case of internal infection, symptoms are mo re likely to appear within a 
matter of days or weeks.  
o have a high likelihood of transferring from P. americana  budwood to a suitable host in 
New Zealand (with low uncertainty) because: 
 imported avocado budwood is intended to generate p lants for planting in New 
Zealand and avocado plants (which are a suitable ho st for these pathogens) 
derived from avocado budwood will be planted and nu rtured to survive in 
optimal or near optimal conditions in controlled or  natural environments, and  
 if the commodity is infected with either of these pathogens at the time of their 
release from PEQ and they are used as propagative m aterial then the 
pathogens will be transferred to a suitable host mu ltiple times.  
o have a high likelihood of establishing in New Zeal and (with moderate uncertainty) 
because: 
 suitable hosts (in the form of cultivated avocados  or native and introduced 
members of the Lauraceae family) are available for the establishment of both 
pathovars,  
 suitable climate is available for the establishmen t of the of the X. campestris  
avocado pathovar, 
 the wetter conditions of New Zealand compared to s outhern California are 
likely to favour establishment of the X. campestris  avocado pathovar, and 
 the suitability of the New Zealand environment for  establishment of the 
X. axonopodis  pathovar cannot be definitively ruled out. 
o may cause moderate overall impact on New Zealand ( with high uncertainty) because: 
 avocados are the only hosts of the X. campestris and X. axonopodis avocado 
pathovars commercially produced in New Zealand, and  
 infection of avocado trees with the X. campestris or X. axonopodis avocado 
pathovar could cause yield losses, and control of a n outbreak could involve 
wide scale destruction of avocado trees (e.g., remo val of all trees in one 
major avocado production area). 
Infection of avocado trees with the X. campestris or X. axonopodis avocado pathovar could cause 
yield losses, and control of an outbreak could invo lve wide scale destruction of avocado trees (e.g., 
removal of all trees in one major avocado productio n area). The following table contains a summary of 
risk assessment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Very low High 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low 
The likelihood of establishing in the New Zealand e nvironment High Moderate 
Impact on the New Zealand economy, environment, hea lth and society Moderate High 
Overall level of assessed risk to New Zealand Moderate High 
6.1.3  Xylella fastidiosa  (bacterial leaf scorch) 
Xylella fastidiosa  is a fastidious xylem-limited bacterium (i.e. it h as specialised nutrient needs and can 
be difficult to culture). It can colonise a very br oad range of plants, including economically importa nt 
crops and environmentally significant plants. It is  a very serious pathogen of some of these plants, 
blocking water transport and causing wilting and de ath. Natural transmission is via specialist xylem-
feeding insects. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Xylella fastidiosa  meets the criteria to be a hazard on avocado budwo od imported to New 
Zealand because it: 
o is not known to be present in New Zealand. New Zea land has country freedom status 
for the species.  
o has the potential to enter New Zealand on avocado budwood (as described in the 
commodity description), establish in New Zealand, a nd cause harm to New Zealand.  
13 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • Xylella fastidiosa  poses an overall high risk (with moderate uncertai nty) on avocado budwood 
imported into New Zealand because it: 
o has a very low likelihood of entering New Zealand on avocado budwood (with high 
uncertainty) because; 
 infection of avocado by X. fastidiosa  appears to be very rare (it has only ever 
been documented in the published literature once, w ith another unpublished 
report); however 
 infections of avocado and many other plant species  are reported  to be 
asymptomatic, and where infections are symptomatic the latent period is not 
known but may be long. Therefore established X. fastidiosa  infections may 
not be detected before release from PEQ; and 
 for the above reasons, X. fastidiosa  infections of avocado may also be more 
common than is reported; 
o has a high likelihood of transferring from avocado  budwood to a suitable host in New 
Zealand (with low uncertainty) because: 
 avocado is a suitable host for X. fastidiosa . 
 avocado plants derived from grafting imported budw ood onto suitable 
rootstock will be planted in New Zealand.  
o has a moderate likelihood of establishing in New Z ealand (with moderate uncertainty) 
because: 
 plants suitable for colonisation by X. fastidiosa  are widely grown throughout 
New Zealand; 
 New Zealand’s temperate climate may be limiting, b ut at least some parts of 
the country are likely to be suitable for the estab lishment and expression of 
diseases caused by X. fastidiosa ; 
 at least one competent vector species is present i n New Zealand, it is widely 
distributed and has a broad host range which includ es avocado as well as 
other economically important and environmentally si gnificant plants. 
o may cause very high overall impacts on New Zealand  (with high uncertainty) 
because: 
 Xylella fastidiosa can cause serious damage to crops and plant-based 
industries that are of high economic importance to New Zealand, for example, 
grapes, summerfruit and citrus; 
 the introduction of X. fastidiosa may result in  market access restrictions for 
nursery stock, ornamentals, and cut flowers, partic ularly to Australia (New 
Zealand’s main trading partner); 
 the cost of a response to an incursion of X. fastidiosa  and/or long-term 
management costs resulting from establishment of th e bacterium are likely to 
be very high; 
 the bacterium is known to be able to colonise envi ronmentally and culturally 
significant native plants, although it is not known  how likely this is to have an 
impact at the population or ecosystem level; 
 very significant socio-cultural impacts (possibly similar to those that resulted 
from New Zealand’s Pseudomonas syringae pv. actinidiae (Psa) outbreak) 
could be expected if some subspecies establish, e.g ., X. fastidiosa  subsp. 
fastidiosa , the cause of Pierce’s disease of grapevines; 
 however impacts may be limited by New Zealand’s te mperate climate 
(depending on the bacterial genotype introduced), a nd the impact on human 
health is considered to be negligible. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Very low High 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low 
The likelihood of establishing in the New Zealand e nvironment Moderate Moderate 
Impacts on the New Zealand economy, environment, he alth and society Very high High 
Overall level of assessed risk to New Zealand High Moderate Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 14 6.2  Fungi 
6.2.1  Akaropeltopsis  sp. (sooty blotch of avocado) 
Akaropeltopsis  sp. is a fungus that causes sooty blotch on the br anches, stems, leaf veins and fruit of 
Persea americana  (avocado). 
Summary of PRA conclusions 
Akaropeltopsis  sp. meets the criteria to be a hazard on imported P. americana  budwood imported to 
New Zealand because: 
o it is not known to be present in New Zealand, 
o has the potential to establish in New Zealand, and  cause harm to New Zealand, and 
o has the potential to enter New Zealand on P. americana  budwood (as described in 
the commodity description). 
• Akaropeltopsis  sp. poses an overall negligible risk on P. americana  budwood imported to New 
Zealand because it: 
o has a negligible likelihood of entering New Zealan d on P. americana  budwood (with 
low uncertainty) because: 
 it can be present on the surface of budwood, but s uch infections are likely to 
be managed by dipping in 1% sodium hypochlorite for  2 minutes upon entry 
into the quarantine facility,  
 if Akaropeltopsis  sp. is imported into PEQ then it is likely to prod uce visible 
symptoms in PEQ. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible Low 
Overall level of assessed risk to New Zealand Negligible Low 
6.2.2  Ambrosia fungi of the Ambrosia Fusarium  Clade (AFC), Graphium  spp. and 
Paracremonium  spp. vectored by beetles of the Euwallacea fornicatus  species complex 
Ambrosia fungi of the Ambrosia Fusarium  Clade (AFC),  Graphium and Paracremonium  are symbionts 
associated with small (1 ─2 mm) ambrosia beetles in the genus Euwallacea . These fungi supply 
essential diet components for the ambrosia beetles and in return rely on the beetles to carry them to a 
new host. By cultivating their fungal symbionts in the xylem of plants, some Euwallacea species have 
managed to expand their host range and become invas ive in new areas of the world. In recent years, 
for example, the Euwallacea fornicatus  complex, together with their symbiotic fungi, have  become a 
concern to the avocado industry in California, Flor ida, Australia, Israel and South Africa. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• The ambrosia fungi of the  Euwallacea fornicatus species complex (the Ambrosia Fusarium  Clade 
(AFC),  Graphium spp. and  Paracremonium spp.) meet the criteria to be a hazard on Persea 
americana  budwood imported to New Zealand because they: 
o are not known to be present in New Zealand, 
o have the potential to enter New Zealand on Persea americana  budwood (as 
described in the commodity description), and 
o have the potential to establish in New Zealand, an d cause harm to New Zealand. 
• The ambrosia fungi of the  Euwallacea fornicatus species complex (the Ambrosia Fusarium 
Clade (AFC),  Graphium spp. and  Paracremonium spp.) pose an overall negligible risk on 
Persea americana  budwood imported to New Zealand because they: 
o have a very low likelihood of entering New Zealand  on Persea americana  budwood 
(with low uncertainty) because:  
15 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand  they are associated with and spread by ambrosia be etles or their beetle 
galleries. Level 3A PEQ has measures in place to ma nage the risks 
associated with insects, wastewater, waste and acci dental transfer, therefore, 
ambrosia beetles carrying ambrosia fungi are highly  unlikely to escape level 
3A PEQ to infect a suitable host;  
 their infection of avocado budwood is likely visib le as necrotic lesions and 
sugar volcanos. The ambrosia fungi of the  Euwallacea fornicatus species 
complex are reported to have localised pathogenicit y (<10cm from beetle 
gallery). Ambrosia beetle entry points and gallerie s will be visible during 
inspection and, thus, infected budwood would be det ected and destroyed 
before being released from PEQ. 
o have a very low likelihood of transferring from th e imported commodity onto a suitable 
host in New Zealand (with moderate uncertainty) bec ause: 
 there are no Euwallacea  species  reported to be present in New Zealand tha t 
could serve as vectors of ambrosia fungi (AFC); and  there are no alternative 
vectors reported to be present in New Zealand, such  as Quadrastichus 
erythrinae  or Xyleborus ferrugineus ; 
 some uncertainty arises from the fact that most fu ngi from the AFC have only 
recently been described, and species within it and their symbiotic 
associations with their ambrosia beetles are still being described. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Very low Low 
The likelihood of transferring from the imported co mmodity onto a suitable host Very low Moderate 
Overall level of assessed risk to New Zealand Negli gible Low 
6.2.3  Colletotrichum  spp. 
This PRA assesses species associated with avocado f ound in two species complexes: the 
Colletotrichum gloeosporioides species complex and the Colletotrichum acutatum species complex. 
The following species will be assessed: Colletotrichum aenigma , C. chrysophilum , C. endophyticum , 
C. jiangxiense , C. queenslandicum  and C. tropicale  are in the C. gloeosporioides species complex 
and C. nymphaceae  is in the C. acutatum species complex.   
Colletotrichum  species in both the gloeosporioides and acutatum species complexes are fungi with a 
wide host and environment range. They are important  plant pathogens but can have endophytic and 
saprotrophic lifestyles. In avocado, Colletotrichum species cause anthracnose in fruit and sometimes 
stem dieback.  
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Colletotrichum spp. ( C. aenigma, C. chrysophilum,  C. endophyticum, C. jiangxiense,  C. 
nymphaeae,  C. queenslandicum, C. tropicale ) meet the criteria to be hazards on imported 
Persea americana  budwood imported to New Zealand because they: 
o are not known to be present in New Zealand,  
o have the potential to enter New Zealand on P. americana  budwood (as described in 
the commodity description), and 
o have the potential to establish in New Zealand, an d cause harm to New Zealand. 
• Colletotrichum  poses an overall moderate risk on P. americana  budwood imported to New 
Zealand because it: 
o has a low likelihood of entering New Zealand on P. americana  budwood (with 
moderate uncertainty) because: 
 Colletotrichum infection under high temperatures (25 – 30° C) and e levated 
relative humidity can produce symptoms in a few day s, but 
 there is uncertainty around the endophytic capabil ities of some Colletotrichum 
species in P. americana budwood which may allow asymptomatic 
Colletotrichum infection during the PEQ period. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 16 o has a high likelihood of transferring from P. americana  budwood to a suitable host in 
New Zealand (with low uncertainty) because: 
 imported avocado budwood is intended to generate p lants for planting in New 
Zealand and avocado plants (which are a suitable ho st for these pathogens) 
derived from avocado budwood will be planted and nu rtured to survive in 
optimal or near optimal conditions in controlled or  natural environments, and  
 if the commodity is infected with these pathogens at the time of their release 
from PEQ and they are used as propagative material then the pathogens 
could be transferred to a suitable host on multiple  occasions.  
o has a high likelihood of establishing in New Zeala nd (with low uncertainty) because: 
 hosts (in the form of cultivated avocados and othe r cultivated crops) are 
available for the establishment of Colletotrichum  species 
 the climate in parts of New Zealand is suitable fo r the establishment of 
Colletotrichum  
o may cause moderate overall impact on New Zealand ( with moderate uncertainty) 
because: 
 the economic impact of Colletotrichum  to New Zealand is considered to be 
moderate, with low uncertainty  
 the impact on the environment from the establishme nt of Colletotrichum  in 
New Zealand is considered to be very low, with mode rate uncertainty  
 the human health impact of Colletotrichum  to New Zealand is considered to 
be negligible, with low uncertainty  
 the sociocultural impact of Colletotrichum to New Zealand is considered to be 
low, with low uncertainty  
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty  
The likelihood of entry on the commodity, given the  commodity description Low Moderate 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low 
The likelihood of establishing in the New Zealand e nvironment High Low 
Impact on the New Zealand economy, environment, hum an health and society Moderate Moderate 
Overall level of assessed risk to New Zealand Moderate Moderate 
6.2.4  Clonostachys pseudochroleuca  (avocado branch dieback and wilting) 
Clonostachys pseudochroleuca is a fungus that is associated with a wide range of  plants and 
environments. It is commonly found as a saprotroph or endophyte but has been recorded as a 
pathogen in avocado, vectored by ambrosia beetles, causing avocado branch dieback and wilting. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Clonostachys pseudochroleuca  meets the criteria to be a hazard on imported Persea 
americana  budwood imported to New Zealand because it: 
o is not known to be present in New Zealand, 
o has the potential to establish in New Zealand, and  cause harm to New Zealand, and 
o has the potential to enter New Zealand on Persea americana  budwood (as described 
in the commodity description). 
• Clonostachys pseudochroleuca  poses an overall negligible risk on Persea americana  
budwood imported to New Zealand because it: 
o has a negligible likelihood of entering New Zealan d on Persea americana  budwood 
(with low uncertainty) because: 
 Clonostachys pseudochroleuca  is associated with and spread by ambrosia 
beetles. Budwood will be treated with miticides and  insecticides. Furthermore, 
Level 3A PEQ has measures in place to manage the ri sks associated with 
insects, wastewater, waste and accidental transfer,  therefore ambrosia 
beetles carrying C. pseudochroleuca  are highly unlikely to escape level 3A 
PEQ to infect a suitable host.  
17 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand  Clonostachys pseudochroleuca  infection in avocado budwood is only found in 
association with ambrosia beetle galleries. Ambrosi a beetle entry points and 
galleries will be visible during inspection and thu s infected budwood would be 
detected and destroyed before they are released fro m PEQ. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible  Low 
Overall level of assessed risk to New Zealand Negligible  Low 
6.2.5  Cophinforma tumefaciens 
Cophinforma tumefaciens is a pathogenic ascomycete fungus that causes stem galls/tumours in 
young and old avocado plants. It is known to cause galls/tumours in Citrus  spp. as well as in other 
host plants. 
Summary of PRA conclusions  
Given the arguments and evidence presented: 
• Cophinforma tumefaciens meets the criteria to be a hazard on imported Persea americana  
budwood imported to New Zealand because it:  
o is not known to be present in New Zealand; 
o has the potential to establish (and spread) in New  Zealand, and cause harm to 
New Zealand, and 
o has the potential to enter New Zealand on Persea americana  budwood (as described 
in the commodity description). 
• Cophinforma tumefaciens poses an overall negligible risk on Persea americana  budwood 
imported to New Zealand because it:  
o has a negligible likelihood of entering New Zealan d on Persea americana  budwood 
(with low uncertainty) because: 
 established C. tumefaciens infections are highly likely to be detected during 
pre-export phytosanitary inspection, on arrival in New Zealand, or while the 
budwood is prepared for grafting,  
 recently infected budwood from contaminated prunin g tools would likely 
develop symptoms 2- 24 weeks after infection within  the PEQ period. 
Searches found no evidence of asymptomatic infectio n or longer latent period 
in avocado and other host plants.   
 Level 3A PEQ has measures in place to manage the r isks associated with 
wastewater, waste, and accidental transfer, therefo re viable C. tumefaciens  
propagules are highly unlikely to escape level 3A P EQ to infect a suitable 
host. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible  Low 
Overall level of assessed risk to New Zealand Negligible  Low  
6.2.6  Diaporthe perseae 
Diaporthe perseae is a fungal plant pathogen that causes stem-end rot  (postharvest) disease in 
avocado. 
Summary of PRA conclusions 
Given the arguments and evidence presented: Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 18 • Diaporthe perseae  meets the criteria to be a hazard on imported Persea americana  (avocado) 
budwood imported to New Zealand because it: 
o is not known to be present in New Zealand 
o has the potential to enter New Zealand on Persea americana  budwood (as described 
in the commodity description). 
o has the potential to establish in New Zealand, and  cause harm to New Zealand. 
• Diaporthe perseae  poses an overall low  risk on Persea americana  budwood imported to New 
Zealand because it: 
o has a high likelihood of entering New Zealand on Persea americana  budwood (with 
low uncertainty) because: 
 It is likely that D. perseae will not be detected from visual inspection during 
export preparation and pre-export phytosanitary ins pection to New Zealand 
and on arrival to New Zealand. In its endophytic ph ase, it can be present on 
leafless avocado without showing visible symptoms  
 The growing period in Post Entry Quarantine (PEQ) level 3A is not likely to 
impact the likelihood of entry of D. perseae because infected budwood that 
are grafted in PEQ level 3A might not show visible symptoms within the PEQ 
growing period  
 The main disease symptom caused by D. perseae (stem-end rot) will not be 
expressed during the growing period in PEQ because it  is usually expressed 
on the fruits after harvest. Fruits are not likely to form and mature to harvest 
state during the time of PEQ.  
o has a high likelihood of transferring from Persea americana  budwood to a suitable 
host in New Zealand (with low uncertainty) because:  
 Avocado ( P. americana ) is a suitable host of D. perseae  
 Avocado budwood derived from grafted imported budw ood onto rootstock will 
be planted in New Zealand. 
o has a high likelihood of establishing in New Zeala nd (with low-moderate uncertainty) 
because: 
 Diaporthe perseae is found in places such as South Africa, Netherland  and 
Australia, part of which have similar climate to pa rts of New Zealand  
 Avocado is a suitable host and is commercially pro duced and commonly 
grown in northern parts of New Zealand, and less fr equently in other parts of 
the country  
 Diaporthe perseae can be spread  by human movement of infected nursery 
stock for planting and movement of infected fruits (fruits producing spores). 
o may cause low overall impact on New Zealand (with moderate uncertainty) because: 
 Diaporthe perseae can result in some postharvest losses that can redu ce 
crop value and marketability, but overall losses ma y not differ from current 
level of stem-end rot diseases in New Zealand  
 Current control methods of control of other stem-e nd rot causing pathogens in 
New Zealand may be effective in controlling disease s caused by D. perseae . 
 It can potentially result in trade barriers with c ountries where it has not been 
reported to be present. However, it is recorded as present in Australia which 
is New Zealand’s major export market. As such, it m ight not have a significant 
impact on export. 
Although there are high likelihoods of entry, expos ure and establishment, D. perseae is a 
less important pathogen of stem-end rot disease tha n other stem-end rot causing fungi 
such as Dothiorella aromatica in Australia and Colletotrichum gloeosporioides and 
Diaporthe spp. already in New Zealand. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description High Low 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low  
The likelihood of establishing in the New Zealand e nvironment High Low-moderate 
Impact on the New Zealand economy, environment, hea lth and society Low Low 
Overall level of assessed risk to New Zealand Low Moderate  
19 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 6.2.7  Diaporthe sterilis 
Diaporthe sterilis  is a fungus that has relatively recently been isol ated from branch cankers on 
avocado orchard plants in Italy. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Diaporthe sterilis meets the criteria to be a hazard on imported Persea americana  budwood 
imported to New Zealand because it: 
o is not known to be present in New Zealand 
o has the potential to enter New Zealand on P. americana  budwood (as described in 
the commodity description), and 
o has the potential to establish in New Zealand, and  cause harm to New Zealand. 
• Diaporthe sterilis poses an overall very low risk on P. americana  budwood imported to 
New Zealand because it: 
o has a high likelihood of entering New Zealand on P. americana  budwood (with 
moderate uncertainty) because: 
 Diaporthe sterilis has been isolated from aboveground plant parts of a vocado 
plants (stems, branches and fruits) and is likely t o be present in infected 
leafless avocado budwood. 
 if D. sterilis is imported on leafless avocado budwood, it is like ly to express 
symptoms in the duration of the time in PEQ and the  biosecurity risk are likely 
to be managed by the growing period of active growt h with a minimum of 
three distinct phenological growing events in 3A PE Q,  
 however, it can potentially be present in asymptom atic leafless, rootless 
avocado budwood that might not be the detected duri ng preparation for 
export, or in phytosanitary inspection pre-export o r on arrival to New Zealand 
(although with high uncertainty). 
o has a high likelihood of transferring from P. americana  budwood to a suitable host in 
New Zealand (with moderate uncertainty) because: 
 avocado ( P. americana ) is a suitable host of D. sterilis . 
 avocado budwood derived from grafted imported budw ood onto rootstock will 
be planted in New Zealand. 
o has a moderate likelihood of establishing in New Z ealand (with moderate uncertainty) 
because: 
 Diaporthe sterilis is found in Italy which has a similar climate to mo st parts of 
New Zealand. 
 avocado is a suitable host and is commercially pro duced and commonly 
grown in northern parts of New Zealand, and less fr equently in other parts of 
the country. 
 It is known to also infect Vaccinium corymbosum (blueberry), which is widely 
grown commercially in parts of the North and South Island of New Zealand. 
 Diaporthe sterilis  can possibly be spread  by human movement of infected 
nursery stock for planting and movement of infected  fruits (fruits producing 
spores). 
o may cause very low overall impact on New Zealand ( with moderate uncertainty) 
because: 
 Diaporthe sterilis can cause trunk cankers and potentially result in s ome 
postharvest losses of avocado. However, overall los ses caused may not differ 
from the current losses caused by other canker and stem-end rot pathogenic 
fungi already present in New Zealand. 
 it has been reported to cause disease symptoms on V. corymbosum 
(blueberry)  (cankers at their bases and brown lesions on stems resulting in 
twig blight).  While such diseases can affect blueb erry production, the impact 
of D. sterilis on blueberry production has not yet been quantified .  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 20 The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description High Moderate  
The likelihood of transferring from the imported co mmodity onto a suitable host High Moderate 
The likelihood of establishing in the New Zealand e nvironment Moderate Moderate 
Impact on the New Zealand economy, environment, hum an health and society Very low Moderate 
Overall level of assessed risk to New Zealand Very low Moderate 
6.2.8  Dothiorella aromatica 
Dothiorella aromatica is a fungal plant pathogen that causes stem-end rot  (postharvest) disease in 
avocado. It has also been associated with stem-end rot disease in mangos. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Dothiorella aromatica meets the criteria to be a hazard on imported Persea americana  
(avocado) budwood imported to New Zealand because i t: 
o is not known to be present in New Zealand 
o has the potential to enter New Zealand on P. americana  budwood (as described in 
the commodity description), and 
o has the potential to establish in New Zealand, and  cause harm to New Zealand. 
• Dothiorella aromatica poses an overall low risk on P. americana  budwood imported to 
New Zealand because it: 
o has a high likelihood of entering New Zealand on P. americana  budwood (with low 
uncertainty) because:  
 it is likely that D. aromatica will not be detected by visual inspection during ex port 
preparation and pre-export phytosanitary inspection  to New Zealand and on 
arrival to New Zealand. In its endophytic phase, it  can be present on leafless 
avocado budwood without showing visible symptoms.  
 the main disease symptom caused by D. aromatica (stem-end rot) will not be 
expressed during the growing period in PEQ because it  is usually expressed on 
the fruits after harvest. Fruits are not likely to form and mature to harvest state 
during the time of PEQ.  
o has a high likelihood of transferring from P. americana  budwood to a suitable host in 
New Zealand (with low uncertainty) because: 
 avocado ( P. americana ) is a suitable host of D. aromatica.  
 avocado budwood derived from grafted imported budw ood onto rootstock will be 
planted in New Zealand. 
o has a high likelihood of establishing in New Zeala nd (with moderate uncertainty) 
because:  
 Dothiorella aromatica is found in South Africa and Australia, parts of wh ich have 
similar climate to parts of New Zealand,  
 avocado is a suitable host and is commercially pro duced and commonly grown in 
northern parts of New Zealand, and less frequently in other parts of the country,  
 Dothiorella aromatica can be spread  by human movement of infected nursery 
stock for planting and movement of infected fruits (fruits producing spores). 
o may cause low overall impact on New Zealand (with moderate uncertainty) because: 
 Dothiorella aromatica can result in some postharvest losses that can redu ce crop 
value and marketability, but overall losses may not  differ from current level of 
stem-end rot diseases in New Zealand  
 current control methods of control of other stem-e nd rot causing pathogens in 
New Zealand may be effective in controlling disease s caused by D. aromatica . 
 it can potentially result in trade barriers with c ountries where it has not been 
reported to be present. However, it is recorded as present in Australia which is 
New Zealand’s major export market. As such, it migh t not have a significant 
impact on export.  
21 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand  Although there are high likelihoods of entry, expo sure and establishment, D. 
aromatica is a less important pathogen of stem-end rot diseas e than other stem-
end rot causing fungi such as Colletotrichum gloeosporioides and Diaporthe spp. 
already in New Zealand. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description High Low 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low  
The likelihood of establishing in the New Zealand e nvironment High Moderate 
Impact on the New Zealand economy, environment, hea lth and society Low Low 
Overall level of assessed risk to New Zealand Low Low  
6.2.9  Elsinoe perseae – avocado scab  
Elsinoe perseae (avocado scab) is a fungal pathogen that causes bro wn scabby lesions on fruit, 
leaves and stems of avocado plants. It can reduce a vocado fruit yield, quality and marketability. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Elsinoe perseae  meets the criteria to be a hazard on Persea americana  budwood imported to 
New Zealand because it: 
o is not known to be present in New Zealand. Elsinoe perseae  was recorded in error in 
New Zealand in 1991 and older literature and some d atabases reflect this. 
o has the potential to enter New Zealand on Persea americana  budwood (as described in the 
commodity description), establish in New Zealand, a nd cause harm to New Zealand. 
• Elsinoe perseae  poses an overall negligible risk on Persea americana  budwood imported to New 
Zealand because it: 
o has a negligible likelihood of entering New Zealan d on Persea americana  budwood (with low 
uncertainty) because: 
 Avocado scab lesions are likely to be detected dur ing pre-export phytosanitary 
inspection, on arrival in New Zealand, or while the  budwood is being prepared for 
grafting.  
 Ungerminated spores remaining on the budwood after  surface disinfection upon 
arrival in PEQ will either die or germinate once th e buds break dormancy and produce 
visible symptoms very rapidly, and most probably wi thin the PEQ period.  
 Symptoms develop in 7–10 days once spores germinat e on susceptible leaves, stems 
or fruit. Searches found no evidence of asymptomati c E. perseae  infections or longer 
latent periods in avocado plants. 
 Elsinoe perseae  spores are spread by watersplash, windborne rain a nd insects 
(thrips). Given the measures in level 3A PEQ to man age risks associated with insects 
and wastewater, waste and accidental transfer, E. perseae  propagules are highly 
unlikely to escape to infect a suitable host. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible Low 
Overall level of assessed risk to New Zealand Negli gible Low 
6.2.10  Gliocladiopsis forsbergii , Gliocladiopsis peggii  and Gliocladiopsis whileyi  
Gliocladiopsis  is a genus of soilborne fungi found mostly in trop ical and sub-tropical regions of the 
world. Species of this genus are regarded as second ary plant pathogens or saprobes. Gliocladiopsis 
forsbergii, G. peggii and  G. whileyi  have been isolated frequently from necrotic roots of avocado trees, 
but pathogenicity studies have so far only been don e for one strain of G. peggii . Genus level Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 22 information is being used where necessary as limite d information about the ecology of these fungi is 
available. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Gliocladiopsis forsbergii, G. peggii and  G. whileyi  meet the criteria to be a hazard on imported 
Persea americana  budwood imported to New Zealand because they: 
o are not known to be present in New Zealand, and 
o have the potential to establish in New Zealand, an d cause harm to New Zealand, and 
o have the potential to enter New Zealand on P. americana  budwood (as described in 
the commodity description). 
• Gliocladiopsis forsbergii, G. peggii and  G. whileyi  pose an overall very low risk on P. 
americana  budwood imported to New Zealand because they: 
o have a low likelihood of entering New Zealand on P. americana  budwood (with high 
uncertainty) because: 
 they are likely soilborne, although other Gliocladiopsis species have been 
recovered as endophytes from stems and leaves, and 
 it is unknown if symptoms would develop in PEQ as these species are likely 
secondary pathogens that can also be saprobic or en dophytic 
o have a high likelihood of transferring from P. americana  budwood to a suitable host in 
New Zealand (with low uncertainty) because: 
 imported avocado budwood is intended to generate p lants for planting in New 
Zealand and avocado plants (which are a suitable ho st for these pathogens) 
derived from avocado budwood will be planted and nu rtured to survive in 
optimal or near optimal conditions in controlled or  natural environments, and  
 if the commodity is infected with either of these pathogens at the time of their 
release from PEQ and they are used as propagative m aterial, then the 
pathogens will be transferred to a suitable host  
o has a high likelihood of establishing in New Zeala nd (with low uncertainty) because: 
 a suitable host in the form of cultivated avocados  is available for their 
establishment, and  
 a suitable climate is available for their establis hment, and 
 other  Gliocladiopsis species have established in New Zealand 
o may cause very low overall impact on New Zealand ( with moderate uncertainty) 
because: 
 their economic impact likely depends on a variety of abiotic and biotic factors 
(such as co-infection with other pathogens), and 
 good orchard management practises are likely to ma nage these species 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty  
The likelihood of entry on the commodity, given the  commodity description Low High 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low 
The likelihood of establishing in the New Zealand e nvironment High Low 
Impact on the New Zealand economy, environment, hum an health and society Very low Moderate 
Overall level of assessed risk to New Zealand Very low Moderate 
6.2.11  Grovesinia moricola  (zonate leaf spot) 
Grovesinia moricola  (zonate leaf spot) is a fungal pathogen that produ ces characteristic target-shaped 
necrotic rings leading to leaf blight and defoliati on in a broad range of host species. The disease ha s 
been reported infecting Persea americana  (avocado) in the USA and Brazil, causing round lea f 
lesions with dark margins. It has the potential to infect a number of economically significant hosts i n 
New Zealand.   
23 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Grovesinia moricola  meets the criteria to be a hazard on P. americana  budwood imported to 
New Zealand because it: 
o has the potential to enter New Zealand on P. americana  budwood, establish and 
cause harm to New Zealand, and 
o is not known to be present in New Zealand. 
• Grovesinia moricola  poses an overall negligible risk on P. americana budwood imported  to 
New Zealand because it: 
o has a negligible likelihood of entering New Zealan d on P. americana  budwood as 
described in the commodity description (with low un certainty) as: 
- the fungus is primarily a foliar pathogen and is n ot strongly associated with 
plant stems, 
- disinfection dip in 2% sodium hypochlorite (as per  the commodity description) 
is likely to be effective in eliminating any infect ion on the surface of avocado 
budwood, and 
- if G. moricola  is imported into PEQ then it is likely to produce visible 
symptoms within the period of growth in PEQ. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible  Low 
Overall Level of assessed risk to New Zealand Negli gible  Low 
6.2.12  Lasiodiplodia pseudotheobromae 
Lasiodiplodia pseudotheobromae  is a fungal plant pathogen that has been reported to cause dieback, 
cankers and postharvest diseases (stem-end rot and fruit rot disease) in many woody plant species 
which includes avocado.  
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Lasiodiplodia pseudotheobromae  meets the criteria to be a hazard on imported Persea 
americana  budwood imported to New Zealand because it: 
o is not known to be present in New Zealand, 
o has the potential to enter New Zealand on Persea americana  budwood (as described 
in the commodity description), and 
o has the potential to establish in and cause harm t o New Zealand. 
• Lasiodiplodia pseudotheobromae  poses an overall moderate risk on P. americana  budwood 
imported to New Zealand because it: 
o has a low likelihood of entering New Zealand on P. americana  budwood (with low-
moderate uncertainty) because: 
 Lasiodiplodia pseudotheobromae has been isolated from the stems, branches 
and fruits of avocado plants and therefore can be a ssociated with leafless 
avocado budwood. 
 Infected budwood is likely to exhibit symptoms suc h as necrotic lesions and 
discolouration of internal tissues that can be visu ally detectable during 
preparation for export or on phytosanitary inspecti on pre-export or on arrival 
in New Zealand.  
 However, L. pseudotheobromae  can potentially be present on asymptomatic 
leafless, rootless avocado budwood that might not b e the detected during 
preparation for export, or in phytosanitary inspect ion pre-export or on arrival 
to New Zealand although with high uncertainty. 
 If L. pseudotheobromae  is imported on leafless avocado budwood, it is lik ely 
to express symptoms in the duration of the time in PEQ.  The biosecurity risk 
is likely to be managed by the period of active gro wth with a minimum of three 
distinct phenological growing events in 3A PEQ. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 24 o has a high likelihood of transferring from P. americana  budwood to a suitable host in 
New Zealand (with low uncertainty) because: 
 avocado ( P. americana ) is a suitable host of L. pseudotheobromae  
 avocado budwood derived from grafted imported budw ood onto rootstock will 
be planted in New Zealand. 
o has a high likelihood of establishing in New Zeala nd (with low uncertainty) because: 
 L. pseudotheobromae  is found in about 23 countries, some of these coun tries 
have a similar climate to New Zealand  
 avocado is a suitable host and is commercially pro duced and commonly 
grown in northern parts of New Zealand, but less fr equently in other parts of 
the country.  
 it is known to affect a wide range of other host p lants that are widely grown 
commercially in orchards and in home gardens in par ts of the North and 
South Island of New Zealand. 
 L. pseudotheobromae  can spread  by human movement of infected nursery 
stock for planting, movement of infected fruits (sp ores produced from the 
fungus present on infected fruit), contaminated soi l, and pruning material. 
o may cause moderate overall impact on New Zealand ( with moderate uncertainty) 
because: 
 L. pseudotheobromae  can potentially cause unwanted impacts in 
New Zealand by reducing the crop value and marketab ility of avocados. 
 it can also cause diseases which result in reduced  yields and affect the 
marketability of other horticultural crops such as Citrus  spp., Vitis vinifera  
(grapes) and Diospyros kaki  (persimmons). These are crops of economic 
value to New Zealand both domestically and internat ionally which together 
are worth over a billion dollars.  
 if it establishes in New Zealand, it can potential ly result in trade barriers with 
countries where it has not been reported to be pres ent.  
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Low  Moderate 
The likelihood of transferring from the imported co mmodity onto a suitable host High Moderate  
The likelihood of establishing in the New Zealand e nvironment High Moderate  
Impact on the New Zealand economy, environment, hea lth and society Moderate-High  Moderate   
Overall level of assessed risk to New Zealand Moder ate-High  Moderate  
6.2.13  Mycosphaerella perseae 
Mycosphaerella perseae is a fungal plant pathogen that causes silver spot disease in Persea 
americana (avocado). Silver spot disease causes lesions on th e leaves of the plant. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Mycosphaerella perseae  meets the criteria to be a hazard on imported Persea americana  
budwood imported to New Zealand because it: 
o is not known to be present in New Zealand; 
o has the potential to establish in New Zealand, and  cause harm to New Zealand, and 
o has the potential to enter New Zealand on Persea americana  budwood (as described 
in the commodity description). 
• Mycosphaerella perseae  poses an overall negligible risk on Persea americana  budwood 
imported to New Zealand because it: 
o has a negligible likelihood of entering New Zealan d on Persea americana  budwood 
(with low uncertainty) because: 
 established M. perseae  infections are highly likely to be detected, and 
infected material removed or destroyed, during prep aration for export, in  
25 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand phytosanitary inspections pre-export or with surfac e disinfection on arrival at 
PEQ in New Zealand; 
 residual biosecurity risks from recent infections or ungerminated conidia on 
the surface of avocado budwood are likely to be man aged by the growing 
period of active growth with a minimum of three dis tinct phenological growing 
events referred to as ‘shoot flush’ in 3A PEQ; 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible  Low 
Overall level of assessed risk to New Zealand Negligible  Low 
6.2.14  Neocosmospora perseae 
Neocosmospora perseae  is a fungal pathogen reported to cause avocado tru nk cankers and is 
probably an opportunistic pathogen infecting the pl ant via wounds.  
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Neocosmospora perseae  meets the criteria to be a hazard on Persea americana  budwood 
imported to New Zealand because it: 
o is not known to be present in New Zealand, 
o has the potential to enter New Zealand on P. americana  budwood (as described in 
the commodity description), and 
o has the potential to establish in New Zealand, and  cause harm to New Zealand. 
• Neocosmospora perseae  poses an overall low risk on P. americana  budwood imported to 
New Zealand because it: 
o has a very low likelihood of entering New Zealand on P. americana  budwood (with 
moderate uncertainty) because: 
 symptoms will usually develop and will be detected  prior to export or within 
the PEQ period; but  
 estimates of time to symptom development are based  on pathogenicity 
testing and natural infections may develop more slo wly; and 
 internal necrosis caused by N. perseae  may not be detected in routine 
inspections of plants in PEQ. 
o has a high likelihood of transferring from P. americana  budwood to a suitable host in 
New Zealand (with low uncertainty) because: 
 avocado ( P. americana ) is a suitable host for N. perseae ; 
 avocado plants derived from grafting imported budw ood onto suitable 
rootstock will be planted in New Zealand.  
o has a high likelihood of establishing in New Zeala nd (with low uncertainty) because: 
 avocado is a host and is commercially produced and  commonly grown 
domestically in northern parts of New Zealand, thou gh less frequently 
elsewhere in the country; 
 Neocosmospora perseae  is reported from an area that has a similar climat e 
to parts of New Zealand;  
 Neocosmospora perseae  can almost certainly spread between host plants in  
New Zealand because conidia (asexual spores) of Fusarium solani  species 
complex such as N. perseae  are typically produced on plant debris on the soil  
surface and dispersed by soil water or water splash  to infect roots or above 
ground tissues of suitable hosts.  
o may cause low overall impact to New Zealand (with moderate uncertainty) because: 
 Neocosmospora perseae  outbreaks are likely to be rare and sporadic but c an 
cause unwanted impacts on avocado production in New  Zealand by 
damaging some trees in some orchards or growing reg ions;  
 however, there is moderate uncertainty that impact s of N. perseae will be 
limited to avocado, since N. perseae  is recently described and some closely 
related species in the Fusarium solani  species complex are reported as 
opportunistic pathogens, causing disease symptoms i n a diverse range of Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 26 plant hosts as well as insects, marine animals, and  humans. Therefore 
N. perseae has the potential for broader unwanted economic, en vironmental 
and human health impacts. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty  
The likelihood of entry on the commodity, given the  commodity description Very low Moderate 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low 
The likelihood of establishing in the New Zealand e nvironment High Low 
Impact on the New Zealand economy, environment, hea lth and society Low Moderate 
Overall level of assessed risk to New Zealand Low Moderate 
 
6.2.15  Neofusicoccum nonquaesitum  
Neofusicoccum nonquaesitum  is a pathogenic fungi from the family Botryoshaeri aceae. They  can 
cause diseases such as stem/branch cankers, necrosi s and dieback in several woody crop plant 
species (grapevine, avocado, and apples) and non-cr op plant species.  
Summary of PRA conclusions  
Given the arguments and evidence presented: 
• Neofusicoccum nonquaesitum meets the criteria to be a hazard on imported Persea 
americana  budwood imported to New Zealand because they:  
o are not known to be present in New Zealand: 
o have the potential to establish in New Zealand, an d cause harm to New Zealand, and 
o have the potential to enter New Zealand on Persea americana  budwood (as 
described in the commodity description). 
• Neofusicoccum nonquaesitum poses an overall moderate risk on Persea americana  budwood 
imported to New Zealand because they:  
o have a low likelihood of entering New Zealand on Persea americana  budwood (with 
moderate uncertainty) because: 
 both species have been isolated from the stems and  branches of avocado 
plants and can be present on leadless avocado budwo od.   
 avocado budwood with established N. nonquaesitum infections can exhibit 
symptoms such as cankers on plant tissues that coul d be detected during 
preparation for export or on arrival in New Zealand  
 Neofusicoccum nonquaesitum can potentially be present on asymptomatic 
leafless avocado budwood that might not be detected  during preparation for 
export and upon arrival in New Zealand, with high u ncertainty  
 If N. nonquaesitum is imported on leafless avocado budwood, the active  
growing period at level 3A PEQ (a minimum of three distinct phenological 
growing events) will likely result in expression of  symptoms.  
o have a high likelihood of transferring from Persea americana  budwood to a suitable 
host in New Zealand (with low uncertainty) because:  
 avocado ( P. americana ) is a suitable host of N. nonquaesitum. 
 avocado plants derived from grafting imported budw ood onto rootstock will be 
planted in New Zealand.  
o have a high likelihood of establishing in New Zeal and (with low uncertainty) because: 
 Neofusicoccum nonquaesitum is reported to be present in five countries, 
parts of which have similar climate to New Zealand.  The climatic conditions in 
some parts of New Zealand are likely to be suitable  for them to establish and 
spread especially the North Island where climatic c onditions are warmer  
 both species are associated with a range of crop a nd non-crop host plants 
such as avocado, blueberry, grapevine, apples, plum  and oak tree species, 
which are commercially grown in both the North and South Island of 
New Zealand   
27 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand  Neofusicoccum nonquaesitum can be spread through the human movement 
of infected nursey stock and contaminated pruning t ools.  
o may cause moderate overall impact on New Zealand ( with moderate uncertainty) 
because: 
 Neofusicoccum nonqaesitum can potentially result in reduced productivity 
and yield loss of avocado. This can have an unwante d impact on both 
domestic and international marketability of avocado  
 infections by N.  nonquaesitum  can affect market access of export of avocado 
to other parts of the world where they are not repo rted to be present  
 Neofusicoccum nonquaesitum can cause disease and result in reduced yields 
of other economic important host plants such as gra pevine, apples and 
blueberries resulting in additional economic loss.  
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty  
The likelihood of entry on the commodity, given the  commodity description Low Moderate 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low 
The likelihood of establishing in the New Zealand e nvironment High Low 
Impact on the New Zealand economy, environment, hum an health and society Moderate Moderate 
Overall level of assessed risk to New Zealand Moderate Moderate 
6.2.16  Pestalotiopsis longiseta 
Pestalotiopsis longiseta  has been reported to cause dieback disease in Persea americana (avocado) 
in China. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Pestalotiopsis longiseta meets the criteria to be a hazard on imported P. americana  budwood 
imported to New Zealand because it: 
o is not known to be present in New Zealand 
o has the potential to establish in New Zealand, and  cause harm to New Zealand, and 
o has the potential to enter New Zealand on P. americana  budwood (as described in 
the commodity description). 
• Pestalotiopsis longiseta poses an overall low risk on P. americana  budwood imported to New 
Zealand because it: 
o has a low likelihood of entering New Zealand on P. americana  budwood (with 
moderate uncertainty) because: 
 Pestalotiopsis longiseta is reported to be associated with avocado as well a s 
other crop plants. 
 In its pathogenic phase of infection, it is likely  to exhibit symptoms if infected 
budwood is grafted in PEQ level 3A.  
 It can be present on avocado budwood (in a latent or endophytic phase) 
without exhibiting symptoms  
o has a high likelihood of transferring from P. americana  budwood to a suitable host in 
New Zealand (with moderate uncertainty) because: 
 It can spread by the human movement of infected nu rsery stock that is  
grafted on to rootstock that will be planted in orc hards in New Zealand.  
o has a moderate likelihood of establishing in New Z ealand (with moderate uncertainty) 
because: 
 Avocado which is a known host is grown commerciall y and in home gardens 
in most parts of New Zealand.  
 It is not likely to be restricted by climate becau se it occurs in both tropical and 
temperate countries some of which have similar clim ate to New Zealand.   
 It can spread by the human movement of infected nu rsery stock for planting.   
 It is not host specific but opportunistic and can infect a wide range of host 
plants. Other crop plants are available in New Zeal and which it can infect.  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 28 o may cause  low overall impact on New Zealand (with moderate  uncertainty) because: 
 it was only recently associated with avocado in Ch ina, with up to 30% of 
young plants dying. The impact it might have on mat ure avocado trees and 
crop yield has not been assessed and quantified.  
 about 16 species from the genus Pestalotiopsis are already recorded to be 
present in New Zealand and they have not been repor ted to affect crop plants 
significantly.  
 It caused between 10-20% yield loss of persimmons in Japan. Persimmons 
are grown in New Zealand with a value of about NZ$ 12 million in export and 
domestic market in 2020.  
The following table contains a summary of risk asse ssment against the criteria:  
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Low Moderate  
The likelihood of transferring from the imported co mmodity onto a suitable host High  Moderate 
The likelihood of establishing in the New Zealand e nvironment Moderate  Moderate  
Impact on the New Zealand economy, environment, hum an health and society Low Moderate 
Overall level of assessed risk to New Zealand Low Moderate 
6.2.17  Phyllachora gratissima  (tar spot) 
Phyllachora gratissima  is a fungal leaf pathogen that causes tar spot on the leaves of Persea 
americana  (avocado). It is considered a minor pathogen that is more frequent in ‘Creole’ avocados. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Phyllachora gratissima  meets the criteria to be a hazard for New Zealand because it: 
o is not known to be present in New Zealand, and 
o has the potential to enter New Zealand on P. americana budwood, establish in and 
cause harm to New Zealand. 
• Phyllachora gratissima  poses an overall negligible risk on P. americana budwood imported to 
New Zealand because it: 
o has a negligible likelihood of entering New Zealan d on P. americana budwood (with 
low uncertainty) as: 
- the fungus is primarily a foliar pathogen and is n ot strongly associated with 
plant stems, 
- disinfection dip in 2% sodium hypochlorite (as per  the commodity description) 
is likely to be effective in eliminating any infect ion on the surface of avocado 
budwood, and 
- if P. gratissima  is imported into PEQ then it is likely to produce visible 
symptoms within the period of growth in PEQ. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible  Low 
Overall Level of assessed risk to New Zealand Negli gible  Low 
6.2.18  Phyllosticta perseae  (leaf spot disease) 
Phyllosticta perseae  is a fungal pathogen known to cause leaf spot dise ase in multiple Persea  
species. Affected plants typically have dark spots in lesions at leaf edges and may lead to leaf death . 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Phyllosticta perseae  meets the criteria to be a hazard for New Zealand because it:  
29 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand o is not known to be present in New Zealand, and 
o has the potential to enter New Zealand on Persea americana  budwood (as described 
in the commodity description), and it can potential ly establish and cause harm to New 
Zealand. 
• Phyllosticta perseae  poses an overall negligible risk on P. americana  budwood imported to 
New Zealand because it: 
o has a negligible likelihood of entering New Zealan d on P. americana  budwood (with 
low uncertainty) as: 
 Phyllosticta perseae  is primarily transmitted on the leaves where it is  highly 
likely to be detected, and infected material remove d or destroyed, during 
preparation for export, in phytosanitary inspection s pre-export or with surface 
disinfection on arrival at PEQ in New Zealand; 
 residual biosecurity risks from new infections or ungerminated conidia on the 
surface of avocado budwood are likely to be managed  by the growing period 
of active growth with a minimum of three distinct p henological growing events 
referred to as ‘shoot flush’ in 3A PEQ; 
 no evidence was found to show that the pathogen ha s latent infections or is 
endophytic in avocado 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible  Low 
Overall Level of assessed risk to New Zealand Negli gible  Low 
6.2.19  Pleiocarpon algeriense  and Cylindrocladiella peruviana  
Pleiocarpon algeriense  and Cylindrocladiella peruviana  are causative agents of black-foot disease of 
grapevines which causes necrosis at the base of roo t stocks, reduced vigor of plants and occasional 
mortality. In avocado trees, both of these organism s cause stem and crown rot. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Pleiocarpon algeriense and Cylindrocladiella peruviana  meet the criteria to be hazards for 
New Zealand because they: 
o are not known to be present in New Zealand, 
o have the potential to enter New Zealand on Persea americana budwood (as 
described in the commodity description), and 
o have the potential to establish [and spread] in Ne w Zealand, and cause harm to 
New Zealand. 
• Pleiocarpon algeriense and Cylindrocladiella peruviana  poses an overall moderate risk on P. 
americana  budwood imported to New Zealand because it: 
o has a low likelihood of entering New Zealand on P. americana  budwood (with high 
uncertainty) as: 
- latent infections of C. peruviana and P. algeriense have been observed in 
avocado orchards as disease has only been observed in ≥3 year old plants, 
- Cylindrocladiella peruviana and P. algeriense  infect cuttings of other host 
species, but there is uncertainty regarding the ass ociation with P. americana 
budwood 
o has a high likelihood of transferring from P. americana  budwood to an appropriate 
host in New Zealand (with low uncertainty) as: 
- imported avocado budwood is intended to generate p lants for planting in New 
Zealand and avocado plants (which are a suitable ho st for these pathogens) 
derived from avocado budwood will be planted and nu rtured to survive in 
optimal or near optimal conditions in controlled or  natural environments, and  
- if the commodity is infected with these pathogens at the time of their release 
from PEQ and they are used as propagative material then the pathogens 
could be transferred to a suitable host on multiple  occasions.  
o has a high likelihood of establishing in New Zeala nd (with low uncertainty) as: 
- hosts (in the form of cultivated avocados and othe r cultivated crops) are 
available for the establishment of C. peruviana and P. algeriense  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 30 - the climate in parts of New Zealand is suitable fo r the establishment of C. 
peruviana and P. algeriense  
o may cause moderate overall impacts on New Zealand (with moderate uncertainty) as: 
- the economic impact of C. peruviana and P. algeriense  to New Zealand is 
considered to be moderate, with moderate uncertaint y  
- the impact on the environment from the establishme nt of C. peruviana and P. 
algeriense  in New Zealand is considered to be very low, with moderate 
uncertainty  
- the human health impact of C. peruviana and P. algeriense  to New Zealand is 
considered to be negligible, with low uncertainty  
- the sociocultural impact of C. peruviana and P. algeriense to New Zealand is 
considered to be low, with low uncertainty  
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty  
The likelihood of entry on the commodity, given the  commodity description Low High 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low 
The likelihood of establishing in the New Zealand e nvironment High Low 
Impacts on the New Zealand economy, environment, he alth and society Moderate Moderate 
Overall Level of assessed risk to New Zealand Moder ate Moderate 
6.2.20  Podosphaera perseae-americanae 
Podosphaera perseae-americanae  is a fungus causing powdery mildew on leaves of Persea 
americana  (avocado) plants. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Podosphaera perseae-americanae  meets the criteria to be a hazard on imported Persea 
americana  budwood imported to New Zealand because it: 
o is not known to be present in New Zealand, 
o has the potential to establish in New Zealand, and  cause harm to New Zealand, and 
o has the potential to enter New Zealand on Persea americana  budwood (as described 
in the commodity description). 
• Podosphaera perseae-americanae  poses an overall very low risk on Persea americana  
budwood imported to New Zealand because it: 
o has a low likelihood of entering New Zealand on Persea americana  budwood (with 
moderate uncertainty): 
 Podosphaera perseae-americanae  is likely to enter PEQ in dormant buds, 
and 
 Podosphaera perseae-americanae  is not likely to survive on avocado 
budwood without causing symptoms throughout the PEQ  period.  
 If symptoms develop, rapid production of airborne spores may not be 
detected early enough and measures in PEQ L3A may n ot prevent spores 
escaping containment facilities. 
o has a low likelihood of transferring from Persea americana  budwood to a suitable host 
in New Zealand (with moderate uncertainty) because:  
 if airborne conidia escape from Level 3A PEQ, expo sure of the pathogen to 
the New Zealand environment may then occur if avoca do plants or plants 
from Lauraceae family are present near the PEQ faci lity. However, the 
amount of inoculum likely to escape is small, and t he conidia would have to 
land on a suitable host (avocado is the only known host of Podosphaera 
perseae-americanae ).  
o has a low likelihood of establishing in New Zealan d (with moderate uncertainty) 
because: 
 potential hosts (in the form of cultivated avocado s or native and introduced 
members of the Lauraceae family) are available for the establishment of 
Podosphaera perseae-americanae   
31 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand  climate consistently suitable for the establishmen t of the Podosphaera 
perseae-americanae  is likely not readily available 
o may cause low overall impact on New Zealand (with moderate uncertainty) because: 
 avocados are the only known host of Podosphaera perseae-americanae  
commercially produced in New Zealand, 
 infection of avocado trees with Podosphaera perseae-americanae  could 
cause yield losses, 
 an outbreak would likely spread quickly within and  between regions, 
 an outbreak could affect avocados grown in gardens  having some 
sociocultural impact, and 
 Podosphaera perseae-americanae  could cause low environmental impact if 
native Lauraceae plants were susceptible to the dis ease 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty  
The likelihood of entry on the commodity, given the  commodity description Low Moderate 
The likelihood of transferring from the imported co mmodity onto a suitable host Low Moderate 
The likelihood of establishing in the New Zealand e nvironment Low Moderate 
Impact on the New Zealand economy, environment, hum an health and society Low Moderate 
Overall level of assessed risk to New Zealand Very low Moderate 
6.2.21  Pseudocercospora purpurea  
Pseudocercospora purpurea  is a fungal plant pathogen causing Pseudocercospor a  spot disease 
resulting in leaf, stem, and fruit spot symptoms in  Persea  spp. including avocado ( P. americana ). The 
disease is a serious pre-harvest disease affecting all cultivars of avocado in warm, humid, and rainy 
climates. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Pseudocercospora purpurea  meets the criteria to be a hazard on imported Persea americana  
budwood imported to New Zealand because it:  
o is not present in New Zealand and is listed as a r egulated organism, 
o has the potential to establish in New Zealand, and  cause harm to New Zealand, and  
o has the potential to enter New Zealand on Persea americana  budwood (as described 
in the commodity description.  
• Pseudocercospora purpurea  poses an overall negligible risk on Persea americana  budwood 
imported to New Zealand because it: 
o has a negligible  likelihood of entering New Zealand on Persea americana  budwood 
(with moderate uncertainty) because: 
 Symptomatic lesions are likely to be detected duri ng pre-export phytosanitary 
inspection, on arrival inspection or while in the P EQ facility for 12 months. 
 The pathogen is known to be latent for approximate ly 3 months after 
penetration of susceptible plant material, after wh ich spots are observed. 
However, given the process undertaken to import avo cado budwood includes 
pre-export inspection, importation, on arrival insp ection and further 
inspections over the period in PEQ for 12 months (a ssuming optimised 
conditions such as a warm, moist, and humid environ ment) the fungus is 
highly likely to produce symptoms before release.  
 Ungerminated spores on the surface of the imported  material are likely to be 
managed by the 1% sodium hypochlorite treatment upo n arrival in PEQ. If 
any ungerminated spores remain viable after the tre atment on the surface of 
the budwood, they will likely either die or germina te once the buds break 
dormancy and produce visible symptoms within the PE Q period. 
 Spores are spread by watersplash (rain and irrigat ion), wind, insects, plant 
debris and contaminated tools and equipment.   Given the measures 
undertaken in level 3A PEQ to manage risks associat ed with wastewater, Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 32 insects, waste, and accidental transfer, P. purpurea spores are unlikely to 
escape and infect a suitable host.  
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible Moderate 
Overall level of assessed risk to New Zealand Negligible Moderate 
6.2.22  Pseudoidium perseae-americanae (powdery mildew of avocado) 
Pseudoidium perseae-americanae is a fungus that causes powdery mildew on the leave s, buds and 
herbaceous stems of Persea americana  (avocado) plants.  
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Pseudoidium perseae-americanae  meets the criteria to be a hazard on imported avoc ado 
budwood imported to New Zealand because it:  
o is not known to be present in New Zealand, 
o has the potential to enter New Zealand on avocado budwood (as described in the 
commodity description). 
o has the potential to establish in New Zealand, and  cause harm to New Zealand, and 
• Pseudoidium perseae-americanae  poses an overall very low risk on avocado budwood 
imported to New Zealand because it: 
o has a very low likelihood of entering New Zealand on avocado budwood (with low 
uncertainty) because: 
 Pseudoidium perseae-americanae has a reasonably wide geographical 
distribution but is mostly limited to tropical/subt ropical climates, 
 It could be unknowingly imported into PEQ on leafl ess avocado budwood 
because mycelium can overwinter on dormant buds, 
 It is likely that P. perseae-americanae would produce symptoms on infected 
plants under suitable conditions and be detected in  PEQ. Therefore, the 
likelihood of infected plants being released from P EQ  is considered to be 
negligible, with low uncertainty, but  
 There is a very low likelihood that airborne conid ia could escape level 3A 
PEQ because they could be produced between inspecti ons and are small 
enough to fit though the vents. However, the amount  of conidia likely to 
escape is small.  
o has a very low likelihood of transferring from avo cado budwood to a suitable host in 
New Zealand (with low uncertainty) because: 
 if airborne conidia escape from Level 3A PEQ, expo sure of the pathogen to 
the New Zealand environment may then occur if avoca do plants are present 
near the PEQ facility. However, the amount of inocu lum likely to escape is 
small, and the conidia would have to land on a suit able host (avocado is the 
only known host of P. perseae-americanae ) under suitable conditions to 
germinate and cause disease, 
o has a moderate likelihood of establishing in New Z ealand (with moderate uncertainty) 
because: 
 Pseudoidium perseae-americanae  is mostly distributed in tropical/subtropical 
climates, indicating that the northern avocado grow ing regions of New 
Zealand may have suitable conditions for establishm ent (warm and humid), 
especially during summer,  
 the pathogen could overwinter as dormant asexual m ycelia in buds,   
 Pseudoidium spp. can spread rapidly because they produce large amounts of 
airborne conidia within a short period of time (3–7  days) and do not require 
free water on plant surfaces to initiate infection,  
 conidia can be transmitted long distances by wind,  but also by human activity 
on people, equipment or vehicles. 
o may cause a negligible overall impact on New Zeala nd (with low uncertainty) 
because:  
33 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand  Pseudoidium perseae-americanae  is host specific to avocado and is only 
reported to cause disease in countries with tropica l/subtropical climates. It is 
usually a minor disease problem but can become seve re in prolonged warm, 
humid and shaded conditions, especially in nurserie s, 
 it is not reported to be associated with fruit and  can be effectively managed 
by fungicide treatments, suggesting that it is unli kely to have major disease or 
trade impacts, 
 Pseudoidium perseae-americanae is unlikely to cause any environmental, 
human health or sociocultural impacts because no re cords of such impacts 
were found in the literature.  
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Very low Low 
The likelihood of transferring from the imported co mmodity onto a suitable host Very low Low 
The likelihood of establishing in the New Zealand e nvironment Moderate Moderate 
Impact on the New Zealand economy, environment, hum an health and society Low Low 
Overall level of assessed risk to New Zealand Very low Low 
6.2.23  Pyrrhoderma noxium  (brown root rot) 
Pyrrhoderma noxium is a tropical and sub-tropical fungus that causes r oot rot in a wide range of host 
species, frequently resulting in plant death. Avoca do is reported to be a highly susceptible host of t his 
fungus.  
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Pyrrhoderma noxium  meets the criteria to be a hazard on P. americana  budwood imported to 
New Zealand because it: 
o is not known to be present in New Zealand, and 
o has the potential to enter New Zealand on P. americana  budwood, establish in 
New Zealand, and cause harm to New Zealand. 
• Pyrrhoderma noxium  poses an overall negligible risk on P. americana budwood imported  to 
New Zealand because it: 
o has a negligible likelihood of entering New Zealan d on P. americana  budwood as 
described in the commodity description (with low un certainty) as: 
 P. noxium  is not reported to be associated with shoots, stem s or leaves of its 
hosts so it is unlikely that avocado budwood cuttin gs would contain mycelia,  
 P. noxium may produce airborne basidiospores which may then b e present 
on the surface of avocado budwood. However, surface  sterilisation of 
avocado budwood (as per the commodity description) is likely to make these 
spores inviable, and 
 symptoms on avocado are severe and develop rapidly , so are likely to be 
observed within the period of PEQ. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria  Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible Low 
Overall Level of assessed risk to New Zealand Negli gible Low 
6.2.24  Raffaelea  spp. (laurel wilt disease) 
The following Raffaelea species were assessed: R. aguacate , R. campbellii , R. canadensis  and R. 
lauricola . Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 34 Raffaelea spp. are typically saprotrophic fungi symbiotically  associated with ambrosia beetles. 
However, Raffaelea lauricola is unique in that it causes the vascular wilt disea se in trees and shrubs 
in the Lauraceae family including Persea americana . Similarly, R. canadensis has also been 
associated with wilt disease. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Raffaelea species ( R. aguacate , R. campbellii , R. canadensis  and R. lauricola ) meet the 
criteria to be a hazard on imported P. americana  budwood imported to New Zealand because 
they: 
o are not known to be present in New Zealand: 
o have the potential to establish in New Zealand, an d cause harm to New Zealand, and 
o have the potential to enter New Zealand on P. americana  budwood (as described in 
the commodity description). 
• Raffaelea  species pose an overall negligible risk on P. americana  budwood imported to New 
Zealand because it: 
o has a negligible likelihood of entering New Zealan d on P. americana  budwood (with 
low uncertainty) because: 
 established Raffaelea  infections are highly likely to be detected, and i nfected 
material removed or destroyed, during preparation f or export, in phytosanitary 
inspections pre-export or on arrival in New Zealand ; 
 residual biosecurity risks from ambrosia entry poi nts or recent infections on 
the surface of avocado budwood are likely to be man aged by the growing 
period of active growth with a minimum of three dis tinct phenological growing 
events referred to as ‘shoot flush’ in 3A PEQ; 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible  Low 
Overall level of assessed risk to New Zealand Negligible  Low 
6.2.25  Rhizoctonia noxia  (thread blight) 
Rhizoctonia noxia  is a fungal pathogen causing thread blight of coff ee and many other plants including 
avocado. Damage from the disease typically occurrs on all parts of the plant except the roots. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Rhizoctonia noxia  meets the criteria to be a hazard for New Zealand because it: 
o is not present in New Zealand, and 
o has the potential to enter New Zealand on the comm odity/pathway (as described), 
establish [and spread] in New Zealand, and cause ha rm to New Zealand. 
• Rhizoctonia noxia  poses an overall negligible risk on Persea americana  budwood imported to 
New Zealand because it: 
o has a negligible likelihood of entering New Zealan d on Persea americana  budwood 
(with moderate uncertainty) as: 
 Rhizoctonia noxia  is not likely to be imported into New Zealand on a vocado 
budwood due to conspicuous symptoms, 
 if an intrepid infection on imported avocado budwo od was not detected 
visually, then the pathogen would likely produce vi sible symptoms in PEQ.   
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible  Moderate 
Overall Level of assessed risk to New Zealand Negli gible  Moderate  
35 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 6.2.26  Rhizoctonia theobromae  (vascular-streak dieback) 
Rhizoctonia theobromae  is a leaf-penetrating, xylem-infecting, fungal pat hogen that is the causal 
agent of vascular-streak dieback of cacao. One repo rt was found of it causing vascular-streak dieback 
in avocado plants. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Rhizoctonia theobromae meets the criteria to be a hazard on imported Persea americana  
(avocado) budwood imported to New Zealand because: 
o it is not known to be present in New Zealand,  
o has the potential to enter New Zealand on P. americana  budwood (as described in 
the commodity description), 
o has the potential to establish in New Zealand, and  cause harm to New Zealand, and 
• Rhizoctonia theobromae poses an overall negligible risk on P. americana  budwood imported 
to New Zealand because it:  
o has a negligible likelihood of entering New Zealan d on P. americana  budwood (with 
moderate uncertainty) because: 
 Rhizoctonia theobromae  has only been reported to infect Theobroma cacao  
(cacao) plants with the exception of one report of it infecting avocado plants , 
 new infections may not be detected prior to export  as symptoms take 3-5 
months to occur, 
 Rhizoctonia theobromae  could be present inside leafless avocado budwood 
and such infections are unlikely to be managed by s urface disinfection,  
 cacao budwood harvested from infected branches can not be used for grafting 
because grafts do not take, meaning that infections  are highly unlikely to be 
spread through grafting in cacao, however, this has  not been tested in 
avocado, 
 if R. theobromae  is imported into PEQ then it is likely to produce visible 
symptoms during the period of containment. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible Low 
Overall level of assessed risk to New Zealand Negligible Low 
6.2.27  Scolecobasidium musae  (sooty blotch and flyspeck (SBFS)) 
Scolecobasidium musae is an epiphytic fungus that has occasionally been r eported to colonise the 
surface of banana and avocado plants. It is conside red to be a part of the sooty blotch and flyspeck 
complex (SBFS) which contains more than 100 species  in 30 genera of Ascomycota and 
Basidiomycota. 
Summary of PRA conclusions 
Scolecobasidium musae meets the criteria to be a hazard on imported Persea americana  budwood 
imported to New Zealand because: 
o it is not known to be present in New Zealand,  
o has the potential to enter New Zealand on P. americana  budwood (as described in 
the commodity description), and 
o has the potential to establish in New Zealand, and  cause harm to New Zealand. 
• Scolecobasidium musae poses an overall negligible risk on P. americana  budwood imported 
to New Zealand because it: 
o has a negligible likelihood of entering New Zealan d on P. americana  budwood (with 
low uncertainty) because: Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 36  it can be present on the surface of budwood but su ch infections are likely to 
be manged by dipping in 1% sodium hypochlorite for 2 minutes upon entry 
into the quarantine facility,  
 if S. musae is imported into PEQ then it is likely to produce v isible symptoms 
in PEQ. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible Low 
Overall level of assessed risk to New Zealand Negligible Low 
6.2.28  Sooty moulds 
Sooty mould is a generic name used to describe a wi de range of fungus species that cover the 
surfaces of above ground plant parts with a black, sooty coating and are generally associated with the  
sugary exudates of sap-sucking insects. Heavy infes tation may inhibit photosynthesis and the 
unsightly mould may degrade the market value of pro duce.  
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• The sooty moulds ( Antennulariella batistae , Calothyrium apiahynum , Capnodium spp., 
Lembosia perseae , Meliola antioquiensis , Asteridiella perseae , Periconiella perseae ) meet the 
criteria to be a hazard on Persea americana  budwood imported to New Zealand because 
they: 
o are not known to be present in New Zealand, and 
o have the potential to enter New Zealand on P. americana  budwood, establish in 
New Zealand, and cause harm to New Zealand. 
• These sooty mould species pose an overall negligib le risk on P. americana budwood imported  
to New Zealand because they: 
o have a negligible likelihood of entering New Zeala nd on P. americana  budwood as 
described in the commodity description (with low un certainty) as: 
• sooty moulds may be present on the surface of budw ood imported into 
New Zealand, but such infections are highly likely to be manged by 1% 
sodium hypochlorite dip for 2 minutes upon entry in to the quarantine facility,  
• if sooty moulds  are imported into PEQ, they may not produce visible  
symptoms during the period of containment but would  become inviable, 
• if growth of sooty moulds occurs the symptoms are highly likely to be detected 
and it is unlikely that spores will be produced pri or to detection, and  
• conditions aiding spore dispersal are unlikely to occur in PEQ. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Negligible Low 
Overall Level of assessed risk to New Zealand Negli gible Low 
6.3  Oomycetes 
6.3.1  Phytophthora mengei  (Phytophthora trunk canker) 
Phytophthora mengei  is a soil borne water mould (oomycete) that causes  trunk cankers in avocado 
(Persea americana ) plants. It can also infect the structural roots, lower limbs and fruit of the plant/tree.  
Summary of PRA conclusions 
Given the arguments and evidence presented:  
37 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • Phytophthora mengei  meets the criteria to be a hazard on P. americana  budwood imported to 
New Zealand because it:  
o is not known to be present in New Zealand, 
o has the potential to enter New Zealand on P. americana  budwood (as described in the 
commodity description), and 
o has the potential to establish in New Zealand, and  cause harm to New Zealand. 
• Phytophthora mengei poses an overall low risk on P. americana  budwood imported to New 
Zealand because it: 
o has a low likelihood of entering New Zealand on P. americana  budwood (with moderate 
uncertainty) because: 
 cankers/lesions on woody tissues have a brown necr otic appearance and are 
likely to be detected on arrival in New Zealand, or  in PEQ.  
 in two studies, P. mengei  symptoms developed on avocado plants within 40 
days once spores germinated on susceptible tissue. Although no evidence was 
found of asymptomatic P. mengei  infections or longer latent periods in avocado 
plants, other Phytophthora pathogens can be asymptomatic, or infect the xylem 
of hosts, and such infections may not be visually d etectable. This highlights 
uncertainty regarding whether P. mengei  infections can be asymptomatic or 
latent for longer periods.  
 Phytophthora spores are spread by watersplash, windborne rain an d insects 
(ants, snails etc). Given the measures in level 3A PEQ to manage risks 
associated with insects and wastewater, waste and a ccidental transfer, P. 
mengei propagules are highly unlikely to escape to infect a suitable host. 
o has a high likelihood of transferring from P. americana  budwood to a suitable host in 
New Zealand (with low uncertainty) because: 
 avocado ( P. americana ) is a suitable host for  P. mengei  
 avocado plants derived from grafting imported budw ood onto suitable rootstock 
will be planted in New Zealand. These plants are li kely be susceptible to P. 
mengei  infection. 
o has a high likelihood of establishing in New Zeala nd (with low uncertainty) because: 
 avocado is the only reliably recorded host of P. mengei . There is a degree of 
uncertainty regarding the host associations of P. mengei  because it is a 
recently described species (2009), formerly recogni sed as P. citricola . Host 
associations attributed to P. citricola  may in fact correspond to P. mengei .  
 avocado is in commercial production and plants are  commonly grown in 
northern parts of New Zealand, though less  frequently elsewhere in the 
country.  
 Phytophthora mengei is found in California, USA, which includes some ar eas 
that have a similar climate to the parts of New Zea land.  
 Phytophthora mengei lesions produce abundant vegetative chlamydospores,   
sexual oospores and flagellated zoospores. Phytophthora  spores can survive 
in adverse environmental conditions for several yea rs and are spread by 
watersplash, windblown rain, animals, insects, huma ns, equipment and 
vehicles. 
o may cause moderate overall impact on New Zealand ( with moderate uncertainty) 
because: 
 Phytophthora mengei has the potential to cause harm to New Zealand by 
reducing orchard health and productivity. The manag ement costs associated 
with the pathogen may be partially mitigated becaus e management of P. 
cinnamomi (already present in NZ) is likely to manage P. mengei . 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty  
The likelihood of entry on the commodity, given the  commodity description Low Moderate 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low 
The likelihood of establishing in the New Zealand e nvironment High Low 
Impact on the New Zealand economy, environment, hea lth and society Moderate Moderate 
Overall level of assessed risk to New Zealand Moder ate Moderate Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 38 6.3.2  Phytophthora palmivora  (bud rot of palms) 
Phytophthora palmivora  is an oomycete (or water mould) that causes a rang e of rot, canker and dieback 
symptoms on various host tissues. 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Phytophthora palmivora  meets the criteria to be a hazard for New Zealand because it: 
o is not known to be present in New Zealand, 
o has the potential to enter New Zealand on Persea americana  budwood (as described 
in the commodity description), establish in and cau se harm to New Zealand, and 
• Phytophthora palmivora  poses an overall low risk on P. americana  budwood imported to 
New Zealand because it: 
o has a low likelihood of entering New Zealand on P. americana  budwood (with 
moderate uncertainty) because: 
 Phytophthora palmivora  has an extensive global distribution, 
 Phytophthora palmivora  can infect stems, indicating that it could be 
associated with budwood, 
 there is no evidence of asymptomatic P. palmivora infections or longer latent 
periods in P. americana  plants, but asymptomatic infections are considered  
possible because other Phytophthora  pathogens can be asymptomatic,  
 infections may be supressed and not visually detec table if suitable 
environmental conditions (wet and warm (above 22° C) ) are not met in PEQ, 
o has a high likelihood of transferring from P. americana  budwood to an appropriate 
host in New Zealand (with low uncertainty) because:  
 Phytophthora palmivora  has a very wide host range including avocado and 
suitable hosts are widespread in New Zealand,  
 avocado plants derived from grafting imported budw ood onto suitable 
rootstock will be planted in New Zealand. These pla nts are likely be 
susceptible to P. palmivora  infection. 
o has a high likelihood of establishing in New Zeala nd (with low uncertainty) because: 
 hosts are widespread in New Zealand,  
 climate matching and modelling suggest that the pa thogen is likely to infect 
plants and spread in northern New Zealand, especial ly in the summer. 
Phytophthora palmivora  may be able to persist in the environment over win ter 
as resistant spores.   
o may cause moderate overall impacts on New Zealand (with moderate uncertainty) 
because: 
 disease expression and spread are likely to be lim ited by climate, particularly 
in the south of New Zealand, though it may be more damaging in sheltered or 
protected environments such as nurseries and greenh ouses.   
 Phytophthora palmivora  causes a range of symptoms/diseases on numerous 
hosts in wet tropical and subtropical areas of the world. Some host plants are 
important economical crops in New Zealand, such as avocado, tomato, 
potatoes, kiwifruit, citrus and orchids. 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria  Rating Uncertainty 
The likelihood of entry on the commodity, given the  commodity description Low Moderate 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low  
The likelihood of establishing in the New Zealand e nvironment High Low 
Impacts on the New Zealand economy, environment, he alth and society Moderate Moderate 
Overall level of assessed risk to New Zealand Moderate Moderate  
39 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 6.4  Viroids 
6.4.1  Avocado sunblotch viroid 
Avocado sunblotch viroid  (ASBVd) is distributed in most avocado-producing a reas globally and 
causes significant reductions in yield and fruit qu ality. All avocado cultivars have been reported as 
susceptible and infected asymptomatic trees play an  important role in the epidemiology and spread of 
this disease 
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Avocado sunblotch viroid  meets the criteria to be a hazard on imported Persea americana  
budwood imported to New Zealand because it: 
o is not known to be present in New Zealand 
o has the potential to establish in New Zealand, and  cause harm to New Zealand, and 
o has the potential to enter New Zealand on P. americana  budwood (as described in 
the commodity description). 
• Avocado sunblotch viroid  poses an overall moderate risk on P. americana  budwood imported 
to New Zealand because it: 
o has a high likelihood of entering New Zealand on P. americana  budwood (with low 
uncertainty) because: 
 Avocado sunblotch viroid  can remain asymptomatic for the entire PEQ period.  
o has a high likelihood of transferring from P. americana  budwood to a suitable host in 
New Zealand (with low uncertainty) because: 
 imported avocado budwood is intended to generate p lants for planting in New 
Zealand and avocado plants (which are a suitable ho st for these pathogens) 
derived from avocado budwood will be planted and nu rtured to survive in 
optimal or near optimal conditions in controlled or  natural environments, and  
 if the commodity is infected with either of these pathogens at the time of their 
release from PEQ and they are used as propagative m aterial then the 
pathogens will be transferred to a suitable host mu ltiple times.  
o has a high likelihood of establishing in New Zeala nd (with low uncertainty) because: 
 a suitable host (in the form of cultivated avocado s) is available for the 
establishment of Avocado sunblotch viroid , and  
 a suitable climate is available for the establishm ent of Avocado sunblotch 
viroid , and 
 Avocado sunblotch viroid  had been reported from New Zealand prior to its 
eradication. 
o may cause moderate overall impact on New Zealand ( with low uncertainty) because: 
 avocados are the only natural hosts of Avocado sunblotch viroid commercially 
produced in New Zealand, and  
 infection of avocado trees with Avocado sunblotch viroid could cause large 
yield losses and significant downgrading in quality  of the fruit, and  
 control of an outbreak could involve wide scale de struction of avocado trees 
(e.g., removal of all infected trees), and  
 there are likely to be negligible trade restrictio ns, and  
 a slow spread of disease incidence.  
The following table contains a summary of risk asse ssment against the criteria: 
Criteria  Rating Uncertainty  
The likelihood of entry on the commodity, given the  commodity description High Low 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low 
The likelihood of establishing in the New Zealand e nvironment High Low 
Impact on the New Zealand economy, environment, hum an health and society Moderate Low 
Overall level of assessed risk to New Zealand Moderate Low Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 40 6.4.2  Potato spindle tuber viroid 
Potato spindle tuber viroid (PSTVd) is a plant pathogen which consists of a sma ll, unencapsidated (no 
coat protein), circular, single-stranded RNA molecu le 356-361 nucleotides in length. It causes disease  
primarily in solanaceous plants, including potato, tomato and capsicum. However, the reported natural 
host range is large and includes avocado.  
Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Potato spindle tuber viroid meets the criteria to be a hazard on imported Persea americana  
budwood imported to New Zealand because it: 
o is not known to be present in New Zealand, and 
o has the potential to enter New Zealand on Persea americana  budwood (as described 
in the commodity description), and 
o has the potential to establish in New Zealand, and  cause harm to New Zealand. 
• Potato spindle tuber viroid poses an overall moderate risk on Persea americana  budwood 
imported to New Zealand because it: 
o has a high likelihood of entering New Zealand on P. americana  budwood (with low 
uncertainty) because: 
 Potato spindle tuber viroid can infect its hosts systemically, and  
 can remain asymptomatic for the entire post entry quarantine (PEQ) period.  
o has a high likelihood of transferring from P. americana  budwood to a suitable host in 
New Zealand (with low uncertainty) because: 
 imported avocado budwood is intended to generate p lants for planting in New 
Zealand and avocado plants (which are a suitable ho st for this pathogen) 
derived from avocado budwood will be planted and nu rtured to survive in 
optimal or near optimal conditions in controlled or  natural environments, and  
 if the commodity is infected with this pathogen at  the time of release from 
PEQ and used as propagative material then the patho gen will be transferred 
to a suitable host multiple times. 
o has a high likelihood of establishing in New Zeala nd (with low uncertainty) because: 
 suitable hosts in the form of cultivated avocados,  tomatoes, capsicum, egg 
plants, potatoes, and reservoir plants in the form of weeds and ornamentals 
are available for the establishment of Potato spindle tuber viroid , and  
 the climate is suitable for the establishment of Potato spindle tuber viroid , and 
 Potato spindle tuber viroid  had occurred transiently in New Zealand prior to i ts 
eradication, and 
 Potato spindle tuber viroid  is readily transmitted by graft and mechanical 
means, seeds, pollen and irrigation systems. 
o may cause moderate overall impact on New Zealand ( with low uncertainty) because: 
 direct impacts would likely occur on the tomato, p otato and capsicum industry 
in New Zealand through yield losses, and  
 indirect impacts would occur from export or trade restrictions imposed by 
other countries, and  
 control of an outbreak would involve wide scale te sting of growing areas and 
destruction of infected plants and trees.  
The following table contains a summary of risk asse ssment against the criteria: 
Criteria  Rating Uncertainty  
The likelihood of entry on the commodity, given the  commodity description High Low 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low 
The likelihood of establishing in the New Zealand e nvironment High Low 
Impact on the New Zealand economy, environment, hum an health and society Moderate Low 
Overall level of assessed risk to New Zealand Moderate Low 
 
   
41 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Annex: Assessment Details 
 
Contents Page  
1.  Risk analysis process 43  
1.1  Overview of the risk analysis process 44  
1.2  Risk assessment criteria 45  
1.3  Hazard identification 46  
1.4  Risk assessment 46  
1.5  Assessment of uncertainties 47  
1.6  Review and consultation 47  
1.7  References for Chapter 1 47  
2.  IRA scope and information 48  
2.1  Descriptions of the commodity and pathway 48  
2.2  General information related to likelihood of entry 51  
2.3  General information related to likelihood of exposu re and establishment 54  
2.4  General information related to impacts of pests and  diseases 58  
2.5  References for Chapter 2 61  
3.  Hazard identification 65  
3.1  Hazard ID scope 65  
3.2  Summary of hazard ID process 65  
3.3  List of Identified Hazards 66  
4.  Pest risk assessments: Bacteria 68  
4.1  Phytoplasmas on avocado 68  
4.2  Xanthomonas campestris  and X. axonopodis  avocado pathovars 82  
4.3  Xylella fastidiosa  – bacterial leaf scorch 94  
5.  Pest risk assessments: Fungi 110  
5.1  Akaropeltopsis  sp. (Sooty blotch of avocado) 110  
5.2  Ambrosia fungi of the Ambrosia Fusarium  Clade (AFC), Graphium  spp. and Paracremonium  
spp. vectored by beetles of the Euwallacea fornicatus  species complex 116  
5.3  Colletotrichum  spp. 128  
5.4  Clonostachys pseudochroleuca – avocado branch dieback and wilting 143  
5.5  Cophinforma tumefaciens  150  
5.6  Diaporthe perseae  157  
5.7  Diaporthe sterilis 167  
5.8  Dothiorella aromatica 175  
5.9  Elsinoe perseae – avocado scab 184  
5.10  Gliocladiopsis forsbergii, Gliocladiopsis peggii an d Gliocladiopsis whileyi 192  
5.11  Grovesinia moricola – zonate leaf spot 199  
5.12  Lasiodiplodia pseudotheobromae  205  
5.13  Mycosphaerella perseae 220  
5.14  Neocosmospora perseae 226  
5.15  Neofusicoccum nonquaesitum  239  
5.16  Pestalotiopsis longiseta  249  
5.17  Phyllachora gratissima  (tar spot) 260  
5.18  Phyllosticta perseae  – leaf spot disease 265  
5.19  Pleiocarpon algeriense  and Cylindrocladiella peruviana  272  
5.20  Podosphaera perseae-americanae  282  
5.21  Pseudocercospora purpurea  290  
5.22  Pseudoidium perseae-americanae  (powdery mildew of avocado) 299  
5.23  Pyrrhoderma noxium  (brown root rot) 308  
5.24  Raffaelea  spp. – laurel wilt disease 314  
5.25  Rhizoctonia noxia (thread blight) 323  
5.26  Rhizoctonia theobromae (vascular-streak dieback) 328  
5.27  Scolecobasidium musae (sooty blotch and flyspeck (S BFS)) 336  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 42 5.28  Sooty moulds 342  
6.  Pest risk assessments: Oomycetes 350  
6.1  Phytophthora mengei  (Phytophthora trunk canker) 350  
6.2  Phytophthora palmivora  (bud rot of palms) 365  
7.  Pest risk assessments: Viroids 382  
7.1  Avocado sunblotch viroid  (ASBVd) 382  
7.2  Potato spindle tuber viroid 390  
Appendix 1.  Summary of taxa excluded at PRA 402  
App 1.1  Avocado Black Streak Disease 402  
App 1.2  Botryobasidium perseae 405  
App 1.3  Ceratocystis fimbriata (Ceratocystis blight) 406  
App 1.4  Diaporthe pascoei  408  
App 1.5  Duke 6 stem pitting 409  
App 1.6  Guignardia foeniculacea  412  
App 1.7  Lasiodiplodia  mahajangana  414  
App 1.8  Microthia  havanensis  416  
App 1.9  Physalospora  abdita  and Physalospora perseae  418  
App 1.10  Plagiostoma  perseae  421  
App 1.11  Pseudomonas  syringae  pathovar causing avocado bacterial blast 423  
App 1.12  Rhizoctonia  solani  426  
App 1.13  Thielaviopsis  sp. 429  
App 1.14  Verticillium  alboatrum  (Verticillium wilt) 430 
App 1.15  Diplodia pseudoseriata  432  
Appendix 2.  Summary of taxa excluded at hazard identification 4 40  
Appendix 3.  Glossary and Abbreviations 463   
43 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 1. Risk analysis process 
The World Trade Agreement on the Application of San itary and Phytosanitary Measures (SPS 
agreement) states that phytosanitary measures must be supported by risk assessment and not 
maintained without sufficient evidence (SPS agreeme nt; WTO 1995). That is, to require additional 
measures, MPI must have evidence that a pest or dis ease would not be sufficiently managed by the 
application of the minimum requirements.  
The Biosecurity New Zealand process for undertaking  an IRA builds on the existing international 
frameworks for risk analysis under the World Organi sation for Animal Health (OIE) and the 
International Plant Protection Convention (IPPC), a nd extends the scope, under the SPS Agreement, 
to include all of the values required by the Biosec urity Act (1993) 4 (the Act).  
The main output is an IRA which is used in the deve lopment or review of an IHS under the Act. An 
IHS specifies the requirements to be met for the ef fective management of risks associated with 
importing risk goods 5. 
The Act requires a chief technical officer to begin  the process of developing an Import Health 
Standard by: “ analysing or assessing the risks associated with im porting a class or description of 
goods” 6. While the Act does not state how the risks are to b e assessed or analysed, it does state that 
the chief technical officer must have regard to cer tain matters when developing an IHS for 
recommendation to the Director-General. A number of  these are part of an IRA as described by the 
OIE and IPPC:  
• The likelihood that the goods will import organism s 7 
• The nature of the organisms that the goods may imp ort 
• The possible effect on human health, the New Zeala nd environment 8, and the New Zealand 
economy of the organisms that the goods may import 
• In relation to requirements proposed for inclusion  in an IHS, the extent to which the 
requirements reduce or manage the likelihood or imp acts of adverse effects from organisms 
that may be imported on or in association with good s 9 
An IRA is also a relevant factor in how a country m eets its obligations under the SPS agreement and 
other agreements such as the Convention on Biologic al Diversity (CBD). Under the SPS agreement, 
risk management measures either must be based on ex isting international standards, guidelines or 
recommendations, or must be supported by a scientif ic justification 10 . Measures must not be 
maintained without sufficient scientific evidence 11 . Measures must also not be unnecessarily trade 
restrictive 12 . In order to meet these obligations, the SPS agree ment requires that measures are based 
on a risk analysis. Under the CBD, countries must c onsider environmental impacts in decision-making 
and prevent the introduction of, and control or era dicate alien species that threaten ecosystems, 
habitats and species.  
 
4Biosecurity Act section 24(4)(b)(iii) “…human healt h, the New Zealand environment, and the New Zealand  economy…” As 
defined in section 2(1), environment includes (a) e cosystems and their constituent parts, including pe ople and their 
communities; and (b) all natural and physical resou rces; and (c) amenity values; and (d) the aesthetic , cultural, economic, and 
social conditions that affect or are affected by an y matter referring to paragraphs (a) to (c).   
5Section 22, Biosecurity Act 1993 
6Section 23(1) Biosecurity Act 1993  
7From Section 2(1) Biosecurity Act 1993: “ organism —(a) does not include a human being or a genetic st ructure derived from a 
human being: (b)includes a micro-organism: (c) subj ect to paragraph (a), includes a genetic structure that is capable of 
replicating itself (whether that structure comprise s all or only part of an entity, and whether it com prises all or only part of the 
total genetic structure of an entity): (d) includes  an entity (other than a human being) declared by t he Governor-General by 
Order in Council to be an organism for the purposes  of this Act: (e) includes a reproductive cell or d evelopmental stage of an 
organism: (f) includes any particle that is a prion ” 
8From section 2(1) Biosecurity Act 1993, “ environment includes— (a) ecosystems and their constituent part s, including people 
and their communities; and (b) all natural and phys ical resources; and (c) amenity values; and (d) the  aesthetic, cultural, 
economic, and social conditions that affect or are affected by any matter referred to in paragraphs (a ) to (c)” 
9Section 23(4)(b) and (d) Biosecurity Act 1993 
10 SPS Agreement 1995 Article3(1) and (3)  
11 SPS Agreement 1995 Article 5(7) 
12 SPS Agreement Article 5(6) Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 44 The Biosecurity New Zealand (BNZ) process is equiva lent to the process for plant health risk analysis 
under the International Standards for Phytosanitary  Measures (ISPM) under the IPPC 13  (the main 
differences being in terminology).  
1.1  Overview of the risk analysis process 
The individual steps in the process for developing an IRA are the same for both the OIE and IPPC. 
However the standards, guidelines and recommendatio ns for animal health (sanitary) and plant health 
(phytosanitary) measures are developed by different  international bodies. This means that there are 
differences in the detail of how IRA is done for an imal health (OIE) and plant health (IPPC). The BNZ 
process and methodology for undertaking an IRA is s ummarised in Figure 1-1. 
 
Figure 1-1: BNZ process and methodology for underta king an import risk analysis 
 
13 ISPM2: Framework for Pest Risk Analysis (FAO 1995).  
 
45 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 1.2  Risk assessment criteria 
For each of the likelihoods of entry, exposure, est ablishment, the following ranking scales will be 
used.  The column containing the “quantitative guid ance” provides a quantitative scale to help guide 
the analyst on the scale of each ranking. 
Scale Criteria Quantitative guidance 
High Extending above the normal or average level Mo re than 2 events in 3 years 
Moderate Around the normal or average level 1 to 2 events in 3 years 
Low Less than average, coming below the normal leve l 1 event in 3 to 20 years 
Very low Close to insignificant 1 event in 20 to 10 0 years 
Negligible Not worth considering; insignificant Les s than 1 event in 100 years 
For consequences, the following ranking scales will  be used against the listed risk evaluation criteri a: 
Scale Criteria Quantitative guidance 
Very High Well above the normal or average level Mo re than 10 billion $NZ 
High Extending above the normal or average level Be tween 1 and 10 billion $NZ 
Moderate Around the normal or average level Between  100 million and 1 billion $NZ 
Low Less than average, coming below the normal 
level Between 10 and 100 million $NZ 
Very low Close to insignificant Between 1 and 10 mi llion $NZ 
Negligible Not worth considering; insignificant  Le ss than 1 million $NZ 
While the values provided in the quantitative guida nce are New Zealand dollars over a 20 to 30 year 
period, the analyst considers how non-economic impa cts can be monetarised (e.g., the dollar value of 
damage to ecosystem services) or considered equival ent (e.g., how much social impact is equivalent 
to these economic values). 
In risk assessment, the uncertainty associated with  each conclusion/contention for each likelihood 
and consequence is stated in each conclusion. The r ationale for the uncertainty rating will be stated in 
the text as follows: 
Scale  Criteria  
High • Scarce or no data available; evidence provided in unpublished reports of unknown 
authenticity; or 
• Few observations and personal communications; and/ or 
• Authors’ or experts’ conclusions var y considerably  
Moderate • Some or only incomplete data available; evidence p rovided in small number of 
references; authors’ or experts’ conclusion vary; o r 
• Limited evidence from field/lab observations; or 
• Solid and complete data available from other speci es that can be extrapolated to 
the species being considered 
Low • Solid and complete data available; strong evidence  in multiple references with 
most authors coming to the same conclusions; or 
• Considerable and consistent experience from field observations  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 46 1.3  Hazard identification 
Hazard identification 14  is the process for identifying pests and diseases associated with imported risk 
goods and which have the ability to cause harm to N ew Zealand. The process consists of compiling a 
list of potential hazards and then assessing them a gainst criteria to see whether they warrant further  
consideration. The hazard identification answers tw o different questions: 
• Does the species meet the criteria to be considere d a biosecurity risk to New Zealand? 
• Is the species potentially associated with the com modity that is being assessed? 
The criteria for a quarantine pest for New Zealand are derived from the Biosecurity Act and the IPPC 
and OIE. These criteria are: 
• Is the pest or disease absent from New Zealand? 
• OR is the pest or disease present in New Zealand, but it meets one of the following criteria? 
o The pest or disease is under official control. 
o The species is a vector of a quarantine pest or di sease. 
o There are subspecific taxa (subspecies, varieties,  strains, etc.) within the pest 
species that are an increased risk to New Zealand c ompared with those already 
present. 
o There are other factors that would mean that the p est or disease may still be of 
concern in associated with imported goods (e.g. inc reased exposure to people 
through imported goods 15 ). 
• AND does the pest or disease have the potential to  establish in New Zealand and harm 
“human health, the New Zealand environment, and the  New Zealand economy 16 ”? 
Association with the commodity is based on: 
• association with the commodity species or genus; 
• association with the specific parts of the commodi ty; and 
• whether a particular pest will stay associated wit h a commodity during preparation and/or 
transit to New Zealand – for example, a large flyin g insect is unlikely to stay on a piece of fruit 
when it is picked. 
Different approaches may be taken to compiling and presenting the list of potential hazards 
depending on the information needed for pests or di seases in each pest/disease group. The approach 
for each group may be determined once the risk mana gement question and risk evaluation criteria 
have been established. The specific approaches to h azard identification used in this import risk 
analysis are discussed further in Chapter 3. 
1.4  Risk assessment 
At the end of hazard identification, the list of ha zards that require risk assessment is compiled. A r isk 
assessment evaluates the likelihood of introduction  (entry, exposure and establishment) and 
magnitude of consequence for a particular hazard, a s well as the uncertainty in the conclusions. The 
SPS agreement describes the factors to take into ac count when assessing risk. These factors include:  
• available scientific evidence;  
• relevant processes and production methods;  
• relevant inspection, sampling and testing methods;   
• prevalence of specific pests or pathogens; 
• relevant ecological and environmental conditions; and 
 
14  Under the IPPC, the hazard identification process is known as pest categorisation in ISPM 2 (FAO 1995 ) and ISPM 11 (FAO 
2013). 
15  One example is venomous spiders on fresh fruit. Ev en if present in a country, there may be a higher l ikelihood of people 
getting bitten if the spiders are associated with f ruit sold at a supermarket. 
16  Biosecurity Act 1993  
47 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • potential damage in the event of the entry, establ ishment or spread of a pest or disease. 
A qualitative approach is suitable for the majority  of import risk analyses and is currently the most 
common type of assessment undertaken to support the  development and review of import 
requirements. 
1.5  Assessment of uncertainties 
The SPS agreement states that measures must be appl ied only to the extent necessary  and must be 
supported by sufficient scientific evidence 17 . Therefore, if there is insufficient evidence indi cating that 
an organism meets the criteria for requiring additi onal measures (the risk evaluation criteria), then the 
lack of evidence suggests that it does not meet the  critera to be a hazard (see section 1.3). However,  
in some cases there may be good reason to consider a pest or disease even when evidence is 
insufficient (e.g. similarity to known pests or dis eases), and that pest or disease may be assessed 
further. If there is insufficient evidence but sign ificant uncertainty, then the decision maker may ap ply 
measures, but under those circumstances the measure s are provisional and further conditions may 
be required 18 .  
Therefore, documenting significant uncertainty is a n essential part of a risk assessment. Uncertaintie s 
such as contradictions in the evidence or a lack of  evidence are documented in the IRA. Where the 
risk assessment identifies significant uncertainty affecting the conclusion, this is indicated in the 
wording of the conclusion. 
1.6  Review and consultation 
Expert review is a fundamental component of a risk analysis to ensure the analysis is based on the 
most up-to-date and credible information available.  
The IRA may be reviewed to check that the IRA is ba sed on the best available and most credible 
information, that the document is clear and logical , that assumptions are valid and that conclusions 
are consistent with the evidence, with other conclu sions in the IRA and with relevant conclusions in 
other assessments.  
1.7  References for Chapter 1 
FAO (1995) International Standard for Phytosanitary Measures ( ISPM) No. 2. Guidelines for pest risk 
analysis.  Secretariat of the International Plant Protection Convention, Food and Agricultural 
Organization of the United Nations, Rome, Italy.  
 
FAO (2013) International Standards for Phytosanitar y Measures (ISPM) No. 11. Pest rick analysis for 
quarantine pests. In International Standard for Phytosanitary Measures N o. 11 . Rome, Italy: 
Secretariat of the International Plant Protection C onvention, Food and Agricultural Organization of th e 
United Nations. 
 
WTO (1995) World Trade Organization (WTO) Sanitary and Phytosanitary Measures Agreement 
(SPS). www.wto.org/english/tratop_e/sps_e/sps_e.htm  Accessed February 
 
 
 
17  SPS Agreement 1995 Article 2.2 
18  SPS Agreement 1995 Article 5.7 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 48 2. IRA scope and information 
This import risk analysis (IRA) has been developed in response to a request to develop a new import 
health standard (IHS) for the importation of avocad o ( Persea americana ) plants for planting. The 
purpose of the IRA is to identify and assess biosec urity risks associated with Persea americana  
budwood/leafless cuttings, and to identify risk man agement options to inform decisions on risk 
management. The decisions that this IRA will inform  are: 
a. whether any pests or diseases on Persea americana  budwood require additional measures. 
b. what measures are available that could manage the p est or disease risks to an appropriate 
level. 
The objective of the IRA is to: 
a. identify pests (mainly pathogens such as viruses, v iroids, bacteria, fungi, oomycetes and 
nematodes) and diseases of unknown aetiology that a re associated with the commodity and 
may require additional measures (i.e. cannot be con tained in a level 3A post-entry quarantine 
facility or be detected in a level 3A post-entry qu arantine during a period of active growth with 
a minimum of three distinct phenological growing ev ents (‘shoot flush’, see section 2.2)). 
b. assess these pests or diseases using a method that provides sufficient evidence about the 
biosecurity risks for a robust and transparent deci sion on whether additional measures are 
required to manage these pests or diseases. 
c. ascertain options for managing the identified risks  to an appropriate level where this 
information is available in the literature. 
For any particular risk good 19 , there is a commodity definition that describes th e minimum condition of 
the commodity that is covered by this IRA. The comm odity definition is important as many pests and 
diseases may not be associated with a commodity tha t is defined in a certain way (e.g. more pests or 
diseases may potentially be associated with a commo dity definition of fresh beans for consumption 
than a commodity definition of frozen beans for con sumption). 
2.1  Descriptions of the commodity and pathway 
This risk analysis considers the effects on the New  Zealand economy, environment, society and 
human health 20  from pests or diseases potentially associated with  the importation of Persea 
americana  budwood. A detailed description of the commodity a nd pathway is provided in Table 2-1. 
Table 2-1: Detailed description of the commodity an d the pathway(s) of entry to New Zealand 
Commodity description  
• Budwood/ leafless cuttings 21 of Persea americana  and all its varieties and cultivars, brought into 
level 3A post-entry quarantine (3A PEQ) for a perio d of active growth with a minimum of three 
distinct phenological growing events (referred to a s ‘shoot flush’).  
• Budwood/ leafless cuttings are taken from mother pl ants. The cuttings do not have leaves, roots or 
soil attached to them, only buds. 
• Budwood/ leafless cuttings are dipped in 1% w/v sod ium hypochlorite for 2 minutes upon entry into 
the quarantine facility. 
• The PEQ period involves visual inspection of plants  for the presence of pests and symptoms. Visual 
inspections by an MPI inspector are usually carried  out during active growing s easons - for other 
 
19  Regulated article under IPPC 
20  Specifically, this IRA covers sections 23(4)(b)(i) , (ii) and (iii) of the Biosecurity Act: 
(i) the likelihood that the goods will import organ isms: 
(ii) the nature of the organisms that the goods may  import: 
(iii) the possible effect on human health, the New Zealand environment, and the New Zealand economy of  the organisms that 
the goods may import 
21  As Persea americana  is an evergreen species, the frequently used commo dity type in the IHS of ‘budwood/ dormant cuttings’  
will be changed to ‘budwood/ leafless cuttings’ to acknowledge the non-dormancy of the species.  
49 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Commodity description  
plants for planting there are two inspections in th e spring, two in the summer and one during the 
slower growth periods. A similar regime will be des igned for avocados. Inspections by a facility 
operator are carried out at least twice a week. 
All imported plants for planting must comply with b asic conditions as set out in MPI Standard 155.02.0 6 
(2020) “Importation of Nursery Stock” (IHS 155.02.0 6) . In addition to a period of PEQ, these include:  
• Clean (including free from soil), inert/ synthetic materials for protection, packaging, and shipping. 
• Phytosanitary certification stating that the export ing country has inspected the commodity and found 
it free of visually detectable regulated pests. 
• Pesticide treatments for insects and mites. 
Pathway description  
Sea or air cargo from countries that have commercia l avocado orchards and publish their research in En glish 
or Spanish languages. 
2.1.1  Taxonomy and biology of Persea americana  
Persea americana Mill. (avocado) is an evergreen tree belonging to t he Lauraceae family which also 
includes plants such as Cinnamomum verum (cinnamon) and Cinnamomum camphora (camphor) 
(WFO 2021b). Although there are about 120 species i n the genus Persea (WFO 2021a), avocado is 
one of the best-known because it is widely cultivat ed for its edible fleshy fruit. 
The probable area of origin of avocado is the easte rn and southern highlands of Mexico, through 
Guatemala to the Pacific coast of Central America ( Knight Jr. 2002). Persea americana is a diverse 
species consisting of a number of botanical varieti es corresponding to three ecological races 
(Mexican, Guatemaland and West Indian) and close re latives (Knight Jr. 2002; Scora et al. 2002; 
CABI 2021) adapted to different climates (Table 2-2 ): 
• Persea americana  var. americana (West Indian) 
• Persea americana  var. drymifolia (Mexican) 
• Persea americana  var. guatemalensis  (Guatemalan) 
o The following contribute to the ancestry of var. guatemalensis : 
 Persea americana var. nubigena  
 Persea americana  var. steyermarkii  
 Persea americana  var. tolimanensis  
 Persea americana  var. zentmeyerii  
• Persea americana  var. floccosa  (wild botanical variety) 
The races can hybridise readily and there are now m any cultivars and varieties in commercial 
production (CABI 2021). Types with predominantly Me xican x Guatemalan germplasm are more 
suited to the subtropical regions, whereas West Ind ian or West Indian x Guatemalan hybrids are 
successful in tropical climates (Knight Jr. 2002; C ABI 2021). In general, propagating an avocado 
variety from seed will yield a different variety to  the mother plant, therefore, avocadoes are usually  
propagated vegetatively (Crane et al. 2019). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 50 Table 2-2: Characteristics of West Indian, Guatemal an and Mexican races of P. americana *, in Florida 
USA (modified from Crane et al. 2019) 
Characteristics Race  
West Indian  Guatemalan  Mexican  
Origin  Tropical lowlands Tropical highlands Tropic al highlands 
Blooming season  February to March  March to April  January to February  
Maturity season  May to September  September to January  Jun e to October  
Development period (fruit set to maturity) 5 to 8 m onths 10 to 15 months 6 to 8 months 
Cold hardiness - General rating  Low  Moderate to High  High  
Cold hardiness - Young trees  -2 to -1°C  -3 to -2°C  -4 to -3°C  
Cold hardiness - Mature trees  -4 to -1°C  -4 to -2°C  -8 to -3°C  
* Tree response to freezing temperatures is influen ced by tree health, stage of growth, and cultural p ractices. Hybrids of 
these races have intermediate characteristics. 
Avocado is now grown in many tropical and subtropic al countries in the Americas, Africa, Asia, 
Europe and Oceania (CABI 2021). Avocado is grown co mmercially and domestically in New Zealand 
and is naturalised in climatically suitable areas o f the country. Approximately 95% of New Zealand’s 
commercial production is of the ‘Hass’ variety (New  Zealand Avocado 2021b), which is of 
predominantly Guatemalan origin but with some Mexic an genes (Newett et al. 2002). 
The avocado tree can grow to 20 metres and are pere nnial. The leaves are sometimes reddish when 
young before turning green. Small greenish-yellow f lowers bloom in clusters (panicles). The fruit is a  
berry, consisting of a single large seed surrounded  by a buttery pulp, and generally does not ripen 
until it falls or is picked from the tree (Crane et  al. 2019). The average range of productive life in  
California has been estimated at 20 to 30 years, wi th an upper estimate of 40 years under favourable 
conditions (Goodall et al. 1971), while trees growi ng in the wild in Mexico have been known to live as  
long as 400 years 22 . 
Based on the established phenology growth model for  avocado (Whiley et al. 1988), avocado has two 
distinct periods of extensive vegetative shoot grow th flushes per year, referred to as ‘growth flush’ or 
‘shoot flush’. A growth flush of the roots (‘root f lush’) either follows or coincides with a growth fl ush of 
aerial parts of the plant (‘shoot flush’) (Whiley 2 002). Growth flushes are followed by periods of 
‘quiescence’. Avocados are alternate or irregular b earing trees, meaning that heavy crops in an “on 
year” alternate with smaller crops in the “off year ”. Alternate bearing can result from a heavy crop o ne 
year inhibiting shoot growth and flowering in the n ext year or from there being sufficient flowers but  
poor fruit set. These cycles may be initiated by en vironmental triggers such as frost or drought and 
maintained by internal physiological mechanisms. Tr ee carbohydrate accumulation, boron deficiency 
and poor pollination may all contribute to this alt ernate bearing pattern (Thorp 2011). Crop 
management practices such as mulching, application of plant growth regulators, orchard design and 
canopy management can all be used to reduce product ion fluctuations (Whiley 2002).  
Avocado trees grown in New Zealand can have two or three growth flushes over a 12-month period. 
According to a study in the western Bay of Plenty, the first flush generally starts in September and 
finishes between mid-December and mid-January and t he second flush runs from mid-January to the 
end of February/ mid-March (Dixon et al. 2008). The re may also be a short period of shoot growth in 
autumn (mid-March to May). There is an obvious alte rnate bearing pattern with heavy fruit set in one 
year followed by poor or absent fruit set the next year. Different numbers of root flushes occurred at  
different times of the year in each study year (Dix on et al. 2008). In general, phenological events 
differed by several weeks from year to year. This v ariation in timing makes timing of tree management 
decisions challenging (Dixon et al. 2008). 
Fruit matures on the tree but generally does not ri pen until it falls or is picked from the tree. As a  
result, individual fruits may be harvested any time  during their period of maturity which can vary 
according to variety (Crane et al. 2019). The main harvest season for Hass avocados in New Zealand 
is September to April (New Zealand Avocado 2021a).  
 
22  http://ucavo.ucr.edu/general/answers.html   
51 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Rationale for minimum of 12 months in L3A PEQ: 
To account for this unpredictable/fluctuation, hold ing plants in PEQ for at least one shoot flush peri od 
of each year (spring or summer) in two subsequent y ears would provide sufficient opportunity for plant  
and pathogen interactions and life-cycles to develo p if the pathogen is present and for plants to be 
inspected for signs of disease. It also provides su fficient growth cycles and time for pre-determined 
testing for presence/absence of specified pathogens  to be conducted. A suitable sequence of growth 
flushes may be one spring, one summer and one subse quent spring growth flush; or alternatively 
consist of two summer and one spring flush periods.    
While plants held in PEQ will not mature and develo p to the stage of flowering or fruit bearing (A 
grafted avocado tree can start producing fruit afte r three years (New Zealand Avocado 2022)), the 
principle of alternate (biennial) or irregular bear ing applies as that characteristic is encoded into the 
avocado genome and not predictable (CABI 2021; New Zealand Avocado 2022).  
Generally, only two growth flushes may be expected annually (‘spring’ and ‘summer’ flush); however, 
environmental conditions in greenhouse facilities m ay be artificially optimised to facilitate addition al 
growth flushes and/or suppresses periods quiescence  (‘dormancy’) during cold weather periods 
(‘winter’ period) (CABI 2021). Therefore, the minim um period in PEQ is set to no less than 12 months. 
2.2  General information related to likelihood of entry 
The following aspects of the commodity and pathway description will affect the likelihood that pests o r 
diseases will enter New Zealand: 
• The scope of the import risk analysis includes Persea americana  budwood collected from all 
growing conditions and production methods from arou nd the world and thus, various climates 
and growing regions need to be considered. 
• While it is reasonable to consider that obviously diseased plants would not be used as a 
source of germplasm, many pathogens are not visible  on the plant surface. Some pathogens 
have obvious symptoms on leaves, flowers, or fruit,  but not stems. Plants infected with such 
pathogens are unlikely to be used as a source of bu dwood by commercial growers using 
known source plants. However, infected plants may b e used for other purposes in the source 
location, such as for breeding programmes, or budwo od may be harvested from plants that 
have not been observed over a long period of time. 
• The import risk analysis therefore covers some pat hogens or diseases with limited 
distributions or infrequent associations with P. americana , or pathogens that have obvious 
symptoms during at least part of the year. These pa thogens have a much lower likelihood of 
being present in P. americana  nursery stock than more widespread pathogens of P. 
americana ; however, they cannot be ruled out as a risk, give n the import risk analysis scope. 
As described in the commodity description: 
• Budwood/ leafless cuttings 23 of Persea americana  and all its varieties and cultivars, brought 
into level 3A post-entry quarantine (3A PEQ) for a period of active growth with a minimum of 
three distinct phenological growing events (referre d to as ‘shoot flush’).  
• Budwood/ leafless cuttings are taken from mother p lants. The cuttings do not have leaves, 
roots or soil attached to them, only buds. 
• Budwood/ leafless cuttings are dipped in 1% w/v so dium hypochlorite for 2 minutes upon 
entry into the quarantine facility. 
• The PEQ period involves visual inspection of plant s for the presence of pests and symptoms. 
Visual inspections by an MPI inspector are usually carried out during active growing seasons 
- for other plants for planting there are two inspe ctions in the spring, two in the summer and 
one during the slower growth periods. A similar reg ime will be designed for avocados. 
Inspections by a facility operator are carried out at least twice a week. 
 
23  As Persea americana  is an evergreen species, the frequently used commo dity type in the IHS of ‘budwood/ dormant cuttings’  
will be changed to ‘budwood/ leafless cuttings’ to acknowledge the non-dormancy of the species. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 52 All imported plants for planting must comply with b asic conditions as set out in MPI Standard 
155.02.06 (2020) “Importation of Nursery Stock” (IH S 155.02.06). In addition to a period of PEQ, 
these include: 
• Clean (including free from soil), inert/ synthetic  materials for protection, packaging, and 
shipping. 
• Phytosanitary certification stating that the expor ting country has inspected the commodity and 
found it free of visually detectable regulated pest s. 
• Pesticide treatments for insects and mites. 
As above, the standard also states that following a rrival in New Zealand all nursery stock (unless 
specified in the schedules of special entry conditi ons) must undergo a period of post entry quarantine  
(PEQ) in order to check for the presence of regulat ed pests and/or diseases. 
The minimum intervention to manage pest risk on Persea americana  budwood/leafless cuttings that 
are not coming from approved offshore facilities wi ll be: 
• Budwood/ leafless cuttings are dipped in 1% w/v so dium hypochlorite for 2 minutes upon 
entry into the quarantine facility, and 
• Level 3A post-entry quarantine (L3A PEQ) for a per iod of active growth with a minimum of 
three distinct phenological growing events (referre d to as ‘shoot flush’). 
Specification for the minimum period of post-entry quarantine for the IHS may be defined as follows. 
The post-entry quarantine period for P. americana  plants for planting:  
a. begins after imported plants held in a quarantin e greenhouse have started active growth.  
i. for plants derived from imported budwood/ leafle ss cuttings, active growth begins 
when all buds grafted from the imported cuttings ha ve developed fully expanded 
leaves;  
b. must include a period of active growth with a mi nimum of three distinct phenological growing 
events (referred to as ‘shoot flush’), each of at l east three months in length.  
c. must not be less than a minimum of 12 months of active growth.  
d. a period of quiescence (‘dormancy’) between summ er and subsequent spring flush period 
must not be artificially suppressed or shortened. 
As outlined in the Facility standard: Post Entry Qu arantine for Plants, the structural and operational  
requirements of L3A PEQ include (MPI 2021):  
• Vents must be screened with stainless steel insect -proof mesh with a maximum opening size 
of 0.04 mm (4.3.1.1 (7)) 
• A temperature controlled growing environment based  on a mechanically ventilated heating 
and cooling system (4.3.1.1 (8)),  
• All tools must be decontaminated (or discarded) be tween use on each plant (4.3.2.7 (2)) 
• All plants must be grown on raised benches with ad equate drainage (4.3.2.7 (6)) 
o All plants must be grown in individual containers (4.3.2.10 (3)).  
• In addition, plants are inspected at least twice p er-week during periods of active growth for 
signs of fungal infection (4.3.2.9 (1)), and sympto ms are diagnosed (3.7.2) and controlled 
when found, so spore production is minimised. Plant s showing symptoms of fungal infection 
will be destroyed, also to prevent spore production . 
• Requirements for wastewater treatment  
o 4.3.2.5 Water (1): Only potable water may be used 
o 4.3.2.5 Water (2): Any water that is collected for  re-use must be disinfected before 
reuse to ensure that it is free from pathogens 
o 4.3.1.1. (2): All water must be decontaminated bef ore leaving the facility using a 
method proven to kill plant disease organisms 
• Prevention of vector-driven pathogen dissemination , contamination of the surrounding 
environment and cross-contamination,  
o 4.3.1.1 Construction (7): Vents must be screened w ith stainless steel insect-proof 
mesh with a maximum opening size of 0.04 mm.  
o 4.3.2.4 Growing medium (1): Plants must be grown i n pasteurised or inert medium  
53 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand o 4.3.2.10 Plant growing conditions (2): All plants must be grown in individual 
containers. 
o 3.4.4 Facility hygiene (2): Plant material form di fferent consignments or different lots 
within the same consignment, must be effectively se gregated to prevent cross-
contamination 
o 3.4.4 (3): Procedures must be put in place to ensu re that there is no mixing of plants 
from different lots or consignments 
o 4.3.2.7 Facility hygiene (6): All plants must be g rown on raised benches with 
adequate drainage 
o 4.3.2.3 (2) yellow sticky traps must be used to mo nitor insects in the facility. 
o 4.3.1.3: the facility must be surrounded by a buff er strip minimum 1m wide which 
must be covered and free of plants 
• Irrigation: Drip irrigation rather than over-head irrigation to be used 
o 4.3.2.10 Plant growing conditions (1): Plant growi ng conditions in L3A – (2) Specific 
plant requirements for irrigation, nutrition, tempe rature and winter chilling must be 
met. 
In summary, in a Level 3A post-entry quarantine fac ility, all water leaving the facility must be 
decontaminated using a method proven to kill plant pathogens. The facility must have vents screened 
with insect-proof mesh with a maximum aperture of 0 .2 mm, must be monitored for insects and must 
be built in such a way that no plants are within 1 m of the facility (MPI 2021). Additionally, plants are 
inspected for signs of infestation or disease at le ast twice a week during active growth and once a 
week during dormancy (MPI 2021). If found, any sign s or symptoms are diagnosed and controlled. 
Therefore, if symptoms are due to fungal infection,  spore production will be minimised. 
All requirements must be met before plants are elig ible for biosecurity clearance and released from 
PEQ. In addition, the Emerging Risks register is ch ecked for new information on potential hazards on 
the pathway that may need assessment. 
A summary of the import pathway of P. americana  budwood into New Zealand from non-MPI 
accredited facilities is given in Figure 2-1 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 54  
Figure 2-1 Summary of the pathway for the import of leafless Persea americana  budwood from non-MPI 
accredited sources 
2.3  General information related to likelihood of exposure  and establishment 
2.3.1  Exposure 
When a pest or disease arrives in a new area, it us ually needs to find or encounter a growing host 
plant or substrate in order to establish. The proce ss of a pest or disease encountering a growing host  
plant or substrate is termed “exposure” in Biosecur ity New Zealand risk assessments. 
In the case of nursery stock, imported plant materi al is maintained in a habitat favourable for plant 
growth and is likely to be multiplied up to substan tial numbers. Promoting the survival and persistenc e 
of the plant material also promotes the survival an d persistence of the associated pests and diseases,  
resulting in a high likelihood of exposure, with lo w uncertainty for pests and diseases associated wit h 
germplasm/propagation pathways. 
Imported avocado budwood (as described, see section  2.1) is intended to generate plants for planting 
in New Zealand. Therefore, avocado plants derived f rom the avocado budwood and released from 
Post Entry Quarantine (PEQ) will be planted and nur tured to survive in optimal or near optimal 
conditions in controlled or natural environments in  New Zealand and used to propagate new plants for 
planting. Consequently, any undetected pests or dis eases associated with avocado plant material at 
 
55 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand the time it is released from PEQ are highly likely to be associated with growing host plants in 
New Zealand, with low uncertainty. 
2.3.2  Establishment and Climate 
Climate factors may impact on the likelihood of pes t or disease establishment in New Zealand. 
New Zealand climates 
New Zealand, in general, exhibits a mid-latitude oc eanic temperate climate (Cfb temperate with 
maritime climate in the Köppen classification (Köpp en 1936; Rubel and Kottek 2010)). Annual 
precipitation varies substantially due to topograph y, from dry eastern and inland areas to very high 
precipitation (on a global scale) in west coast are as 24 . The driest New Zealand climates barely reach 
a conventional water deficit on average (although t hey can do so in extreme years and months). The 
New Zealand climate ‘space’ can be visualised as a three-dimensional simplified climate niche (Figure 
5 in Halloy 2021). This represents the average mont hly temperature and precipitation for each month 
of the year for 42 New Zealand climate stations. 
As a consequence of being a small landmass in a lar ge ocean, New Zealand has relatively low diurnal 
and seasonal temperature fluctuations (equable clim ate). Rainfall is close to evenly distributed 
between summer and winter. These features are simil ar in equatorial climates. However, there can be 
relatively rapid variations between days as large w eather systems alternate over the oceans. 
Although such variations may also occur in continen tal climates, a key difference for organisms is the  
proximity of these variations to biological thresho lds (such as frost). 
Unlike many Northern Hemisphere continental climate s with reliable lengthy warm and cold periods, a 
small temperature variation in a mild oceanic clima te means a more significant change in the number 
of days crossing threshold degrees, which may in so me cases restrict the ability of some organisms to 
establish. This feature is also common to smaller l and masses and mountains of the Southern 
Hemisphere, which is why, globally, some of the mos t similar climate conditions to New Zealand are 
in the montane regions of the Andean Yungas cloud f orests and grasslands (Halloy et al. 2008). This 
is reflected in high morphological similarities of adaptations (Halloy and Mark 1996). 
Together with tussock grasslands, temperate rainfor ests are the global biome climate types most 
represented in New Zealand. The northernmost areas of New Zealand approximate subtropical 
temperature conditions, with an ability to grow a r ange of subtropical plants. 
The northern part of New Zealand is the most climat ically suitable for the establishment of new pests 
and diseases coming from subtropical or tropical cl imates. The area includes Kaitaia, Kerikeri, 
Whangarei, Auckland (New Zealand’s largest city) an d Tauranga. The latter two cities both contain 
large active seaports. These are also the main avoc ado producing areas of New Zealand (see section 
2.4.3). 
Avocado is grown commercially mainly in the Bay of Plenty and Northland (87% of production areas). 
Together with Auckland (7% of avocado production) a nd Waikato (3%), these four regions are 
grouped in NIWA (2001) ‘Northern New Zealand’ clima te zone because of the broad similarity of their 
climates. Within the Northern New Zealand climate z one there is some variation, but it can be broadly 
described as a subtropical maritime climate with lo w diurnal and moderate seasonal temperature 
variations. A wide variety of crops grow in this mi ld climate, including avocados, k ūmara, and kiwifruit, 
as well as citrus, asparagus, berry fruits and a va riety of other subtropical fruits (Plant & Food 
Research 2020). 
Mean annual temperatures range from 13.8 °C (Hamilton) to 15.7 °C (Kaitaia, Whangarei) 25 . The mean 
range of temperature between warmest and coldest mo nths is 8.8 °C. The mean of the coldest month 
 
24  This summary is written with crop pests and diseas es in mind, focusing on the climate in inhabited an d cultivated areas of 
New Zealand. Rainy outliers (e.g. Milford and Mt Co ok) and high mountain climates are not considered, as they represent 
extremes with relatively low human and agricultural  activity 
25  Data for this section is calculated from NIWA`s cl imate database ( https://cliflo.niwa.co.nz/ ) representing the ‘normal’ from 
1981-2010. For futher detail please refer to (Hallo y 2021). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 56 increases from 8.9° C (Hamiltion) to 12.1 °C (Kaitaia). Means for the warmest months vary from  18.8° C 
to 20.2° C. In Northland typical summer daytime maxi mum air temperatures range from 22° C to 26° C, 
but seldom exceed 30° C. Winter daytime maximum air temperatures range from 12° C to 17° C (NIWA 
2021).  
Both hot and cold temperatures are mitigated by the  maritime equable climate (Halloy 2021). 
Temperatures above 30° C are rare, as are frosts. Th ere are typically over 300 frost free days (for 
0° C) and frosts below -2° C occur rarely north of Au ckland (Ward and Clothier 2020). 
Growing degree days above 10° C (GDD 10 ) for 2019 ranged from above 1700 (Hamilton) to clo se to 
2400 (Whangarei) (Stats NZ Tatauranga Aotearoa 2020 ). 
Annual precipitation ranges from just over 1100 mm (Hamiltion) to over 1300 mm (Pukekohe and 
most or Northland). Precipitation is distributed fa irly evenly over the year, with slightly lower amou nts 
in summer. Combined with warmer summers and cooler winters, there may be water stress during the 
summer, requiring supplementary irrigation (Ward an d Clothier 2020) and there may be excess water 
in winter. 
Avocados have a requirement for well drained, well aerated soils (Dirou 2003; Ward et al. 2019). This 
is an important consideration, in addition to clima te, in understanding where avocado (and its pests 
and diseases) can thrive. Some of avocado’s serious  pathogens become a problem when roots are 
subjected to insufficient aeration and excess water logging. 
The climate overlap between New Zealand and where a  pest or disease has been reported can be 
assessed using the tool described in Phillips et al . (2018). This tool is based on the composite (or 
climate) match index (CMI) CLIMEX-MCR of CLIMEX ver sion 3.3. The tool allows the comparison of 
New Zealand’s climate in general or more specifical ly, with areas where a pest or disease occurs 
overseas. The CMI range extends from 0 to 1; the hi gher the CMI, the more similar the climate of the 
region to which the CMI pertains and the New Zealan d climate. A CMI of 0.7 or more between the 
New Zealand climate and the existing range of the p athogen or disease may indicate a high likelihood 
of climatic suitability for that pest or diseases t o establish in New Zealand (Phillips et al. 2018). 
For many of the pests or diseases assessed, this to ol may be a sufficient indication of climatic 
suitability in New Zealand for the pest or disease to establish. A whole-world map with CMI data from 
Phillips et al. (2018) is provided in Figure 2-2. W hen using the tool, the map can be enlarged to show  
more detail at a regional level.  
57 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand  
Figure 2-2 Climate match index (CMI). World climate  similarities with All New Zealand (Phillips et al.  
2018). 
Shifting New Zealand climates with climate change 
The global climate is warming rapidly and will cont inue to warm even faster as a result of greenhouse 
gas emissions (IPCC 2013, 2018; WMO 2019). Several studies have examined the effects of these 
changes on the New Zealand climate (NIWA 2017; Mini stry for the Environment 2018). Warming 
temperatures and changing precipitation patterns wi ll affect existing biodiversity, pests and diseases , 
and will change the likelihood of establishment of new arrivals (Gerard et al. 2013; Kean et al. 2015) . 
However, climate change is not just a scenario for the future. Average New Zealand temperatures 
have risen substantially over the last century, wit h concomitant but more variable changes in 
threshold and extreme conditions (including frosts,  heatwaves, droughts, tropical storms, etc). Sea 
surface temperatures (SSTs) around New Zealand are closely correlated with atmospheric warming, 
and in recent decades (since 1981), have been risin g in the order of 0.1–0.3° C per decade (Sutton 
and Bowen 2019). This would equate to 1–3° C per cen tury, close to the modelled predictions for 
2100. Such trends are, to some degree, hidden by in ter-annual variability, but are already significant  
for the biota, agriculture and human occupation. 
These ‘shifting goal posts’ may lead to some confus ion when reading climate change scenarios. 
Climate scenarios are expressed as degrees of chang e up to 2100, for example, a 2° C increase. 
However, the baseline for that increase may not be explicit to the reader. The baseline is sometimes 
referred to as ‘conditions pre-industrial age’, or ‘beginning of 20th century’. Other times, it may be  the 
‘1961–1990 average’, or more recently, the ‘1981–20 10’ average. Because of the continuous change 
since the pre-industrial period, the first baseline  would lead to a 2° C increase by 2100. However, 
adding the same 2° C to a 1981–2010 baseline would m ean ~3° C increase by 2100 in respect to pre-
industrial conditions. 
In New Zealand, some of the last years have already  approximated a 2° C increase on pre-industrial 
levels. Although cool years will still occur, for a n organism, some conditions in some years already 
approximate some models for 2100. Model scenarios f or temperature increases for 2100 depend on 
many factors, but most scientists now expect there is little chance of keeping the increases below 2° C  
(Wallace-Wells 2017). For illustration’s sake, expl oring a conservative 2° C average increase (as in 
Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 58 NIWA scenarios 26 ) and a 10-mm monthly increase in precipitation all ows us to investigate the 
consequences without making any judgement as to whi ch is more likely. 
We can then consider the likelihood of such scenari os. To give an idea of how conservative a +2° C is, 
consider that the average temperature in the last c entury has already climbed >1° C over pre-industrial  
values. As averages shift, so do the extremes of th e distribution and the thresholds for frosts, degre e 
days, etc. Note, for example, that the midpoint of July 2009–2018 is where extreme warm years were 
in 1928–1937; the extreme has already become the no rm (Figure 2-3)27 . Moreover, the pace of 
increase is accelerating, greenhouse gas emissions are still rising, and a series of potential tipping  
points may soon be breached. Due to prolonged lag t imes, the abrupt decline in emissions triggered 
from March 2020 due to the Covid-19 pandemic are no t likely to affects trends in the next decades. If 
such declines were to continue, they could reduce t he centennial temperature increase. 
 
Figure 2-3 : Schematic normalised frequency distribution of mean  monthly temperatures for July (left) 
and January (right) for Wellington, New Zealand.  
The blue line is 1928–1937, the orange line 2009–20 18, calculated from NIWA National Climate 
Database ( https://cliflo.niwa.co.nz/ ). Note that actual frequency distributions tend to  skew further right.  
As a result of such shifts, in future scenarios, fr osts decrease substantially, by 30% (RCP 2.6) to 50 % 
(RCP 8.5 28 ) for the year 2040 (Ministry for the Environment 2 018). 
2.4  General information related to impacts of pests and d iseases 
2.4.1  Potential for spread 
Availability of host species is unlikely to be a li miting factor for the spread in New Zealand of pest s 
associated with avocado. Avocado is grown commercia lly and domestically in New Zealand and is 
naturalised in areas climatically suitable. For oli gophagous pests (a narrow host range, but wider tha n 
avocado itself), plants in the same family as avoca do (Lauraceae) are the most likely potential hosts.  
There are a number of native and exotic Lauraceae s pecies present in New Zealand (section 2.4.2). 
 
26  2° C is an 'in between' of the 0.7° C to 3° C range o f scenarios in NIWA: https://niwa.co.nz/our-science /climate/information-and-
resources/clivar/scenarios, 20171221. However, in m ore detail, https://ofcnz.niwa.co.nz/#/localCharts shows an increase to 
2100 of 2° C (RCP 6) to 3° C (RCP 8.5) annual mean (f or six-model average) for Christchurch. Annual prec ipitation remains 
almost the same. Spring ° C and mm follow the same p attern. Summer (DJF) increases less (1.5° C to 2.3° C ). For rainfall, 
possible increases are around 10 mm; however, there  will be considerable geographic variation and this  is only illustrative. 
27  Note that climatologists typically prefer to use 3 0 years to represent a climatic period. Decadal per iods are, however, useful 
for biological systems, as a decade is a long enoug h time to determine whether an organism can perish,  establish or invade. 
28  In the latest IPCC report, RCPs (representative co ncentration pathways) are used to indicate emission  scenarios, where 2.6 
and 8.5 are the lowest and highest (e.g. IPCC 2013;  Ministry for the Environment 2018).  
 
59 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand For polyphagous pests (a wide host range) many suit able host species are likely to be present in 
New Zealand. 
The majority of commercial avocado production (see section 2.4.3) takes place in the warmer frost-
free areas of the upper North Island from Northland  to the Bay of Plenty; however, some commercial 
production occurs in other regions of the North Isl and and in the upper South Island (Table 2-4). 
Domestic avocado trees are likely to be found in fr ost-free areas especially in the upper North Island . 
Other Persea  relatives in New Zealand are assumed to be grown i n captivity or cultivation only and 
not naturalised or widely grown (see section 2.4.2) .  
The New Zealand native species of Lauraceae (see se ction 2.4.2) are most commonly found in the 
upper North Island, although Beilschmiedia tawa  occurs as far south as the northern South Island 
(Allan 1982; NZPCN 2021). Non-native species of Lau raceae in New Zealand are largely grown in 
captivity/cultivation and are not naturalised, howe ver, camphor laurel (Cinnamomum camphora ) and 
bay tree ( Laurus nobilis ) are fully naturalised (Table 2-3). 
The probable area of origin of avocado is Mexico/Ce ntral America. It is now grown in many tropical 
and subtropical countries in the Americas, Africa, Asia, Europe and Oceania (CABI 2021). The 
Climate Match Index (CMI) for New Zealand with many  of these countries is below 0.7, indicating a 
poor climate match (see section New Zealand climates ). However, for some countries/regions, e.g. 
France, Greece, Portugal, Spain, California, Chile,  Argentina, the CMI is 0.7–0.9, indicating a good o r 
very good climate match. This means that at least s ome pathogens that are associated with imported 
avocado plants are likely to encounter favourable c onditions for establishment and spread and for 
disease expression, at least in the warmer parts of  New Zealand. 
2.4.2  Potential impacts on plant species other than Persea americana  
Members of the same plant family share many pests a nd diseases in common. There is a strong 
relationship between how closely related different plant species are and how likely they are to share 
pests and diseases (for example, see Gilbert and We bb 2007) 29 . In addition to P. americana  the 
following Persea  species are known to be present in New Zealand: P. borbonia , P. lingue , and P. 
thunbergia . However, these species are probably growing only infrequently under cultivation and not 
naturalised as only P. americana  is listed in the Manaaki Whenua – Landcare Researc h New Zealand 
plants database and the NZPCN website. 
Persea  is a member of the Lauraceae family. There are a n umber of native and exotic Lauraceae 
species present in New Zealand. Other genera in the  family in New Zealand include Beilschmiedia , 
Cassytha  and Litsea  (native and some endemic; none are considered thre atened (NZPCN 2021)) and 
Laurus , Cinnamomum  and Cryptocarya  (exotic, introduced as ornamentals and, in the cas e of the bay 
tree Laurus nobilis , for culinary purposes; some species are naturalis ed) (Table 2-3). Therefore, pests 
and diseases which are associated with avocado, but  have a wider host range, have the potential for 
environmental and socio-cultural impacts. 
Table 2-3: Species in the family Lauraceae reported  as present in New Zealand in the Biota NZ (2022) a nd 
NZPCN (2021) databases. 
Species  Common name  New Zealan d Biostatus  
Native species  
Beilschmiedia tarairi  (A.Cunn.) Benth. & 
Hook.f. ex Kirk  taraire Endemic. Not threatened 
Beilschmiedia tawa  (A.Cunn.) Benth. & 
Hook.f. ex Kirk  tawa Endemic. Not threatened 
Cassytha paniculata  R.Br. taihoa, mawhai  Native – not endemic . Not threatened  
Cassytha pubescens  R.Br. taihoa, mawhai  Non -endemic  
 
29 This phenomenon is widely used in risk assessment a nd policy setting for plant health (Gilbert and Web b 2007). See 
www.pnas.org_cgi_doi_10.1073_pnas.0607968104   Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 60 Species  Common name  New Zealan d Biostatus  
Litsea calicaris (Sol. ex A.Cunn.) Benth. & 
Hook.f. ex Kirk  mangeao, tangeao Endemic. Not threatened 
Exotic species  
Cinnamomum camphora  (L.) J.Presl  camphor laurel  Fully naturalised  
Cinnamomum loureiroi  Nees   Present in captivity/cultivation/culture  
Cinnamomu m cassia   Present in captivity/cultivation/culture  
Cryptocarya obovata  R.Br.  Present in captivity/cultivation/culture 
Laurus nobilis  bay tree, laurel  Fully naturalised  
Laurus azorica  (Seub.) Franco   Present in captivity/cultivation/culture  
Persea amer icana  Mill avocado  Fully naturalised  
Neolitsea sericea  (Blume) Koidz   Present in captivity/cultivation/culture  
Lindera benzoin  (L.) Blume   Present in c aptivity/cultivation/culture  
Sassafras tzumu  (Hemsl.) Hemsl.   Present in captivity/cultivation/culture  
Sassafras albidum  (Nutt.) Nees   Present in captivity/cultivation/culture  
Machilus thunbergii  Siebold & Zucc.   Present in captivity/cultivation/culture  
2.4.3  Potential for economic impacts to the avocado industry 
The New Zealand avocado industry comprises around 3 ,937 hectares divided between approximately 
1,034 growers with most commercial production takin g place in the Bay of Plenty, Auckland and 
Northland (Table 2-4, Figure 2-4). The most commonl y grown variety is ‘Hass’ (NZIER 2016). Most 
avocados are sold as fresh produce although some ar e processed as avocado oil. Most produce is 
grown for the export market. 
Table 2-4: Distribution of avocado (area planted, ha) by Regio nal Councils, year ended 30 June 2017 
(Stats NZ Tatauranga Aoteaora 2021) 
Region Hectares Region Hectares 
North Island of New Zealand South Island of New Zealand  
Northland  2,000 Tasman - 
Auckland 430 Nelson - 
Waikato 100 Marlborough - 
Bay of Plenty 2,200 West Coast - 
Gisborne  50 Canterbury 30 
Hawke's Bay  20 Otago 10 
Taranaki 20 Southland S* 
Manawatū-Whanganui - Chatham Islands - 
Wellington 10   
Total North Island 4,820 Total South Island 40 
Total New Zealand 4,870 
*S – data suppressed for reasons of confidentiality  
A number of packhouses, fruit marketing companies a nd exporters are involved in the industry to 
market and sell avocados both domestically and over seas (NZIER 2016). In 2020 there were 13 
licensed exporters, located in Northland, Auckland and Bay of Plenty, and 12 registered packers 
dealing with New Zealand avocados (NZ Horticulture Export Authority 2021). 
Growers were estimated to have produced 39,078 tonn es of avocados in 2019/2020 (Plant & Food 
Research 2020). New Zealand domestic sales of fresh  avocado fruit were worth NZ$50.6 million 
(Plant & Food Research 2020). In 2020, export sales  (free-on-board value) of fresh fruit were worth 
NZ$100.1 million (Plant & Food Research 2020). Dome stic sales of avocado oil were worth $2.6  
61 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand million in 2019/20 and export sales (free-on-board value) worth $9.3 million in 2020 (Plant & Food 
Research 2020). 
 
Figure 2-4: Main avocado growing areas in New Zeala nd 
Australia is the main export destination with 75% o f total export earnings in the year ended June 2020  
(Table 2-5). Asian markets, particularly Thailand, South Korea, Taiwan, Japan and Singapore, 
account for most of the remainder. 
Avocado is of significant economic importance to Ne w Zealand, although not comparable to crop 
plants such as kiwifruit, grapevine or pine (NZIER 2016). Avocado was one of the four dominant fruit 
export products in 2020 (the others being kiwifruit , grape wine and apples) (Plant & Food Research 
2020). 
Table 2-5: Avocado export markets 2020 (year ending  June) (NZ Horticulture Export Authority 2021) 
Market  Volume (tonnes)  Value ($NZ FOB)  
Australia  18,018  83,958,924  
Thailand  1,727  9,786,986  
South Korea  1,051  5,663,720  
Taiwan  603  3,617,522  
Japan  673  3,217,124  
Singapore  633  2,687,279  
China  302  1,258,401  
India  194  1,023,353  
Malaysia  163  660,228  
Hong Kong  66  246,835  
New Caledonia  37  180,240  
Fiji  16  68,225  
United Arab Emirates  17  66,115  
Indonesia  9 46,208  
United States of America  1 13,937  
Pacific Islands  1 8,270  
French Polynesia  0 1,254  
Total  23,512  $112,504,621  
2.5  References for Chapter 2 
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filicopsida, gymnospermae, dicotyledones . P D Hasselberg Government Printer; Wellington, Ne w 
Zealand. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
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Accessed December 2021 
Crane, J H; Balerdi, C F; Maguire, I (2019) Avocado growing in the Florida home landscape . UF/IFAS 
Extension, University of Florida, https://edis.ifas.ufl.edu/pdf/MG/MG21300.pdf  
Dirou, J F (2003) Avocado growing. In N C f T Horti culture (Ed.), (third edition ed., Vol. Agfact H6.1 .1, 
pp. 1-8). Alstonville, Australia: 
https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0 003/119739/avocado-growing.pdf . 
Dixon, C C; Hofstee, B; Elmsly, T A (2008) Hass’ av ocado tree phenology 2004-2009 in the western 
bay of Plenty. New Zealand Avocado Growers' Association Annual Res earch Report 8: 35-57. 
Gerard, P J; Barringer, J R F; Charles, J G; Fowler , S V; Kean, J M; Phillips, C B, et al. (2013) 
Potential effects of climate change on biological c ontrol systems: case studies from New Zealand. 
BioControl 58(2): 149-162. 
Gilbert, G S; Webb, C O (2007) Phylogenetic signal in plant pathogen-host range. Proceedings of the 
National Academy of Sciences 104(12): 4979-4983. 
Goodall, G E; Little, T M; Rock, R C; Platt, R G; R eed, A D (1971) Useful life of avocado trees in 
commercial orchards in California .  
Halloy, S (2021) Climate similarity of overseas Avo cado growing areas to New Zealand. In Piritahi  
(pp. 1-17): 
https://piritahi.cohesion.net.nz/Sites/BFSRA/Biosec urity/Climate%20similarity%20of%20overseas%20 
Avocado%20growing%20areas%20to%20New%20Zealand.docx ?d=w90edd2e27b2645b7a3e86aa0e 
d372721 . 
Halloy, S R P; Beck, S G; Ledezma, J C (2008) Centr al Andean grasslands (central and southern 
Peru, western Bolivia, northern Chile and northwest ern Argentina). In B Peart (ed) Compendium of 
regional templates on the status of temperate grass lands conservation and protection.  IUCN: Quito, 
Ecuador. 
Halloy, S R P; Mark, A F (1996) Comparative leaf mo rphology spectra of plant communities in New 
Zealand, the Andes and the European Alps. Journal of the Royal Society of New Zealand 26(1): 41-
78. 
IPCC (2013) Climate Change 2013: The Physical Science Basis. Co ntribution of Working Group I to 
the Fifth Assessment Report of the Intergovernmenta l Panel on Climate Change . Cambridge, United 
Kingdom and New York, NY, USA.  
IPCC (2018) Summary for Policymakers . Geneva, Switzerland.  
Kean, J M; Brockerhoff, E G; Fowler, S V; Gerard, P  J; Logan, D P; Mullan, A B, et al. (2015) Effects 
of climate change on current and potential biosecur ity pests and diseases in New Zealand . 
Wellington, New Zealand.  
Knight Jr., R J (2002) History, distribution and us es. In A W Whiley; B Schaffer; B N Wolstenholme 
(eds) Avocado: Botany, Production and Uses.  CABI: Wallingford, United Kingdom. 
Köppen, W (1936) Das geographische system der klimate  (Vol. 1). Gebrüder Borntraeger; Berlin, 
Germany. 
Ministry for the Environment (2018) Climate change projections for New Zealand: atmosph ere 
projections based on simulations from the IPCC Fift h Assessment . Wellington, New Zealand.  
MPI (2021) Facility Standard: Post Entry Quarantine for Plants . Ministry for Primary Industries, 
https://www.mpi.govt.nz/dmsdocument/11368-Post-Entr y-Quarantine-forPlants-Facilities-Standard   
63 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand MPI Standard 155.02.06 (2020) Ministry for Primary Industries Standard 155.02.06 Importation of 
Nursery Stock. In. 
New Zealand Avocado (2021a) General questions. https://industry.nzavocado.co.nz/contact/faq-and-
help/faq-and-help-guide/   
New Zealand Avocado (2021b) Varieties. https://www.nzavocado.co.nz/varieties/   
New Zealand Avocado (2022) Backyard growing. https://www.nzavocado.co.nz/backyard-growing/  
Accessed April 2022 
Newett, S D E; Crane, J H; Balerdi, C F (2002) Cult ivars and rootstocks. In A W Whiley; B Schaffer; B 
N Wolstenholme (eds) Avocado: Botany, Production and Uses.  CABI: Wallingford, United Kingdom. 
NIWA (2001) Overview of New Zealand's Climate. In NIWA : https://niwa.co.nz/education-and-
training/schools/resources/climate/overview . 
NIWA (2017) Climate change scenarios for New Zealan d. https://niwa.co.nz/our-
science/climate/information-and-resources/clivar/sc enarios#regional  Accessed December 2021 
NIWA (2021) Climate data and activities. https://niwa.co.nz/education-and-
training/schools/resources/climate  Accessed November 2021 
NZ Horticulture Export Authority (2021) Avocado ind ustry profile. https://www.hea.co.nz/2012-05-11-
03-05-28/avocado-trade  Accessed December 2021 
NZIER (2016) How valuable is that plant species? Application of a method for enumerating the 
contribution of selected plant species to New Zeala nd's GDP . Wellington, New Zealand.  
NZPCN (2021) New Zealand Plant Conservation Network . https://www.nzpcn.org.nz/  Accessed June 
2021 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
Rubel, F; Kottek, M (2010) Observed and projected c limate shifts 1901 - 2100 depicted by world 
maps of the Köppen-Geiger climate classification. Meteorologische Zeitschrift 19(2): 135-141. 
Scora, R W; Wolstenholme, B N; Lavi, U (2002) Taxon omy and botany. In A W Whiley; B Schaffer; B 
N Wolstenholme (eds) Avocado: Botany, Production and Uses.  CABI: Wallingford, United Kingdom. 
Stats NZ Tatauranga Aoteaora (2021) Agricultural pr oduction statistics: June 2020 (final). 
https://www.stats.govt.nz/information-releases/agri cultural-production-statistics-june-2020-final  
Accessed November 2021 
Stats NZ Tatauranga Aotearoa (2020) Growing degree days. In Stats_NZ - Tatauranga Aotearoa : 
https://www.stats.govt.nz/indicators/growing-degree -days . 
Sutton, P J H; Bowen, M (2019) Ocean temperature ch ange around New Zealand over the last 36 
years. New Zealand Journal of Marine and Freshwater Resear ch 53(3): 305-326. 
Thorp, G (2011) Avocado alternate bearing research . Horticulture Australia Ltd., Sydney, Australia.  
Wallace-Wells, D (2017) The uninhabitable earth, an notated edition. In: Intelligencer New York. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 64 Ward, R; Clothier, B (2020) Evaluation of selected horticultural crops for Ward  and surrounding areas . 
Plant & Food Research,  
Ward, R; Funnell, K; Clothier, B (2019) Evaluation of selected horticultural crops for Kaip ara District 
Council: Progress Report 2 . Plant & Food Research, 
https://www.kaipara.govt.nz/uploads/kickstart/Evalu ation%20of%20selected%20horticultural%20crops 
%20for%20Kaipara%20District%20Council%20Progress%20 Report%202.pdf  
WFO (2021a) Persea  Mill. http://www.worldfloraonline.org/taxon/wfo-400002884 6  Accessed 
December 2021 
WFO (2021b) World Flora Online. Published on the In ternet. http://www.worldfloraonline.org/  
Accessed December 2021 
Whiley, A (2002) Crop management. In A W Whiley; B Schaffer; B N Wolstenholme (eds) Avocado: 
Botany, Production and Uses.  CABI: Wallingford, United Kingdom. 
Whiley, A W; Cull, B W; Pegg, K G; Saranah, J B (19 88) Manage avocado tree growth cycles for 
productivity gains. Queensland Agricultural Journal 114: 29-36. 
WMO (2019) WMO Statement on the State of the Global Climate in  2018 . Geneva, Switzerland.  
  
65 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 3. Hazard identification 
A hazard is a pest or disease that is associated wi th imported risk goods and import pathways and 
that has the ability to cause harm to New Zealand. Hazard identification (hazard ID) is the process 
where, depending on the scope of the IRA, a list of  pests and diseases potentially associated with the  
commodity is compiled and then assessed against spe cified criteria, in order to determine which 
species require further assessment (section 1.3). T he objective for hazard identification in this IRA is 
to identify all pests and diseases that require fur ther risk assessment to determine which ones may 
require additional measures to those in the commodi ty description.  
In order to identify pests and diseases that requir e further risk assessment, potential hazards were 
considered using the following criteria: 
• Potential to meet the criteria to be a quarantine pest 
• Association with the commodity 
• Potential to meet risk evaluation criteria for add itional measures. 
Pathogens which meet the risk evaluation criteria a re those that cannot be contained in a Level 3A 
post-entry quarantine facility or be detected in Le vel 3A post-entry quarantine during a period of act ive 
growth with a minimum of three distinct phenologica l growing events (‘spring-flush’). These may 
include pathogens with the following traits: 
• The pathogens can be latent for long periods (more  than 12 months, such as fungi which can 
be endophytic or pathogens which may only show symp toms under certain growing 
conditions). 
• The pathogens can rapidly produce copious quantiti es of wind-dispersed spores. 
• The pathogens are vector-transmitted, and there ar e vectors present in New Zealand and the 
vectors are small and mobile enough to enter a 3A p ost-entry quarantine facility, acquire the 
pathogen and then escape from the facility. 
While the ability of a pest or disease to establish  and cause impacts is part of the definition of a 
hazard, this is generally only considered indicativ ely at the hazard identification stage. It is asses sed 
in depth at the risk assessment stage. Similarly, t he ability of a pathogen to not be contained during  a 
period of active growth in Level 3A PEQ is consider ed very broadly at the hazard ID stage and is 
considered at depth during risk assessment. 
3.1  Hazard ID scope 
• Pests (mainly pathogens such as viruses, viroids, bacteria, fungi, oomycetes and nematodes) 
and diseases of unknown aetiology associated with P. americana  plants for planting from any 
country. 
• Information is restricted to that in English and S panish language sources. 
3.2  Summary of hazard ID process 
• Automated literature search supplemented by manual  searches of additional sources 
o Sources included databases such as CABI, EPPO, USD A Fungal database, Web of 
Science (process outlined in the BNZ Guidelines for  Undertaking an Import Risk 
Analysis Version 1.0) 
• Some organisms are not considered further because risks are considered adequately 
managed by the commodity and pathway descriptions ( e.g, arthropods, molluscs, vertebrates) 
• Reduced list screened against hazard id criteria t o produce list of hazards for risk assessment 
Sixty-one species were identified at the hazard ide ntification stage as requiring further pest risk 
assessment. These species were grouped into thirty- five PRAs of which 29 pests and diseases were 
found to present a sufficient level of risk to be c onsidered for measures (Table 5-1). These Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 66 conclusions were based on a species potentially mee ting criteria for being a quarantine pest, being 
associated with the commodity, and potentially not being managed by basic measures (including the 
period in L3A PEQ) (Table 5-1). 
Groups (e.g. genera or family) or high-profile spec ies that did not meet the criteria for requiring pe st 
risk assessment are listed in Appendix 1, along wit h the rationale for excluding them at the hazard 
identification stage. 
3.3  List of Identified Hazards 
From the list of potential hazards identified from the literature and other sources, the pests and 
diseases listed in Table 3-1 were identified throug h hazard ID to be hazards.  For each of thse 
hazards a PRA was completed with the resulting risk  level identified. 
Table 3-1: Summary of IRA conclusions based on path ogen groups or species for which PRAs were 
carried out. PRA conclusion includes overall risk [ uncertainty] of each pathogen. 
Pest/disease group  Species requiring PRAs PRA conclusions 
Bacteria Phytoplasmas on avocado Moderate (vector) [high] 
Negligible (no vector) [low]  
Xanthomonas campestris and X. axonopodis  Moderate [high]  
Xylella fastidiosa  High [moderate]  
Fungi Akaropeltopsis sp. Negligible [low]  
Ambrosia fungi of the Ambrosia Fusarium 
Clade  Negligible [low] 
Colletotrichum spp. Moderate [moderate]  
Clonostachys pseudochroleuca  Negligible, [low]  
Cophinforma  tumefaciens  Negligible [low]  
Diaporthe perseae Low [moderate] 
Diaporthe sterilis  Very low [moderate]  
Dothiorella aromatica  Low [low] 
Elsinoe perseae  Negligible [low]  
Gliocladiopsis spp. Very low [moderate]  
Grovesinia moricola  Negligible [low]  
Lasiodiplodia pseudotheobromae Moderate – high [moderate] 
Mycosphaerella perseae  Negligible [low]  
Neocosmospora perseae  Low [mod erate] 
Neofusicoccum nonquaesitum  Moderate [moderate]  
Pestalotiopsis longiseta  Low [moderate]  
Phyllachora gratissima Negligible [low]  
67 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Pest/disease group  Species requiring PRAs  PRA conclusions  
Phyllosticta perseae  Negligible [low] 
Pleiocarpon algeriense and Cylindrocladiella 
peruviana  Moderate [moderate] 
Podosphaera perseae -americanae  Very low [low]  
Pseudocercospora purpurea  Negligible [moderate]  
Pseudoidium perseae -americanae  Very low [low]  
Pyrrhoderma noxium  Negligible [low]  
Raffaelea spp. Negligible [low]  
Rhizoctonia noxia  Negligible [low]  
Rhizoctonia theobromae  Negligible [low]  
Scolecobasidium musae  Negligible [low]  
Sooty moulds  Negligible [low]  
Oomycetes Phytophthora mengei  Moderate [moderate]  
Phytophthora palmivora  Moderate [moderate]  
Viroids Avocado sunblotch viroid Moderate [low] 
Potato spindle tuber viroid  Moderate [low]  
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 68 4. Pest risk assessments: Bacteria 
4.1  Phytoplasmas on avocado 
Phytoplasmas are bacteria that lack cell walls. The y colonise the phloem of their plant hosts as well 
as various parts of their insect vectors. Phytoplas ma infection is associated with a wide range of 
symptoms affecting all plant parts and can be fatal  to the plant.  Phytoplasmas belonging to the 
stolbur group (16SrXII), likely ‘Candidatus Phytopl asma solani’, (16SrXII-A) have been identified in 
symptomatic avocado trees in Spain, and an unidenti fied phytoplasma has been identified in 
symptomatic avocado trees in Chile. 
4.1.1  Taxonomic description 
Name: Persea americana –infecting phytoplasmas  
Kingdom/Class/Family: Bacteria/Mollicutes/Acholeplasmataceae  
Taxonomic notes:  Phytoplasmas are a well-defined clade in the class  Mollicutes but cannot be 
classified by traditional methods. Phytoplasmas can  be classified into “candidate” (‘ Candidatus’ ) 
species by 16S rRNA gene sequences and they can als o be classified into 16S rRNA gene groups 
and sub-groups based on restriction fragment length  polymorphism (RFLP). There are currently over 
30 16S rRNA groups and over 160 sub-groups recognis ed. There are currently around 40 recognised 
‘Candidatus ’ species. Each of these corresponds to a 16S rRNA gene sub-group, but not every sub-
group has been classified into a recognised candida te species.  In the latter cases the 16Sr sub-group  
number and name can be used. 
The species concept is defined within the phytoplas mas, but the appropriate level at which to conduct 
a risk assessment is often unclear. In this case, t he phytoplasmas involved cannot be assigned 
definitely to a ‘ Candidatus ’ species; it can only be said that they are Persea americana- infecting 
phytoplasmas (avocado-infecting phytoplasmas), with  further information from one record (Laviña et 
al. 2002) that the phytoplasma detected is in the “ stolbur” group, likely ‘ Ca. P. solani’ (16SrXII-A). The 
other record (Bäuerle Bascuñán 2002) is of an undet ermined phytoplasma. 
4.1.2  Hazard identification 
New Zealand biostatus 
Persea americana –infecting phytoplasmas are not known to be present  in New Zealand: 
Only two phytoplasmas are known to be present in Ne w Zealand, neither of which have been reported 
in association with avocado (S Veerakone, pers. com m.; L Liefting pers. comm.; Veerakone et al. 
2015; NZOR 2021; PPIN 2021): 
• ‘Candidatus  Phytoplasma australiense’ infecting Apium , Coprosma , Cordyline,  
Gomphocarpus , Phormium , Potentilla , Solanum  and Rubus ; and  
• ‘Candidatus  Phytoplasma pruni’ causing a (desirable) branching  phenotype in Euphorbia.   
It is very unlikely that the avocado-infecting phyt oplasmas are already present in New Zealand 
because they are not likely to be either of these t wo phytoplasmas. The phytoplasmas from avocado 
trees in Spain is not the same strain as the ‘ Ca. P. pruni’ recorded in New Zealand because this is i n 
group 16SrXIII (not 16SrXII, stolbur group, as reco rded by Laviña et al. 2002).  The phytoplasmas 
recorded from avocado trees in Spain by Laviña et a l. (2002) or in Chile by Bäuerle Bascuñán (2002) 
are very unlikely to be ‘ Candidatus Phytoplasma australiense’, although this is one of the 
phytoplasmas within the 16SrXII “stolbur” group. ‘ Ca. P. australiense’ is only known to be present in 
New Zealand and Australia (L Liefting pers. comm.; Liefting 2020) and has not been reported from 
Spain or Chile. Furthermore, neither phytoplasma fo und in New Zealand has been recorded in New 
Zealand on avocado plants. Therefore, the current a ssessment has been carried out assuming that  
69 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand the phytoplasmas reported by Laviña et al. (2002) a nd Bäuerle Bascuñán (2002) are not present in 
New Zealand. 
Avocado-infecting phytoplasmas are associated with Persea americana  budwood because: 
• Persea americana  is a known host of at least one phytoplasma (Bäuer le Bascuñán 2002; 
Laviña et al. 2002); 
• Phytoplasmas occur in association with budwood, as  they are systemic through the plant 
phloem sieve tubes (Marcone 2009). 
Avocado-infecting phytoplasmas have the potential t o establish (and spread) in New Zealand 
because: 
• If an infected plant grown from infected budwood i s released from PEQ undetected the 
infected plant will be multiplied and planted in Ne w Zealand avocado orchards. Plants 
originating from the original budwood may be infect ed, so avocado trees may be infected by 
these phytoplasmas. 
• If competent vectors are present in New Zealand, t hey may transmit the phytoplasma/s to 
other New Zealand originating avocado trees and pot entially to other hosts, depending on the 
vector’s host range. 
Avocado-infecting phytoplasmas have the potential t o cause harm to New Zealand because: 
• They may infect avocado trees and potentially caus e yield loss, plant decline and death. 
While this has not been reported in avocado trees i nfected with phytoplasmas, phytoplasmas 
have caused this type of damage in other hosts (Agr ios 2005). 
• Depending on vector availability within New Zealan d and the identity of the phytoplasma, the 
avocado-infecting phytoplasmas may cause decline or  death in other plant hosts in New 
Zealand, as phytoplasmas have previously been repor ted to do (Agrios 2005). Some 
phytoplasmas e.g. ‘ Ca. P. solani’ have very wide host ranges (Quaglino 202 0). 
Given the arguments and evidence above, avocado-inf ecting phytoplasmas meet the criteria to be 
hazards on Persea americana  budwood (as in the commodity description) imported  to New Zealand. 
4.1.3  Risk assessment 
Detections and identity of avocado-infecting phytop lasmas 
Spanish detection (Laviña et al. 2002) 
Laviña et al. (2002) reported finding “stolbur phyt oplasma” on Hass cultivar avocado trees in Spain.  
They observed typical phytoplasma symptoms: leaf ro ll, leaf vein chlorosis with the leaves becoming 
small and abnormally red, and dwarfing; the symptom s were irregularly distributed on infected trees. 
Leaves from eight symptomatic plants taken from aff ected plots and leaves from two symptomless 
plants taken from healthy plots were analysed for p hytoplasma infection by PCR assays. The stolbur 
phytoplasma was detected in trees by PCR using a st olbur-specific nonribosomal primer pair, or by 
nested PCR with 16S rDNA primers pairs. Symptomatic  and asymptomatic trees were sampled in 
May, July, and October 2000, but phytoplasmas were detected only in samples collected from 
symptomatic trees in July. Phytoplasmas were detect ed by universal primers in all symptomatic 
samples analysed in July, whereas stolbur-specific primers gave positive results in only 75% of the 
symptomatic samples. RFLP analysis confirmed the ph ytoplasma belonged to the stolbur group. 
The phytoplasma found in avocado trees in Spain was  described as “stolbur” (Laviña et al. 2002). 
Stolbur can refer to the overall 16SrXII “stolbur” group, or specifically to 16 SrXII-A “Stolbur” (= 
‘Candidatus Phytoplasma solani’). The stolbur phytoplasma refer red to by Laviña et al. (2002) could 
be any of the phytoplasmas now recorded in the 16Sr XII “stolbur” group (Table 4-1) but is most likely 
to be ‘ Ca. P. solani’ (see explanation below). There are curre ntly thirteen groups (XII-A to XII-O) 
within the 16SrXII “stolbur” group, including five ‘ Candidatus  Phytoplasma’ species. However, Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 70 ‘Candidatus Phytoplasma australiense’ is only known to be prese nt in New Zealand and Australia 
(although there are some erroneous reports from oth er countries) (L Liefting pers. comm.). 
However, Laviña et al. (2006) studied Bois Noir dis ease in Spain and said it was caused by “ the 
stolbur phytoplasma , which belongs to the stolbur group, also referred  to as the 16SrXII-A group . 
The disease is widespread in different vine growing  regions in Spain, such as La Rioja, Navarra, 
Cataluña and Aragón. In Spain it has also been show n to affect different crops such as carrot, tomato,  
pepper, strawberry, avocado  and asparagus .” They cited Laviña et al. (2002) as evidence that  this 
phytoplasma was found in avocado. It is therefore l ikely that when Laviña et al. (2002) refer to “the 
stolbur phytoplasma” they are referring to the 16Sr XII-A group, which they said in 2006 was found in 
avocado. This is ‘ Candidatus Phytoplasma solani’. 
Table 4-1 Phytoplasma names and groups coming under  16SrXII – “stolbur”. 16SrXII-A to I from 
Bertaccini and Lee (2018). The “stolbur” found on a vocado in Spain by Laviña et al. (2002) could be an y 
of these although it is almost certain not to be ‘C a. P. australiense’. It is most likely to be ‘Ca. P . solani’. 
16Sr grouping Strain (acronym) ‘Candidatus’ species 
XII-A “Stolbur” ‘Ca. P. solani’ 
XII-B Australian grapevine yellows (AUSGY)  ‘Ca. P. australiense’  
XII-C Strawberry lethal yellows (StrawLY)  
XII-D Japanese hydrangea phyllody ‘Ca. P. japonicum’ 
XII-E Yellows diseased strawberry (StrawY) ‘Ca. P. fragariae’ 
XII-F “Bois noir” (BN -Op30)   
XII-G “Bois noir” (N -Fc3)   
XII-H Bindweed yellows (BY-S57/11) ‘Ca. P. convolvuli’ 
XII-I Potato strain from China (169/Hezuo 88)  
XII-J*   
XII-K*    
XII-N**    
XII-O***    
*New subgroups described in Quaglino et al. (2017) 
**New subgroup described by Eroglu et al. (2010) 
***New subgroup described in Kazeem et al. (2021) 
Chilean detection (Bäuerle Bascuñán 2002) 
In a master’s thesis Bäuerle Bascuñán (2002) report ed the detection of an unidentified phytoplasma 
on symptomatic avocado trees in Quillón, Chile, usi ng nested PCR. Phytoplasmas were not detected 
when conventional PCR was used. Nested PCR is more sensitive than conventional (or direct) PCR 
(Haqqi et al. 1988). Symptoms observed on infected trees were dwarfism, general chlorosis, short 
internodes, bud proliferation, and deformation of n ew leaves. 
Biology and epidemiology of avocado-infecting phyto plasmas 
Phytoplasmas are bacteria lacking cell walls. They are found in the phloem sieve tubes of host plants,  
and in insect vectors, and can multiply in both the  plant and insect hosts (Bertaccini and Lee 2018). 
They are obligate biotrophic organisms, which canno t survive outside their plant or insect hosts 
(Oshima et al. 2004). Phytoplasmas spread systemica lly through the plant by passing through phloem 
sieve plate pores (Marcone 2009). 
Phytoplasma diseases are known from more than a tho usand plant species worldwide (Agrios 2005). 
They are quite often associated with severe and rap idly spreading plant diseases (Bertaccini and Lee 
2018). Phytoplasmas are associated with a wide rang e of symptoms including virescence and 
phyllody of flowers, sterility, leaf yellowing, los s of apical dominance generating the proliferation of 
axillary buds with witches’ broom formation, abnorm al internode elongation, abnormal root growth, 
generalised stunting, and a general decline that is  sometimes fatal to the plant (Agrios 2005; 
Bertaccini and Lee 2018). Infection can also be asy mptomatic (Bertaccini and Lee 2018). 
There are two main mechanisms of transmission known  for phytoplasmas: natural transmission by 
phloem-feeding insect vectors, but also by propagat ion or grafting of infected material.  
71 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Experimentally, phytoplasmas can be transmitted bet ween plants via the vascular connection formed 
by dodder ( Cuscuta  spp.). Phytoplasmas are not reported to be spread by mechanical transmission 
(Lee et al. 2000), and only uncommonly by seed (Sat ta et al. 2019).  
Vectoring 
Phytoplasmas are naturally spread between plants by  insects in the hemipteran families Cicadellidae 
(leafhoppers) and Psyllidae (psyllids) and superfam ily Fulgoroidea (plant hoppers). These insects 
feed on the phloem of infected plants; therefore th e phytoplasmas’ host range is dependent on the 
host range of their vectors (Bertaccini and Lee 201 8). The phytoplasma subgroups vary in the 
specificity of their relationships with insect vect ors (Lee et al. 1998). Insect vectors have been 
identified for relatively few phytoplasma diseases and typically when new phytoplasma diseases are 
discovered little is known about the disease epidem iology (Weintraub and Beanland 2006).   
Grafting 
When phytoplasma-infected plants are grafted, often  only a percentage of the resulting plants are 
infected with phytoplasmas. Some experiments examin ed rates of transmission of phytoplasma from 
infected hosts to grafted plants, showing varying r ates (Table 4-2). 
Table 4-2: Percentage of phytoplasma infected plants resulting  from grafting. Some care is needed in 
interpreting these results, as different hosts, phy toplasmas and experimental techniques were used.  
Host Phytoplasma / 
phytoplasma caused 
disease % of phytoplasma 
infected plants 
resulting from the 
grafting  Reference 
Grapevines Bois noir phytoplasma 3% Osler et al. (1997) 
1.7% Credi et al. (2007) 
Apple Apple proliferation 0-30% Pedrazzoli et al. (2008) 
6.13% Magnago et al. (2002) 
90% Jarausch et al. (2000) 
80-97% Jarausch et al. (1999) 
Apple to 
periwinkle Apple proliferation 60% Aldaghi et al. (2007) 
Pear Undetermined phytoplasma 29-85% Pastore et al. (199 8) 
European stone fruit yellows 
phytoplasma (EFSY) 69-94% Jarausch et al. (1999) 
Japanese 
plum ‘Ca. Phytoplasma prunorum’ Initially 53% Pastore et al. (2008) 
Apricot EFSY Plants in 5 cultivars out 
of 10 infected Pastore et al. (2001) 
Japanese 
plum EFSY Plants in all cultivars 
infected Pastore et al. (2001) 
4.1.4  Likelihood of entry 
This assessment is made on the basis that avocado-i nfecting phytoplasmas are present in the 
countries from which avocado budwood is being impor ted. 
Phytoplasmas are associated with avocado trees (Bäu erle Bascuñán 2002; Laviña et al. 2002). As 
phytoplasma infection in avocado plants has only be en reported in the literature twice, it is likely t hat it 
is not common. Avocado is a high volume, widely gro wn, high value crop, and it is likely that if 
phytoplasma infection was a more common problem in avocado it would have been reported more 
frequently. However, phytoplasma infection can be a symptomatic (Bertaccini and Lee 2018) so it is 
possible that avocado trees are infected with phyto plasma more frequently than symptoms are 
observed, although asymptomatic infection was not r eported by Laviña et al. (2002) or Bäuerle 
Bascuñán (2002). So it is unlikely that budwood int ended for importation into New Zealand would be 
taken from phytoplasma infected trees. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 72 The volume of budwood entering New Zealand PEQ will  be very low, all budwood is grown into plants 
which are kept growing in PEQ for a year and PEQ do es not have space for many plants.  Therefore it 
is unlikely that phytoplasma infected budwood would  enter PEQ – it is unlikely that the few budwood 
cuttings taken for PEQ would be taken from infected  plants. 
As phytoplasmas are systemic through the phloem sie ve tube elements (Marcone 2009), budwood 
cuttings taken from infected avocado plants could b e infected with phytoplasmas. This infection is 
internal to the budwood so the likelihood of entry of the phytoplasmas would not be reduced by the 
surface sterilisation dip of budwood cuttings in di lute sodium hypochlorite (bleach dip). 
Avocado budwood will enter PEQ and plants will be g rown from the budwood for a period no shorter 
than 3 growth flush periods (and at least 12 months ).  During this period the plants are likely to be 
exposed to New Zealand summer-like conditions for p art of the time. It is likely that any phytoplasma 
infecting the imported avocado budwood would expres s symptoms in the resulting plants during this 
PEQ period, although there is no information availa ble on how frequently phytoplasma infections of 
avocado plants are asymptomatic. Avocado plants are  checked at least twice weekly during periods 
of active growth. If phytoplasma-like symptoms are observed, a universal phytoplasma PCR test 
would be undertaken, which would be likely to detec t any phytoplasma. 3A PEQ does not include pre-
determined testing for phytoplasmas using PCR. 
Given the arguments and evidence above, that is:  
• One or more phytoplasmas have been reported to inf ect avocado ( P. americana ) trees; 
• It is unlikely that avocado budwood is taken from phytoplasma-infected trees, since infections 
appear to be uncommon;  
• There is only a low volume of budwood entering PEQ , which lowers the likelihood that 
infected budwood would enter PEQ even further; 
• Avocado-infecting phytoplasmas occur in associatio n with budwood, as phytoplasmas are 
systemic through the plant phloem sieve tube elemen ts, and will not be reduced by budwood 
surface sterilisation;  
• Plants will be held in PEQ and any avocado plants with phytoplasma infection are likely to 
show symptoms, and if so, diagnostic PCR tests will  likely detect phytoplasma; 
• However, some phytoplasma infections are asymptoma tic so it is possible that infection would 
not be detected in PEQ;   
• 3A PEQ does not automatically include pre-determin ed phytoplasma PCR testing; 
Therefore, the likelihood of avocado-infecting phyt oplasmas entering New Zealand associated with 
Persea americana  budwood is considered to be very low, with moderat e uncertainty. 
4.1.5  Likelihood of exposure 
This assessment is made on the basis that avocado-i nfecting phytoplasmas have entered 
New Zealand undetected. 
When a pest or disease arrives in a new area, it us ually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for some 
phytoplasmas.   
If avocado plants are infected with phytoplasmas at  the time of their release from Post Entry 
Quarantine (PEQ) they will be planted in New Zealan d or used to propagate new plants for planting 
(see section 2.3.1 for additional information about  exposure).  
Given the arguments and evidence above, the likelih ood of exposure of avocado-infecting 
phytoplasmas in New Zealand from Persea americana  budwood is considered to be high, with low 
uncertainty.  
73 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 4.1.6  Likelihood of establishment 
This assessment is made on the basis that avocado-i nfecting phytoplasmas have been successfully 
exposed to suitable host plants in the New Zealand environment. 
As mentioned in the exposure step above, it is like ly that avocado-infecting phytoplasmas will be 
present in avocado trees in New Zealand originating  from imported budwood, and plants propagated 
from these e.g. by grafting, and plants taken from these grafted plants. It is not clear what percenta ge 
of grafted avocado plants taken from infected mothe r plants would be infected, likely less than 100%. 
Percentages of grafted plants also being infected b y phytoplasmas ranging from 97% to as low as 1-
2% have been recorded from some hosts (Table 4-2).   
Plants that show symptoms of a phytoplasma infectio n are unlikely to be propagated from. If 
asymptomatic infected avocado trees are released fr om PEQ and used to graft new trees, it is likely 
that phytoplasma symptoms will develop eventually, and the presence of phytoplasma infected 
avocado in New Zealand will become known. The avoca do nurseries and industry are likely to then 
put in measures such as genetic testing to detect p hytoplasma infections in trees which are to be 
used for grafting, and only use trees with a negati ve result. In this way, spread via grafting could b e 
reduced and potentially controlled in New Zealand. Then the only main way the phytoplasma could 
spread is through insect vectors. 
There is a high degree of uncertainty in whether th ere will be a competent vector in New Zealand, for 
transmission between avocado trees, and from avocad o trees to other hosts. As the phytoplasmas 
infecting avocado in southern Spain and Quillón in Chile are not known (other than in Laviña et al. 
(2002) it was a stolbur phytoplasma, likely ‘Ca. P. solani’), the vectors of the avocado-associated 
phytoplasmas are not known. Therefore it is not kno wn whether a competent vector is present in 
New Zealand. The known vectors of ‘ Ca . P. solani’ are Hyalesthes obsoletus (main vector), Reptalus 
panzer, Pentastiridius leporinus, Anaceratagallia r ibauti, and Reptalus quinquecostatus. These 
insects, and other insects in these genera, are not  recorded from New Zealand (NZOR 2021; PPIN 
2021). However, insects in the same families are pr esent and it is not clear whether these can vector 
‘Ca . P. solani’ or other phytoplasmas.  
Two insects in the Hemiptera superfamily Fulgoroide a have been found on avocado in New Zealand, 
but it is not known if these could act as a vector of the phytoplasmas found in avocado. As mentioned 
above, some insects in Fulgoroidea are known to be vectors of some phytoplasmas. Adults of the 
introduced kiwifruit pest ( Scolypopa australis (Fulgoroidea: Ricaniidae)) (passion vine hopper) ha ve 
been reported on avocado plants in the wild in New Zealand (Logan et al. 2002; PPIN 2021). There 
are weak associations of another species with avoca do. Four live nymphs of Siphanta acuta 
(Fulgoroidea: Flatidae) were found on avocado leave s in a visual survey on a commercial site in the 
Bay of Plenty, and pupae and egg masses were found on avocado leaves from another sample 
(PHA13737). In another case S. acuta eggs were laid on export avocado fruit (PHA2977, PP IN 2021). 
It is possible that a competent vector could enter and establish in New Zealand in the future. Many 
exotic psyllids have established in New Zealand pre viously, such as Bactericera cockerelli (tomato-
potato psyllid), Cardiaspina fiscella (brown lace lerp psyllid), Ctenarytaina eucalypti (blue-gum psyllid) 
(NZFFA 2009, 2022a). There are also many adventive species of Acizza (NZFFA 2022b) and “about 
a third of the New Zealand psyllid species are adve ntive” (Gordon 2010).  
As the phytoplasma and possible vectors involved ar e not known, it is not possible to say whether 
there will be enough suitable host plants present i n New Zealand for this phytoplasma to establish.  
There are plenty of avocado trees present in New Ze aland, but it is not clear whether the phytoplasma 
can establish long term in avocado trees. If it is ‘ Ca. P. solani’, many plants could be potential hosts. 
More than 100 species, belonging to 40 different fa milies and 22 orders have been recorded to be 
infected by ‘ Ca. P. solani’. This includes wild plants, ornamental p lants, and major and minor crops. 
Crops affected include grapevines, tomato, potato, capsicum, celery, carrot, parsley, and garden bean 
(Quaglino 2020). 
Climate is not likely to be a barrier to establishm ent of these avocado-infecting phytoplasmas. The 
avocado-infecting phytoplasmas were reported from a reas which have a CMI (Composite Match 
Index, an index of climate similarity) of ≥0.7, indicating a similar climate to the whole of N ew Zealand, Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 74 or northern New Zealand (Auckland and Northland Cro sby code regions) respectively (Phillips et al. 
2018; Roigé and Phillips 2021). Climate matches ran ge from 0 to 1, with a higher number indicating a 
more similar climate.  Northern New Zealand is curr ently one of the areas with the greatest production  
of avocado (the other is the Bay of Plenty). The re levant areas of southern Spain (major avocado 
growing areas) have a climate match with all of New  Zealand of 0.8-0.9 (Halloy 2021); and mostly 0.7 
but some 0.6 and 0.8 with northern New Zealand. Qui llón in Chile has a climate match with all of New 
Zealand, and with northern New Zealand, of 0.8 (Phi llips et al. 2018; Roigé and Phillips 2021). 
Therefore the phytoplasma is present in climates in  Spain and Chile which are similar to climates in 
New Zealand and northern New Zealand, and climates throughout New Zealand are likely to be 
suitable for the establishment of avocado-infecting  phytoplasmas.  
Given the arguments and evidence above, that is: 
• Asymptomatic infected avocado plants released from  PEQ will be used for grafting. Avocado 
trees originating from these are likely to be infec ted, and likely to be spread widely in avocado 
growing areas; 
• However if phytoplasma symptoms appear in avocado trees in New Zealand the avocado 
industry and nurseries will likely start testing fo r phytoplasma and only use clean stock;  
• It is uncertain whether there will be a competent vector in New Zealand. Known ‘ Ca. P. solani’ 
vectors are not known to be present, but insects in  the same family are present. 
• Two insects with the potential to be vectors have been reported on avocado in New Zealand; 
• It is possible that another competent vector could  enter and establish in New Zealand in the 
future, and some related species have established h ere;  
• If there is a competent vector in New Zealand pote ntially other host plants (e.g. grapevine, 
tomato, potato, capsicum) could be infected with th e phytoplasma found in avocado trees; 
• Climate is not likely to be a barrier to the estab lishment of these avocado-infecting 
phytoplasmas in New Zealand; 
the likelihood of avocado-infecting phytoplasmas es tablishing in New Zealand in avocado trees 
originating from imported budwood is considered low , with moderate uncertainty. The likelihood of it 
establishing in unrelated avocado trees and other p lant species hosts is moderate with high 
uncertainty if a competent vector is present in New  Zealand and low with high uncertainty if there is 
no competent vector in New Zealand. So the overall likelihood of the phytoplasma establishing in 
New Zealand is considered to be moderate with high uncertainty if a competent vector is present in 
New Zealand and low with high uncertainty if there is no competent vector in New Zealand. It is 
considered that there is a low-moderate likelihood of there being a competent vector present in 
New Zealand (with high uncertainty). 
4.1.7  Impacts in New Zealand 
If there is no vector, then the only plants that wi ll be impacted are some avocado trees propagated 
from the infected mother plant/s which were release d from PEQ, and any other avocado trees 
propagated from those, if the industry does not sta rt testing for phytoplasma in graft source trees. I f 
there is a vector, then the phytoplasma may be able  to be spread to more un-related (i.e. not related 
through grafting) avocado trees, or to other host p lant species.  
Economic impacts 
There is very high uncertainty in the determined le vel of economic consequences, for the following 
reasons 
• It is not known which phytoplasmas were found on a vocado (one was in the stolbur group, 
likely ‘ Ca. P. solani’). 
• It is not known if there will be a competent insec t vector in New Zealand to transmit 
phytoplasma from avocado plant to avocado plant or to other plant species. 
• It is not known what plants may host this phytopla sma in New Zealand, and what the potential 
severity of disease could be caused by this phytopl asma on those hosts.  
75 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand If there is no vector, then the only plants that wi ll be impacted are some avocado trees propagated 
from the infected mother plant/s which were release d from PEQ, and any other avocado trees 
propagated from those, if the industry does not sta rt testing for phytoplasma in graft source trees. S o 
phytoplasma impacts would be limited to the damage the disease does to these avocado trees. It is 
not known how badly the phytoplasma would affect th e tree; if it would cause reduced yield of 
avocado fruit or tree decline or death. There is no  evidence of avocado tree decline or death. The two  
published records of phytoplasma in avocado (Bäuerl e Bascuñán 2002; Laviña et al. 2002) only 
recorded mild phytoplasma symptoms on the observed infected trees; and did not state anything 
about more serious effects which would likely have been mentioned if they were present. Therefore if 
there is no vector present in New Zealand economic consequences are considered to be very low, 
with moderate uncertainty. 
If there is a vector, then the phytoplasma may be a ble to be spread to more un-related (i.e. not relat ed 
through grafting) avocado trees, or to other host p lant species. If the phytoplasma can be transmitted  
to other host plant species, then economic conseque nces could be quite large. As mentioned above, 
‘Ca.  P. solani’ can affect more than 100 plant species and have serious crop losses on grapevines (as 
bois noir), potatoes, tomatoes, capsicum and others  (Quaglino et al. 2013; Quaglino 2020), some of 
which are of very high economic importance to New Z ealand.  Wine exports for example, were worth 
$NZ1.91 billion in 2020; domestic and export produc tion of potato, tomato and capsicum were worth 
$NZ1.07 billion, $NZ143 million and $NZ60 million r espectively (Plant & Food Research 2020). It is 
not known how much the presence of ‘ Ca. P. solani’ in this crop would reduce these amounts.  
Therefore with a competent vector present in New Ze aland economic consequences are considered 
to be moderate with very high uncertainty. 
Given the arguments and evidence above, that is: 
• There is very high uncertainty in the level of eco nomic consequences because the 
phytoplasma involved is not known, the presence of a competent vector in New Zealand 
is not known, and the possible host plants that cou ld be affected and the severity of 
disease on those plants is not known. 
• If there is no competent vector in New Zealand, th e likely plants infected would be limited 
to avocado trees grafted from infected plants from PEQ and their offspring, and possibly 
industry would stop grafting from infected plants. 
• If there is a competent vector in New Zealand, oth er crop plants may be affected but it is 
difficult to know which without knowing the phytopl asma or vector. Some phytoplasmas 
such as ‘ Ca. P. solani’ can have major impacts on many crop plan ts including reduced 
crop yield and plant decline and death.  
The economic consequences of avocado-infecting phyt oplasmas to New Zealand is considered to be: 
• with a competent vector in New Zealand: moderate w ith very high uncertainty; and  
• without a competent vector in New Zealand: very lo w, with moderate uncertainty.  
Environmental impacts 
The environmental consequences have a very high unc ertainty, for similar reasons as those listed in 
the economic consequences section above.   
A different phytoplasma has already had a large env ironmental impact in New Zealand.  One of the 
two phytoplasmas known from New Zealand, ‘ Ca. P. australiense’,  has particularly affected the iconic 
cabbage tree, Cordyline australis, with many trees killed by this infection ( Cordyline sudden decline) . 
In New Zealand ‘Ca. P. australiense’ is also associated with the diseas es Phormium yellow leaf 
(affecting flax), and Coprosma lethal decline (affecting coprosma). ‘ Ca. P. australiense’ is also 
associated with several weed and crop plants in New  Zealand (Liefting et al. 2011).  Note that it is 
assumed that the avocado phytoplasmas reported by L aviña et al. (2002) and Bäuerle Bascuñán 
(2002) are not ‘Ca.  P. australiense’; however, this gives an example o f phytoplasma impacts on native 
plants in New Zealand.  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 76 There is a very low likelihood that the phytoplasma  could lead to decline or death in several species of 
native plants and trees, so the environmental impac ts are considered to be low, with high uncertainty.  
This requires the presence of a competent vector. 
Given the arguments and evidence above, the impact on the environment from the establishment of 
avocado-infecting phytoplasmas in New Zealand if th ere is a competent vector is considered to be low 
with high uncertainty. If there is not a competent vector in New Zealand, the impact on the 
environment is considered to be negligible with low  uncertainty. 
Human health impacts 
No evidence was found of any human health impacts f or phytoplasmas, as expected because 
phytoplasmas are exclusively plant pathogens, found  in plant phloem or insect vectors. 
Given the arguments and evidence above, the human h ealth impact of avocado-infecting 
phytoplasmas to New Zealand is considered to be neg ligible, with low uncertainty. 
Sociocultural impacts 
There is also high uncertainty in this estimation, for the same reasons – uncertain phytoplasma, 
uncertain vectors, uncertain hosts, uncertain impac ts on those hosts. 
There is a very low likelihood that some garden pla nts (both amenity and food plants) and street 
amenity trees could decline or die. ‘ Ca. P. solani’ can impact grapevines, potato, capsicum,  tomatoes 
and other plants which are grown in home gardens, a s well as domestic avocado trees. This could 
lead to low sociocultural impacts. 
There is a very low likelihood that avocado-infecti ng phytoplasmas could have impacts on Maori 
taonga plant species. A phytoplasma already present  in New Zealand (‘ Ca. P. australiense’) causes 
decline and death of t ī k ōuka (cabbage tree) and harakeke (flax) (Liefting et  al. 2011), and there is a 
very low likelihood that a new avocado-infecting ph ytoplasma could impact native taonga plant 
species also. This depends on the presence of a com petent vector.  
Given the arguments and evidence above, the sociocu ltural impact of avocado-infecting 
phytoplasmas to New Zealand if a competent vector i s present is considered to be low, with high 
uncertainty. If no competent vector is present in N ew Zealand the sociocultural impact is considered 
to be negligible with low uncertainty. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, health and society if there is a 
competent vector in New Zealand is considered to be  moderate, with high uncertainty. The overall 
impact if there is not a competent vector in New Ze aland is considered to be very low, with low 
uncertainty.  
4.1.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is very low (with moderate  uncertainty); 
• assuming entry, the likelihood of exposure is high  (with low uncertainty); 
• assuming successful exposure, the likelihood of es tablishment is moderate (with high 
uncertainty) if there is a competent vector in New Zealand, and low (with high uncertainty) 
if there is not a competent vector; 
• the overall impact on the New Zealand economy, env ironment, health and society is 
considered to be moderate (with high uncertainty) i f there is a competent vector present 
in New Zealand, and very low (with low uncertainty)  if there is no competent vector 
present in New Zealand.  
77 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand the overall level of assessed risk to New Zealand f rom avocado-infecting phytoplasmas on imported 
Persea americana budwood (as in the commodity description) is consid ered to be moderate (with 
high uncertainty) if there is a competent vector pr esent in New Zealand; and negligible (with low 
uncertainty) if there is no competent vector. It is  considered that there is a low-moderate likelihood  of 
a competent vector being present in New Zealand, wi th high uncertainty. 
4.1.9  Management considerations 
Symptoms 
In the two known detections of phytoplasma in avoca do plants, symptoms shown by infected trees 
were  
• leaf roll, leaf veinal chlorosis with the leaves b ecoming small and abnormally red, and 
dwarfing. These symptoms were irregularly distribut ed on infected trees (Laviña et al. 2002). 
• dwarfism, general chlorosis, short internodes, bud  proliferation, deformation of new leaves 
were observed in a Hass avocado orchard in Quillón,  VIII region [Chile] in October 1999 
(Bäuerle Bascuñán 2002). 
It is likely that these symptoms would be exhibited  in phytoplasma infections in avocado plants in 
PEQ. It is possible that other generally known phyt oplasma symptoms may be exhibited too, such as 
leaf yellowing, loss of apical dominance and witche s’ broom type growth, generalised stunting, 
general decline and possible plant death (Agrios 20 05; Bertaccini and Lee 2018). 
ISPM 27 ( Diagnostic protocols for regulated pests: DP 12: Ph ytoplasmas ) has a very useful section 
on phytoplasma testing which goes some way towards answering the remaining management 
questions (references included in this quote are no t included in the reference list; FAO 2016):  
“Polymerase chain reaction (PCR) techniques are the  method of choice for phytoplasma 
detection. Successful molecular detection of phytop lasmas is dependent on appropriate 
sampling of plant tissue and reliable nucleic acid extraction methods …. Phytoplasmas 
can be unevenly distributed and in an uneven titre throughout a plant, particularly in 
woody hosts, and symptomatic tissue is optimal for phytoplasma detection …. 
Symptomless infection can occur in some plant hosts  and if this is suspected it is 
important to thoroughly sample different tissues of  the plant. 
Phytoplasma titre in the plant host affects the rel iability of the PCR test …. Phytoplasma 
titre can be affected by phytoplasma strain or spec ies, host plant species, timing of 
infection and climatic conditions. The timing for s ampling plant tissues is important as 
location in the plant and titre of phytoplasmas may  be affected by seasonal changes ….   
For most phytoplasma diseases, leaves with symptoms  are the best sources of samples 
for diagnosis. Phytoplasmas reside in the phloem si eve elements of infected plants and 
therefore the leaf petioles and midveins, stems or inner bark are often used for DNA 
extraction. In some cases (e.g. X-disease phytoplas ma), fruit peduncles contain the 
highest phytoplasma titre ….. Although phytoplasmas  can be detected in roots and bark 
scrapings of dormant trees, generally it is best to  test for phytoplasmas at the end of 
summer.” 
Known environmental conditions conducive to symptom  expression 
For phytoplasma in avocado plants, environmental co nditions conducive to symptom expression are 
not known specifically, as there are only two publi cations of this relationship (Bäuerle Bascuñán 2002 ; 
Laviña et al. 2002), and these papers did not go in to environmental conditions. Probably summer like 
conditions, see discussion in “optimal season” ques tion below. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 78 Taking samples for testing – plant parts maximising  detection 
Phytoplasma distribution and titre are known to var y throughout a plant and over time. Testing 
symptomatic tissue (e.g. symptomatic leaves) is opt imal, but where symptomless expression is 
suspected it is important to thoroughly sample diff erent tissues of the plant. Phloem containing plant  
parts such as leaf petioles and midveins, stems or inner bark are often used (FAO 2016). Testing in 
only one part of the plant can lead to false negati ve results when the plant does in fact have a 
phytoplasma infection (e.g. Donkersley et al. 2019) . 
Laviña et al. (2002) prepared DNA for PCR from leaf  petioles, midribs, and trunk phloem of 
symptomatic trees (and from asymptomatic as control s). They did not state which of these plant parts 
gave positive samples, or if they separated out the  plant part types, but they did get positive result s 
for many of their samples, so at least some if not all of these plant parts gave positive results in 
symptomatic trees.  
Bäuerle Bascuñán (2002) used mainly the midribs of the shoot leaves for PCR testing for 
phytoplasmas and obtained positive results in sympt omatic trees. 
The optimum season for conducting detection testing  
The optimum season for conducting detection testing  is likely the end of summer. Symptoms were 
seen on infected trees in summer (1999) in Spain (L aviña et al. 2002) and October 1999 in Chile 
(mid-summer, Bäuerle Bascuñán 2002). Furthermore wh ile Laviña et al. (2002) tested for 
phytoplasmas in May, July, and October in the year 2000, they only detected phytoplasma in samples 
collected in July (mid-summer).  
For phytoplasmas in general, generally it is best t o test for phytoplasmas at the end of summer (FAO 
2016). So summer like conditions would be best for testing. 
PCR tests for phytoplasmas 
Level 3 PEQ does not include pre-determined PCR tes ts for phytoplasmas. If universal phytoplasma 
PCR tests were used, either conventional nested-PCR  or qPCR (MPI 2018), with multiple plant parts 
across the plant tested (as phytoplasma titre diffe rs across the plant), the risk of entry of this 
phytoplasma would be considered to be reduced to ne gligible. 
4.1.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing period 
(a period of active growth with a minimum of three distinct phenological growing events referred to as  
‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Likely usual phytoplasma symptoms. Infected avocado s have shown symptoms of leaf roll, leaf veinal 
chlorosis, with small red leaves, dwarfing, general  chlorosis, short internodes, bud proliferation, 
deformation of new leaves. 
o What are the known environmental conditions conduci ve to symptom expression? 
Probably summer-like conditions. 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Phloem containing plant parts from multiple areas a cross the plant as the plant may have uneven 
phytoplasma titre throughout the plant.  
79 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand o What is the optimum season for conducting detection  testing? 
Late summer. 
4.1.11  References 
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Wallingford, UK. 
MPI (2018) Persea americana (avocado) Post-entry quarantine testing manual. In:  Ministry for 
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essentials/forest-health-pests-and-diseases/Pests/C tenarytaina-eucalypti/Eucalyptus-blue-gum-
psyllid/   
NZFFA (2022a) Cardiaspina fiscella , the brown lace lerp psyllid. https://www.nzffa.org.nz/farm-
forestry-model/the-essentials/forest-health-pests-a nd-diseases/Pests/Cardiaspina-fiscella/   
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health-pests-and-diseases/Pests/Acacia-psyllids/   
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evolution suggested from the complete genome sequen ce of a plant-pathogenic phytoplasma. Nature 
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Osler, R; Vindimian, M E; Filippi, M; Carraro, L; R efatti, E (1997) Possibilità di propagazione del 
giallume della vite (legno nero) a mezzo del materi ale vivaistico. Informatore Fitopatologico 47(11): 
61-63. 
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susino cino-giapponese ( Prunus salicina  Lindl) a infezioni ottenute mediante innesti di ma teriale 
infetto da ‘ Candidatus  Phytoplasma prunorum’. Atti Giornate Fitopatologiche 2: 585-588.  
81 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Pastore, M; Piccirillo, P; Simeone, A M; Tian, J; P altrinieri, S; Bertaccini, A (2001) Transmission by  
patch grafting of ESFY phytoplasma to apricot ( Prunus armeniaca  L.) and Japanese plum ( Prunus 
salicina  lindl). Acta horticulturae 550: 339-344. 
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phytoplasma infection of three pear varieties graft ed on different rootstocks. Acta horticulturae 472: 
673-680. 
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proliferation transmission by grafting in different  periods of the year. Acta horticulturae 781: 489-493. 
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algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
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https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
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Database. Accessed June 2021 
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10.1079/CPC.108243.20210104834).  
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and -K 16SrXII subgroups and distinct single nucleo tide polymorphism genetic lineages among 
‘Candidatus  Phytoplasma solani’ strains associated with bois n oir in Central Italy. Australasian Plant 
Pathology 46(1): 31-34. 
Quaglino, F; Zhao, Y; Casati, P; Bulgari, D; Bianco , P A; Wei, W, et al. (2013) ‘ Candidatus  
Phytoplasma solani’, a novel taxon associated with stolbur- and bois noir-related diseases of plants. 
International Journal of Systematic and Evolutionar y Microbiology 63(Pt_8): 2879-2894. 
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algorithm (CLIMEX) for pest risk analysis. Ecological Informatics 61: 1-13. 
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Pathogenic Bacteria - II.  Springer Singapore. 
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the plant virus, viroid, liberibacter and phytoplas ma records for New Zealand. Australasian Plant 
Pathology 44: 463-514. 
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51(1): 91-111. 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 82 4.2  Xanthomonas campestris  and X. axonopodis  avocado pathovars 
Xanthomonas species are gram-negative bacteria that infect a wi de range of crops and wild plants. 
Two pathovars (strains that cause the same disease on the same host range) of Xanthomonas 
associated with disease in avocado ( Persea americana ) have been reported in the literature: 
X. campestris causing bacterial canker in California; and X. axonopodis  causing bacterial leaf spot in 
the Seychelles.  
Because there is very little information associated  with Xanthomonas  on avocado, information for the 
genus will be used where information for the pathov ars is lacking. 
4.2.1  Taxonomic description 
Scientific name: Xanthomonas campestris  
Order/Family: Xanthomonadales/ Xanthomonadaceae  
Other names include : Bacillus campestris, Pseudomonas campestris (EPPO 2020) 
Taxonomic notes: The  papers identifying the Xanthomonas isolated from avocado in California 
(Cooksey and Azad 1992; Cooksey et al. 1993) used c omparisons of morphology, biochemical 
characteristics, isozyme analysis and RFLP to assig n the isolates to X. campestris . These papers 
predate a major revision of Xanthomonas taxonomy based on DNA-DNA hybridisation of 183 stra ins 
of the genus,  which reassigned 65 pathovars and strains of X. campestris  to 15 different species  
(Vauterin et al. 1995). It is therefore unclear whi ch species the Californian Xanthomonas  isolates from 
avocado belong to. 
Scientific name: Xanthomonas axonopodis 
Order/Family: Xanthomondales/ Xanthomonadaceae 
Taxonomic notes: The paper identifying the Xanthomonas isolated from avocado in the Seychelles 
used multilocus sequence analysis to assign the iso lates to X. axonopodis (Pruvost et al. 2009) sensu 
Vauterin et al. (1995). The species-level identity of this pathovar is therefore likely to be correct.  
4.2.2  Hazard identification 
Xanthomonas campestris is present in New Zealand (NZOR 2021; Biota NZ 2022 ) whereas X. 
axonopodis is recorded as absent from New Zealand (NZOR 2021; Biota NZ 2022) . The 
Xanthomonas campestris and  X. axonopodis  avocado pathovars are not known to be present (i.e . not 
listed as present in the literature) in New Zealand  (Young et al. 2010; MPI 2021; NZOR 2021; PPIN 
2021). However, there are records of other X. axonopodis pathovars being present in New Zealand 
(e.g. X. axonopodis pv. begonia , X. axonopodis pv. glycines , X. axonopodis pv. poinsetticola ) (Biota 
NZ 2022).  The only record of Xanthomonas from avocado ( Persea americana ) in New Zealand is a 
specimen lodged with the National Collection of Pla nt Pathogenic Bacteria (NCPPB) in the UK, 
identified as belonging to X. hortorum (Parkinson et al. 2009). Because collection details  for this 
specimen are not supplied, it is not known if this is a field collected bacterium or an isolate from a  
bacterial collection in New Zealand. Additionally, since details of symptoms are not supplied for this  
specimen it is not possible to determine if it is a  representative of either of the pathovars being 
assessed here. Therefore, there is insufficient evi dence to indicate that either the X. campestris or the 
X. axonopodis avocado pathovars are present in New Zealand. 
The X. campestris and  X. axonopodis  avocado pathovars have the potential to establish (and spread) 
in New Zealand because: 
• hosts (in the form of cultivated avocados or nativ e and introduced members of the Lauraceae 
family) are available for their establishment (NZPC N 2021), and  
83 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • suitable climate is available for their establishm ent (Cooksey et al. 1993; Phillips et al. 2018; 
California Avocado Commission 2020). 
The X. campestris and  X. axonopodis  avocado pathovars have the potential to cause harm  to New 
Zealand because: 
• the X. campestris avocado pathovar causes bacterial canker of avocado s (Cooksey et al. 
1993; Eskalen and Faber 2016), 
• the X. axonopodis avocado pathovar causes bacterial leaf spot of avoc ados (Pruvost et al. 
2009), and 
• avocados are an important commercial crop in New Z ealand. In the 2019–2020 financial year, 
export sales of fresh avocados earned NZ$112.3 mill ion and domestic sales earned NZ$ 50.6 
million (Plant & Food Research 2020). 
The X. campestris and  X. axonopodis  avocado pathovars are associated with P.  americana  budwood: 
• Persea americana  is a known host of both pathovars (Cooksey et al. 1993; Pruvost et al. 
2009), and 
• both  pathovars can be associated with P. americana budwood either intercellularly, in the 
vascular system or as epiphytes (Rudolph 1993; Stal l et al. 1993; Jacques et al. 2016). 
Given the arguments and evidence above, both the X. campestris and  X. axonopodis  avocado 
pathovars meet the criteria to be hazards on P. americana  budwood (as in the commodity description) 
imported to New Zealand. 
4.2.3  Risk assessment 
Biology and epidemiology of Xanthomonas avocado pat hovars 
Host range 
The host range of Xanthomonas pathovars is typically narrow and generally restric ted to a single 
species or a small number of representatives within  a single family but a small number of pathovars 
have broader host ranges. For example, X. campestris pv. campestris  is able to infect all members of 
the Brassicaceae family (Jacques et al. 2016). Ther efore, it is likely that the host range of the 
Xanthomonas pathovars being assessed here is restricted to P. americana  although it may include 
other members of the Lauraceae family . The Xanthomonas avocado pathovars assessed in this PRA 
have been recorded in California, USA (Cooksey and Azad 1992; Cooksey et al. 1993) and the 
Seychelles (Pruvost et al. 2009). 
Symptoms 
The X. campestris avocado pathovar causes lesions on trunks and branc hes. The lesions appear as 
sunken dark areas with a necrotic, watery pocket un derneath. The lesions develop into cankers that 
split and ooze fluid that dries to a powdery white residue. Cankers are usually 2-10cm in diameter and  
usually appear at the base of trees before spreadin g upwards, usually in a straight line along one sid e 
of the trunk or branch. Necrotic streaks extend abo ve and below the necrotic lesions underneath 
cankers (Cooksey et al. 1993; Eskalen and Faber 201 6). 
Genetic and pathogenic variability has been observe d for the X. campestris avocado pathovar 
(Cooksey and Azad 1992). In California, 26 strains were isolated from avocado canker symptoms and 
some of these strains appeared to be nonpathogenic (but genetically related to pathogenic strains) 
(Cooksey and Azad 1992). It remains unclear whether  the canker is caused by a single pathovar or a 
mixture of strains from other hosts (Cooksey and Az ad 1992). 
The X. axonopodis avocado pathovar causes small, black, water-soaked,  angular leaf lesions on 
avocados. These lesions sometimes coalesce into lar ger lesions (Pruvost et al. 2009). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 84 Life cycle and transmission 
In nature, cells of Xanthomonas  are deposited on plant surfaces by water splash or  aerosols. They 
may enter a prolonged, asymptomatic, epiphytic phas e, persisting on the plant surface for up to 
several months before entering plant cells and caus ing symptoms. Because xanthomonads lack 
active mechanisms for entering plants, they can onl y enter host plants through natural openings such 
as stomata (gas exchange pores found in plant epide rmis) or hydathodes (water secreting pores 
along the leaf margins of some plants), or through wounds. High relative humidity favours penetration 
of bacteria into plants (Rudolph 1993; Stall et al.  1993; Ryan et al. 2011).  
Many pathogenic xanthomonads show a high degree of tissue specificity, either invading the vascular 
system of hosts (after entry through hydathodes or wounds) or the mesophyll tissue (after entry 
through stomata) but some species or pathovars are capable of colonising both (Ryan et al. 2011). 
There is no information on which tissues are coloni sed by either the X. campestris or  X. axonopodis  
avocado pathovar. In addition, there are some epiph ytic xanthomonads that are not plant pathogens 
(Vauterin et al. 1996) which can interfere with dia gnosis of pathogenic xanthomonads (Taylor et al. 
2002). 
Multiplication of bacteria within plant tissues is accompanied by the degeneration of plant tissues. 
Most xanthomonads are highly competent in causing i nfection and even a single bacterial cell can be 
enough to cause infection (Rudolph 1993; Stall et a l. 1993). 
Long distance spread of xanthomonads is generally b y human movement of contaminated or infected 
propagative materials, which is the main pathway fo r international spread of xanthomonads (Stall et 
al. 1993). Shorter-distance spread is generally by wind-blown water (e.g. rain splash) (Stall et al. 
1993). A wide range of dispersal distances is possi ble with this dispersal method, with studies of 
citrus canker in Florida recording spread distances  of between 12m and 3.5km, although tornadoes 
and tropical storms can be associated with spread o f up to 11km (Gottwald 2000). 
Time to symptom development and factors influencing  symptom expression 
The timeline of symptom development following infec tion by the X. campestris  avocado pathovar is 
not well described but Cooksey et al. (1993) note t hat, in their experiments, necrosis was visible on 
avocado stems four weeks after inoculation. However , in this experiment, wounded plants were 
inoculated with very high levels of inoculum (i.e. 1011 cfu compared to other studies which tend to 
use < 108 cfu, Pruvost et al. 2009) and thus, demon strated a bias to cause infection (Cooksey et al. 
1993). Detailed information on the factors affectin g symptom development of the X. campestris  
avocado pathovar  is unavailable, although drought stress and boron d eficiency may promote 
symptom development (Eskalen and Faber 2016).  
The timeline of symptom development following infec tion by the X. axonopodis  avocado pathovar is 
also not well described. In inoculation experiments , where the youngest leaves of an avocado plant 
were infiltrated with a concentrated bacterial susp ension via a needleless syringe, symptoms 
developed in 6-8 days (Pruvost et al. 2009). No fur ther information on factors affecting symptom 
development is available for the X. axonopodis  avocado pathovar. 
Although symptom expression of other xanthomonads i s affected by factors such as temperature and 
humidity, optimum levels of these variables for sym ptom expression differ between species and 
pathovars (Stall et al. 1993). For example, optimum  in vitro growth temperatures can range from 20–
23˚C for cool weather adapted Xanthomonas  such as X. populi (Ridé and Ridé 1992) to 30 ˚C for 
warm weather adapted types like X.  citri  subsp. citri (Stall et al. 1993). Development of walnut blight 
caused by X. arboricola  pv. juglandis , on the other hand, appears to not be influenced b y temperature 
(CABI 2021b). Given the range of temperature and hu midity optima for species and strains of 
Xanthomonas  the information cannot be generalised to the avoca do pathovars being assessed here. 
4.2.4  Likelihood of entry 
This assessment is made on the basis that the X. campestris and X. axonopodis avocado pathovars 
are present in the countries where avocado budwood is being imported from. The X. campestris  
85 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand avocado pathovar is only reported from the United S tates of America (Cooksey and Azad 1992; 
Cooksey et al. 1993) and the bacterial canker it ca uses is known to be widespread only in California 
(Eskalen and Faber 2016). The X. axonopodis avocado pathovar is only reported from the Seychell es 
(Pruvost et al. 2009). 
In plants, Xanthomonas  can colonise all aerial plant parts (i.e. stems, t wigs, leaves, flowers, buds, 
roots, and seeds) either intercellularly, in the va scular system, or as epiphytes (Rudolph 1993; Stall  et 
al. 1993; Jacques et al. 2016). Therefore the X. campestris and X. axonopodis avocado pathovars 
can be associated with avocado budwood.  
Symptoms of bacterial canker caused by the X. campestris avocado pathovar can develop in a matter 
of weeks (Cooksey and Azad 1992), and symptoms of b acterial leaf spot caused by the X. 
axonopodis  avocado pathovar can develop in a few days (Pruvos t et al. 2009) under experimental 
conditions. However, it is possible that asymptomat ic infections of both pathovars also exist because 
asymptomatic infections (either latent infections o r epiphytic growth) have been reported from other 
xanthomonads. For example, experimentally infecting  tissue cultured Anthurium andraeanum 
(flamingo flower) with X. axonopodis pv. dieffenbachiae (the causal agent of anthurium blight) caused 
latent infection in 1-7% of calli (the undifferenti ated cell masses formed from the source tissue), wi th 
no symptoms or turbidity of the medium for over thr ee months. The pathogen was also able to survive 
in a small percentage of shoots without producing s ymptoms for over a year (Norman and Alvarez 
1994). Although latent infections by Xanthomonas  have been reported, it is likely that symptoms 
would be expressed by most infected plants during t he PEQ period. 
Asymptomatic survival of xanthomonads as epiphytes for long periods is also documented. For 
example, X. phaseoli  pv. manihotis (the causal agent of bacterial blight of cassava) c an survive 
asymptomatically as an epiphyte on cassava leaves i n the field for eight months during the dry 
season, only causing symptoms once the rainy season  has begun (Stall et al. 1993). In addition, 
some xanthomonads may survive in the field, without  causing symptoms, for several months in plant 
structures. For example, experimental contamination  of field-grown peach trees with X.  arboricola  pv. 
pruni (causal agent of bacterial spot of stone fruits and  almonds) showed that the pathogen was able 
to survive in buds and leaf scars for 6-7 months wi thout causing symptoms (Zaccardelli et al. 1998).  
It is not known how long the X. campestris and X. axonopodis avocado pathovars could survive as 
epiphytes on avocado budwood in PEQ without causing  symptoms. Depending on the temperature 
and relative humidity within PEQ, and in the absenc e of overhead irrigation to simulate rainfall, the 
appropriate environmental conditions for symptom de velopment may be absent throughout the entire 
PEQ period. The routine surface disinfection of bud wood entering PEQ (dipping in 1% sodium 
hypochlorite for 2 minutes) will reduce the surface  population of the bacterium but is not likely to 
completely eliminate it, especially if cells are fo und deep within crevices of buds. Therefore, it is 
possible that a small population of epiphytic bacte ria may survive asymptomatically throughout the 
PEQ period and enter New Zealand.  
The bud grafting process may introduce epiphytic ba cteria into the rootstock, making symptom 
expression during PEQ likely. However, it is also p ossible for a small number of cells to be present o n 
only the tip of a bud and not at the cutting site, which would leave the epiphytic population 
undisturbed without introducing bacteria into the p lant. Again, this could result in a small populatio n of 
epiphytic bacteria surviving asymptomatically throu ghout the PEQ period and entering New Zealand. 
Given that xanthomonads are highly competent in cau sing infection (Rudolph 1993; Stall et al. 1993), 
even a small population may be enough for establish ment. 
Given the arguments and evidence above, that is:  
• the X. campestris and X. axonopodis avocado pathovars could survive as epiphytes on 
avocado budwood in PEQ without causing symptoms for  the PEQ period (minimum of 12 
months) (Rudolph 1993; Stall et al. 1993; Jacques e t al. 2016), but 
• in the case of internal infection symptoms are mor e likely to appear within a matter of days or 
weeks (Cooksey and Azad 1992; Pruvost et al. 2009) 
the likelihood of the X. campestris and X. axonopodis avocado pathovars entering New Zealand 
associated with P. americana  budwood is considered to be very low. Given that t here are only three Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 86 peer-reviewed publications and one extension docume nt about these avocado pathogens, the 
uncertainty of this conclusion is high. 
4.2.5  Likelihood of exposure 
This assessment is made on the basis that the X. campestris and X. axonopodis avocado pathovars 
have entered New Zealand undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for both the 
X. campestris and X. axonopodis avocado pathovars.   
If avocado plants are infected with either the X. campestris or X. axonopodis avocado pathovar at the 
time of their release from PEQ and they are planted  in New Zealand or used to propagate new plants 
for planting (see section 2.3.1 for additional info rmation about exposure) then these pathovars will b e 
transferred to a suitable host multiple times. Prom oting the growth and survival of hosts promotes the  
growth and survival of associated pathogens.  
Given the arguments and evidence above, the likelih ood of exposure of the X. campestris and 
X. axonopodis avocado pathovars in New Zealand from P. americana  budwood is considered to be 
high, with low uncertainty. 
4.2.6  Likelihood of establishment 
This assessment is made on the basis that the X. campestris and X. axonopodis avocado pathovars 
have been successfully exposed to a suitable host p lant in the New Zealand environment. 
If the host range of the two avocado pathovars is o nly P. americana then hosts in the form of 
cultivated avocados will be available for their est ablishment in the North Island (see section 2.3). I f the 
host range includes other members of the family Lau raceae then the number of potential host species 
available for the establishment of these pathovars is greatly increased – there are five native and fo ur 
introduced species (in addition to P. americana ) from the Lauraceae family found in New Zealand 
(NZPCN 2021). 
The X. campestris avocado pathovar is reported from San Diego, Orange , Los Angeles, Ventura and 
Santa Barbara counties of southern California (Cook sey et al. 1993). The avocado growing regions in 
these counties (California Avocado Commission 2020)  have a similar climate to parts of New 
Zealand, including  the Auckland and Northland regi ons, as indicated by a climate match index of ≥0.7 
(Phillips et al. 2018) when these locations are com pared with all of New Zealand. Seasonal climate 
ellipses show considerable overlap between avocado growing areas in California and New Zealand, 
although Californian sites have warmer winters, are  hotter in summer and drier overall (this is 
compensated for by irrigation) (Halloy 2021). There fore, climate suitable for the establishment of the  
X. campestris avocado pathovar is likely to occur in at least som e parts of New Zealand, especially in 
the north of the North Island. In addition, because  wetter conditions favour the establishment of 
xanthomonads (Stall et al. 1993), and conditions in  New Zealand are wetter compared to those of 
southern California (Beck et al. 2018), New Zealand  conditions are likely to be more favourable for th e 
establishment of the X. campestris avocado pathovar. In addition, there are records of  other X. 
axonopodis pathovars being present in New Zealand (e.g. X. axonopodis pv. begonia , X. axonopodis 
pv. glycines , X. axonopodis pv. poinsetticola ) (Biota NZ 2022) further suggesting New Zealand ha s a 
favourable climate for these species. 
The X. axonopodis avocado pathovar is reported only from the Seychell es (Pruvost et al. 2009). No 
climate match data are available for the Seychelles  but the climate is generally warmer and wetter 
than that of New Zealand (World Bank Group 2021). T he suitability of the New Zealand environment  
87 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand for establishment of this pathovar cannot be defini tively ruled out because remote island distribution s 
may not be reflective of the fundamental niche of a  species but rather of geographic isolation. 
Based on the currently available information, the X. campestris avocado pathovar has not spread 
beyond southern California. Rather than indicating a lack of invasive potential, this could be related  to 
the fact that avocado in the USA is only grown over  a small area (213 Km 2) in California and Florida 
(Ag Marketing Resource Center 2018) and that intern ational trade in avocado nursery stock from the 
USA is likely to be of a high phytosanitary standar d. Similarly, although the X. axonopodis avocado 
pathovar is not reported to have spread outside the  Seychelles, this is most likely due to the 
extremely low volume of plant and plant product exp orts from the Seychelles (International Trade 
Centre 2021). 
Several other xanthomonads are well known to be inv asive outside their native range, including 
X. citri pv. citri (citrus canker), X. vasicola pv . vasculorum (bacterial leaf streak of corn) and 
X. translucens pv . translucens (bacterial leaf streak of barley) (Triplett and Pat el 2020; CABI 2021d). 
Given the arguments and evidence above, that is: 
• hosts (in the form of cultivated avocados or, pote ntially native and introduced members of the 
Lauraceae family) are available for the establishme nt of the X. campestris  and X. axonopodis 
avocado pathovars (NZPCN 2021),  
• suitable climate is available for the establishmen t of the of the X. campestris  avocado 
pathovar (Cooksey et al. 1993; Phillips et al. 2018 ; California Avocado Commission 2020),  
• the wetter conditions of New Zealand compared to s outhern California (Beck et al. 2018) are 
likely to favour establishment of the X. campestris  avocado pathovar, and 
• the suitability of the New Zealand environment for  establishment of the X. axonopodis  
pathovar cannot be definitively ruled out 
the likelihood of the X. campestris and X. axonopodis avocado pathovars establishing in New Zealand 
is considered high, with moderate uncertainty (beca use of the lack of information specific to these 
pathovars). 
4.2.7  Impacts in New Zealand 
In California bacterial canker caused by the X. campestris avocado pathovar is considered to be an 
unimportant though widespread disease. Because wet conditions favour the penetration of 
xanthomonads into plants (Stall et al. 1993), and b ecause New Zealand has a wetter climate than 
southern California (Beck et al. 2018) it is possib le that the impacts of the X. campestris avocado 
pathovar would be more severe here than in Californ ia. The relatively high wind speeds across New 
Zealand 30  will also favour longer distance spread of the pat hogen. 
No major outbreak of bacterial leaf spot of avocado  caused by the X. axonopodis pathovar has been 
reported in the Seychelles archipelago since 2003 ( Pruvost et al. 2009). No further information on the  
importance of this disease in the Seychelles is ava ilable. Although the Seychelles have a wetter 
climate than New Zealand (World Bank Group 2021), N ew Zealand has higher wind speeds 30  which 
could result in more widespread impacts of the X. axonopodis avocado pathovar should it establish 
here. 
There is no cure known for infections by any specie s or pathovar of Xanthomonas  and control is 
usually achieved by use of less susceptible varieti es, use of windbreaks, disinfection of tools and 
equipment, application of copper-based treatments, and removal of infected trees. However, none of 
these methods are fully effective (Vítor Rodrigues et al. 2019) and control of outbreaks can involve 
wide-scale removal and destruction of host plants ( Gottwald 2000). The main in-field management for 
bacterial canker caused by the X. campestris avocado pathovar in California is keeping trees in good 
condition and removing severely diseased trees (Esk alen and Faber 2016). 
 
30  Information obtained from the “Global Wind Atlas 3 .0, a free, web-based application developed, owned and operated by the 
Technical University of Denmark (DTU). The Global W ind Atlas 3.0 is released in partnership with the W orld Bank Group, 
utilizing data provided by Vortex, using funding pr ovided by the Energy Sector Management Assistance P rogram (ESMAP). For 
additional information: https://globalwindatlas.inf o” Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 88 Economic impacts 
Because it is likely that avocados are the only com mercially produced hosts of the X. campestris and 
X. axonopodis avocado pathovars in New Zealand, it is likely that  economic impacts will be limited to 
the avocado industry. In 2020, the export values fo r avocado was $112.3 million and the domestic 
value was $50.6 million (Plant & Food Research 2020 ). Infection with a xanthomonad may impact 
yields, as is the case with infection by other xant homonads, although yield losses vary widely 
between pathovars. For example, X.  arboricola  pv. corylina  (hazelnut blight) can cause up to 10% 
mortality and yield losses of 1-10% in hazelnuts (C ABI 2021a), whereas X.  a.  pv. juglandis  (walnut 
blight) can cause up to 100% crop loss of walnuts i f not controlled (CABI 2021b). Infection may also 
impact marketability, as is the case with plums inf ected by X. a. pv. pruni  (bacterial canker of stone 
fruit) which are reduced in size and often unmarket able (CABI 2021c). 
In California, trees severely affected by the X. campestris  avocado pathovar are reported to have low 
yields on one branch or the whole tree (Eskalen and  Faber 2016) although yield loss estimates are 
not provided. There is no information on the impact  of the X. axonopodis avocado pathovar but even if 
this pathogen were confined to only leaf mesophyll,  it could affect yields or marketability of fruits due 
to a decrease in the plant’s photosynthetic area. 
Given that there is no cure for infection by any sp ecies or pathovar of Xanthomonas  (Vítor Rodrigues 
et al. 2019) and that control of an outbreak may in volve wide scale removal and destruction of host 
plants (Gottwald 2000), the impacts of trying to co ntrol an outbreak of the X. campestris or 
X. axonopodis avocado pathovars may be severe for the avocado ind ustry. Eradication may not be 
possible, as has been the case with X. citri subsp. citri (citrus canker) in the USA (United States 
Department of Agriculture 2020). 
If there were an outbreak of the X. campestris or X. axonopodis avocado pathovar in one of the major 
avocado-producing regions in New Zealand, it is lik ely that the outbreak could be contained to that 
region by limiting human-assisted dispersal of the pathogen. Spread within a region could, however, 
be quite rapid, especially if there was a storm dur ing the outbreak.  
Given the arguments and evidence above, that is: 
• avocados are the only hosts of the X. campestris and X. axonopodis avocado pathovars 
commercially produced in New Zealand, 
• avocado in an economically important domestic and export crop in New Zealand and 
infection of avocado trees with the X. campestris or X. axonopodis avocado pathovar 
could cause yield losses, and control of an outbrea k could involve wide scale destruction 
of avocado trees (e.g. removal of all trees in one major avocado production area). 
the economic impact of the X. campestris and X. axonopodis avocado pathovars to New Zealand is 
considered to be moderate, with high uncertainty (b ecause there are no specific data on losses 
caused by these pathovars and impacts of xanthomona ds vary widely). 
Environmental impacts 
Although the host range is likely to be restricted to Persea americana , the host range of the 
X. campestris and X. axonopodis avocado pathovars may include other species of the family 
Lauraceae, which may include the five native Laurac eae species found in New Zealand (NZPCN 
2021). There are no reports of Xanthomonas causing significant disease in wild plants or natur al 
environments (google scholar search terms [Xanthomo nas AND disease and "wild plants"] and 
[Xanthomonas AND disease and "natural environments" ]). However, a response to an outbreak of the 
X. campestris or X. axonopodis avocado pathovar may involve the removal of potenti al alternative 
hosts in the outbreak area. This was the case with the 2004 citrus canker outbreak in Australia, which  
involved the removal and destruction of 175,000 nat ive citrus trees ( Citrus glauca ) (Senate Standing 
Committee on Rural and Regional Affairs and Transpo rt 2006). This sort of environmental impact is, 
however, likely to be localised and short-lived.  
89 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Given the arguments and evidence above, the impact on the environment from the establishment of 
X. campestris and X. axonopodis avocado pathovars in New Zealand is considered to b e very low, 
with high uncertainty.  
Human health impacts 
There are no known human health impacts associated with either the X. campestris  or X. axonopodis 
avocado pathovars. 
Sociocultural impacts 
A response to an outbreak of the X. campestris or X. axonopodis avocado pathovars may involve the 
removal of infected or exposed avocado trees growin g on residential properties. This was the case 
with the attempted eradication of citrus canker fro m Florida in the 1990s (Schubert et al. 2001). This  is 
likely to cause distress to affected residents, how ever, this impact is likely to be localised and sho rt-
lived. In addition, if not eradicated, the pathogen  may affect the appearance of trees and yield in 
home gardens. 
Given the arguments and evidence above, the sociocu ltural impact of X. campestris and 
X. axonopodis avocado pathovars to New Zealand is considered to b e very low, with high uncertainty. 
Overall impact to New Zealand 
The overall impact of the X. campestris and X. axonopodis avocado pathovars on the New Zealand 
economy, environment, health and society is conside red to be moderate, with high uncertainty. 
4.2.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is very low 
• assuming entry, the likelihood of exposure is high  
• assuming successful exposure, the likelihood of es tablishment is high 
• the overall impact on the New Zealand economy, env ironment, health and society is 
considered to be moderate. 
the overall level of assessed risk to New Zealand f rom the X. campestris and X. axonopodis avocado 
pathovars on imported P. americana budwood (as in the commodity description) is consid ered to be 
moderate, with high uncertainty.  
4.2.9  Management considerations 
There is no information on what sort of environment al conditions are likely to induce symptom 
expression in either The Xanthomonas campestris or X. axonopodis avocado pathovar. Although 
symptom expression of other xanthomonads is affecte d by factors such as temperature and humidity, 
optimum levels of these variables for symptom expre ssion differ between pathovars (Stall et al. 1993) 
so the information cannot be generalised to the avo cado pathovars being assessed here. 
A large number of tests for the detection and ident ification of various Xanthomonas pathovars in both 
symptomatic and asymptomatic tissue have been devel oped (Catara et al. 2021). These include: 
• serological methods such as: immunofluorescence; a nd enzyme-linked immunosorbent 
assay (ELISA),  
• molecular methods such as: conventional and quanti tative real-time PCR (qPCR); 
sequencing; DNA-DNA hybridisation; fingerprinting; and Clustered Regularly Interspaced 
Short Palindromic Repeat (CRISPR) genotyping, and Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 90 • other methods such as bioassays and biochemical te sts. 
These tests have been developed for the detection a nd identification of particular species or 
pathovars of Xanthomonas and not as generic tests . Generic PCR tests for the identification of 
members of the genus Xanthomonas have been developed (Adriko et al. 2014) but they h ave not 
been validated for either of the two pathovars bein g assessed here. In addition, validation (through 
sequencing) cannot occur as there are no reference cultures in any international culture collections. 
Sequencing of the DNA gyrase subunit B ( gyrB ) gene is a useful identification tool which has be en 
shown to work for a large number of Xanthomonas species (Parkinson et al. 2009). It is likely that this 
test could be used for a species level identificati on of Xanthomonas present in avocado budwood. In 
the absence of reference sequence data for the X. campestris or X. axonopodis avocado pathovar 
this test would not be able to provide a definitive  pathovar identification. Furthermore, these two 
avocado pathovars have not been formally described and there are no reference cultures available. 
Therefore, if a X. campestris or X. axonopodis  is isolated, there would be an inability to determ ine if 
these pathovars are the same as described in Califo rnia ( X. campestris ) or the Seychelles ( X. 
axonopodis ). 
There is no information on the best sampling regime  (in terms of plant part or season) to identify 
either of these pathovars from asymptomatic tissues . However, generally spring and early summer 
are the best seasons for detecting bacterial pathog ens including other xanthomonads (R. Taylor, 
pers. comm.; An et al. 2019).  It is possible to ha ve misting in PEQ to provide conducive conditions f or 
other bacterial pathogens such as Xylella and Pseudomonas (R. Taylor, pers. comm.). 
4.2.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
The Xanthomonas campestris  avocado pathovar causes lesions on trunks and bran ches which 
develop into cankers (usually 2-10 cm in diameter) that split and ooze fluid that dries to a powdery 
white residue (Cooksey et al. 1993; Eskalen and Fab er 2016). Lesions on budwood or young plants 
could be much smaller than this. The X. axonopodis avocado pathovar causes small, black, water-
soaked, angular leaf lesions on avocados which some times coalesce into larger lesions (Pruvost et al. 
2009). 
o What are the known environmental conditions conduci ve to symptom expression? 
There is no information on what sort of temperature  and humidity levels are likely to induce symptom 
expression in either the X. campestris or X. axonopodis avocado pathovar. Although symptom 
expression of other xanthomonads is affected by fac tors such as temperature and humidity, optimum 
levels of these variables for symptom expression di ffer between species and pathovars (Stall et al. 
1993). For example, optimum in vitro growth temperatures can range from 20–23˚C for cool  weather 
adapted Xanthomonas  such as X. populi (Ridé and Ridé 1992) to 30 ˚C for warm weather adap ted 
types like X. citri  subsp. citri (Stall et al. 1993). Development of walnut blight c aused by X. arboricola  
pv. juglandis , on the other hand, appears to not be influenced b y temperature (CABI 2021b). Given 
the range of temperature and humidity optima for sp ecies and strains of Xanthomonas  the information 
cannot be generalised to the avocado pathovars bein g assessed here. The use of overhead irrigation 
to simulate rainfall could induce symptom expressio n of epiphytic Xanthomonas populations, 
however, it would increase the risk of the disease spreading between plants. 
What are the limitations to taking samples for pote ntial testing? 
o What  plant part should be tested in order to maximise t he chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
There is no information on which tissues are coloni sed by X. campestris .  Leaf tissue would be tested 
for leaf spotting pathogens (e.g. X. axonopodis ) which would also detect epiphytic populations (R.  
Taylor, pers. comm.).    
91 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand o What is the optimum season for conducting detection  testing? 
There is no specific information on the optimum sea son for conducting detection testing to maximise 
the detection of either the X. campestris or X. axonopodis avocado pathovar in the case of 
asymptomatic infection. However, generally spring a nd early summer are the best seasons for 
detecting bacterial pathogens (R. Taylor, pers. com m.; An et al. 2019). It is possible to have misting  in 
PEQ to provide conducive conditions for other bacte rial pathogens such as Xylella and Pseudomonas 
(R. Taylor, pers. comm.). 
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in the Seychelles of Xanthomonas axonopodis genetic cluster 9.2 causing bacterial leaf spot of 
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arboricola pv. pruni on peach in Italy. Journal of Plant Pathology 80(2): 125-132. 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 94 4.3  Xylella fastidiosa  (bacterial leaf scorch) 
Xylella fastidiosa  is a fastidious xylem-limited bacterium (i.e. it h as specialised nutrient needs and can 
be difficult to culture). It can colonise a very br oad range of plants, including economically importa nt 
crops and environmentally significant plants. It is  a very serious pathogen of some of these plants, 
blocking water transport and causing wilting and de ath. Natural transmission is via specialist xylem-
feeding insects. 
4.3.1  Taxonomic description 
Scientific name:  Xylella fastidiosa  Wells et al., 1987 
Order/Family: Xanthomonadales/Xanthomonadaceae 
Other names: There are no other scientific names. Common names f or the diseases caused by this 
bacterium include Anaheim disease, California vine disease, citrus variegated chlorosis, leaf scorch o f 
almond/ coffee/ oleander, olive quick decline syndr ome, peach phony disease, Pierce's disease, plum 
leaf scald and dwarf disease of lucerne/ alfalfa (E PPO 2021). 
Taxonomic notes: Xylella fastidiosa  is a genetically diverse species that has been ass ociated with a 
wide range of plant diseases. The American represen tatives of the species were initially divided into 
three subspecies 31  based on DNA-DNA hybridization data:  
• Xylella fastidiosa  subsp. fastidiosa, the cause of Pierce's disease of grapevines (among other 
diseases) (Vanhove et al. 2019); 
• Xylella fastidiosa  subsp. multiplex , the causal agent of several diseases in almonds, oaks, 
summerfruit and shade trees (Landa et al. 2020; Joh nson et al. 2021); and 
• Xylella fastidiosa  subsp. pauca , which causes disease in citrus and coffee; and wh ich has 
recently been found to cause olive quick decline sy ndrome in Italy (Vanhove et al. 2019).  
Multilocus sequence typing (MLST) 32  sequence data has confirmed the status of these su bspecies, 
and suggested a fourth, X. fastidiosa  subsp. sandyi . Two additional subspecies, X. fastidiosa  subsp. 
morus  and X. fastidiosa  subsp. tashke  have also been proposed (Almeida and Nunney 2015; Sicard 
et al. 2018). 
4.3.2  Hazard identification 
Xylella fastidiosa  is not known to occur in New Zealand in any of its  forms 
• The species is reported absent in Biota NZ (2022) and is not recorded in PPIN (2021). 
• It and its subspecies are regulated pests and unwa nted and notifiable organisms (ONZPR 
2021). 
• New Zealand has country freedom status for X. fastidiosa  (ONZPR 2021). Country freedom in 
this case is based on historical freedom; no system atic surveys have been carried out to 
determine the presence of this bacterium in New Zea land. The possibility that it is present in 
one or more of its forms cannot be discounted. For example, X. fastidiosa  is likely to have 
 
31  Below the subspecies level, the further MLST class ification of isolates into sequence types (unique g enotypes 
based on the seven loci used in MLST) has provided insights about X. fastidiosa  evolution and host specificity 
(Almeida and Nunney 2015). However, Landa et al. (2 020)  note that while MLST is particularly powerful for t he 
taxonomy of recombinogenic taxa ( X. fastidiosa  is naturally competent), it is also possible that strains belonging 
to the same ST may not be phylogenetically related or share similar traits such as host plant range. 
32  MLST is a method that categorizes isolates into se quence types (STs) based on the alleles present at (usually) 
seven house-keeping loci (Baldi and La Porta 2017).  Assessment of genetic diversity in X. fastidiosa  is still 
principally based on MLST even though the number of  available draft and complete genomes of X. fastidiosa  is 
rapidly increasing (Saponari et al. 2019).   
95 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand been in France for at least 15 years –and possibly much longer– before its first detection 
there (Soubeyrand et al. 2018).  
Xylella fastidiosa  has the potential to establish and spread in New Z ealand: 
• Suitable hosts (including avocado plants) are avai lable in many areas of New Zealand. Xylella 
fastidiosa  (at the species level) is able to colonise a very wide range of plant species. The 
current EFSA database (Delbianco et al. 2021) inclu des over 600 plant species reported to be 
infected by the bacterium. These species include im portant crop, ornamental and native plant 
species, many of which are common throughout New Ze aland. 
• However, the climate may limit the development and  spread of diseases caused by X. 
fastidiosa . The optimal temperature range for its growth is 2 6–28° C (Baldi and La Porta 
2017). Diseases caused by this bacterium are more c ommon in tropical and subtropical 
regions (Janse and Obradovic 2010), and its distrib ution, spread and/or expression may be 
limited in some parts of New Zealand. However, CLIM EX predictions by MPI (2020)  indicated 
that all of the North Island is highly suitable for  the establishment of X. fastidiosa . 
Xylella fastidiosa  has the potential to cause harm to New Zealand bec ause: 
• It can cause severe plant pathologies leading to h uge economic losses. Some examples are 
Pierce’s disease of grapevines, olive quick decline , oak bacterial leaf scorch, phony peach 
disease, citrus variegated chlorosis and almond lea f scorch (EPPO 2021). Some of these 
hosts, such as grapes, summerfruit and citrus, are of high economic importance to New 
Zealand. In addition, sentinel host plant testing o verseas has shown that X. fastidiosa is able 
to infect iconic native plant species such as Kauri  and Pohutukawa (Groenteman et al. 2015). 
• Xylella fastidiosa  has been reported to cause disease in avocado, an important commercial 
crop in New Zealand. In 2020, export sales of fresh  avocados earned NZ$100.1 million and 
domestic sales earned NZ$50.6 million, while export  sales of avocado oil earned $NZ9.3 
million (Plant & Food Research 2020). 
Xylella fastidiosa is associated with avocado budwood because: 
• Avocado has been reported as a host of X. fastidiosa  (CAC and CMCC 2003; Montero-Astúa 
et al. 2008); 
• Xylella fastidiosa  infections are systemic. The bacterium exists with in the xylem tissues of its 
host plants (Almeida and Nunney 2015) and can there fore be associated with leafless, 
rootless avocado budwood cuttings.  
Given the arguments and evidence above, X. fastidiosa  meets the criteria to be a hazard on avocado 
budwood (as in the commodity description) imported to New Zealand. 
4.3.3 Risk assessment  
Biology and epidemiology of Xylella fastidiosa 
Host range 
At the species level, X. fastidiosa  has a very wide “host range”. The current EFSA dat abase 
(Delbianco et al. 2021) includes over 600 plant spe cies reported to be colonised by the bacterium. 
The concept of X. fastidiosa  as a generalist pathogen with a wide host range is  accurate in the sense 
that a very large number of plant species have been  demonstrated to sustain infections. However, 
very few of these plants sustain the infections lon g-term and become symptomatic. Mounting 
evidence suggests that specific clades of X. fastidiosa  cause disease in a limited number of plant 
species, while still being capable of colonizing ma ny other species as harmless endophytes. Specific 
symptomatic hosts are only susceptible to isolates in one or a limited number of X. fastidiosa  clades, 
with the result that specific clades (at the subspe cies level and lower) of X. fastidiosa  have a small 
number of symptomatic host plant species that are l argely non-overlapping (Yuan et al. 2010; Almeida 
and Nunney 2015; Sicard et al. 2018; Nunney et al. 2019). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 96 Association with avocado 
The only published record of avocado as a host of X. fastidiosa  is from Costa Rica (Montero-Astúa et 
al. 2008). Symptomatic trees were found in the fiel d in at least two distinct geographical locations 
(Alajuela and San José provinces) during the 1990s.  Culture attempts were not successful 33  but 
Xylella  fastidiosa  infection was detected using DAS-ELISA 34  (in 188 of 227 trees tested) and PCR 
(from two grafted seedlings and 7 field trees). The  PCR method followed Pooler and Hartung (1995).  
The specificity of this test has been validated ove r a number of years and it is still listed in the I PPC 
diagnostic protocol for Xylella fastidiosa  (FAO 2018). Seedlings that were grafted with ELISA -positive 
budwood developed scorch symptoms. GenBank sequence s EU021997 to EU022000 showed 99 to 
100% sequence identity to a Pierce's disease strain  from California (Temecula1) and 94 to 95% to a 
citrus variegated chlorosis strain from Brazil (Fou nd-5). EFSA (2015) report this record, citing X. 
fastidiosa subsp. fastidiosa  as the “putative subspecies”, while Delbianco et a l. (2021) reports 
“subspecies unknown”. In North America, X. fastidiosa subsp. fastidiosa  is primarily associated with 
Pierce’s disease of grapevine but it has a number o f other hosts, notably almond (Nunney et al. 
2019). 
In California, tests for X. fastidiosa  were reported to “come up positive on avocado in s ome areas” by 
the California Avocado Commission (CAC and CMCC 200 3). Test methods were  not reported and no 
identification below species level was provided. No  direct symptoms were identified or linked to 
positive Xylella  test results in these detections.  
No other reports of X. fastidiosa infecting avocado have been found in searches of th e scientific 
literature, databases (including the most current E FSA host plant database (Delbianco et al. 2021)), 
Google and Google Scholar searches or in the MPI Em erging Risk System (all searches carried out in 
English language in December 2021). 
Geographical distribution 
Xylella fastidiosa  is native to the Americas, where it exists as a nu mber of subspecies, strains and 
serotypes. Sampling and MLST analysis have indicate d that the component subspecies evolved in 
geographical isolation and have distinct geographic al and host ranges (Almeida and Nunney 2015; 
Sicard et al. 2018; Landa et al. 2020). 
The first observed detection of X. fastidiosa  outside the Americas was from Taiwan in 2002 (Su e t al. 
2013). Since that time, it has spread to Italy (Den ancé et al. 2017; Cunty et al. 2020); France 
(Denancé et al. 2017); Germany (eradicated, Jeger e t al. 2018); Spain (Cunty et al. 2020) and 
Portugal (EPPO 2021).  
For regulatory purposes, the following countries ar e not recognised by MPI as free from X. fastidiosa : 
all countries in Europe, the Americas and the Carib bean; India, Taiwan and Iran 35  (as at 22 January 
2022). 
Symptoms in avocado 
Field infections were observed in avocado trees in at least two localities in Costa Rica. Symptoms 
were reported to include chlorotic mottling, margin al scorch, deformation of leaves, defoliation, 
shortening of internodes, and branch dieback. These  symptoms were not uniformly distributed in the 
tree, and the results of ELISA tests of individual trees also varied with the season and branches 
tested (Montero-Astúa et al. 2008). 
Avocado is reported to be asymptomatically infected  with X. fastidiosa : 
• In Costa Rica, symptoms in infected trees were not  uniformly distributed in the tree; some 
branches were symptomatic while others were not (Mo ntero-Astúa et al. 2008). 
 
33  However, it is known that Xylella  cannot be cultured from all hosts (Rapicavoli et a l. 2018) 
34  ELISA tests have been known to generate false posi tives (R. Taylor, pers.comm.).  
35  https://www.mpi.govt.nz/dmsdocument/1152/direct , https://www.mpi.govt.nz/dmsdocument/15655  
97 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • In California, no symptoms were associated with X. fastidiosa  infections (CAC and CMCC 
2003). 
Reproduction and transmission 
Xylella fastidiosa  colonises the xylem network of plants, where it ca n move up- and downstream. In 
susceptible hosts, where the bacteria are able to m ultiply, they can form high populations within the 
plant, leading to high frequencies of blocked xylem  vessels, which are usually correlated with disease  
symptom development and severity (EFSA 2015).  
Natural spread of the bacterium is through transmis sion by its insect vectors, specialist xylem-feedin g 
hemipterans (mostly sharpshooters and spittlebugs; Almeida and Nunney 2015). Invasion of new 
regions is accomplished only by long-distance dispe rsal of infected vectors or by the movement of 
infected plant material (Almeida and Nunney 2015). The bacterium is graft transmitted. Montero-Astúa 
et al. (2008)  demonstrated graft transmission in avocado. Fifteen  greenhouse-grown, ELISA-negative 
avocado seedlings were grafted with budwood from an  ELISA-positive tree. Eight of the 15 seedlings 
developed scorch symptoms and one also showed chlor otic mottling and deformation, though the 
time to development of these symptoms was not repor ted. In two of the grafted seedlings, positive 
PCR results were obtained. Xylella fastidiosa  is not known to be seed transmitted (EFSA 2015; 
Parkinson and Malumphy 2020). 
Vectors 
Known or potential vectors are currently considered  to include (and to be limited to) three groups of 
hemipterans:  
• all sharpshooters (species in the subfamily Cicade llinae, superfamily Membracoidea); 
• all species in the superfamily Cercopoidea (spittl ebugs and or froghoppers), and 
• all cicada species (superfamily Cicadoidea) (EFSA 2013, 2015; Cornara et al. 2019). 
Sharpshooters are not known to be present in New Ze aland, so potential vectors here are limited to 
spittlebugs and cicadas: 
• Spittlebugs: within the superfamily Cercopoidea, o nly the family Aphrophridae 36  is known to 
be present in New Zealand, with a fauna comprised o f 16 species. The only known vector is 
the introduced European meadow spittlebug Philaenus spumarius , which is widespread and 
has a broad host range. Fifteen other species are k nown, 14 of which are native (Lariviere et 
al. 2010). 
• Over 30 cicada species are known, all are endemic (Lariviere et al. 2010). However, there is 
very little evidence of X. fastidiosa  transmission by cicadas (Sicard et al. 2018; Corna ra et al. 
2019). 
There is no evidence of X. fastidiosa  genotype-vector specificity, i.e., all insect vect ors are thought to 
be capable of transmitting all X. fastidiosa  genotypes. This lack of specificity increases the likelihood 
that X. fastidiosa  isolates introduced into a novel environment will be transmitted by endemic vector 
species (Almeida and Nunney 2015; Sicard et al. 201 8). However, transmission efficiency is highly 
variable among vectors and their hosts. It may diff er for different vector species on the same host 
plant, or the same vector species feeding on differ ent tissues of the same plant (Almeida and Nunney 
2015). Thus, the impact of an introduction will dep end on the interaction of which subspecies of 
pathogen is introduced, the plants susceptible to t his strain, and the vectors which use the plant as 
hosts.  
Asymptomatically infected plants are likely to harb our lower bacterial populations, and this is likely  to 
affect acquisition by the vector. Plants that harbo ur larger bacterial populations distributed through out 
the plant are more likely to result in vector infec tion than plants with low bacterial populations, wh ich 
usually do not become systemic or induce severe dis ease symptoms (EFSA 2015). However 
 
36  Sometimes regarded as Aphrophorinae, a subfamily o f the Cercopidae (e.g. by ONZPR 2021). This 
classification follows Lariviere et al. (2010), EPP O (2021) and the Arthemis database (INRAE-CBGP 2020 ). 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 98 asymptomatic plants are potentially infectious. The ir importance appears to vary among 
pathosystems, for example, they appear to be import ant for Pierce’s disease in Northern California 
but not for citrus variegated chlorosis (CVC) in Br azil (Sicard et al. 2018; White et al. 2020).  
Time to symptom development 
There is no information available regarding the tim e to symptom development for X. fastidiosa  in 
avocado plants. Montero-Astúa et al. (2008) demonst rated graft transmission in avocado but did not 
report time to symptom development. In the only oth er report of X. fastidiosa  infecting avocado (CAC 
and CMCC 2003), infections were reported to be asym ptomatic. 
In other plant species colonised by X. fastidiosa , the timing and extent of symptom development vary  
greatly (EPPO 2018). In some hosts, the plant or tr ee can be killed rapidly. Some plants may remain 
asymptomatic for varying periods (latent period) be fore the bacterium begins to replicate within the 
host and colonizes large parts of the plant xylem. Variation in the asymptomatic period is significant  
for different host and pathogen subspecies combinat ions, for example from a median of up to 1 month 
in ornamental plants and up to 10 months in olive, for subsp. pauca (Bragard et al. 2019) or several 
years for other Xylella subspecies in other plants (Parkinson and Malumphy 2020). It is clear that X. 
fastidiosa  has one of the longest symptomless periods amongst  some of the most dangerous plant 
diseases (White et al. 2020). Additionally, New Zea land’s relatively cool temperatures could result in  
latent periods becoming even longer (Parkinson and Malumphy 2020 for the UK). 
However, under natural conditions, many X. fastidiosa  hosts are always asymptomatic (EFSA 2013; 
Sicard et al. 2018). In these hosts, the bacterium does not usually move systemically within the plant  
and vectors are less likely, but still able, to acq uire it (Hopkins and Purcell 2002; Parkinson and 
Malumphy 2014; Sicard et al. 2018).   
4.3.4 Likelihood of entry 
This assessment is made on the basis that X. fastidiosa  is present in the countries from which 
avocado budwood is being imported. However, there i s a high level of uncertainty associated with 
assessing the likelihood of entry. Xylella fastidiosa  infection of avocado has currently only been 
reported once in the published scientific literatur e, from Costa Rica. There is also an unpublished 
report from California. These infections therefore appear to be very rare. However, X. fastidiosa  
infections can be asymptomatic, or can cause sympto ms that may be mistaken for other conditions, 
such as physiological stress. It is possible that i n Costa Rica and California, X. fastidiosa  infections of 
avocado are more widespread than are reported. Simi larly, it is possible that in other countries where  
X. fastidiosa  is present, the bacterium may colonise avocado wit hout having yet been reported.  
Xylella fastidiosa  infections are systemic. The bacterium exists with in the xylem tissues of its host 
plants and may therefore be associated with leafles s, rootless avocado budwood cuttings, and would 
not be affected by surface sterilisation of budwood  cuttings in dilute sodium hypochlorite.  
It is unlikely that symptomatic avocado budwood mat erial would be used for germplasm. However, 
infections are reported to be asymptomatic in avoca do. They may also have long latent periods, as is 
reported in other hosts (the time to symptom develo pment in avocado is not reported). For these 
reasons, infected material may not be detected duri ng preparation for export or in pre-export 
phytosanitary inspections or on arrival in New Zeal and.  
As part of the commodity description, all imported avocado germplasm, will undergo a growing period 
of active growth with a minimum of three distinct p henological growing events (‘shoot flush’) in 3A 
PEQ (minimum of one year). Since infections in many  hosts are reported to be asymptomatic or may 
have very long latent periods, it is likely that th e period spent in 3A PEQ is not sufficient to manag e 
the risk of X. fastidiosa  being present in imported avocado budwood that is released from PEQ. 
It is likely that the subspecies reported from avoc ado in Costa Rica is X. fastidiosa subsp.  fastidiosa , 
but otherwise it is unknown which bacterial genotyp es can colonise avocado. Other genotypes may 
be more likely to colonise avocado as endophytes th at do not produce symptoms. These genotypes  
99 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand still represent a risk to New Zealand because if as ymptomatic plants are exposed to vectors in 
New Zealand it is still possible for the bacterium to be acquired and spread. 
The bacterium also exists within the bodies of its insect vectors, so X. fastidiosa  may also be 
introduced through the entry of viruliferous vector s, which are able to feed on and infect susceptible  
hosts. However, it is assumed that the mandatory pe sticide treatment (Chapter 2) will be effective in 
managing the risk of introducing any live insect ve ctors or their eggs 37  that may be associated with 
imported avocado budwood. In addition, Level 3A PEQ  has physical and operational measures in 
place to manage the risks associated with arthropod s, wastewater, waste and accidental transfer, 
therefore insect vectors carrying X. fastidiosa  are highly unlikely to escape level 3A PEQ to infe ct a 
suitable host. 
Given the arguments and evidence above, that is:  
• infection of avocado by X. fastidiosa  appears to be very rare (it has only ever been 
documented once in the published literature); howev er 
• infections of avocado and many other hosts are rep orted to be asymptomatic. Where 
infections are symptomatic the latent period is not  known but may be long. Therefore 
established X. fastidiosa  infections may not be detected before release from  PEQ, and 
• for the above reasons, X. fastidiosa  infections of avocado may also be more common than  is 
reported; 
the likelihood of X. fastidiosa  entering New Zealand (being released from PEQ 38 ) associated with 
avocado budwood is considered to be very low , with high  uncertainty. 
4.3.5 Likelihood of exposure 
This assessment is made on the basis that X. fastidiosa  has entered New Zealand undetected. 
When a plant pest or pathogen arrives in a new area , it usually needs to encounter a growing host 
plant in order to establish. The process of moving from or with the commodity into a suitable 
environment to allow establishment is termed exposu re.  
On some pathways, contaminating organisms need to a ctively or passively leave the import pathway 
(i.e., move from the pathways) in order to find a g rowing host plant. However imported nursery stock, 
in particular high value nursery stock, is itself i ntended to generate plants for planting in New Zeal and. 
Plants released from PEQ will be grown with care, p romoting the survival of both the plants and their 
exotic bacterial populations. Many plants may event ually be derived from the released material, so 
that multiple populations of the bacterium may also  be present in New Zealand. This is particularly 
true in the case of pathogens such as X. fastidiosa , which can infect plants asymptomatically. 
Successful exposure in this context is thus conside red to mean that plants derived from imported 
avocado budwood infected with X. fastidiosa  are growing successfully in the New Zealand 
environment 39 , either as plants being multiplied in nurseries or  planted in New Zealand avocado 
orchards. Avocado plants are perennial. The average  range of productive life in California has been 
estimated at 20 to 30 years, with an upper estimate  of 40 years under favourable conditions (Goodall 
et al. 1971), while trees growing in the wild in Me xico have been known to live as long as 400 years 40 . 
Infected trees may therefore remain present as sour ces of bacterial inoculum for many years, until 
their removal or death.  
 
37  Note that X. fastidiosa  is not passed from adult hemipterans to their eggs  (Almeida and Nunney 2015), so the 
accidental importation of live egg masses via any p athway is not in itself capable of introducing the bacterium. 
However, such incursions may give rise to the estab lishment of competent exotic vector species. 
38  In the form of plants grown from imported budwood that has been grafted onto New Zealand sources avoc ado 
rootstock 
39  This definition may not necessarily apply in other  situations. 
40  http://ucavo.ucr.edu/general/answers.html  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 100 Given the arguments and evidence above, the likelih ood of exposure of X. fastidiosa  in New Zealand 
from avocado budwood is considered to be high, with  low uncertainty. 
4.3.6 Likelihood of establishment 
This assessment is made on the basis that X. fastidiosa  has been successfully exposed to a suitable 
host plant/s in the New Zealand environment.  
To establish a permanent or persistent population, the organism must generally be able to move to 
new hosts, and the environment must be favourable f or its survival. Natural spread of X. fastidiosa  is 
through transmission by its insect vectors. Unless a competent vector is present, it can only move to 
new hosts by human-mediated means such as grafting to other avocado plants. It is likely that 
imported budwood will be widely propagated, since i t is of high value. It is uncertain to what degree 
this is likely to spread the bacterium to healthy r ootstock. The only information available for avocad o 
is from one small trial: Montero-Astúa et al. (2008 ) found that around 50% (8/15) of healthy seedlings  
developed symptoms after being grafted with infecte d budwood, and around 13% (2/15) tested 
positive for X. fastidiosa  by PCR. It is possible that X. fastidiosa  populations could persist in avocado 
orchards for an indefinite period even in the absen ce of a vector, since infections can be 
asymptomatic and trees are long-lived. Symptomatic trees are unlikely to be propagated from and 
may be removed, so that eventually infections that are transmitted solely by propagation to avocados 
may die out. 
If competent vectors are present, the bacterium has  the potential to spread naturally to other plants 
(including other, “native” avocado plants that are New Zealand grown), depending on the host range 
of the vector and the susceptibility of those plant s to the bacterium. This means the host range of th e 
bacterium is dependent on the host ranges of its ve ctors.  
The establishment and spread of X. fastidiosa  therefore depends on a combination of several fact ors:  
i) the presence of competent vectors, ii ) the presence of suitable host plants and iii ) the suitability of 
the environment. 
Vectors 
At least one known vector species, the introduced E uropean meadow spittlebug Philaenus spumarius , 
is present in New Zealand. This spittlebug has an e xtremely wide host range and is the main vector of 
olive quick decline syndrome ( X. fastidiosa  subsp. pauca ) in Italy (Cornara et al. 2017). It has been 
collected throughout much of New Zealand and from v ery many common crop, weed and amenity 
plants (Lariviere et al. 2010), including avocado ( PPIN 2021). It therefore has the potential to feed on 
infected avocado plants (in nurseries or orchards) and to transmit the bacterium to other plants in th e 
managed estate. It has also been collected on a num ber of native plants (see Environmental Impacts  
section below). This means this vector is also capa ble of moving the bacterium from the managed to 
the natural estate. 
Other potential vectors are present in New Zealand.  Fifteen additional spittlebug species have been 
reported: the introduced Australian Bathyllus albicinctus  and 14 native species. Their host ranges 
include crop and amenity plants in addition to many  native plants (Lariviere et al. 2010). Around 30 
native cicada species are known, however the role o f cicadas in X. fastidiosa  transmission is unclear. 
The bacterium therefore has the potential to spread  naturally both within and between the managed 
and natural estates in New Zealand.  
Host plants 
A very large number of plant species (over 600) hav e been demonstrated to sustain X. fastidiosa  
infections, including many important crop, ornament al and native plants common throughout New 
Zealand.  
Each bacterial subspecies is thought to have a larg ely non-overlapping set of symptomatic host plants 
(Yuan et al. 2010; Nunney et al. 2019), so the rang e of hosts that will be impacted upon in an  
101 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand incursion of any particular genotype is likely to b e limited. For example, the putative subspecies 
associated with the Costa Rican disease of avocado is X. fastidiosa  subsp . fastidiosa . In North 
America, this subspecies is primarily associated wi th grapevine (commonly grown in New Zealand), 
though it has a number of other hosts including alm ond (Nunney et al. 2019). Nevertheless, non-
symptomatic hosts are colonised by the bacterium an d they may act as reservoirs of infection (Sicard 
et al. 2018). Therefore, it is unlikely that the pr esence of suitable host plants will be a limiting f actor to 
the establishment of the bacterium.  
Suitability of the New Zealand environment 
At the species level, X. fastidiosa  survival is limited by cold temperatures. The opti mal growing 
temperature of the pathogen is 26–28° C. It is usual ly limited to the tropical and subtropical areas of  
North and South America and in general diseases cau sed by the bacterium are not reported from 
areas with low winter temperatures or at high altit udes (Hopkins and Purcell 2002; Baldi and La Porta 
2017; Godefroid et al. 2019).  
However, the responses to climate for each subspeci es may vary. Some subspecies have been found 
in much colder countries, such as Canada (Baker 201 7). Baker (2017) suggested that X. fastidiosa  
subsp. multiplex  provides the greatest likelihood of establishment in the United Kingdom, since none 
of the other subspecies have yet been found in temp erate climates. For New Zealand, CLIMEX 
predictions by Hoddle (2004)  indicated that cold stress would exclude X. fastidiosa  (Pierce’s disease) 
from most of New Zealand’s wine production areas. H owever, CLIMEX predictions by MPI (2020)  
indicated that all of the North Island is highly su itable for the establishment of X. fastidiosa , while the 
South Island is overall less suitable.  
There is a high level of uncertainty in assessing t he impact of climate on the establishment of X. 
fastidiosa : 
• It is not known which X. fastidiosa  genotype could be introduced into New Zealand with  
avocado budwood. It is likely that the subspecies i nfecting avocado in Costa Rica is X. 
fastidiosa  subsp. fastidiosa , in which case its distribution, host range, sprea d and/or 
expression may be limited in this country (Hoddle 2 004). Symptomatic infections of avocado 
by X. fastidiosa  have only been reported from two localities in Cos ta Rica: Alajuela province, 
with a CMI (Composite or Climate Matching Index) of  0.4 and San José province, with CMIs 
varying from 0.4 to 0.6 (match is with all of New Z ealand; Phillips et al. 2018), meaning that 
the New Zealand climate may not be highly suitable for disease development, at least not in 
avocado. If other, yet unreported genotypes, are as sociated with avocado, particularly subsp. 
multiplex , distribution and spread are likely to be wider an d/or expression more severe. 
• Xylella fastidiosa  is likely to be more widely distributed than curre nt records suggest because 
it is difficult to identify on the basis of symptom s (Baker 2017). 
• Due to the lack of data on impacts from areas with  cooler summer temperatures, it is not 
known what the direct impact of X. fastidiosa  may be in temperate regions such as the U.K. 
(Parkinson and Malumphy 2020) or New Zealand. 
• The severity of X. fastidiosa -induced diseases has recently increased, possibly due to global 
warming (Godefroid et al. 2019). 
Given the arguments and evidence above, that is: 
• plants suitable for colonisation by X. fastidiosa  are widely grown throughout New Zealand; 
• some parts of New Zealand are likely to be suitabl e for the establishment and expression of 
diseases caused by X. fastidiosa ; 
• at least one competent vector species is present i n New Zealand, it is widely distributed and 
has a broad host range which includes avocado as we ll as other economically important and 
environmentally significant plants; 
the likelihood of X. fastidiosa  establishing in New Zealand is considered to be mo derate, with 
moderate uncertainty. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 102 4.3.7 Impacts in New Zealand 
Xylella fastidiosa  is an obligatory plant and insect vector colonizer  that can only spread by the 
movement of infected plant material or through the movement of its vectors. It is genetically diverse at 
the species level, and evidence indicates that spec ific clades cause disease in a small number of host  
plants that are largely non-overlapping, while colo nising many other plant species as a harmless 
endophyte. The impact of any invasion will depend o n the bacterial genotype that is introduced, the 
plants susceptible to this genotype and the vectors  which feed on those plants. Abiotic variables such  
as climate are also important, and responses to cli mate by different genotypes may also be variable. 
Thus the epidemiology and dynamics of each pathosys tem are distinct and depend on complex 
biological and ecological interactions between the plant, pathogen, and vector over short and long 
time periods (Yuan et al. 2010; Almeida and Nunney 2015; Baker 2017; Sicard et al. 2018; Nunney et 
al. 2019).  
There is therefore a high level of uncertainty in a ssessing the potential impacts of an incursion or t he 
establishment of X. fastidiosa  in New Zealand.  
Economic impacts 
Xylella fastidiosa  can cause severe plant pathologies such as Pierce’ s disease of grapevines, olive 
quick decline, oak bacterial leaf scorch, phony pea ch disease, citrus variegated chlorosis and almond 
leaf scorch. These can lead to huge economic losses , for example: 
• costs incurred by the Pierce’s disease strain ( X. fastidiosa  subsp. fastidiosa ) on the grape 
industry in California alone are estimated to amoun t to hundreds of millions of dollars annually 
(Tumber et al. 2014);  
• the CoDiRo strain of X. fastidiosa  subsp. pauca , which is associated with olive quick decline 
syndrome (OQDS) in southern Italy, has killed milli ons of olive trees in Apulia, causing 
unprecedented socio-economic issues (Godefroid et a l. 2019); 
• Phony peach disease (PPD) has caused severe yield loss in Georgia and elsewhere in the 
southeastern United States, with millions of PPD-in fected trees being removed from peach 
orchards over the last century. The disease remains  a production constraint, and 
management options are few (Johnson et al. 2021). 
Some of the bacterium’s highly susceptible hosts, s uch as grapes, summerfruit and citrus, are of very 
high economic importance to New Zealand. Wine expor ts for example, were worth $NZ1.8 billion in 
2019; domestic and export production of summerfruit  and citrus were worth almost $NZ120 million 
and $NZ70 million respectively (Plant & Food Resear ch 2019). The putative subspecies associated 
with avocado in Costa Rica is subsp. fastidiosa . The establishment of X. fastidiosa  subsp. fastidiosa  
in New Zealand would be likely to impose the greate st losses on the economically important wine 
industry, since wine grapes are highly susceptible and wine production is concentrated in warmer 
areas. Subspecies multiplex appears to have the widest host range in terms of p lant species 
expressing disease symptoms (EFSA 2015) and is thou ght to be more tolerant of temperate climates 
(Baker 2017), so impacts of this genotype could be more severe depending on its realised host range 
in New Zealand. 
Xylella fastidiosa  is known to colonise the native Leptospermun scoparium  (manuka; Groenteman et 
al. 2015), the source of the valuable manuka honey industry. New Zealand’s pure honey exports in 
2018/19 were worth $355 million, slightly over half  of which was monofloral manuka honey and a 
further significant proportion was multifloral manu ka honey (MPI 2019). Little is known about the 
potential impacts of X. fastidiosa  on manuka but, given the value of the honey export  industry, even a 
low level of impact could be significant.  
Nurseries could have significant financial losses f rom impacts on susceptible plants and also due to 
movement restrictions.  New Zealand’s plant product ion (nursery) industry is worth an estimated $500 
million per year (NZPPI 2019), including significan t native plant production. Some native plants are 
known hosts. 
There is little information on which to assess impa cts on the avocado industry. Infection of avocado i s 
very rarely reported, and impacts have not been qua ntified. However, the CMIs for the localities  
103 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand where the only symptomatic infections have been rep orted with all of New Zealand are low (0.4–0.6) 
(Phillips et al. 2018), suggesting that climate con ditions in avocado growing areas in New Zealand 
may not be ideal for symptom expression. 
Nielsen et al. (2019) assessed the economic impact of Xylella  in New Zealand. These authors 
concluded that although economic impacts assessment s have been carried out for Australia and for 
California, it is not possible to extrapolate these  to the New Zealand situation for reasons discussed  at 
the beginning of this section. However, they conclu ded that horticultural production worth between 
$301 million per year and $1.7 billion per year wou ld be at risk if X. fastidiosa  became established in 
New Zealand.  
The introduction of X. fastidiosa  would very likely result in a costly response and potentially in trade 
restrictions for nursery stock commodities and cut flowers and foliage. Restrictions for X. fastidiosa  
are not generally imposed on fresh produce or seeds  since these pathways are considered unlikely to 
introduce the bacterium (EFSA 2015). Australia, New  Zealand’s most important trading partner, is 
considered to be free of X. fastidiosa  (EPPO 2021). The establishment, or even an incursi on of X. 
fastidiosa  is likely to result in trade disruption since the bacterium is considered to be their highest 
priority plant pest 41 . 
Given the arguments and evidence above, that is: 
• Xylella fastidiosa can cause serious damage to crops and plant-based i ndustries that are 
of high economic importance to New Zealand, for exa mple, grapes, summerfruit, citrus; 
• the introduction of X. fastidiosa may result in  market access restrictions for nursery stock 
and cut flowers, particularly to Australia which is  New Zealand’s main trading partner; 
• the costs of responding to an incursion of X. fastidiosa and/or  long-term management 
costs resulting from establishment if the bacterium  are likely to be very high; 
• but considering that impacts on some crops may be limited by New Zealand’s temperate 
climate (depending on the bacterial genotype introd uced); 
the economic impact of X. fastidiosa  to New Zealand is considered to be very high, with  high 
uncertainty. 
Environmental impacts 
Sentinel host plant testing overseas has shown that  X. fastidiosa  is able to infect a range of native 
plants, including cabbage tree ( Cordyline australis ), kauri ( Agathis australis ), manuka ( Leptospermum 
scoparium ), p ōhutukawa ( Metrosideros  spp.) and several Coprosma and  Pittosporum  species 
(Groenteman et al. 2015). In this study, although p lants displaying typical Xylella  symptoms were 
preferentially sampled, a definitive link between s ymptoms and infection has not yet been 
established 42 . However, it is highly likely that infection with X. fastidiosa  will cause disease symptoms 
on at least some native plants in at least some are as of New Zealand.  
The bacterium has the potential to spread from the managed estate to the natural estate and within 
the natural estate. One known vector species, the s pittlebug P. spumarius, is widespread in New 
Zealand and has a host range that includes native a nd crop species. It has been collected feeding on 
avocado (PPIN 2021) and on a number of native plant s. Examples include P ōhutukawa ( Metrosideros 
excelsa ) (Plant-SyNZ 2022), Nothofagus  sp. (e.g. NZAC04158227; NZAC 2021), Phormium  (e.g. 
NZAC04158089; NZAC 2021), Pseudopanax arboreus (as Neopanax arboretum ) (e.g. 
NZAC04171451; NZAC 2021), Olearia nummulariifolia  and O. virgata (e.g. NZAC04171172 and 
NZAC04171473 respectively; NZAC 2021), Veronica salicifolia  (Lariviere et al. 2010) and Melicytus 
ramiflorus  (Sandanayaka and Charles 2006).  
In addition, there are a number of native spittlebu gs which are potential vectors. Some of these 
species, e.g. Carystoterpa fingens  and C. vagans , also have indicative host ranges that include 
introduced and native plants (Lariviere et al. 2010 ).  
 
41  https://www.awe.gov.au/biosecurity-trade/pests-dis eases-weeds/plant/national-priority-plant-pests-201 9. 
42  research is currently being carried out to address  this in the Better Border Biosecurity (B3) collabo ration.  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 104 There is uncertainty associated with predicting the  level of environmental impacts that could result 
from an incursion of X. fastidiosa . Although it is likely that infection would produc e disease in some 
native plants, it is not known how likely this is t o have an impact at the population or ecosystem lev el, 
and the climate suitability will vary with the geno type of X. fastidiosa  that is introduced. 
However, given the arguments and evidence above, th e impact on the New Zealand environment 
from the establishment of X. fastidiosa  is considered to be moderate, with high uncertaint y. 
Health impacts 
Xylella fastidiosa  is not known to pose risks to human health, and no  evidence was found of this 
bacterium causing human health issues. Searches usi ng the term ‘ Xylella fastidiosa ’ in Pubmed, 
Google Scholar, CAB abstracts and Google found no m ention of adverse effects on humans and 
animals. 
Given the arguments and evidence above, the health impact of X. fastidiosa  to New Zealand is 
considered to be negligible, with low uncertainty. 
Sociocultural impacts 
As with other impacts, the sociocultural impacts of  X. fastidiosa  establishment are expected to be 
variable depending on the particular genotype invol ved. Very high socio-cultural impacts could be 
expected if Pierce’s disease (subsp. fastidiosa ) established and the climate was suitable for dise ase 
expression. Impacts could potentially be similar to  those that resulted from New Zealand’s Psa 
(bacterial canker of kiwifruit or Pseudomonas syringae pv.  actinidiae ) outbreak. Job and income 
losses impacted not only on growers but on whole co mmunities that supported the industry (Vanneste 
2017).  
Xylella fastidiosa  can infect amenity plants that are valued in modif ied environments, e. g. oaks 
(Quercus  spp.), elms ( Ulmus  spp.) and poplars ( Populus  spp.) (Delbianco et al. 2021). However, it is 
uncertain to what extent such amenity trees might b e affected in the New Zealand climate. The 
bacterium is also able to infect a range of native species of high cultural significance, such as kaur i, 
cabbage tree, p ōhutukawa and manuka. These impacts are discussed un der “ Environmental impacts ” 
above.  
Nurseries could have significant financial losses f rom impacts on plants and also due to restrictions 
on movement of many plants, possibly leading to job  losses or even closure of some businesses  
(Parkinson and Malumphy 2020). New Zealand’s nurser y industry employs approximately 4000 
people (NZPPI 2019). 
Given the arguments and evidence above, the sociocu ltural impact of X. fastidiosa to New Zealand is 
considered to be moderate to high, with high uncert ainty. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, health and society is considered to be 
very high, with high uncertainty. 
4.3.8 Overall level of assessed risk to New Zealand  
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of X. fastidiosa  entering New Zealand associated with avocado budwo od is 
considered to be very low (with high uncertainty); 
• assuming entry, the likelihood of exposure is cons idered to be high (with low uncertainty); 
• assuming successful exposure, the likelihood of es tablishment is considered to be 
moderate, with moderate uncertainty; 
• the overall impact on the New Zealand economy, env ironment, health and society is 
considered to be very high (with high uncertainty)  
105 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand the overall level of risk to New Zealand from X. fastidiosa  on imported avocado  budwood is assessed 
as high, with moderate uncertainty. 
4.3.9 Management considerations 
Diseases caused by X. fastidiosa  are often characterized by leaf scorch, defoliatio n, foliage wilt and a 
general decline in vigour (FAO 2018). However, symp toms are not a good diagnostic indicator for X. 
fastidiosa . Their expression is heterogeneous, depending on t he host plant species, X. fastidiosa  
genotype and the climatic conditions (FAO 2018). Wh en present they can mimic symptoms of water 
stress or physiological disorders (FAO 2018). More importantly, asymptomatic infections of X. 
fastidiosa  occur frequently, with colonised plants either exh ibiting very long latent periods or 
remaining symptomless (EFSA 2013; Sicard et al. 201 8). 
Temperature and stress are important factors for sy mptom expression, with bacterial growth generally 
faster at higher temperatures, however the optimal temperature may depend on the bacterial 
genotypes that are introduced (Parkinson and Malump hy 2020). 
The distribution and concentration of X. fastidiosa  within the plant can vary seasonally. In general, 
sampling should be performed during the period of a ctive growth and the best plant material to test is  
the leaf petiole and the midrib of mature leaves fr om either asymptomatic or symptomatic plant 
material. 
Xylella fastidiosa  is a fastidious bacterium and its strains are diff icult to isolate, even from 
symptomatic plants, and difficult to grow in axenic  (pure) culture. Detection is based on serological 
methods (ELIZA, etc), and a variety of molecular me thods including:  
• DNA extraction using a number of commercially avai lable kits 
• conventional and real time polymerase chain reacti on (PCR) using a variety of primers and 
probes, 
• loop-mediated isothermal amplification (LAMP). 
A multilocus sequence typing (MLST) approach has be en described for the identification of X. 
fastidiosa  subspecies. 
4.3.10 Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Diseases caused by X. fastidiosa  are often characterized by leaf scorch, defoliatio n, foliage wilt and a 
general decline in vigour (FAO 2018). Symptoms repo rted in avocado include chlorotic mottling, 
marginal scorch, deformation of leaves, defoliation , shortening of internodes, and branch dieback 
(Montero-Astúa et al. 2008). 
However, symptoms are not a good diagnostic indicat or for X. fastidiosa . Their expression is 
heterogeneous, depending on the host plant species,  X. fastidiosa  genotype and the climatic 
conditions (FAO 2018). When present they can mimic symptoms of water stress or physiological 
disorders (FAO 2018).  
More importantly, asymptomatic infections of X. fastidiosa  occur frequently, with colonised plants 
either exhibiting very long latent periods or remai ning symptomless (EFSA 2013; Sicard et al. 2018). 
Asymptomatic infections are reported to occur in av ocado, and even where infections are 
symptomatic, the symptoms may not be uniformly expr essed in the plant. Montero-Astúa et al. (2008) 
observed that some branches showed symptoms while o thers in the same avocado plant did not. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 106 o What are the known environmental conditions conduci ve to symptom expression? 
Many X. fastidiosa  infections are asymptomatic, including some of tho se reported in avocado. Where 
symptoms are expressed, they are usually more prono unced in stressed plants, particularly those that 
are water deficient (FAO 2018; Bragard et al. 2019) . Temperature is also an important factor for 
symptom expression. Diseases caused by X. fastidiosa  are more common in tropical and subtropical 
regions (Janse and Obradovic 2010). Feil and Purcel l (2001)  determined that the optimal growth rate 
(in vitro ) of the bacterium causing Pierce’s disease of grap evine ( X. fastidiosa subsp.  fastidiosa ) was 
28° C. They postulated that temperatures between 25 and 32° C may be critical for disease 
development because of the rapid bacterial growth r ate at these temperatures, whereas temperatures 
below 12 to 17° C and above 34° C may affect the surv ival of X. fastidiosa  in plants. Other subspecies 
are likely to have different temperature responses,  for example X. fastidiosa subsp. multiplex  is 
considered to be more cold-tolerant due to the more  temperate distribution of the diseases it causes 
(Baker 2017) . However, symptom expression is likely to be reduced  at lower temperatures for all 
bacterial genotypes (Parkinson and Malumphy 2020). 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Samples should be taken from parts close to the sym ptoms and preferably consist of stems that have 
mature symptomatic leaves with petioles and woody t wigs. Individual leaves with petioles can also be 
sampled. The best plant material to test for the pr esence of X. fastidiosa  is the leaf petiole and the 
midrib of mature leaves from either asymptomatic or  symptomatic plant material. Samples of necrotic 
and dead tissue or sections of the plant at an adva nced stage of infection are not suitable for 
diagnosis, as saprophytes quickly colonize this tis sue, interfering with the isolation or detection of  the 
pathogen (FAO 2018). A diagnostic protocol is provi ded by FAO (2018) as an annex to ISPM 27. 
o What is the optimum season for conducting detection  testing? 
The distribution and concentration of X. fastidiosa  within the plant can vary seasonally. In general, 
sampling should be performed during the period of a ctive growth of the plants (Hopkins 1980). This is 
usually from late spring to autumn in temperate zon es. For asymptomatic plants, sampling is also 
possible during the period of active growth. In tem perate regions or in deciduous plants, sampling 
after warm periods (e.g., late summer–early autumn)  increases the probability of accurate bacterial 
detection because the bacteria do not move into the  new season’s growth until the middle of summer. 
However, for tropical plant species grown indoors, sampling may be performed all year round when 
plants are exhibiting periods of active growth (FAO  2018). 
4.3.11 References 
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Disease 99(11): 1457-1467. 
Baker, R (2017) Updating the UK rapid pest risk analysis for Xylell a fastidiosa.  DEFRA, UK. 
https://pdf4pro.com/view/updating-the-uk-rapid-pest -risk-analysis-for-xylella-178fb9.html  
Baldi, P; La Porta, N (2017) Xylella fastidiosa : host range and advance in molecular identificatio n 
techniques. Frontiers in Plant Science 8. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Bragard, C; Dehnen ‐Schmutz, K; Di Serio, F; Gonthier, P; Jacques, M A;  Jaques Miret, J A, et al. 
(2019) Update of the scientific opinion on the risk s to plant health posed by Xylella fastidiosa  in the 
EU territory. EFSA Journal 17(5).  
107 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand CAC; CMCC (2003) A pest management strategic plan for avocado produc tion in California.  
https://ipmdata.ipmcenters.org/documents/pmsps/CAav ocado.pdf  
Cornara, D; Cavalieri, V; Dongiovanni, C; Altamura,  G; Palmisano, F; Bosco, D, et al. (2017) 
Transmission of Xylella fastidiosa  by naturally infected Philaenus spumarius  (Hemiptera, 
Aphrophoridae) to different host plants. Journal of Applied Entomology 141(1-2): 80-87. 
Cornara, D; Morente, M; Markheiser, A; Bodino, N; T sai, C; Fereres, A, et al. (2019) An overview on 
the worldwide vectors of Xylella fastidiosa . Entomologia Generalis 39(3): 157-181. 
Cunty, A; Legendre, B; Jerphanion, P; Juteau, V; Fo rveille, A; Germain, J F, et al. (2020) Xylella 
fastidiosa  subspecies and sequence types detected in Philaenus spumarius  and in infected plants in 
France share the same locations. Plant Pathology 69(9): 1798-1811. 
Delbianco, A; Gibin, D; Pasinato, L; Morelli, M (20 21) Update of the Xylella  spp. host plant database – 
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subspecies and sequence types are associated with t he emergence of Xylella fastidiosa  in natural 
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for regulated pests. DP 25: Xylella fastidiosa.  Rome. DP_25_2018_Xylellafastidiosa_2018-09-21.pdf 
(ippc.int) 
Feil, H; Purcell, A H (2001) Temperature-dependent growth and survival of Xylella fastidiosa  in vitro 
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Goodall, G E; Little, T M; Rock, R C; Platt, R G; R eed, A D (1971) Useful life of avocado trees in 
commercial orchards in California .  
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invasion threats: novel insect-pathogen-natural ene my associations with native New Zealand plants in 
southern California. Biological Invasions 17(5): 1299-1305. 
Hoddle, M S (2004) The potential adventive geograph ic range of glassy-winged sharpshooter, 
Homalodisca coagulata  and the grape pathogen  Xylella fastidiosa : implications for California and 
other grape growing regions of the world. Crop Protection 23(8): 691-699. 
Hopkins, D L (1980) Seasonal concentration of the P ierce's disease bacterium in grapevine stems, 
petioles and leaf veins. Phytopathology 71: 415-418. 
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(Ed.), (V1 ed.): Portail Data INRAE. 
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Plant Pathology 92: S35-S48. 
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Updated pest categorisation of Xylella fastidiosa . EFSA Journal 16(7). 
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peach industry in the southeastern U.S.A. CABI Agriculture and Bioscience 2(1). 
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United States. Phytopathology® 100(6): 601-611. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 110 5. Pest risk assessments: Fungi 
5.1  Akaropeltopsis  sp. (Sooty blotch of avocado) 
Akaropeltopsis  sp. is a fungus that causes sooty blotch on the br anches, stems, leaf veins and fruit of 
Persea americana  (avocado). 
5.1.1  Taxonomic description  
Scientific name: Akaropeltopsis  sp. Batista & Peres, 1966  
Order/Family: Microthyriales/Micropeltidaceae  
Other names include : Stomiopeltis citri Bitancourt (sooty blotch of citrus) has been descri bed in the 
literature as the causative agent of sooty blotch o f avocado (Kotze and Theron 1979). However, 
morphological analysis suggests that Stomiopeltis citri is not synonymous Akaropeltopsis  sp., and that 
causative agent of sooty blotch of avocado is in fa ct Akaropeltopsis  sp. (Theron et al. 1981).  
Taxonomic notes: Akaropeltopsis  is similar to Stomiopeltis  (Theiss.) and other genera in the family 
Micropeltidaceae. This family is characterised by g enera that grow superficially on the cuticle of 
plants. Akaropeltopsis  sp. resembles Stomiopeltis citri (sooty blotch of citrus)  morphologically but 
differs by having 16-spored asci. Their similarity has resulted in misidentifications and a degree of 
uncertainty regarding the causative agent of sooty blotch on avocado is reflected in the literature 
(Kotze and Theron 1979; Theron et al. 1981). 
5.1.2  Hazard identification 
Akaropeltopsis  sp. is not known to be present in New Zealand: 
• Akaropeltopsis  sp. is not listed in either Biota NZ (2022) or PPI N (2021). 
• The regulatory status of Akaropeltopsis  sp.  has not been assessed (ONZPR 2021). 
Akaropeltopsis  sp. has the potential to establish (and spread) in  New Zealand because: 
• The reported host of Akaropeltopsis  sp. is P. americana . Avocado plants are commonly 
grown in New Zealand, in home gardens and commercia l production, mainly in the north of 
the North Island.  
• The climate is unlikely to limit its development a nd spread:  Akaropeltopsis  sp. is found in 
South Africa which has a Climate Match Index (CMI) ≥ 0.7 indicating a similar climate to the 
whole of New Zealand (Phillips et al. 2018). 
Akaropeltopsis  sp. has the potential to cause harm to New Zealand  because: 
• It does not parasitise the host and the blotches a re only on the surface, but they reduce the 
marketability and value of avocado fruit (Theron et  al. 1981; Smith et al. 1985; Smith et al. 
1987; Coates et al. 2001), 
• Avocados are an important commercial crop in New Z ealand. In the 2018–2019 financial 
year, export sales of fresh avocados earned NZ$110 million and domestic sales earned NZ$ 
56.5 million (Plant & Food Research 2019). 
Akaropeltopsis  sp. is associated with P. americana  budwood because: 
• Persea americana  is a known host of Akaropeltopsis  sp. (Smith et al. 1985; Smith et al. 1987) 
• Akaropeltopsis  sp. occurs on the branches and stems of avocado pl ants (Smith et al. 1985).  
111 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Given the arguments and evidence above, Akaropeltopsis  sp. meets the criteria to be a hazard on P. 
americana  budwood (as in the commodity description) imported  to New Zealand. 
5.1.3  Risk assessment 
Biology and epidemiology of Akaropeltopsis sp. 
Akaropeltopsis  sp. is an unspecified species of fungi from the Mi cropeltidaceae family, that causes 
sooty blotch on avocado. The mycelium grows superfi cially on the cuticle of the host tissue. Although 
the organism does not parasitise the host, it produ ces blotches that spoil the appearance of the fruit  
and decreases its market value.   
Host range  
Similarities between Akaropeltopsis  sp. found on avocado and A. marchaeriifolii  found on leaves of a 
Machaerium  sp. in Brazil have been reported but these species  have not been confirmed to be 
conspecific (Theron et al. 1981; Smith et al. 1987) . No other records of Akaropeltopsis  sp. causing 
sooty blotch on other hosts were found in the liter ature, suggesting that Akaropeltopsis  sp. is limited 
to P. americana . 
Distribution 
There are multiple, reliable records of Akaropeltopsis  sp. causing sooty blotch on avocado in South 
Africa (Theron et al. 1981; Smith et al. 1985; Smit h et al. 1987; Korsten et al. 1997).  
There is little information on the distribution of Akaropeltopsis  sp. elsewhere in the world, and the 
records of its distribution are largely unsubstanti ated or unconfirmed (Theron et al. 1981; Smith et a l. 
1987; Queensland Government 2001), as follows: 
 Sooty blotch on avocado in Australia has been repo rted to be caused by a range of causative 
agents, including Stomiopeltis  sp. (Coates et al. 2001; Willingham 2002; Cooke et  al. 2009), 
Akaropeltopsis  spp./ Stomiopeltis  spp. complex (Queensland Government 2001), and mul tiple 
non -specified fungi (Allen 2004). Given that the causat ive agents of sooty blotch on avocado 
have been confused in the past due to the high leve l of morphological similarity between 
Akaropeltopsis  and Stomiopeltis (Theron et al. 1981; Smith et al. 1987), and that t here were 
no records found describing Akaropeltopsis  sp. on avocado in Australia, there is uncertainty 
regarding the presence of Akaropeltopsis  sp. in Australia.  
 Akaropeltopsis  sp. has been reported to be present and associated  with avocado in 
Colombia, but this is based on international litera ture compilation and not from direct 
observation. According to the USDA (2016), the pres ence of Akaropeltopsis  sp. in Colombia 
is ‘doubtful’. 
 Akaropeltopsis  sp. appears to be similar to A. marchaeriifolii  found on leaves of a 
Machaerium  sp. in Brazil, but these species have not been con firmed to be conspecific 
(Theron et al. 1981; Smith et al. 1987). No other r ecords were found in the literature of 
Akaropeltopsis  sp. causing sooty blotch in Brazil. 
Table 5-1. The potential geographic distribution of  Akaropeltopsis  sp. causing Sooty blotch on 
avocado.  
Country  CMI43  range Notes References 
Australia  0.4 - 1.0 Presence is uncertain Coates et al. (2001); Queensland Government (2001);  
Willingham (2002); Cooke et al. (2009) 
Brazil  0.3 - 0.9 Presence is uncertain Theron et a l. (1981); Smith et al. (1987) 
Columbia  0.3 - 0.8 Presence is uncertain USDA (201 6) 
South Africa  0.5 - 0.9 Presence is confirmed  Theron et al. (1981); Smith et al. (1985); Smith et  al. (1987) 
 
43 Climate Match Index (CMI) with all of New Zealand ( Phillips et al. 2018). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 112 Symptoms  
Avocado sooty blotch is characterised by sooty blot ches on the branches, stems, leaf veins and fruit 
(Smith et al. 1985). The blotchy appearance is due to irregularly shaped mycelial mats that grow on 
the plant surface. Mycelium originates from ascospo res or mycelial fragments and initially appear as 
small light brown spots on the plant surface (Smith  et al. 1987). Over the summer season, the 
mycelium spreads over the plant, turns to a charcoa l black colour and becomes thick and uneven, 
resulting in the characteristic sooty blotched appe arance (Queensland Government 2001; Allen 
2004). When new flushes emerge in spring they contr ast in colour to the darkened twigs from the 
previous season. Mycelium usually takes at least tw o seasons to colonise the leaves. Akaropeltopsis  
sp. penetrates the wax layer of the plant but not t he cuticle or the epidermal cells, and therefore do es 
not cause rotting or damage of plant tissues. Haust oria have not been observed (Kotze and Theron 
1979; Theron et al. 1981; Smith et al. 1985; Smith et al. 1987; Coates et al. 2001).  
Optimal conditions for growth and symptom developme nt 
Mycelial growth is responsible for the sooty blotch ed appearance on the surface of the plant, and is 
promoted by surface moisture (dew, rain, high humid ity), low airflow, shade and warm temperatures 
(Allen 2004). Mycelium grows and spreads over the p lant surface during summer (Smith et al. 1987). 
Reproduction and transmission  
The mycelium of  Akaropeltopsis  sp. produces and releases large amounts of airborn e spores at the 
onset of summer rains (Cooke et al. 2009). These sp ores are the primary source of spread and 
infection, and germinate readily in a film of moist ure on the surface of a host plant (Smith et al. 19 85). 
Ascospores are 14-16 μm x 4-5 μm (Smith et al. 1985). 
5.1.4  Likelihood of entry 
There is potential for Akaropeltopsis  sp. to be imported into post-entry quarantine on a vocado 
budwood, in which case it would be likely to produc e visible symptoms in PEQ:  
• Akaropeltopsis  sp. appears to be restricted to South Africa. Ther e are several 
unconfirmed/unreliable records of its presence in A ustralia, Brazil and Colombia. 
• it can be associated with leafless avocado budwood  because it colonises the surface of 
branches, stems, leaves and fruit (Smith et al. 198 5). 
• budwood/leafless cuttings are dipped in 1% sodium hypochlorite for 2 minutes upon entry into 
the quarantine facility, which is considered to red uce the risk of importing Akaropeltopsis  sp. 
into PEQ to very low, with low uncertainty. 
• if Akaropeltopsis  sp. is imported into PEQ, it is highly likely to p roduce visible symptoms in 
PEQ because it is reported to grow and spread under  warm and wet conditions. 
• airborne spores are 14-16 μm x 4-5 μm (Smith et al. 1985), indicating they may escape f rom 
because the mesh screen over the level 3A PEQ vents  is required to have a maximum 
opening size of 0.04 mm 2 (MPI 2021). 
• however, the fungus is slow growing and takes mont hs to produce spores (Smith et al. 1985) 
so it would be detected by plant inspections well b efore spores are produced. Furthermore, 
spore production is promoted by rain (Cooke et al. 2009), suggesting that conditions in level 
3A PEQ would not be conducive to spore production b ecause there is no overhead irrigation 
(MPI 2021). 
Given the arguments and evidence above, that is:  
• Akaropeltopsis  sp. has a limited global distribution, with high u ncertainty. 
• it can be present on the surface of budwood (Smith  et al. 1985), but such infections are highly 
likely to be manged by 1% sodium hypochlorite for 2  minutes upon entry into the quarantine 
facility. 
• if Akaropeltopsis  sp. is imported into PEQ then it is highly likely to produce visible symptoms 
in level 3A PEQ.  
113 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • the fungus is unlikely to sporulate in level 3A PE Q because it takes months to produce spores 
and PEQ conditions may not be conducive to spore pr oduction.  
the likelihood of Akaropeltopsis  sp. entering New Zealand associated with P. americana  (avocado) 
budwood is considered to be negligible , with low  uncertainty.   
5.1.5  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of Akaropeltopsis  sp. entering New Zealand associated with P. americana  
budwood is considered to be negligible with low unc ertainty. Therefore, continuing the 
assessment is considered unnecessary; and 
the overall level of risk to New Zealand from Akaropeltopsis  sp. on imported P. americana budwood is 
considered to be negligible, with low uncertainty.  
5.1.6  Management considerations 
Avocado sooty blotch is characterised by sooty blot ches on the branches, stems, leaf veins and fruit 
(Smith et al. 1985). The blotchy appearance is due to mycelial mats that grow on the plant surface 
during the summer (Smith et al. 1987; Queensland Go vernment 2001; Allen 2004). Growth and spore 
production is promoted by surface moisture (dew, ra in, high humidity), low airflow, shade and warm 
temperatures (Allen 2004; Cooke et al. 2009). Akaropeltopsis  sp. does not parasitise the host and the 
blotches are only on the surface of the plant (Ther on et al. 1981; Smith et al. 1985; Smith et al. 198 7; 
Coates et al. 2001). 
There were no reports found in the literature of as ymptomatic Akaropeltopsis  sp. infections on 
avocado. In case the sodium hypochlorite dip treatm ent fails to penetrate into creases and folded 
plant surfaces, plant parts such as buds could be t ested to maximise the chances of detection of the 
pest in PEQ. 
Sooty blotch is effectively controlled with petrole um-based oil sprays and copper sprays (Coates et al . 
2001). Fungicides used to control anthracnose are c onsidered to be effective against sooty blotch 
(Queensland Government 2001; Aglave 2018). These in clude azoxystrobin and copper hydroxide 
(Eskalen and Faber 2016). 
5.1.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Avocado sooty blotch is characterised by sooty blot ches on the branches, stems, leaf veins and fruit 
(Smith et al. 1985). The blotchy appearance is due to mycelial mats that grow on the plant surface. 
Mycelia originates from ascospores or mycelial frag ments. Akaropeltopsis  sp. infection initially 
appears as small light brown spots on the plant sur face (Smith et al. 1987). Over the summer season, 
mycelia spread over the plant, turns to a charcoal black colour and becomes thick and uneven, 
resulting in the characteristic sooty blotched appe arance (Queensland Government 2001; Allen 
2004). When new flushes emerge in spring, they cont rast in colour to the darkened twigs from the 
previous season. Mycelium usually takes two seasons  to colonise the leaves. Haustoria44 have not 
been observed (Smith et al. 1985; Smith et al. 1987 ). Akaropeltopsis  sp. does not parasitise the host 
 
44  Haustoria are specialised fungal hypha that penetr ate the tissues of a host and absorbs nutrients and  water. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 114 and the blotches are only on the surface of the pla nt (Theron et al. 1981; Smith et al. 1985; Smith et  
al. 1987; Coates et al. 2001). 
o What are the known environmental conditions conduci ve to symptom expression? 
Mycelial growth is responsible for the sooty blotch ed appearance on the surface of the plant, and is 
promoted by surface moisture (dew, rain, high humid ity), low airflow, shade and warm temperatures 
(Allen 2004). Mycelium grows and spreads over the p lant surface during summer (Smith et al. 1987). 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
There were no reports found in the literature of as ymptomatic Akaropeltopsis  sp. infections on 
avocado. In case the sodium hypochlorite dip treatm ent fails to penetrate into creases and folded 
plant surfaces, plant parts such as buds could be t ested to maximise the chances of detection of the 
pest in PEQ  
o What is the optimum season for conducting detection  testing?  
Mycelial growth and sporulation is promoted by mois ture (dew, rain, high humidity), low airflow, shade  
and warm temperatures (Allen 2004). Mycelium grows and spreads over the plant surface during 
summer (Smith et al. 1987), and large amounts of ai rborne spores are produced and released at the 
onset of summer rains (Cooke et al. 2009), indicati ng that summer is the optimum season for 
conducting detection testing. 
5.1.8  References 
Aglave, B (2018) Handbook of Plant Disease Identification and Manage ment . CRC Press. 
Allen, R N (2004) Avocado diseases. In N S W D o Ag riculture (Ed.). Agfacts: Agfacts. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Coates, L M; Willingham, S L; Pegg, K G; Cooke, A W ; Dean, J R; Langdon, P W B (2001) Field and 
postharvest management of avocado fruit diseases. I n D o P I Queensland Horticulture Institute (Ed.): 
Queensland Horticulture Institute, Department of Pr imary Industries. 
Cooke, T; Persley, D; House, S (2009) Diseases of Fruit Crops in Australia . CSIRO Publishing,; 
Australia. 
Eskalen, A; Faber, B A (2016) Anthracnose. 
https://www2.ipm.ucanr.edu/agriculture/avocado/Anth racnose/   
Korsten, L; De Villiers, E E; Wehner, F C; Kotzé, J  M (1997) Field sprays of Bacillus subtilis  and 
fungicides for control of preharvest fruit diseases  of avocado in South Africa. Plant Disease 81(5): 
455-459. 
Kotze, J M; Theron, E M (1979) South African Avocado Growers’ Association Research  Report for: 
sooty blotch of avocados . 
https://www.avocadosource.com/Journals/SAAGA/SAAGA_ 1979/SAAGA_1979_PG_47-48.pdf  
MPI (2021) Facility Standard: Post Entry Quarantine for Plants . Ministry for Primary Industries, 
https://www.mpi.govt.nz/dmsdocument/11368-Post-Entr y-Quarantine-forPlants-Facilities-Standard  
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021  
115 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX ‘match climates regional’  
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2019) FreshFacts: New Zealand Horticulture. . The New Zealand Institute for 
Plant and Food Research Ltd; Auckland, New Zealand. ,  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Queensland Government (2001) Avocado information ki t Reprint - information current in 2001. In (pp. 
21). 
Smith, E; Kotzé, J; Wehner, F (1985) Sooty blotch o f avocado caused by Akaropeltopsis  sp. 
Phytophylactica 17(2): 101-102. 
Smith, E M; Kotze, J M; Wehner, F C (1987) Occurren ce and control of avocado sooty blotch. South 
African Avocado Growers' Association Yearbook 10: 111-113. 
Theron, E M; Kotze, J M; Wehner, F C (1981) The cau se of sooty blotch of avocados. South African 
Avocado Growers’ Association Yearbook 4: 80. 
USDA (2016) Importation of Fresh Fruit of Avocado, Persea americana Miller var. ‘Hass’, into the 
Continental United States from Colombia: A Pathway- Initiated Risk Assessment. In U S D o A (USDA) 
(Ed.), (4 ed.): United States Department of Agricul ture (USDA), Animal and Plant Health Inspection 
Service (APHIS). 
Willingham, S L (2002) Field management of avocado postharvest diseases. In D o P I Queensland 
Horticulture Institute (Ed.), (pp. 88). Sydney, Aus tralia: Horticultural Australia Ltd. 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 116 5.2  Ambrosia fungi of the Ambrosia Fusarium  Clade (AFC), Graphium  spp. and 
Paracremonium  spp. (vectored by beetles of the Euwallacea fornicatus  
species complex) 
Ambrosia fungi of the Ambrosia Fusarium  Clade (AFC),  Graphium and Paracremonium  are symbionts 
associated with small (1 ─2 mm) ambrosia beetles in the genus Euwallacea . These fungi supply 
essential diet components for the ambrosia beetles and in return rely on the beetles to carry them to a 
new host. By cultivating their fungal symbionts in the xylem of plants, some Euwallacea species have 
managed to expand their host range and become invas ive in new areas of the world. In recent years, 
for example, the Euwallacea fornicatus  complex, together with their symbiotic fungi, have  become a 
concern to the avocado industry in California, Flor ida, Australia, Israel and South Africa. 
5.2.1  Taxonomic description 
Taxonomic scope:  The taxonomic scope of this PRA are ambrosia fungi  (Table 5-2 and Table 5-3) 
vectored by beetles in the Euwallacea fornicatus  species complex (Coleoptera: Scolytinae) (Table 
5-4), known to attack living avocado trees and caus ing dieback.  
The Ambrosia Fusarium  Clade: The primary symbionts associated with Euwallacea  are fusaria that 
form a monophyletic group within Clade 3 of the Fusarium solani  species complex (FSSC), known as 
the Ambrosia Fusarium  Clade (AFC, Kasson et al. (2013)). Recently, it wa s proposed that species in 
the FSSC, including the AFC species, be placed in t he genus Neocosmospora (Sandoval-Denis et al. 
2019). However, this change has not been widely acc epted and new AFC species are still being 
described as Fusarium  (Aoki et al. 2021; Lynn et al. 2021). To date, at least 23 AFC species are 
known, some of which are yet to be described (Table  5-2). The list of AFC fungi is currently being 
updated and is expected to keep expanding, as is th e list of their associated beetle species (Aoki et 
al. 2021; Jiang et al. 2021; Lynn et al. 2021).  
Table 5-2. Species of the Ambrosia Fusarium  Clade (AFC) and associated beetle species, 
assembled from Kasson et al. (2013), Owens et al. ( 2018), Carrillo et al. (2019), Aoki et al. 
(2021), Lynn et al. (2021) and Jiang et al. (2021).  Fusarium  species in bold  indicate isolates from 
avocado. Associated Euwallacea  beetle vector is provided where known. 
Scientific name AFC species Associated beetle species 
Fusarium ambrosium AF-1 Euwallacea perbrevis  (TSHBa)  
Fusarium euwallaceae  AF-2 E. fornicatus  (PSHB)  
Fusarium floridanum AF-3 E. interjectus (formerly  Xyleborus interjectus ) 
Fusarium oligoseptatum AF-4 E. validus (formerly  Xyleborus validus ) 
Fusarium tuaranense  AF-5 unknown 
Fusarium sp. AF-6 E. perbrevis  (TSHBa)  
Fusarium obliquiseptatum AF-7 Euwallacea sp.  
Fusarium duplospermum AF-8 E. perbrevis  (TSHBa)  
Fusarium sp. AF-9 Xyleborus ferrugineus  
Fusarium drepaniforme AF-10 unknown 
Fusarium papillatum AF-11 E. perbrevis  (TSHBa) 
Fusarium kuroshium AF-12 E. kuroshio  (KSHB), E. fornicatus  (PSHB), E. interjectus  
Fusarium sp. AF-13 E. fornicatus  (PSHB), E. perbrevis (TSHBa) 
Fusarium sp. AF-14 E. fornicatus  (PSHB), E. perbrevis (TSHBa)  
Fusarium sp. AF-15 E. fornicatus  (PSHB)  
Fusarium sp. AF-16 E. fornicatus  (PSHB), E. perbrevis (TSHBa)   
117 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Scientific name AFC species Associated beetle species 
Fusarium sp. AF-17 E. fornicatus  (PSHB), E. perbrevis (TSHBa)  
Fusarium sp. AF-18 E. fornicatus  (PSHB), E. kuroshio  (KSHB), E. perbrevis 
(TSHBa)  
Fusarium rekanum AF-19 E. perbrevis (TSHBa), E. similis  
Fusarium akasia AF-20 E. perbrevis (TSHBa), E. similis  
Fusarium awan 45  AF-21 E. similis  
Fusarium mekan AF-22 E. similis  
Fusarium variasi AF-23 unknown 
Fusarium warna AF-24 E. perbrevis (TSHBa) 
Graphium  spp. and Paracremonium  spp. ambrosia fungi:  
Auxillary (or secondary) fungi of Euwallacea  ambrosia beetles, such as Graphium  spp. and 
Paracremonium  spp. are also isolated from other ambrosia beetle genera, such as Scolytodes, 
Megaplatypus  or Xyleborus  (Baker and Norris 1968; Kola řík and Hulcr 2009; Ceriani-Nakamurakare 
et al. 2016). Although some of them have recently g ained attention because they were commonly 
associated with Euwallacea  fornicatus  disease complex on avocado (Table 5-3), most of the m have 
not been described.  
Table 5-3. Graphium  spp. and Paracremonium  spp. ambrosia fungi isolated from avocado 
(bold), assembled from Na et al. (2018), Lynch et a l. (2016) and Carrillo et al. (2019). Associated 
Euwallacea  beetle vector is provided where known.  
Scientific name Associated beetle species 
Graphium euwallaceae E. fornicatus  (PSHB)  
Graphium sp. Euwallacea sp. (TSHB, unknown clade)  
Graphium sp. E. fornicatus  (PSHB)  
Graphium sp. E. fornicatus  (PSHB)  
Graphium sp. E. fornicatus  (PSHB)  
Graphium kuroshium E. fornicatus  (PSHB), E. kuroshio  (KSHB)  
Paracremonium sp. E. fornicatus  (PSHB), Euwallacea sp. (TSHB, unknown clade)  
Paracremonium pembeum E. fornicatus  (PSHB), E. kuroshio  (KSHB)  
The Euwallacea fornicatus  species complex  
The Euwallacea fornicatus  species complex (Table 5-4) and their vectored sym biotic fungi have 
recently become invasive outside their native range , South East Asia, and a concern for the avocado 
industry in various regions of the world (Carrillo et al. 2019; Freeman et al. 2019). 
Table 5-4. The Euwallacea fornicatus  species complex (Smith et al. 2019; Lynn et al. 20 21). 
Scientific name Other names 
Euwallacea fornicatus  (Eichhoff, 1868) (=  E. tapatapaoensis (Schedl, 1951); 
= E. whitfordiodendrus (Schedl, 1942)) PSHB; Polyphagous Shot Hole Borer 
Euwallacea fornicatior  (Eggers, 1923) (= E. schultzei  (Schedl, 1951)) TSHBb; Tea Shot Hole Borer Clade b  
Euwallacea perbrevis (Schedl, 1951) TSHBa; Tea Shot Hole Borer Clade a 
Euwallacea kuroshio  Gomez & Hulcr, 2018 KSHB; Kuroshio Shot Hole Borer  
 
45 Fusarium awan  is the only ambrosia fungus isolated from the myca ngia of an Euwallacea  species that does not group 
phylogenetically within the Ambrosia Fusarium  Clade (AFC), but still within the Fusarium solani  species complex (FSSC) (Lynn 
et al. 2021). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 118 Note: The main ambrosia fungi associated with the Euwallacea  fornicatus  species complex of 
concern to the avocado industry, particularly in in vaded areas, such as California, Israel, Australia and 
South Africa, are Fusarium euwallaceae , F. kuroshium , Graphium euwallaceae,  G. kuroshium  and 
Paracremonium pembeum (Lynch et al. 2016; Na et al. 2018; Freeman et al. 2019). However, recent 
evidence suggests a non-specific relationship betwe en the ambrosia fungi associated with the 
Euwallacea  fornicatus  complex and potential for symbiont switching withi n the Euwallacea  genus 
(Carrillo et al. 2019; Carrillo et al. 2020a; Jiang  et al. 2021; Lynn et al. 2021). Hence, different f ungi-
beetle combinations (Table 5-2 and Table 5-3) may b e associated with Euwallacea  beetle galleries in 
avocado budwood. 
5.2.2  Hazard identification 
The ambrosia fungi of the  Euwallacea fornicatus species complex (the Ambrosia Fusarium  Clade 
(AFC),  Graphium spp. and  Paracremonium spp.) are not known to be present in New Zealand: 
• Fusarium euwallaceae, F. kuroshium, F. oligoseptatu m, F. tuaranense, F. obliquiseptatum, F. 
duplospermum, F. drepaniforme, F. papillatum, F. re kanum, F. akasia, F. awan, F. mekan, F. 
variasi, F. warna, G. euwallaceae, G. kuroshium and  P. pembeum are not listed in either 
Biota NZ (2022), NZOR (2021), PPIN (2021) or ONZPR (2021). 
The ambrosia fungi of the  Euwallacea fornicatus species complex (the Ambrosia Fusarium  Clade 
(AFC),  Graphium spp. and  Paracremonium spp.) can be associated with Persea americana  budwood 
because: 
• Persea americana  is a known host of some of the ambrosia fungi (AF- 2, AF-6 to 8, AF-12 to 
18, Table 5-2) associated with the  Euwallacea fornicatus species complex (Carrillo et al. 
2019; Freeman et al. 2019);  
• the beetle vectors in the  Euwallacea fornicatus species complex infect preferably small live 
branches and stems of P. americana (Mendel et al. 2017) used for budwood. 
The ambrosia fungi of the  Euwallacea fornicatus species complex (the Ambrosia Fusarium  Clade 
(AFC),  Graphium spp. and  Paracremonium spp.) have the potential to establish (and spread) in New 
Zealand because: 
• Persea americana  (avocado) is a known host (Lynch et al. 2016; Na e t al. 2018; Freeman et 
al. 2019) of ambrosia fungi of the  Euwallacea fornicatus species complex (AFC,  Graphium 
spp. and  Paracremonium spp.);  
• multiple potential host plants and reproductive ho sts of the Euwallacea fornicatus species 
complex, such as Acer negundo, Ricinus communis, Quercus robur, Pers ea americana 
(Eskalen et al. 2013; Lynch et al. 2016; Na et al. 2018) are widely grown in New Zealand 
(NZPCN 2021) in home gardens, landscaping and comme rcial production;  
• ambrosia fungi of the  Euwallacea fornicatus species complex (AFC,  Graphium spp. and  
Paracremonium spp.) have been isolated from avocado trees in area s with a climate match 
index (CMI) ≥ 0.7 indicating a similar climate to the whole of N ew Zealand (Phillips et al. 
2018; Carrillo et al. 2020a);  
• There are no Euwallacea  vectors reported to be present in New Zealand (NZO R 2021). Other 
species (>25) of shot hole borers are reported from  New Zealand and it is not known whether 
they could serve as vectors of AFC fungi. However, AFC fungi isolated from avocado have so 
far only been reported to be vectored by Euwallacea  species (Table 5-2) and the scenario of 
symbiont switching to ambrosia beetles outside the genus Euwallacea , is considered unlikely 
with current available information (Kasson et al. 2 013; Aoki et al. 2021).  
The ambrosia fungi of the  Euwallacea fornicatus species complex (the Ambrosia Fusarium  Clade 
(AFC),  Graphium spp. and  Paracremonium spp.) have the potential to cause harm to New Zeala nd 
because: 
• the ambrosia fungi and their associated ambrosia b eetles can cause dieback and death of 
economically important hosts, such as Citrus  spp. and avocado (Aoki et al. 2019), and  
119 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • the ambrosia fungi of the  Euwallacea fornicatus species complex and their associated 
ambrosia beetles are not host specific (>75 host pl ant families) and can severely affect 
natural ecosystems (Eskalen et al. 2013; Coleman et  al. 2019). 
Given the arguments and evidence above, the ambrosi a fungi of the  Euwallacea fornicatus species 
complex (AFC,  Graphium spp. and  Paracremonium spp.) meet the criteria to be a hazard on Persea 
americana  budwood (as in the commodity description) imported  to New Zealand. 
5.2.3  Risk assessment 
Biology and epidemiology of the ambrosia fungi of t he Euwallacea fornicatus  species complex 
(the Ambrosia Fusarium  Clade (AFC), Graphium  spp. and Paracremonium  spp.) 
Ambrosia symbiosis background 
Ambrosia symbioses consist of reciprocally obligate  mutualisms between ambrosia beetles, a group 
of specialized wood-boring weevils (Scolytinae and Platypodinae), and their symbiotic ambrosia fungi 
(Joseph and Keyhani 2021). Ambrosia beetle females carry their fungal symbionts in special organs, 
called mycangia, to a host tree where they burrow i nto the sapwood and construct galleries to house 
their brood and fungal gardens (Joseph and Keyhani 2021). Ambrosia fungi are a polyphyletic group 
and at least 16 independent evolutionary origins of  fungus farming by ambrosia beetles have been 
reported. One of them are fungi from the Ambrosial Fusarium Complex (AFC) farmed by Euwallacea 
species (Aoki et al. 2019; Mendel et al. 2021).  
The genus Euwallacea   
Euwallacea is a genus of over 40 ambrosia beetle sp ecies within the tribe Xyleborini (Freeman et al. 
2016). Euwallacea species have pre-oral mycangia wh ich harbor fungal communities from the 
Ambrosial Fusarium Complex (AFC) (order Hypocreales ), which are their primary (obligate) symbionts 
(Carrillo et al. 2019). In addition, they are somet imes associated with fungi in the orders Microascal es 
and Ophiostomatlaes, which are their secondary or a uxiliary symbionts (Carrillo et al. 2019). 
Euwallacea species are engaged in obligate mutualis m with at least 23 AFC fungi (Table 5-2). In 
addition, at least six Graphium species and two Par acremonium species (Table 5-3) have been 
reported to be associated with Euwallacea species ( Carrillo et al. 2019). These symbiotic fungi have 
co-evolved with the beetles in mutualisms providing  the beetles with nutritional supplement from low-
nutrient xylem tissue, while the fungi receive reli able dispersion and direct inoculation into plant h osts 
(Carrillo et al. 2019). Because species of Euwallac ea do not feed directly on their host plant but on 
their xylem inhabiting fungal symbionts, their host  range is usually wide and likely depends on 
whether their primary symbionts can be cultivated i n the host (Mendel et al. 2021). 
The Euwallacea fornicatus  species complex 
Members of the Euwallacea fornicatus  species complex and their symbiotic fungi have rec ently 
invaded areas of the United States, Australia, Cost a Rica, Guatemala, Israel, Panama and South 
Africa, where they have become a concern to the avo cado industry, urban areas and natural 
ecosystems (Carrillo et al. 2019). At least 4 diffe rent beetle species (Table 5-4), all morphologicaly  
similar, are associated with different suites of am brosia fungi (Table 5-2 and Table 5-3). Whereas the  
vast majority of ambrosia beetle species attack dyi ng or dead trees, the Euwallacea fornicatus 
species complex and their symbionts have a wide hos t range and are known to attack live and healthy 
trees, including avocado (Hulcr et al. 2017). 
Host range and preference 
Ambrosia beetles from the Euwallacea fornicatus spe cies complex have a vast host range, including 
over 400 plant species in 75 families, many of whic h are reproductive hosts (e.g. Acer negundo, 
Ricinus communis, Quercus robur, Persea americana) (Eskalen et al. 2013; Gomez et al. 2019). The 
known host range continues to grow and is frequentl y updated. A recent study showed that out of 412 
tree species attacked by Euwallacea fornicatus (PSH B) approximately 20% were suitable for 
reproduction of the beetle (Mendel et al. 2021). It  was hypothesised that the AFC fungal species plays  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 120 a major role in which tree species is suitable for reproduction of the beetle (Mendel et al. 2021). 
Mendel et al. (2017) found that although all examin ed avocado cultivars were attacked by the beetles 
there seem to be differences in preference. In gene ral, the variety Hass was much more susceptible 
than Ettinger to beetle attack although the varieti es Reed, Nabal and Pinkerton were also markedly 
affected (Mendel et al. 2017). The increased beetle  attacks of the Hass variety is reflected in 
approximately 30% of the Hass trees displaying bran ch wilting compared to only 2% of the trees of 
Ettinger (Mendel et al. 2017).  
Symptoms on avocado 
On avocado, the Euwallacea fornicatus  beetle-disease complex causes branch wilting, dieb ack and 
tree mortality (Mendel et al. 2017). Typical signs of beetle attack at junctions of small and mid-size  
shaded branches often show the presence of white su gar volcanoes (Carrillo et al. 2016). Fusarium 
euwallaceae, F. kuroshium, Graphium euwallaceae , G. kuroshium  and Paracremonium pembeum  
have been shown to be weak pathogens causing lesion s (necrotic tissue) associated with the sugar 
exudation reactions when inoculated on young health y avocado (Lynch et al. 2016; Na et al. 2018; 
Freeman et al. 2019). Usually, it is the combined a ction of the mechanical beetle burrowing and 
localized pathogenicity of the ambrosia fungi (Lync h et al. 2016) that together cause cambial necrosis , 
branch dieback and tree mortality on avocado (Mende l et al. 2012). The occurrence and severity of 
wilting and dieback symptoms are related to the deg ree of beetle infestation in the wood (Mendel et 
al. 2021). Large and medium diameter avocado branch es were more resistant to beetle attack, 
compared to thin branches (Mendel et al. 2017). Eff ectively, gallery density increased as branch 
diameter decreased (Mendel et al. 2017). Concomitan tly, in large and medium diameter branches, 
extensive sugar exudation occurred and beetle attac k rarely progressed to the formation of natal 
galleries, whereas minimal sugar exudation was obse rved in thin branches (Mendel et al. 2017). This 
was more evident in the branches that were weakened  by repeated attacks followed by successful 
beetle colonization. For example, Euwallacea fornicatus  (referred to as  E. whitfordiodendrus,  PSHB) 
preferred and successfully colonized branches that had been previously attacked by its conspecifics, 
and reproduction was much higher in these branches,  as opposed to initial attacks (Mendel et al. 
2017). Thus, small avocado branches, such as budwoo d cuttings, could have beetle galleries with 
visible entry holes of about 0.85 mm in diameter (C arrillo et al. 2020b) or be potentially inoculated with 
ambrosia fungi from failed beetle attacks (Mendel e t al. 2021).  
Survival of primary and secondary ambrosia fungi in  live and in dead xylem of avocado 
An inoculation study on avocado host trees of culti vars 'Hass' and 'Ettinger' showed that G. 
euwallaceae  and P. pembeum  could not be recovered from live xylem after 3 ─4 months or 2 months, 
respectively (Freeman et al. 2019). Similar surviva l patterns were obtained from other tested plant 
hosts: inoculation of the fungi into healthy xylem indicated that both G. euwallaceae  and P. pembeum  
disappeared rapidly, whereas F. euwallaceae  survived for extended periods, while the xylem tis sue 
remained viable (Freeman et al. 2019). Auxilary fun gal symbionts Graphium  and Paracremonium  
remained viable and continued to thrive in dry and dead galleries, perhaps serving as food for the 
late-emerging adults and therefore appearing not to  be involved in pathogenicity (Freeman et al. 
2019). These findings strongly suggest that surviva l of AFC primary symbionts may last for extended 
periods in the live tissue whereas auxilary fungi ( Graphium  spp. and Paracremonium  spp.) may 
persist in their aposymbiotic phase in dying or dea d xylem. Hence, in case of inoculated live avocado 
budwood Graphium  spp. and Paracremonium  spp. would likely disappear after 2 months without  their 
symbiotic beetles.  
Different roles of the ambrosia fungi Fusarium , Graphium  and Paracremonium  associated with 
Euwallacea  species in avocado 
Mounting evidence suggests that Euwallacea  spp. need their Fusarium  symbionts (AFC) to survive 
and reproduce (Freeman et al. 2019), whereas their Graphium spp. and Paracremonium spp. 
symbionts are seen as auxiliary fungi (Carrillo et al. 2020a). For example, diet experiments showed 
that Euwallacea spp. were able to reproduce with th eir Fusarium and Graphium associates but could 
not survive or reproduce on P. pembeum alone (Carri llo et al. 2019; Freeman et al. 2019). Similarly, 
Carrillo et al. (2020a) showed that when solely rea red on auxilary fungi, beetles had no or only very 
few male offspring. Although the exact role of the ambrosia fungi is not yet fully understood, it appe ars 
that Fusarium (AFC) is required for the process of establishment in a living tree, i.e. establishment of  
121 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand beetle galleries and first food source for female b eetles in avocado (Freeman et al. 2016). During the  
colonization process, Graphium spp. and Paracremoni um spp. appear to be the main food source for 
development of the larvae (Freeman et al. 2016; Fre eman et al. 2019). Freeman et al. (2019) found 
that in invaded areas mainly the species Fusarium e uwallaceae was used as the food source for the 
adult beetles and hatching larvae, whereas G. euwal laceae served predominantly as food for the 
establishment of beetle larvae and callow adults.  
Vectors 
Members of the Euwallacea fornicatus  species complex have been reported as pests of avo cado 
(Carrillo et al. 2019) and as vectors of xylem-inha biting Fusarium (AFC), Graphium spp. and 
Paracremonium spp. (Aoki et al. 2019; Carrillo et a l. 2019). Currently, there are no Euwallacea  spp. 
reported from New Zealand (NZOR 2021; PPIN 2021). H owever, there are at least 25 other ambrosia 
beetles present in New Zealand, including xyleborin e ambrosia beetles (Brockerhoff et al. 2003; 
NZOR 2021) and polyphagous ambrosia beetles that have been reported from avoca do, such as 
Xylosandrus spp. (Virgen et al. 2021) . Lateral transfer of fungal symbionts has been repor ted between 
sympatric ambrosia beetle species, possibly facilit ated by the beetles colonizing the same host 
(Kola řík and Hulcr 2009; Carrillo et al. 2014; Ceriani-Na kamurakare et al. 2016; Carrillo et al. 2019). 
However, outside the genus Euwallacea, only one other ambros ia beetle species (Xyleborus 
ferrugineus) has been reported to have an associati on with an AFC species (i.e., AF-9, so far not 
isolated from avocado), and with Graphium and Acremonium-like species (Baker and Nor ris 1968; 
Paciura et al. 2010; Kasson et al. 2013). Xyleborus ferrugineus is not reported to occur in N ew 
Zealand (NZOR 2021). The gall wasp Quadrastichus er ythrinae was also hypothesised to be an 
alternative vector of two AFC fungi (isolates it-1 and it-2) on Erythrina trees in Japan (Takashina et  al. 
2020). The potentially alternative vector Q. erythr inae is not reported to be present in New Zealand 
(NZOR 2021). Thus, there are no known vectors of AFC fungi from avocad o (Table 5-2) currently  
reported from New Zealand (Bateman et al. 2016; Joseph and Keyhani 2021; NZOR  2021). 
5.2.4  Likelihood of entry 
The ambrosia fungi of the  Euwallacea fornicatus species complex (the Ambrosia Fusarium  Clade 
(AFC),  Graphium spp. and  Paracremonium spp.) are associated with ambrosia beetle infestati on and 
beetle galleries in avocado (Lynch et al. 2016; Car rillo et al. 2019; Freeman et al. 2019). Small 
branches are preferred over bigger stems for beetle  galleries in the host avocado (Freeman et al. 
2019). Therefore, ambrosia fungi and their beetles  could be associated with leafless, rootless 
avocado budwood cuttings.  
The routine surface disinfection of budwood enterin g PEQ (dipping in 1% sodium hypochlorite for 2 
minutes) will most likely not eliminate infection, given the fungus will be associated with beetle 
galleries where the surface disinfection may not re ach. However, if avocado budwood cuttings have 
an established infection, it is likely that beetle galleries will be detected, and infected material 
removed or destroyed, during phytosanitary inspecti ons on arrival in New Zealand.  
The results of Freeman et al. (2019) suggest that Graphium euwallaceae, G. kuroshium and 
Paracremonium pembeum would only survive PEQ on dead xylem. In live xylem  (as in fresh budwood 
cuttings) the fungi would likely disappear after 2 months (Freeman et al. 2019). Primary ambrosia 
fungi from the AFC, such as F.  euwallaceae were shown to survive in live xylem for more than 2 5 
months (Freeman et al. 2019). This infection, howev er, remains localized near the beetle entrance 
holes and galleries, typically at the base of a bra nch, and results in wilt and dieback of individual 
branches (Freeman et al. 2019; Kendra et al. 2020; Mendel et al. 2021). 
As part of the commodity description, all imported avocado germplasm will undergo a growing period 
of active growth with a minimum of three distinct p henological growing events referred to as ‘shoot 
flush’ in 3A PEQ. This period in 3A PEQ will impact  on likelihood of entry in the following manner: 
• ambrosia beetle galleries (i.e. entry holes and su gar exudates) will be visible during 
inspection and thus infected budwood would be detec ted and destroyed before plants are 
released from PEQ, and Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 122 • budwood will be treated with miticides and insecti cides, which are unlikely to affect ambrosia 
beetles residing internally (see section 2.2). Howe ver, Level 3A PEQ has measures in place 
to manage the risks associated with insects, wastew ater, waste and accidental transfer (see 
section 2.2), therefore ambrosia beetles and their fungal symbionts are highly unlikely to 
escape level 3A PEQ to infect a suitable host. 
Therefore, the residual biosecurity risks are likel y to be managed by the growing period of active 
growth with a minimum of three distinct phenologica l growing events referred to as ‘shoot flush’ in 3A  
PEQ. 
Given the arguments and evidence above, that is:  
• established infections and beetle galleries are hi ghly likely to be detected, and infected 
material removed or destroyed, during preparation f or export, in phytosanitary inspections 
pre-export or on arrival in New Zealand; 
• residual biosecurity risks from ambrosia entry poi nts or recent infections on the surface of 
avocado budwood are likely to be managed by the gro wing period of active growth with a 
minimum of three distinct phenological growing even ts referred to as ‘shoot flush’ in 3A PEQ 
the likelihood of ambrosia fungi of the  Euwallacea fornicatus species complex (the Ambrosia 
Fusarium Clade (AFC),  Graphium spp. and  Paracremonium spp.) entering New Zealand associated 
with Persea americana  budwood is considered to be very low, with low unc ertainty. 
5.2.5  Likelihood of exposure 
This assessment is made on the basis that ambrosia fungi of the  Euwallacea fornicatus species 
complex (the Ambrosia Fusarium Clade (AFC),  Graphium spp. and  Paracremonium spp.) have 
entered New Zealand on avocado budwood as in the co mmodity description undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand.   
If avocado plants are infected with ambrosia fungi of the  Euwallacea fornicatus species complex (the 
Ambrosia Fusarium  Clade (AFC),  Graphium spp. and  Paracremonium spp.) at the time of their 
release from Post Entry Quarantine (PEQ) they will be planted in New Zealand or used to propagate 
new plants for planting (see section 2.3 for additi onal information about exposure).  
Primary ambrosia fungi of the  Euwallacea fornicatus species complex live in obligate mutualism with 
Euwallacea  ambrosia beetles and depend on their beetle vector s to carry and inoculate them into the 
xylem of a new host (Lynn et al. 2021). No known ve ctors are reported to be present in New Zealand 
(see section Vectors, NZOR (2021)).  
The ambrosia fungi associated with the Euwallacea fornicatus  species complex on avocado have so 
far been shown to have localised pathogenicity (<10  cm spread of beetle entry or inoculation point) in  
avocado and no systemic infection by these fungi is  currently known (Mendel et al. 2017; Freeman et 
al. 2019). Thus, the here assessed ambrosia fungi w ould remain localised, in the individual avocado 
branch. 
Given the arguments and evidence above, the likelih ood of ambrosia fungi of the  Euwallacea 
fornicatus species complex transferring from Persea americana  budwood onto a host in New Zealand 
is considered to be very low, with moderate uncerta inty. 
Therefore, further assessment is considered unneces sary at this time, and likelihoods of 
establishment and impacts to New Zealand were not a ssessed.  
123 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.2.6  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood above, that:   
• the likelihood of ambrosia fungi of the  Euwallacea fornicatus species complex (the Ambrosia 
Fusarium Clade (AFC),  Graphium spp. and  Paracremonium spp.) entering New Zealand 
associated with Persea americana  budwood (as described in the commodity description , and 
taking into account the proposed growing period of active growth with a minimum of three 
distinct phenological growing events referred to as  ‘shoot flush’ in 3A PEQ) is considered to 
be very low, with low uncertainty;  
• the likelihood of transferring from the imported c ommodity onto a suitable host is considered 
to be very low, with moderate uncertainty; 
• therefore, continuing the assessment was considere d unnecessary; and 
the overall level of risk to New Zealand from ambro sia fungi of the  Euwallacea fornicatus species 
complex (the Ambrosia Fusarium  Clade (AFC),  Graphium spp. and  Paracremonium spp.) on imported 
Persea americana budwood (as in the commodity description) is consid ered to be negligible, with low 
uncertainty.  
5.2.7  Management considerations 
Pesticides and trapping 
Infections with ambrosia fungi of the  Euwallacea fornicatus species complex (the Ambrosia Fusarium 
Clade (AFC),  Graphium spp. and  Paracremonium spp.) and their beetles are inside of hardwood. 
Thus, the fungi and the beetles are difficult to co ntrol with systemic insecticides, contact insectici de, 
fungicides or biological control (Eatough Jones et al. 2017). No pesticide combination provided 
substantial control over time (Eatough Jones et al.  2017). Trapping of female beetles of the  
Euwallacea fornicatus species complex might reduce damage. For example, α-copaene was shown to 
be equal in attraction to quercivorol, a food-based  attractant and the standard lure for E. nr. fornicatus  
(Kendra et al. 2020); moreover, a combination of α-copaene and quercivorol lures resulted in 
synergistic attraction and improved pest detection (Kendra et al. 2020). This two-component lure has 
field longevity of 3 months and a sampling range of  30–35 m (Kendra et al. 2020). 
Molecular identification 
Carrillo et al. (2020b) developed multiplex real-ti me quantitative PCR assays using hydrolysis probes 
targeting the β-tubulin gene to detect, distinguish, and quantify ambrosia fungi associated with the 
polyphagous shot hole borer (PSHB; Euwallacea fornicatus , Fusarium euwallaceae , Graphium 
euwallaceae  and Paracremonium pembeum ) as well as the Kuroshio shot hole borer (KSHB; 
Euwallacea kuroshio , Fusarium kuroshium  and Graphium kuroshium ).  
5.2.8  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Symptom expression with beetle galleries: Infection with the ambrosia fungi of the  Euwallacea 
fornicatus species complex (the Ambrosia Fusarium  Clade (AFC),  Graphium spp. and  
Paracremonium spp.) is usually associated with ambrosia beetles o r their galleries (Carrillo et al. 
2020b; Mendel et al. 2021). External symptoms assoc iated with beetle galleries are visible (small 
holes of about 1 mm and sugar exudates) (Carrillo e t al. 2020b). White powdery exudate on the outer 
bark is associated with beetle holes and wood under  exit holes of galleries will reveal brown necrosis  
(Mendel et al. 2017). Older plants also show black pitch symptoms (i.e. black exudate found on 
branches) and branch dieback and wilting (Mendel et  al. 2017). The ambrosia fungi associated with Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 124 the Euwallacea fornicatus  species complex on avocado have so far been shown to have localised 
pathogenicity (<10 cm spread of beetle entry or ino culation point) in avocado and no systemic 
infection by these fungi is currently known (Mendel  et al. 2017; Freeman et al. 2019), as opposed to 
other ambrosia fungi, such as in the genus Raffaelea (Joseph and Keyhani 2021). Thus, symptom 
expression of the ambrosia fungi of the  Euwallacea fornicatus species complex (AFC,  Graphium spp. 
and  Paracremonium spp.) is expected to be in close proximity to beetl e galleries in the host avocado 
(from entry point, Mendel et al. (2017)) and extern al symptoms associated with beetle galleries are 
expected to be visible.  
Symptom expression without beetle galleries: Inoculation of avocado branches with ambrosia 
fungi of the  Euwallacea fornicatus species complex (AFC,  Graphium spp. and  Paracremonium spp.) 
could result from beetle attacks without the beetle  establishing galleries or colonising the xylem. 
Inoculation of 30 cm detached healthy 2.54 cm woody  shoots of avocado and seedlings with 
Fusarium kuroshium , F. euwallaceae , Graphium euwallaceae,  G. kuroshium and Paracremonium 
pembeum  resulted in visible lesions (necrotic tissue) with  lengths that varied between 4 and 14 cm 
from 5 days to 4 weeks of incubation at 25° C (Lynch  et al. 2016; Na et al. 2018). Paracremonium 
pembeum  produced longer lesions than G. euwallaceae  (Lynch et al. 2016). Plants infected with G. 
euwallaceae  showed lesions with an average length of 6.4 ± 2.8  cm, and those infected with G. 
kuroshium  showed lesions with an average length of 7.6 ± 4.1  cm (Na et al. 2018). Avocado seedlings 
inoculated with F. kuroshium  produced lesions with an average length of 3.15 ± 1.8 cm, and seedlings 
inoculated with F. euwallaceae  produced lesions with an average length of 6.89 ± 2.1 cm (Na et al. 
2018). Although not all fungi associated with the  Euwallacea fornicatus species complex have been 
described and their pathogenicity studied, generall y, fungi from the AFC isolated from avocado and 
other hosts show very similar symptoms of lesions a nd dieback (Kasson et al. 2013; Carrillo et al. 
2016; Mendel et al. 2017; Aoki et al. 2019; Freeman  et al. 2019; Aoki et al. 2021; Lynn et al. 2021). 
Thus, it is assumed that symptom expression would l ikely be visible in case of successful infection, 
especially during the first months of PEQ.  
Survival of ambrosia fungi in healthy young avocado  branches and seedlings: A long-term 
inoculation study of avocado branches with Graphium euwallaceae  and P. pembeum  showed that 
both fungi could not be recovered from live avocado  tissue after 3 ─4 months or 2 months, 
respectively (Freeman et al. 2019). However, Freema n et al. (2019) recovered G. euwallaceae  and P. 
pembeum  from dead xylem of avocado and concluded that the fungi could survive long-term in dead 
xylem as opposed to live avocado tissue. Thus, afte r active growth with a minimum of three distinct 
phenological growing events referred to as ‘shoot f lush’ in Level 3A PEQ it is highly likely that the 
fungi G. euwallaceae,  G. kuroshium and Paracremonium pembeum  would not survive in live avocado 
tissue. This is in contrast to F. euwallaceae  which could be recovered from live tissue after 25  months 
of inoculation (Freeman et al. 2019). However, in b oth natural infection and pathogenicity tests in 
avocado, F. euwallaceae and F. kuroshium could only be isolated from discoloured (light brow n) 
xylem tissues or beetle galleries but not from adja cent healthy (white) xylem tissue close to the 
stained point (Na et al. 2018; Freeman et al. 2019) . This suggests that only the primary ambrosia 
fungi of Euwallacea  (AFC) could survive the PEQ period in live tissue of avocado, however, they 
would likely remain localised in discoloured (light  brown) xylem tissues in close proximity of 
inoculation.  
o What are the known environmental conditions conduci ve to symptom expression? 
Graphium euwallaceae  has been shown to have a growth temperature range from 20 ─35° C with an 
optimum growth at 25° C (Lynch et al. 2016). Paracremonium pembeum  has been shown to have a 
growth temperature range from 15 ─35° C with an optimum growth at 30 ─35° C (Lynch et al. 2016). 
Similarly, Na et al. (2018) showed a growth tempera ture range from 10 ─40° C with optimal growth at 
30° C for G. euwallaceae and G. kuroshium . Similarly, F. euwallaceae  and F. kuroshium  had an 
optimal growth at 25° C (Na et al. 2018; Freeman et al. 2019). Therefore, high temperatures > 25° C 
would likely be conducive to symptom expression. 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
125 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand There is no evidence that Fusarium euwallaceae , F. kuroshium,  Graphium euwallaceae,  G. 
kuroshium  and Paracremonium pembeum  can cause asymptomatic infections and thus, there is no 
information on which plant part should be tested to  maximise the detection in the case of 
asymptomatic infection. The fungi would likely be i n close proximity of beetle galleries and beetle 
galleries have been found more frequently in small branches of avocado and close to the base of a 
branch, up to 30 cm from the branching points (Mend el et al. 2017). In both natural infection and 
pathogenicity tests in avocado, F. euwallaceae and F. kuroshium could only be isolated from 
discoloured (light brown) xylem tissues or beetle g alleries but not from adjacent healthy (white) xyle m 
tissue close to the stained point (Na et al. 2018; Freeman et al. 2019). Some uncertainty arises from 
the fact that not all AFC fungi (Table 5-2) isolate d from avocado have been tested for pathogenicity. 
o What is the optimum season for conducting detection  testing? 
In Israel, beetle attacks and lesion frequency on a vocado were highest during late summer, July to 
September (Mendel et al. 2017). Moreover, the growt h of Fusarium euwallaceae , F. kuroshium,  
Graphium euwallaceae,  G. kuroshium  and Paracremonium pembeum  has been shown highest at 
warmer temperatures > 25° C (Lynch et al. 2016; Na e t al. 2018). Thus, warm seasons have a higher 
potential for detecting the fungi. 
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species in California. Plant Disease 102(6): 1154-1164. 
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2021 
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range expansion and increasing damage potential of Euwallacea nr. fornicatus (Coleoptera: 
Curculionidae) in Florida. Florida Entomologist 101(2): 229-236. 
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synnematous bark beetle-associated fungi from China , including Graphium carbonarium  sp. nov. 
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the Euwallacea Fornicatus  (Coleoptera: Curculionidae: Scolytinae) complex af ter the rediscovery of 
the “lost” type specimen. Insects 10(9): 261. 
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distribution of Fusarium solani  isolates associated with Erythrina decline in Japa n. Plant Disease 
104(3): 731-742. 
Virgen, M O E; Solorio, A B; Velasco, C R; Falcón-B rindis, A; Medina, K B A D; Parra, M L D B, et al. 
(2021) Bark and ambrosia beetles (Coleoptera: Curcu lionidae) associated with avocado in Nayarit, 
Mexico. International journal of tropical insect science . 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 128 5.3  Colletotrichum  spp. 
This PRA assesses species associated with avocado f ound in two species complexes: the 
Colletotrichum gloeosporioides species complex and the Colletotrichum acutatum species complex. 
The following species will be assessed: Colletotrichum aenigma , C. chrysophilum , C. endophyticum , 
C. jiangxiense , C. queenslandicum  and C. tropicale  are in the C. gloeosporioides species complex 
and C. nymphaceae  is in the C. acutatum species complex.   
Colletotrichum  species in both the gloeosporioides and acutatum species complexes are fungi with a 
wide host and environment range. They are important  plant pathogens but can have endophytic and 
saprotrophic lifestyles. In avocado, Colletotrichum species cause anthracnose in fruit and sometimes 
stem dieback.  
5.3.1  Taxonomic description 
Scientific name: Colletotrichum aenigma  B. S. Weir & P. R. Johnston (2012) 
Taxonomic notes: Colletotrichum aenigma  is part of the gloeosporioides  species complex which is 
defined genetically on the basis of multi-gene phyl ogenies (Weir et al. 2012).  
Scientific name: Colletotrichum chrysophilum  W.A.S. Vieira, W. G. Lima, M. P. S. Câmara & V.P. 
Doyle (2017) 
Taxonomic notes:  Colletotrichum chrysophilum  is part of the gloeosporioides  species complex 
(Vieira et al. 2017) which is defined genetically o n the basis of multi-gene phylogenies (Weir et al. 
2012).  
Scientific name: Colletotrichum endophyticum  Manamgoda, Udayanga, L. Cai & K. D. Hyde (2013)  
Other names include : Colletotrichum endophytica  Manamgoda, Udayanga, L. Cai & K. D. Hyde 
(2013) 
Taxonomic notes:  Colletotrichum endophyticum  is part of the gloeosporioides  species complex 
(Manamgoda et al. 2013) which is defined geneticall y on the basis of multi-gene phylogenies (Weir et 
al. 2012).  
Scientific name: Colletotrichum jiangxiense  F. Liu and L. Cai (2015)  
Taxonomic notes:  Colletotrichum jiangxiense  is part of the gloeosporioides  species complex (Liu et 
al. 2015) which is defined genetically on the basis  of multi-gene phylogenies (Weir et al. 2012).  
Scientific name: Colletotrichum nymphaeae (Passerini) Aa (1978) 
Other names include : Colletotrichum mahoniae Fabric. 1950 (Damm et al. 2012) , Ascochyta 
nymphaeae Passerini 1876 (Damm et al. 2012), Ramularia nymphaeae  Bres. (1894)  (Damm et al. 
2012), Phyllosticta nymphaeae (Passerini) Passerini (1888) (EPPO 2020)  
Taxonomic notes: Colletotrichum nymphaeae is part of the acutatum  species complex which 
includes destructive pathogens on fruits such as st rawberry, citrus, apple, olive, cranberry and 
blueberry (Damm et al. 2012). A morphological featu re of species within the C. acutatum  species 
complex include the ‘acute ends’ of the conidia (Da mm et al. 2012).  
Scientific name: Colletotrichum queenslandicum B. S. Weir & P. R. Johnston (2012) 
Other names include : Colletotrichum gloeosporioides  var. minus  Simmonds (1968) (EPPO 2020)  
129 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Taxonomic notes: Colletotrichum queenslandicum  is part of the gloeosporioides  species complex 
which is defined genetically on the basis of multi- gene phylogenies (Weir et al. 2012).  
Scientific name: Colletotrichum tropicale Rojas, Rehner & Samuels (2010) 
Taxonomic notes: Colletotrichum tropicale  is part of the gloeosporioides  species complex (Rojas et 
al. 2010) which is defined genetically on the basis  of multi-gene phylogenies (Weir et al. 2012). 
Order/Family: Glomerellales/Glomerellaceae 
5.3.2  Hazard identification 
Colletotrichum spp. ( C. aenigma, C. chrysophilum,  C. endophyticum, C. jiangxiense,  C. nymphaeae,  
C. queenslandicum, C. tropicale ) are not known to be present in New Zealand: 
• Colletotrichum chrysophilum , C. endophyticum  and C. jiangxiense are not listed in either Biota 
NZ (2022), NZOR (2021) or PPIN (2021) 
• Colletotrichum aenigma , C. nupharicola , C. queenslandicum  and C. tropicale are recorded as 
absent from New Zealand in Biota NZ (2022), NZOR (2 021) and are not listed in PPIN (2021) 
o Colletotrichum nymphaeae  has an organism report in PPIN (2021) stating it i s not 
present in New Zealand 
• Colletotrichum aenigma, C. chrysophilum,  C. endophyticum, C. jiangxiense,  C. nymphaeae,  
C. queenslandicum, C. tropicale  are not listed in ONZPR (2021) 
Colletotrichum spp. have the potential to establish (and spread) i n New Zealand because: 
• Persea americana (avocado) is a known host (Weir et al. 2012; Sharma  et al. 2017; Fuentes ‐
Aragón et al. 2020) that is widely grown in New Zea land, in home gardens and commercial 
production, mainly in the north of the North Island . 
• Colletotrichum  spp. cause anthracnose in avocado in regions aroun d the world (e.g. Israel, 
Mexico) (Sharma et al. 2017; Fuentes ‐Aragón et al. 2020) that have a climate match index  
(CMI) ≥ 0.7 indicating a similar climate to the whole of N ew Zealand (Phillips et al. 2018). 
Colletotrichum spp. have the potential to cause harm to New Zealan d because: 
• Colletotrichum spp. cause anthracnose in avocado which causes sunk en necrotic black 
lesions on the fruit (Sharma et al. 2017). The fung us survives between fruiting cycles on 
leaves and twigs on trees (Sharma et al. 2017). Les ions would reduce marketability of fruits. 
• avocados are an important commercial crop in New Z ealand. In the 2019–2020 financial year, 
export sales of fresh avocados earned NZ$112.3 mill ion and domestic sales earned NZ$ 50.6 
million (Plant & Food Research 2020) 
Colletotrichum spp. is associated with P. americana  budwood because: 
• Persea americana  is a known host of Colletotrichum spp. (Weir et al. 2012; Sharma et al. 
2017; Fuentes ‐Aragón et al. 2020); 
• Colletotrichum spp. have been isolated from branches and stems of P. americana  (Sharma et 
al. 2017). 
Given the arguments and evidence above, Colletrotrichum spp. meet the criteria to be hazards on P. 
americana  budwood (as in the commodity description) imported  to New Zealand. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 130 5.3.3  Risk assessment 
Biology and epidemiology of Colletotrichum spp. 
Hosts and geographical distribution 
The Colletotrichum  spp. assessed in this pest risk analysis have a wi de geographic and host range 
(Table 5-6).  
Symptoms 
Fruit anthracnose is the most common symptom of Colletotrichum infection (Dowling et al. 2020; 
Fuentes ‐Aragón et al. 2020). However, many species in the C. glorosporioides  species complex infect 
leaves, crowns, stems, twigs and petioles (Sharma e t al. 2017; Dowling et al. 2020). Infections of 
leaves, stems and twigs are commonly observed in ap ples and strawberries (Dowling et al. 2020). 
Symptom severity can vary among species within a sp ecies complex as well as among species 
complexes (Dowling et al. 2020). 
In P. americana (avocado), the Colletotrichum spp. assessed in this PRA commonly cause fruit 
anthracnose (Sharma et al. 2017; Fuentes ‐Aragón et al. 2020). Initial symptoms include small  
necrotic black spots (< 1mm) on the exocarp (i.e., outer layer of skin of fruit) (Velázquez-del Valle et 
al. 2016; Fuentes ‐Aragón et al. 2020). These black spots become large r and more sunken over time 
(Fuentes ‐Aragón et al. 2020). In some cases, an orange, pink  conidial mass will form on the surface 
of the lesions (Sharma et al. 2017). In severe infe ctions, fruit drop occurs in early fruit developmen t 
stages (Fuentes ‐Aragón et al. 2020). Symptoms on larger fruit reduc e the quality of the fruit which are 
not suitable for export (Fuentes ‐Aragón et al. 2020). 
In Israel, a study was conducted to determine Colletotrichum species associated with avocado trees 
(Sharma et al. 2017). Six orchards were surveyed fr om which 5 fruits, 5 twigs and 5 leaves were 
collected from each of 5 trees (450 samples). From these samples, 576 isolates of Colletotrichum 
species were collected. Of these isolates, 94.88% w ere isolated from fruit, 19.87% were isolated from 
green leaves, 18% from dry leaves and 10.93% from g reen twigs (Sharma et al. 2017). Low infection 
values of 0.9% were isolated from dry and dead twig  tissues (Sharma et al. 2017). Collected plant 
samples (fruit, fresh leaves, twigs) produced anthr acnose symptoms after 7–10 days when 
maintained under humid conditions (Sharma et al. 20 17). 
Inoculated avocado fruits produced necrotic lesions  at 4-days post inoculation (dpi) and the quality o f 
the fruits was visibly affected at 7 dpi (Fuentes ‐Aragón et al. 2020; Ayvar-Serna et al. 2021). 
Members of the C. gloeosporioides species complex appear to be more virulent than mem bers in 
other species complexes (i.e., the acutatum species complex), producing lesions between 29.1 mm  to 
34.6 mm in length (Fuentes ‐Aragón et al. 2020). Species in the gloeosporioides  complex tend to show 
high sporulation at 7 dpi in comparison to members in other complexes (Fuentes ‐Aragón et al. 2020). 
The majority of the Colletotrichum species assessed in this analysis have been recorde d to cause fruit 
rot in avocado (i.e., C. nymphaceae , C. tropicale , C. chrysophilum , C. endophyticum , C. jiangxiense ) 
(Shivas et al. 2016; Sharma et al. 2017; Vieira et al. 2017; Fuentes ‐Aragón et al. 2020). Two species, 
C. aenigma  (Sharma et al. 2017) and C. queenslandicum  (Shivas et al. 2016) have been recorded on 
stems, however, description of symptoms on stems is  lacking. Colletotrichum aenigma  has also been 
recorded producing leaf spots (Sharma et al. 2017).  
Latency of symptoms 
Symptoms do not always appear when plants are colon ised with Colletotrichum  species. For 
example, C. acutatum  has been observed germinating and sporulating on s ymptomless strawberry 
and blueberry leaves (Dowling et al. 2020). Symptom s can be delayed as survival of inoculum of the 
pathogen in the form of quiescent germinated appres soria on leaves and twigs may occur, especially 
during dry, summer seasons (Sharma et al. 2017). Qu iescent infections on immature fruit are also 
common (Dowling et al. 2020). Spores can remain dor mant on fruit surface until conditions that favour 
infection (Dowling et al. 2020).   
131 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Some Colletotrichum  spp. have the ability to be endophytic (e.g. C. endophyticum and C. tropicale ) 
(Rojas et al. 2010; Manamgoda et al. 2013), however  there is debate whether stem-end rot 
pathogens (i.e. anthracnose disease causing organis ms) are endophytes living in the stems, 
branches and pedicels of the avocado canopy which g row into the fruits (Hartill et al. 2002). It is mo st 
likely anthracnose pathogens are symptomless phello phytes (i.e. fungi growing in bark and phellem 
tissue) (Hartill et al. 2002). Endophytes would hav e the ability to grow down xylem elements whereas 
phellophytes would require to break through cell ba rriers before entering the xylem (Hartill et al. 
2002). In New Zealand, treatment of avocado fruit ( with their pedicel) with a systemic fungicide 
(Benlate) reduced fruit rot in comparison to fruit treated with a contact fungicide (Captan), suggesti ng 
a possibility that infections may be endophytic (Ha rtill et al. 2002). 
Reproduction and transmission 
Conidia of Colletotrichum species are transmitted via water-splash (Cannon et  al. 2012; Dowling et al. 
2020) and can be produced on all host tissues (Ploe tz 2003). Infection occurs via a germinating spore 
on the surface of a plant producing an appressorium  and germination is favoured by warm and moist 
conditions (Dowling et al. 2020). The appressorium penetrates the plant cuticle and sometimes 
epidermal cells of the plant (Cannon et al. 2012). For example, fruits are usually the main plant part  
that becomes infected, as recorded for C. acutatum (acutatum species complex) and infection usually 
occur after ripening when the appressorium penetrat es the host (Ploetz 2003). New leaf flushes also 
tend to be most susceptible (Ploetz 2003). 
There are slight differences between C. acutatum (within the acutatum species complex) and C. 
gloeosporioides  (within the gloeosporioides species complex) on their optimal growth temperatur es, 
infection, reproduction and overwintering (Table 5- 5). These species are used as representative of 
their species complexes (Dowling et al. 2020). 
Table 5-5: A comparison between Colletotrichum gloeosporioides  and C. acutatum  based on 
key characteristics of their life cycle and life st ages (adapted from Dowling et al. 2020). 
Species Colletotrichum gloeosporioides Colletotrichum acutatum 
Spread Rainsplash and wind Rainsplash 
Optimal temperature 30°C 25°C 
Infection Best known for infecting vegetative 
tissue but can also infect fruit Best known for infecting fruit but can 
also infect vegetative tissue 
Reproduction Both sexual and asexual stages found 
in the field Only asexual stage found in the field 
Overwintering On dead wood, plant debris and 
alternate hosts On mummified fruit, infected twigs and 
symptomless transplants 
In addition to overwintering on plant debris, conid ia may also lie dormant in the soil (EPPO 2021). It  is 
the sexual stage of Colletotrichum that occurs more frequently on plant debris (Dowlin g et al. 2020). 
Dead leaves within a tree canopy can be a main sour ce of inoculum, as described for C. 
gloeosporioides  (within the gloeosporioides species complex) (Jeffries et al. 1990). 
The majority of Colletotrichum species have a hemibiotrophic infection strategy: t he fungus develops 
biotrophic hyphae inside the host which later trans itions to necrotrophic secondary mycelia (Lu et al.  
2018). The biotrophic phase results in infected tis sue remaining externally symptomless (Cannon et 
al. 2012) and symptoms may only appear after harves t. 
5.3.4  Likelihood of entry 
Colletotrichum species have a wide distribution (Table 5-6). Speci es have been recorded in areas 
where avocado is produced including Australia (Weir  et al. 2012; Shivas et al. 2016), Mexico 
(Fuentes ‐Aragón et al. 2020), Israel (Sharma et al. 2017) an d Sri Lanka (Adikaram and Yakandawala 
2020). In these regions, Colletotrichum species cause fruit anthracnose. In Australia, C. 
queenslandicum  has caused stem dieback (Shivas et al. 2016). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 132 Infection of Colletotrichum  in avocado is mainly associated with fruit lesions  and necrosis (Fuentes ‐
Aragón et al. 2020), but has been isolated from lea ves, twigs and stems (Sharma et al. 2017; MPI 
2021). Therefore, Colletotrichum species could be associated with leafless, rootless  avocado 
budwood cuttings. 
Symptoms can be delayed as survival of inoculum of the pathogen in the form of quiescent 
germinated appressoria on leaves and twigs may occu r, especially during dry, summer seasons. Rain 
and elevated humidity increase levels of rot sympto ms (Sharma et al. 2017). For example, samples 
from different parts of avocado trees in orchards ( fruits, twigs and leaves) were collected and 
maintained in a moist chamber at room temperature ( 20–25° C); anthracnose symptoms were 
observed after 7–10 days under these humid conditio ns (Sharma et al. 2017). 
It is not known if any of the Colletotrichum species listed here could survive as endophytes on 
avocado budwood in PEQ without causing symptoms. So me of the species assessed here have been 
recorded as endophytes in other plant species. Colletotrichum tropicale has been recorded as an 
endophyte from a leaf of Theobroma cacao (Rojas et al. 2010). Colletotrichum endophyticum has also 
been recorded as an endophyte in the grass species Pennisetum purpureum (Manamgoda et al. 
2013).  Given the endophytic abilities of these Colletotrichum species on plants hosts other than 
avocado, there is some uncertainty regarding their endophytic capabilities in avocado budwood. 
Furthermore, depending on the temperature and relat ive humidity within PEQ, and in the absence of 
overhead irrigation to simulate rainfall, the appro priate environmental conditions for symptom 
development may be absent throughout the entire PEQ  period. However, it has been recorded that 
new leaf flushes tend to be the most susceptible to  infection (Ploetz 2003).  
The routine surface disinfection of budwood enterin g PEQ (dipping in 1% sodium hypochlorite for 2 
minutes) will reduce the surface population of the Colletotrichum species but is not likely to completely 
eliminate it, especially if fungi are located deep within crevices of buds. Furthermore, some 
Colletotrichum species seem to only express symptoms when fruits b egin to ripen on plants (Sharma 
et al. 2017). Therefore, it is possible that a smal l population of fungi may survive asymptomatically 
throughout the PEQ period and enter New Zealand.  
Given the arguments and evidence above, that is:  
• Colletotrichum infection under the right conditions (in a moist ch amber at room temperature 
20–25° C) can produce symptoms in a few days (Sharma  et al. 2017), but 
• uncertainty around the endophytic capabilities of some Colletotrichum species in P. 
americana budwood may allow asymptomatic Colletotrichum infection during the PEQ period, 
the likelihood of Colletotrichum  species entering New Zealand associated with P. americana  budwood 
is considered to be low, with moderate uncertainty.  
5.3.5  Likelihood of exposure 
This assessment is made on the basis that Colletotrichum species have entered New Zealand 
undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for Colletotrichum 
species.   
If avocado plants are infected with Colletotrichum  at the time of their release from PEQ they will be  
planted in New Zealand or used to propagate new pla nts for planting (see section 2.3 for additional 
information about exposure).  
Given the arguments and evidence above, the likelih ood of exposure of Colletotrichum  in 
New Zealand from P. americana  budwood is considered to be high, with low uncerta inty.  
133 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.3.6  Likelihood of establishment 
This assessment is made on the basis that Colletotrichum species have been successfully exposed to 
a suitable host plant in the New Zealand environmen t. 
Colletotrichum  has a broad host range (Table 5-6) and many of its  hosts are either grown 
commercially in New Zealand (e.g., kiwifruit, apple s, strawberries, grapes) or as backyard plants in 
many home gardens. Therefore, hosts for the establi shment of Colletotrichum  are readily available. 
Colletotrichum  species are also found across a broad geographic r ange from countries (Table 5-6) 
that have a similar climate to the whole of New Zea land, as well as to the Auckland and Northland 
regions, as indicated by a climate match index of ≥0.7 (Phillips et al. 2018). For example, seasonal 
climate ellipses show considerable overlap between avocado growing areas in Mexico, Israel and 
New Zealand, although Mexico sites have overall war mer average monthly temperatures (Halloy 
2021). Therefore, climate suitable for the establis hment of the Colletotrichum  is readily available, 
especially in the north of the North Island. In add ition, because wetter conditions favour the 
establishment of Colletotrichum species (Sharma et al. 2017), and conditions in New  Zealand are 
wetter, on average, compared to those of Mexico and  Israel (Halloy 2021), New Zealand conditions 
are likely to be more favourable for the establishm ent of the Colletotrichum species. 
Given the arguments and evidence above, that is: 
• hosts (in the form of cultivated avocados and othe r cultivated crops) are available for the 
establishment of Colletotrichum  species 
• suitable climate (Table 5-6) is available for the establishment of Colletotrichum (Phillips et al. 
2018) 
the likelihood of Colletotrichum  establishing in New Zealand is considered to be hi gh, with low 
uncertainty. 
Table 5-6: Geographic and host range of Colletotrichum  spp. Climate match index (CMI) ≥ 0.7 
indicates countries with a similar climate to the w hole of the New Zealand (Phillips et al. 2018). 
Region Country CMI Species 
complex Species Host Reference 
Africa Kenya  0.4–0.8  acutatum C. nymphaeae Fragaria vesca Damm et al. (2012) 
South 
Africa  0.5–0.9  acutatum C. nymphaeae Fragaria x ananassa Damm et al. (2012) 
Protea cynaroides Damm et al. (2012) 
Protea magnifica Damm et al. (2012) 
Protea repens Damm et al. (2012) 
Zimbabwe  0.5–0.7  acutatum C. nymphaeae Capsicum annuum  Damm et al. (2012) 
Asia China 0.4–0.9 acutatum C. nymphaeae Fragaria sp. Dowling et al. (2020) 
gloeosporioides C. aenigma Malus sp. Dowling et al. (2020) 
Fragaria sp. Dowling et al. (2020) 
Vitis sp. Dowling et al. (2020) 
C. tropicale Coffea arabica Cao et al. (2019) 
Areca catechu Cao et al. (2020) 
C. endophyticum Camellia sinensis Wang et al. (2016) 
Mangifera indica Li et al. (2019) 
C. jiangxiense Camellia sinensis Liu et al. (2015) 
India  0.2–0.5  acutatum C. nymphaeae Pelargonium graveolens Damm et al. (2012) 
Indonesia  0.3–0.6  acutatum C. nymphaeae Capsicum sp. Damm et al. (2012) 
Japan  0.6–0.8  gloeosporioides C. aenigma Pyrus pyrifolia Weir et al. (2012) Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 134 Region Country CMI Species 
complex Species Host Reference 
Malus sp. Dowling et al. (2020) 
Fragaria sp. Dowling et al. (2020) 
C. tropicale Litchi chinensis Weir et al. (2012) 
acutatum C. nymphaeae Malus sp. Dowling et al. (2020) 
Vaccinium corymbosum Dowling et al. (2020) 
Korea 0.6–0.7 acutatum C. nymphaeae Malus sp. Dowling et al. (2020) 
Philippines  0.3–0.6  gloeosporioides C. tropicale Mangifera indica Dela Cueva et al. 
(2021) 
Sri Lanka  0.4–0.6  acutatum C. nymphaeae Hevea brasiliensis Adikaram and 
Yakandawala (2020) 
gloeosporioides C. endophyticum Persea americana Adikaram and 
Yakandawala (2020) 
Thailand  0.3–0.5  acutatum C. nymphaeae Leaf litter Damm et al. (2012) 
gloeosporioides C. endophyticum Pennisetum purpureu m Manamgoda et al. 
(2013) 
Central 
America Costa Rica 0.3–0.6 acutatum C. nymphaeae Fragaria sp. Dowling et al. (2020) 
Cuba  0.5  gloeosporioides C. tropicale Annona cherimola Garcia and Manzano 
(2017) 
Panama  0.4–0.6  gloeosporioides  C. tropicale  Theobroma cacao Rojas et al. (2010) 
Trichilia tuberculata Rojas et al. (2010) 
Viola surinamensis Rojas et al. (2010) 
Cordia aliodora Rojas et al. (2010) 
Annona muricata Rojas et al. (2010) 
C. chrysophilum Genipa americana Vieira et al. (2017) 
Theobroma sp. Vieira et al. (2017) 
Puerto Rico  0.5–0.6  gloeosporioides C. chrysophilum Mycopteris taxifol ia Vieira et al. (2017) 
Europe Belgium 0.9 acutatum C. nymphaeae Malus sp. Dowling et al. (2020) 
Fragaria sp. Dowling et al. (2020) 
Bulgaria  0.8–0.9  acutatum C. nymphaeae Fragaria x ananassa  Damm et al. (2012) 
France  0.9  acutatum C. nymphaeae Fragaria x ananassa Damm et al. (2012) 
Italy  0.7–0.9  acutatum C. nymphaeae Anemone  sp. Damm et al. (2012) 
Fragaria x ananassa Damm et al. (2012) 
Mahonia aquifolium Damm et al. (2012) 
Netherlands  0.9  acutatum C. nymphaeae Anemone  sp. Damm et al. (2012) 
Anemone coronaria  Damm et al. (2012) 
Fragaria x ananassa Damm et al. (2012) 
Nuphar luteum Damm et al. (2012) 
Nymphaea alba Damm et al. (2012) 
Oenothera sp. Damm et al. (2012) 
Phaseolus sp. Damm et al. (2012) 
Portugal 0.8–0.9  acutatum C. nymphaeae Olea europaea Damm et al. (2012) 
Fragaria sp. Dowling et al. (2020) 
Spain  0.7–0.9  acutatum C. nymphaeae Fragaria x ananassa Damm et al. (2012)  
135 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Region Country CMI Species 
complex Species Host Reference 
Switzerland 0.7–0.9 acutatum C. nymphaeae Fragaria sp. Dowling et al. (2020) 
United 
Kingdom  0.8–0.9  acutatum C. nymphaeae Fragaria vesca Damm et al. (2012) 
Photinia sp. Damm et al. (2012) 
gloeosporioides C. aenigma Fragaria sp. Dowling et al. (2020) 
Middle 
East Iran 0.4–0.8 acutatum C. nymphaeae Fragaria sp. Dowling et al. (2020) 
Israel 0.5–0.7  acutatum  C. nymphaeae Anemone  sp. Damm et al. (2012) 
Fragaria x ananassa Damm et al. (2012) 
gloeosporioides C. aenigma Persea americana Sharma et al. (2017) 
C. chrysophilum Persea americana Sharma et al. (2017); 
Khodadadi et al. 
(2020) 
C. nymphaeae Fragaria x ananassa Damm et al. (2012) 
North 
America Canada  0.2–0.9  acutatum C. nymphaeae Leucaena sp. Damm et al. (2012) 
Mexico  0.3–0.8  acutatum C. nymphaeae Persea americana Fuentes ‐Aragón et al. 
(2020) 
C. tropicale Origanum vulgare Ayvar-Serna et al. 
(2020) 
gloeosporioides C. tropicale Persea americana Fuentes ‐Aragón et al. 
(2020) 
C. chrysophilum Persea americana Fuentes ‐Aragón et al. 
(2020) 
C. jiangxiense Persea americana Fuentes ‐Aragón et al. 
(2020) 
C. nymphaeae Fragaria sp. Damm et al. (2012) 
USA  0.5–0.8  acutatum C. nymphaeae Malus sp. Dowling et al. (2020) 
Prunus persica  Dowling et al. (2020) 
Fragaria sp. Dowling et al. (2020) 
gloeosporioides C. chrysophilum Malus domestica Khodadadi et al. 
(2020) 
C. tropicale Malus sp. Dowling et al. (2020) 
C. nymphaeae Protea sp. Damm et al. (2012) 
C. nymphaeae Fragaria sp. Shivas and Tan 
(2009) 
gloeosporioides  C. 
queenslandicum Carica papaya Weir et al. (2012) 
Carica sp. Weir et al. (2012) 
Persea americana Weir et al. (2012) 
Fiji 0.4  acutatum  C. tropicale Annona sp. Costa et al. (2019) 
gloeosporioides  C. 
queenslandicum Coffea sp. Weir et al. (2012) 
South 
America Brazil 0.4–0.9  gloeosporioides C. chrysophilum Musa sp. Vieira et al. (2017) 
acutatum C. nymphaeae Vitis sp. Dowling et al. (2020) 
Malus pumila Damm et al. (2012) 
Colombia 0.3–0.8 acutatum C. nymphaeae Fragaria sp. Dowling et al. (2020) Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 136 5.3.7  Impacts in New Zealand 
Many Colletotrichum species in the acutatum , boninense  and  gloeosporioides species complexes are 
already present in New Zealand (e.g., C. alienum , C. aotearoa , C. cigarro , C. fioriniae , C. fructicola , 
C. karstii , C. perseae  and C. siamense ) (Hofer et al. 2021). These species have been isol ated from 
avocado producing fruit staining symptoms known as “tannin stain” (Hofer et al. 2021). In addition, C. 
acutatum and C. glorosporioides  have been known to occur in avocado orchards since  the 1980s 
causing anthracnose in fruit (Hartill 1991). These Colletotrichum species are also successful 
postharvest pathogens because of latent infections;  the majority of infection occurs while fruit is 
stored or is on market shelves (Dean et al. 2012). 
Management of Colletotrichum in avocado orchards are in place, however, species have different 
sensitivities to fungicides (Hartill 1991; Hofer et  al. 2021). For example, benomyl is effective again st 
C. gloeosporioides  but not C. acutatum  (Hartill 1991; Everett and Korsten 1998). In New Z ealand, a 
combination of copper fungicide sprays and periodic  removal of dead branches and twigs within the 
canopy of orchards decreases the overall incidence of postharvest rots of avocado (Hartill 1991). 
Economic impacts 
Given the broad host range of the Colletotrichum  species in this assessment, it is likely that avoc ados 
would not be the only commercially produced hosts a ffected by these pathogens (Table 5-6). 
Outbreaks of these species can be devastating. For example, bitter-rot of apple caused by C. 
acutatum and C. gloeosporioides species complexes can result in the loss of up to 5 0% of crops in 
optimal conditions (González and Sutton 2004; Dowli ng et al. 2020). In some cases, greater than 75% 
tree defoliation is observed by harvest time which weakens trees and reduces yield (González and 
Sutton 2004). Before the use of synthetic fungicide s, a bitter-rot outbreak in the United States resul ted 
in losses of $400 million (in today’s currency) (Do wling et al. 2020). Similarly, epidemics of C.  
acutatum causing anthracnose in strawberries has been observ ed in Florida and North Carolina (Delp 
1980), Israel (Freeman and Katan 1997), Brazil (Hen z 1991) and Bulgaria (Jelev et al. 2008). In 
Bulgaria, disease incidence reached 90% in some reg ions and percentage of diseased plants 
averaged 50% in some fields (Jelev et al. 2008). So me of these outbreaks have occurred despite the 
use of fungicide control measures (Dowling et al. 2 020). 
Colletotrichum acutatum is present in New Zealand (Biota NZ 2022) but other  species in the acutatum 
species complex that are assessed here have also be en recorded on strawberries and are not 
present in New Zealand (e.g. C. nymphaeae ). Some Colletotrichum  species are resistant to specific 
fungicides and in some cases, fungicide resistance limits chemical management options for diseases 
caused by Colletotrichum species (Dowling et al. 2020); this fungicide resis tance has mainly been 
observed in the USA with C. acutatum  (EPPO 2021). However, there is variability among s pecies 
even within the same species complex. For example, C. nymphaeae  (C. acutatum species complex) 
show moderate sensitivity to benomyl fungicide in c ulture (i.e., percentage of mycelial growth 
inhibition ranged from 33–71%) whereas species with in the C. gloeosporioides species complex (not 
those assessed in this PRA) show high sensitivity t o benomyl fungicide (i.e., percentage of mycelial 
growth inhibition is > 94%) (Moral et al. 2021). A captan-benomyl mixture has been used in strawberry 
crops in New Zealand (EPPO 2021) indicating that so me species of Colletotrichum  assessed in this 
PRA may have varying responses to fungicides used i n New Zealand. 
Specifically in avocados, 90% of avocado trees in b ackyards in the Leonardo Bravo municipality in 
Guerrero, Mexico had symptoms of fruit anthracnose caused by C. jiangxiense  (Ayvar-Serna et al. 
2021). Anthracnose outbreaks occur annually in Mexi co, mainly in areas of high relative humidity and 
temperatures (Fuentes ‐Aragón et al. 2020). 
In 2020, the export value for apples was $876.3 mil lion with a much smaller proportion sold 
domestically (Plant & Food Research 2020). The expo rt values for avocado was $112.3 million and 
the domestic value was $50.6 million (Plant & Food Research 2020). Strawberries had an export 
value of $6.2 million and a domestic value of $27.5  million (Plant & Food Research 2020). The 
Colletotrichum species assessed in this document are not listed as  a quarantine pest according to the 
importing countries phytosanitary requirements (ICP R) and thus there would be no immediate impacts 
on export pathways.  
137 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Given the arguments and evidence above, that is: 
• some species in both C. acutatum and C. gloeosporioides  species complexes are already 
present in New Zealand and cause anthracnose sympto ms (Hofer et al. 2021), 
• appropriate in-field fungicides and management opt ions are used in New Zealand to 
control for anthracnose symptoms (Hartill 1991), 
• fungicide resistance has been reported for some Colletotrichum species (Dowling et al. 
2020; Hofer et al. 2021) and C. nymphaceae demonstrate moderate sensitivity to 
benomyl fungicide, 
• the host range of Colletotrichum indicates not only the avocado but also the apple a nd 
strawberry industry could be affected which togethe r are valued at $1.07 billion (sum of 
both domestic and export),  
the economic impact of Colletotrichum  to New Zealand is considered to be moderate, with low 
uncertainty. 
Environmental impacts 
It is unknown if any of the Colletotrichum species assessed here have known native New Zealand  
plant hosts. However, other species in the acutatum and gloeosporioides species complexes are 
known to associate with native New Zealand plant sp ecies. For example, C. acutatum  has been 
isolated from Coprosma lucida and Coprosma macrocarpa (Biota NZ 2022). Colletotrichum 
gloeosporioides has been isolated from Kunzea ericoides  as a leaf endophyte (Biota NZ 2022). 
Given the possibility of Colletotrichum species living as pathogens, saprotrophs and endoph ytes on 
plants and in the soil, this group of fungi could h ave a wide range of environmental impacts. Living a s 
endophytes in native hosts may allow Colletotrichum to survive before spilling over into economically 
important crop species or vice versa (Power and Mit chell 2004). 
Given the arguments and evidence above, the impact on the environment from the establishment of 
Colletotrichum  in New Zealand is considered to be low, with moder ate uncertainty. 
Human health impacts 
There has been one record of a Colletotrichum species in the gloeosporioides  species complex with 
the potential to cause human health impacts. The st udy demonstrated, in mice, that Camellia sinensis  
infected with the endophyte Colletotrichum gloeosporioides  damaged renal function and that 
increased attention is needed in tea processing (Li  et al. 2017). However, there is no evidence that 
the Colletotrichum species assessed here cause human health impacts. 
Given the arguments and evidence above, the human h ealth impact of Colletotrichum  to New Zealand 
is considered to be negligible, with low uncertaint y. 
Sociocultural impacts 
Anthracnose diseases caused by Colletotrichum  species are mostly evident after harvest and in 
storage and on shelves in markets (Dean et al. 2012 ). If left unmanaged Colletotrichum  infected fruits 
could cause declines in edible fruit in markets. Av ocado has become popular and is widely consumed 
in New Zealand. It is commonly grown in home garden s in some parts of the country. A similar impact 
could be seen in apples and strawberries. 
Given the arguments and evidence above, the sociocu ltural impact of Colletotrichum to New Zealand 
is considered to be low, with low uncertainty. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, human health and society is 
considered to be moderate, with moderate uncertaint y. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 138 5.3.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is low 
• assuming entry, the likelihood of exposure is high  
• assuming successful exposure, the likelihood of es tablishment is high 
• the overall impact on the New Zealand economy, env ironment, human health and society 
is considered to be moderate 
the overall level of assessed risk to New Zealand f rom Colletotrichum  on imported Persea americana 
budwood (as in the commodity description) is consid ered to be moderate, with moderate uncertainty. 
5.3.9  Management considerations 
Colletotrichum spp. cause fruit anthracnose in P.a americana (avocado). Initial symptoms include 
small necrotic black spots (< 1mm) on the exocarp ( i.e., outer layer of skin of fruit) (Velázquez-del 
Valle et al. 2016; Fuentes ‐Aragón et al. 2020). These black spots become large r and more sunken 
over time (Fuentes ‐Aragón et al. 2020). In some cases, an orange, pink  conidial mass will form on the 
surface of the lesions (Sharma et al. 2017). In sev ere infections, fruit drop occurs in early fruit 
development stages (Fuentes ‐Aragón et al. 2020). Symptoms on larger fruit reduc e the quality of the 
fruit which are not suitable for export (Fuentes ‐Aragón et al. 2020). Colletotrichum aenigma  has also 
been recorded producing leaf spots (Sharma et al. 2 017). 
Many species in the C. glorosporioides  species complex infect leaves, crowns, stems, twig s and 
petioles (Dowling et al. 2020) and thus, lesions ma y appear on these plant parts; however, there is 
limited evidence of these symptoms on avocado. 
Rain and elevated humidity increase levels of rot s ymptoms (Sharma et al. 2017). High temperatures 
(i.e. 25 – 30° C) are also optimal for Colletotrichum growth (Dowling et al. 2020). 
PCR tests are readily available for Colletotrichum species. The ITS gene region, commonly used for 
fungal identification, can distinguish among Colletotrichum species complexes; however, specific 
species identification is difficult and requires a multigene sequencing approach (Shivas et al. 2016; 
Dowling et al. 2020). Shivas et al. (2016) highligh ts specific primers that cover four gene regions us ed 
to identify individual Colletotrichum species. 
5.3.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Many species in the C. glorosporioides  species complex infect leaves, crowns, stems, twig s and 
petioles (Dowling et al. 2020) and thus, lesions ma y appear on these plant parts; however, there is 
limited evidence of these symptoms on avocado.  Colletotrichum aenigma  has been recorded 
producing leaf spots (Sharma et al. 2017).  Symptom s are most likely to appear of fruit, which are 
unlikely to be present on plants in PEQ. 
o What are the known environmental conditions conduci ve to symptom expression? 
Rain and elevated humidity increase levels of rot s ymptoms (Sharma et al. 2017). High temperatures 
(i.e. 25 – 30° C) are also optimal for Colletotrichum growth (Dowling et al. 2020). 
What are the limitations to taking samples for pote ntial testing?  
139 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Fruit is most commonly associated with Colletotrichum infections; however, this pathogen has been 
isolated from leaves, twigs and stems of avocado (S hivas et al. 2016; Sharma et al. 2017). Sharma et 
al. (2017) collected samples from these areas of th e plant, many of which were asymptomatic. These 
samples were placed in a moist chamber at room temp erature where they were inspected for the 
appearance of anthracnose symptoms (Sharma et al. 2 017). Anthracnose symptoms were observed 
after 7–10 days in the collected fruits, leaves and  twigs maintained under these humid conditions 
(Sharma et al. 2017). 
o What is the optimum season for conducting detection  testing? 
Optimum season would be during warm (i.e., 25–30° C) , humid periods which provide the optimal 
conditions for the growth of Colletotrichum  
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143 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.4  Clonostachys pseudochroleuca (avocado branch dieback and wilting)  
Clonostachys pseudochroleuca is a fungus that is associated with a wide range of  plants and 
environments. It is commonly found as a saprotroph or endophyte but has been recorded as a 
pathogen in avocado, vectored by ambrosia beetles, causing avocado branch dieback and wilting. 
5.4.1  Taxonomic description 
Scientific name: Clonostachys pseudochroleuca Schroers (2001) 
Order/Family: Hypocreales/Bionectriaceae 
Other names include : Bionectria pseudochroleuca  Schroers & Samuels (2001) 
Taxonomic notes: Bionectria pseudochroleuca is the teleomorph and Clonostachys 
pseudochroleuca  is the anamorph stage. Clonostachys pseudochroleuca is the preferred name 
(Robert et al. 2005; Rossman et al. 2013). 
5.4.2  Hazard identification 
Clonostachys pseudochroleuca is not known to be present in New Zealand: 
• Clonostachys pseudochroleuca is not listed in either Biota NZ (2022), NZOR (2021 ) or PPIN 
(2021). 
• Clonostachys pseudochroleuca is not listed in ONZPR (2021). 
Clonostachys pseudochroleuca  has the potential to establish (and spread) in New  Zealand because: 
• Persea americana  (avocado) is a known host (Burbano-Figueroa et al.  2018) that is widely 
grown in New Zealand, in home gardens and commercia l production, mainly in the north of 
the North Island. 
• Clonostachys pseudochroleuca  causes branch dieback and wilting in tropical and subtropical 
regions in Columbia (Burbano-Figueroa et al. 2018).  Regions in Columbia have a climate 
match index (CMI) ≥ 0.7 indicating a similar climate to the whole of N ew Zealand (Phillips et 
al. 2018).  
• Clonostachys pseudochroleuca  is vectored by Xylosandrus morigerus , Xyleborus volvulus , 
and Premnobius cavipennis  (Burbano-Figueroa et al. 2020), none of which are present in 
New Zealand. However, other species in Xylosandrus  are present in New Zealand, such as 
the recently established X. crassiusculus  (Ministry for Primary Industries 2020). However, i t is 
not known whether X. crassiusculus  is a vector for C. pseudochroleuca as this ambrosia 
beetle has not been recovered from infected trees. 
Clonostachys pseudochroleuca  has the potential to cause harm to New Zealand bec ause: 
• Clonostachys pseudochroleuca  and their associated ambrosia beetles  cause avocado branch 
dieback and wilting (Burbano-Figueroa et al. 2018).  Infection by C. pseudochroleuca  is 
associated with ambrosia beetle entry points and ga lleries which result in damage and 
discolouration on branches and trunks of avocado tr ees and wilting of trees. 
• avocados are an important commercial crop in New Z ealand. In the 2019–2020 financial year, 
export sales of fresh avocados earned NZ$112.3 mill ion and domestic sales earned NZ$50.6 
million (Plant & Food Research 2020). 
Clonostachys pseudochroleuca  is associated with Persea americana  budwood because: 
• Persea americana  is a known host of Clonostachys pseudochroleuca  (Burbano-Figueroa et 
al. 2018); 
• Clonostachys pseudochroleuca  infects branches and stems of P. americana . Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 144 Given the arguments and evidence above, Clonostachys pseudochroleuca  meets the criteria to be a 
hazard on Persea americana  budwood (as in the commodity description) imported  to New Zealand. 
5.4.3  Risk assessment 
Biology and epidemiology of Clonostachys pseudochro leuca 
Host range 
Species of Clonostachys are common soil inhabitants, plant decomposers and endophytes found in 
tropical and subtropical regions (Abreu et al. 2014 ). Some members are also antagonists of other 
fungi and oomycetes including Botrytis cinerea , Fusarium oxysporum , Rhizoctonia solani , 
Phytophthora palmivora  and Pythium ultimum  (Abreu et al. 2014). Selected strains of Clonostachys  
have been developed as biocontrol agents on a comme rcial scale (Abreu et al. 2014). 
Clonostachys pseudochroleuca  (teleomorph: Bionectria pseudochroleuca ) is a common soil fungus 
but has been isolated as a pathogen (Burbano-Figuer oa et al. 2018), endophyte (da Silva et al. 2021), 
saprotroph (Schroers 2001; Moreira et al. 2016; Hua nraluek et al. 2020) and mycoparasite (da Silva 
et al. 2021) on a variety of hosts (Huanraluek et a l. 2020) (Table 5-7). 
Burbano-Figueroa et al. (2018) recorded Clonostachys pseudochroleuca  as pathogenic on avocado 
(West-Indian race, Persea americana var. americana ) causing avocado branch dieback and wilting 
disease in association with ambrosia beetles. This fungus has  been recorded as a pathogen on 
avocado only (Burbano-Figueroa et al. 2018); it is more commonly attributed to saprotrophic or 
endophytic habitats in other hosts (Schroers 2001) (Table 5-7).  
Table 5-7: Known host range and geographic distribu tion of Clonostachys pseudochroleuca 
Continent Country Host Plant part  CMI Reference 
Asia Thailand Prunus  sp. Dead branch 0.3-0.5 Huanraluek et al. (2020) 
South 
America Brazil Soil - 0.3-0.9 Moreira et al. (2016) 
Brazil Phoradendron perrottetii  0.3-0.9 da Silva et al. (2021) 
Brazil Lychnophora pinaster  0.3-0.9 da Silva et al. (2021) 
Brazil Solanum tuberosum  0.3-0.9 Abreu et al. (2014) 
Brazil Saccharum officinarum  0.3-0.9 Abreu et al. (2014) 
Colombia Persea americana  Trunk and 
branches 0.3-0.8 Burbano-Figueroa et al. 
(2018) 
French Guiana Palm tree Palm sheathing 
base 0.4 Schroers (2001) 
French Guiana Decaying wood  0.4 Schroers (2001) 
French Guiana  Hypoxylon  sp.  0.4 Schroers (2001) 
Guyana  Mauritia  sp. Decaying trunk 0.4-0.6 Schroers (2001) 
Peru Vitis vinifera Rootstock 0.4-0.8 Torcato et al. (2020) 
Peru Vaccinium corymbosum Twigs and stems 0.4-0.8 Torcato et al. (2020) 
Venezuela Palm tree Sheath 0.3-0.8 Schroers (2001) 
Oceania Papua New Guinea Soil  0.3-0.7 Schroers (2001) 
Australia - - 0.4-1 Schroers (2001) 
Central 
America Puerto Rico  Guarea sp Bark of dead tree 0.5-0.6 Schroers (2001) 
Puerto Rico  Nectriopsis sp. Bark 0.5-0.6 Schroers (2001)  
145 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Vectors 
Clonostachys pseudochroleuca  infection in avocado is associated with and vector ed by ambrosia 
beetles including Xylosandrus morigerus , Xyleborus volvulus , and Premnobius cavipennis  (Burbano-
Figueroa et al. 2020). These ambrosia beetles are c ommonly associated with forests and agroforestry 
habitats in the Neotropics (Burbano-Figueroa et al.  2020) and are not present in New Zealand (NZOR 
2021; PPIN 2021; Biota NZ 2022). Xylosandrus morigerus is regulated and an unwanted pest in New 
Zealand (ONZPR 2021). Other species in Xylosandrus  are present in New Zealand, such as the 
recently established X. crassiusculus  (Ministry for Primary Industries 2020). However, i t is not known 
whether X. crassiusculus  is a vector for C. pseudochroleuca as this ambrosia beetle has not been 
recovered from infected trees.  
Symptoms 
Clonostachys pseudochroleuca causes avocado branch dieback and wilting (Figure 5 -1). Avocado 
trees exhibit signs of damage by boring insects in trunks and branches, in addition to branch dieback 
and wilting (Burbano-Figueroa et al. 2020). White p owdery exudate is observed on the outer bark 
associated with beetle holes on the trunk and main branches of trees (Burbano-Figueroa et al. 2018). 
In old trees (> 15 m height), black gum pitchout is  observed: black exudate covers entire branches 
and sometimes entire trunks (Burbano-Figueroa et al . 2018; Burbano-Figueroa et al. 2020). Older 
trees also demonstrate brown discoloration of bark surrounding ambrosia beetle galleries (Burbano-
Figueroa et al. 2020). Wood under exit holes of gal leries reveal brown necrosis (Burbano-Figueroa et 
al. 2018). Both adults and larvae of the above ment ioned ambrosia beetles are found inside the borer 
galleries (Burbano-Figueroa et al. 2018).  
 
Figure 5-1: Symptoms associated with avocado branch  dieback and wilting. A) Multiple 
ambrosia beetle entry points and white exudate (per seitol production) in a trunk. B) Black 
pitch (black exudate) on trunk of tree which is ind icative of multiple exposures to beetles and 
fungal infection. C, D, E) Production of perseitol and evidence of ambrosia entry points in 
young trees. Photo is sourced and permission grante d from Oscar Burbano-Figueroa 
(Burbano-Figueroa et al. 2020). 
Burbano-Figueroa et al. (2018) re-inoculated 6-mont h old avocado seedlings with C. pseudochroleuca  
isolated from diseased trees in their initial surve ys by wounding seedlings and placing mycelial plugs  
into the wounds (Burbano-Figueroa et al. 2018). Exp anding lesions were observed within a month on 
all inoculated seedlings (Burbano-Figueroa et al. 2 018). It is most likely the combined effects of the  
fungus and ambrosia beetles that cause dieback and wilting in avocado plants. The ambrosia beetles 
listed above (especially X. morigerus ) are significant pests of crop and ornamental tree s (CABI 2021). 
Xylosandrus volvulus  and P. cavipennis  have been associated with wilting and dieback in p lantations 
of Tectona grandis (teak) (Burbano-Figueroa et al. 2020).  
Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 146 Reproduction and transmission 
Clonostachys pseudochroleuca produces ascospores (i.e. sexual spores of Ascomyco ta) and conidia 
(i.e. asexual spores) (Schroers 2001). Conidiophore s (i.e. structure producing conidia) were not 
observed on natural substratum but have been observ ed in culture; the anamorph (i.e. asexual stage) 
is mainly associated with soil substrates (Schroers  2001). In comparison, teleomorph specimens (i.e., 
sexual stage) are found on natural substrates such as decaying plant material or bark of dead trees. 
There is no evidence of C. pseudochroleuca  producing chlamydospores (i.e., thick-walled long lived 
spores able to survive adverse environmental condit ions). The most widely studied species, 
Clonostachys rosea , is a species in this genus that is known to produ ce chlamydospores under harsh 
environments such as unfavourable pH and low temper atures (Sun et al. 2020). There was no 
evidence in the literature on whether other species  in this genus can produce chlamydospores. 
The main mode of transmission is through ambrosia b eetles as described above (Burbano-Figueroa 
et al. 2020). Clonostachys pseudochroleuca  is an ambrosia fungus and infection in avocado has  not 
been found without the presence of ambrosia beetle galleries (Burbano-Figueroa, pers. comm). 
In culture, optimum growth temperatures for C. pseudochroleuca  is between 24-30° C (Schroers 
2001). Environmental models indicate disease expres sion is favoured when the mean diurnal range in 
temperature is higher than 10° C and temperatures in  the wettest quarter of the year are 22.5° C 
(Burbano-Figueroa et al. 2020). Disease suitability  is also highest in areas with variations in monthl y 
precipitation of 70%, low precipitation (200 mm) in  the wettest month and no precipitation in the drie st 
quarter of the year (Burbano-Figueroa et al. 2020).  Disease suitability decreases sharply when 
precipitation increases in either the wettest month  or driest quarter (Burbano-Figueroa et al. 2020). 
Disease does not occur in areas with precipitation in the wettest month and driest quarter is greater 
than 600 mm (Burbano-Figueroa et al. 2020). It is l ikely that severe droughts would trigger disease 
events; drought events provoke water related-stress  in trees which favour attacks of pathogens and 
pests, including ambrosia beetles (Burbano-Figueroa  et al. 2020; Reverchon et al. 2021). 
5.4.4  Likelihood of entry 
Clonostachys pseudochroleuca  has a wide distribution in subtropical and tropica l areas where 
avocado is produced (Table 1). However, the avocado  branch dieback and wilting disease it causes 
has only been recorded in Colombia (Burbano-Figuero a et al. 2018). 
Infection of C. pseudochroleuca  is associated with ambrosia beetle infestation and  is associated with 
beetle galleries (Burbano-Figueroa et al. 2018). Clonostachys pseudochroleuca has been isolated 
from branches and trunks of avocado trees inside th ese galleries (Figure 1). Avocado seedlings 
inoculated with C. pseudochroleuca  through wounds also resulted in lesions on branche s (Burbano-
Figueroa et al. 2018). Therefore, the fungus could be associated with leafless, rootless avocado 
budwood cuttings.  
Clonostachys pseudochroleuca  is an ambrosia fungus and infection in avocado has  not been found 
without the presence of ambrosia beetle galleries ( Burbano-Figueroa, pers. comm). Ambrosia fungi 
depend on and are cultivated by ambrosia beetles (R everchon et al. 2021). Therefore, if avocado 
budwood cuttings have an established C. pseudochroleuca  infection, it is likely that beetle galleries 
will be detected, and infected material removed or destroyed, during phytosanitary inspections on 
arrival in New Zealand.  
The routine surface disinfection of budwood enterin g PEQ (dipping in 1% sodium hypochlorite for 2 
minutes) will most likely not eliminate infection, given the fungus will be associated with beetle 
galleries where the surface disinfection may not re ach. 
As part of the commodity description, all imported avocado germplasm will undergo a growing period 
of active growth with a minimum of three distinct p henological growing events referred to as ‘shoot 
flush’ in 3A PEQ. This period in 3A PEQ will impact  on likelihood of entry in the following manner:  
147 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • ambrosia beetle galleries will be visible during i nspection and thus infected budwood would 
be detected and destroyed before plants are release d from PEQ. 
• Clonostachys pseudochroleuca  is spread by ambrosia beetles (Burbano-Figueroa et  al. 
2018). Budwood will be treated with miticides and i nsecticides (see section 2.2). Furthermore, 
Level 3A PEQ has measures in place to manage the ri sks associated with insects, 
wastewater, waste and accidental transfer (see sect ion 2.3), therefore ambrosia beetles 
carrying C. pseudochroleuca  are highly unlikely to escape level 3A PEQ to infe ct a suitable 
host. 
Therefore, if C. pseudochroleuca  is imported on avocado, the residual biosecurity r isks are likely to be 
managed by the growing period of active growth with  a minimum of three distinct phenological 
growing events referred to as ‘shoot flush’ in 3A P EQ. 
Given the arguments and evidence above, that is:  
• established C. pseudochroleuca  infections are highly likely to be detected, and i nfected 
material removed or destroyed, during preparation f or export, in phytosanitary inspections 
pre-export or on arrival in New Zealand; 
• residual biosecurity risks from ambrosia entry poi nts or recent infections on the surface of 
avocado budwood are likely to be managed by the gro wing period of active growth with a 
minimum of three distinct phenological growing even ts referred to as ‘shoot flush’ in 3A PEQ 
o symptoms in inoculated plants are observed within one month after inoculation; 
the likelihood of Clonostachys pseudochroleuca  entering New Zealand associated with Persea 
americana  budwood is considered to be negligible, with low u ncertainty. 
Therefore,  further assessment is considered unnece ssary at this time, and likelihoods of exposure 
and establishment, and impacts to New Zealand were not assessed. 
5.4.5  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood above, that:   
• the likelihood of C. pseudochroleuca  entering New Zealand associated with Persea 
americana  budwood (as described in the commodity description , and taking into account the 
proposed growing period of active growth with a min imum of three distinct phenological 
growing events referred to as ‘shoot flush’ in 3A P EQ) is considered to be negligible with low 
uncertainty;  
• therefore, continuing the assessment was considere d unnecessary; and 
the overall level of risk to New Zealand from C. pseudochroleuca  on imported Persea americana 
budwood (as in the commodity description) is consid ered to be negligible, with low uncertainty.  
5.4.6  Management considerations 
Clonostachys pseudochroleuca  and their vectors, ambrosia beetles, cause visible  damage on stems 
of avocado plants. Infection by C. pseudochroleuca  is unlikely without a vector (Burbano-Figueroa, 
per. comm). Therefore, C. pseudochroleuca  is highly unlikely to persist as an asymptomatic i nfection 
on susceptible tissues. 
Ambrosia beetle and their associated fungi commonly  infest stressed trees due to drought events 
(Burbano-Figueroa et al. 2020; Reverchon et al. 202 1) and thus development of symptoms would be 
more common under high temperatures and dry environ ments. Ambrosia beetles are unlikely to 
attack healthy plants (Reverchon et al. 2021). 
Clonostachys spp. can be detected with specific primers for PCR targeting the β-tubulin gene region 
(Abreu et al. 2014) if symptoms are detected in PEQ . Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 148 5.4.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Clonostachys pseudochroleuca  infection in avocado is only associated with ambro sia beetle galleries 
(Burbano-Figueroa et al. 2018) and causes avocado b ranch dieback and wilting (Figure 1). Symptoms 
include signs of damage by boring insects in trunks  and branches. White powdery exudate on the 
outer bark is associated with beetle holes and wood  under exit holes of galleries will reveal brown 
necrosis (Burbano-Figueroa et al. 2018). Older plan ts also show black pitch symptoms (i.e. black 
exudate found on branches) (Burbano-Figueroa et al.  2018). 
o What are the known environmental conditions conduci ve to symptom expression? 
Clonostachys pseudochroleuca  is vectored by ambrosia beetles and beetle attacks  are unlikely to be 
associated with healthy trees (Reverchon et al. 202 1). Drought events that increase stress in tree 
hosts are more likely to increase ambrosia beetle i nfestation and subsequent infection by C. 
psuedochrolecua  (Burbano-Figueroa et al. 2020). Therefore, high te mperatures and dry environments 
would be conducive to symptom expression. 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections? 
There is no evidence C. pseudochroleuca  causes asymptomatic infections and thus, there is no 
information on which plant part should be tested to  maximise the detection of C. pseudochroleuca  in 
the case of asymptomatic infection.  
o What is the optimum season for conducting detection  testing? 
Drought conditions exacerbate avocado branch diebac k and wilting disease caused by C. 
pseudochroleuca  and ambrosia beetles (Burbano-Figueroa et al. 2020 ). Black pitch symptoms grow 
during the dry season as well (Burbano-Figueroa, pe rs. comm). However, black pitch symptoms are 
commonly found in older trees and after multiple in festations by ambrosia beetles (Burbano-Figueroa 
et al. 2020). 
5.4.8  References 
Abreu, L M; Moreira, G M; Ferreira, D; Rodrigues-Fi lho, E; Pfenning, L H (2014) Diversity of 
Clonostachys  species assessed by molecular phylogenetics and MA LDI-TOF mass spectrometry. 
Fungal biology 118: 1004-1012. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Burbano-Figueroa, O; Arcila, A; Vasquez, A M; Carra scal, F; Salazar Pertuz, K; Moreno-Moran, M, et 
al. (2018) First report of Bionectria pseudochroleuca  causing dieback and wilting on avocado in the 
Serrania de Perijá, Colombia. Plant Disease 102(1): 238. 
Burbano-Figueroa, O; Osorio-Almanza, L; Cardona, A M A (2020) Spatial distribution of avocado 
branch dieback and wilting (ABDW) vectored by ambro sia beetles in the Caribbean South America. 
Tropical plant pathology 45(4): 363-375. 
CABI (2021) Xylosandus morigerus  (brown twig beetle). https://www.cabi.org/isc/datasheet/57238  
Accessed November 2021  
149 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand da Silva, H A O; Teixeira, W D; Borges, Á V; Silva Junior, A L; Alves, K S; Rodrigues Junior, O M, et 
al. (2021) Biocontrol of potato early blight and su ppression of Alternaria grandis  sporulation by 
Clonostachys spp. Plant Pathology 70(7): 1677-1685. 
Huanraluek, N; Jayawardena, R S; Aluthmuhandiram, J  V S; Chethana, K W T; Hyde, K D (2020) 
Bionectria pseudochroleuca , a new host on Prunus sp. in northern Thailand. Studies in Fungi 5: 358-
367. 
Ministry for Primary Industries (2020) Granulate am brosia beetle. 
https://www.mpi.govt.nz/biosecurity/major-pest-and- disease-threats/granulate-ambrosia-beetle/  
Accessed November 2021 
Moreira, G M; Abreu, L M; Carvalho, V G; Schroers, H-J; Pfenning, L H (2016) Multilocus phylogeny 
of Clonostachys  subgenus Bionectria  from Brazil and description of Clonostachys chloroleuca  sp. 
nov. Mycological Progress 15(10-11): 1031-1039. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Reverchon, F; Contreras-Ramos, S M; Eskalen, A; Gue rrero-Analco, J A; Quiñones-Aguilar, E E; 
Rios-Velasco, C, et al. (2021) Microbial biocontrol  strategies for ambrosia beetles and their 
associated phytopathogenic fungi. Frontiers in Sustainable Food Systems 5(313). 
Robert, V; Stegehuis, G; Stalpers, J (2005) The Myc oBank engine and related databases. 
https://www.mycobank.org/  Accessed October 2021 
Rossman, A Y; Seifert, K A; Samuels, G J; Minnis, A  M; Schroers, H-J; Lombard, L, et al. (2013) 
Genera in Bionectriaceae, Hypocreaceae, and Nectria ceae (Hypocreales) proposed for acceptance or 
rejection. IMA Fungus 4(1): 41-51. 
Schroers, H J (2001) A monograph of Bionectria  (Ascomycota, Hypocreales, Bionectriaceae) and its 
Clonostachys anamorphs. Studies in Mycology 46: 1-214. 
Sun, Z B; Li, S D; Ren, Q; Xu, J L; Lu, X; Sun, M H  (2020) Biology and applications of Clonostachys 
rosea . Journal of Applied Microbiology 129(3): 486-495. 
Torcato, C; Gonçalves, M F M; Rodríguez-Gálvez, E; Alves, A (2020) Clonostachys viticola  sp. nov., a 
novel species isolated from Vitis vinifera . International Journal of Systematic and Evolutionar y 
Microbiology 70(7): 4321-4328. 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 150 5.5  Cophinforma tumefaciens 
Cophinforma tumefaciens is a pathogenic ascomycete fungus that causes stem galls/tumours in 
young and old avocado plants. It is known to cause galls/tumours in Citrus  spp. as well as in other 
host plants. 
5.5.1  Taxonomic description 
Scientific name: Cophinforma tumefaciens  (Hedges) F. Liu, Crous & L. Cai (2021)  
Order/Family:  Botryosphaeriales/Botryoshaeriaceae  
Other names include: Sphaeropsis tumefaciens Hedges (1911) , Sphaeropsis tumefaciens var. citri 
N.D. Sharma (1974).  
Taxonomic notes: Sphaeropsis tumefaciens  was recently named Cophinforma tumefaciens due to 
recent taxonomic revision based on DNA phylogeny  (Zhao et al. 2021; Index Fungorum 2022).   
5.5.2  Hazard identification 
Cophinforma tumefaciens is not known to be present in New Zealand: 
• Cophinforma tumefaciens  is not listed in either Biota NZ (2022), (PPIN 202 1) or (NZOR 
2021). 
• Cophinforma tumefaciens  is listed as regulated and an unwanted organism in  ONZPR (2021). 
Cophinforma tumefaciens  has the potential to establish (and spread) in New  Zealand because: 
• host plants such as avocado and Citrus  spp. are grown commercially and in home gardens, i n 
northern and southern parts of New Zealand,  
• Cophinforma tumefaciens  can spread by human movement of infected nursery s tock to 
avocado and citrus growing areas,  
• climate is unlikely to be a barrier to its establi shment and spread in New Zealand because it is 
reported to occur in places (Table 1), which have a  similar climate (CMI ≥ 7) to New Zealand.  
Cophinforma tumefaciens  has the potential to cause harm to New Zealand bec ause: 
• Cophinforma tumefaciens  has been associated with and shown to cause stem t umours in 
young and old avocado plants in Mexico (Fucikovsky 1992).  
• Diseases caused by C. tumefaciens  can potentially reduce the productivity of avocado  and 
citrus trees as well as some ornamental plants in N ew Zealand.  Avocado is an important 
commercial crop in New Zealand worth up to $110 mil lion in domestic sales and up to $56.6 
million in international sales (Plant & Food Resear ch 2020). In 2019, limes, lemons and 
mandarins had a domestic value of NZ$41 million, wi th lemons and mandarins having export 
values of NZ$8 million (Plant & Food Research 2020) . 
Cophinforma tumefaciens  is associated with Persea americana  budwood because: 
• Persea americana  is a known host of  C. tumefaciens (Fucikovsky 1992; Baker et al. 2008); 
• Cophinforma tumefaciens  can cause stem tumours on avocado stems, twigs and  branches 
(Fucikovsky 1992; Baker et al. 2008).  
Given the arguments and evidence above, C. tumefaciens  meets the criteria to be a hazard on 
Persea americana  budwood (as in the commodity description) imported  to New Zealand.  
151 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.5.3  Risk assessment 
Biology and epidemiology of Cophinforma tumefaciens  
General biology and host range of Cophinforma tumefaciens  
Cophinforma tumefaciens  is an ascomycete fungus that can cause stem knot d isease in woody plant 
species (Nazerian et al. 2006; Dale et al. 2021). I t was first isolated from Citrus spp. that were 
affected by knot disease in Jamaica (Naylor 1963). It is known to infect woody plant species by 
causing galls/tumours on stems, branches, and trunk s. It has caused diseases in Citrus spp. and 
avocado as well as several ornamental species such as Callistemon spp. and Illex spp (Table 5-8) .  
Disease caused by C. tumefaciens can be related to water stress. Dieback symptoms an d plant death 
have been observed to be more severe in warm and we t conditions followed by a period of drought 
(Dale et al. 2021). The disease can be controlled b y cutting and destroying infected branches, treatin g 
pruning wounds with protective paint. Pruning tools  used to should be disinfected using disinfectant 
such as 10% Clorox after use to prevent spreading t he disease to uninfected plants (Ridings and 
Marlatt 1975). 
Table 5-8: The distribution, host range and disease s caused by Cophinforma tumefaciens . 
*(Phillips et al. 2018)  
Symptoms  
Cophinforma tumefaciens causes galls (swelling and growth) that occurs on s tems, branches, and 
trunks of infected plants (Naylor 1963; Fucikovsky 1992; Fucikovsky 1994; Brown et al. 2012). Galls Continent Country  State/Region Host plants Symptoms/disease CMI* Reference  
Asia  Iran  Mazandran  Citrus sinensis 
(Tomson navel)  Stem knot disease  0.7-0.8  Nazerian et al. (2006)  
North 
America Jamaica   Citrus spp.  Knot disease  0.5-0.6  Naylor (1963)  
 Mexico  Villa Guerrero, 
Veracruz Persea americana 
(avocado)  Stem tumours  0.4-0.6  Fucikovsky (1992)  
United 
States  Adjuntas Puerto 
Rico  Citrus spp. Citrus knot disease  0.6  (Hedges and Tenny 
1912; Rodriguez et al. 
1985a)  
Florida  Carissa macrocarpa , 
Nerium oleander  Galls  0.5-0.6  Farr and Rossman 
(2021)  
Florida  Schinus 
terebinthifolius  Stem galls  0.5-0.6  (Marlatt and Ridings 
1979; Farr and 
Rossman 2021)  
Florida 
(DeSoto,Glades, 
Highlands and 
Polk)  Hypericum 
edisonianum 
(Edison’s St. John’s-
wort)  Stem tumours (galls)  0.5  Van de Kerckhove et 
al. (2002)  
Florida  Illex spp. (hollies)  Stem gall and 
witches broom 
disease  0.5-0.6  Brown et al. (2012)  
Florida (Dade 
County)  Callistemon viminalis 
(weeping 
bottlebrush)  Stem galls and 
cankers  0.5  Marlatt and Ridings 
(1974)  
- Eucalyptus cinerea  Stem galls and 
cankers   (Farr et al. 1989; 
Yuan 1998)  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 152 can occur in large numbers and can lead to girdling  and eventual death of affected twigs (Fucikovsky 
1994; Baker et al. 2008). It can lead to death of e ntire plants in severe cases (Fucikovsky 1994).  
Infections by C. tumefaciens  causes galls beneath the bark of the plant which e ventually cracks 
revealing pycnidia (fungal fruiting structures). Th e pathogen can be spread wind and by water splash, 
and infect plants through wounds (Brown et al. 2012 ; Dale et al. 2021). 
Hard woody galls appear as knots which are either r ounded or elongated and occur along the stem. 
Knots occur smooth on young branches and new growth  and may become broken, sunken and 
cankerous on old infection (Naylor 1963).  They can  be also be found on older parts of the stem and 
even close to the rootstock (Naylor 1963; Blazquez and Hunt 1967). Knots (1-4cm diameter on stems) 
can girdle twigs and branches causing dieback and “ witches broom effect” (deformed of mass of twigs 
and branches) (Marlatt and Ridings 1974; Nazerian e t al. 2006). 
Cophinforma tumefaciens  caused tumours of different sizes (up to 8cm) and shapes on branches and 
young stems of avocados in Mexico (Fucikovsky 1992) .  Fucikovsky (1994) observed knots in up to 
80% of grafted avocado plants that were placed unde r trees infected with C. tumefaciens (Baker et al. 
2008).  
Transmissions and spread  
Cophinforma tumefaciens  causes galls beneath the bark of the plant which e ventually cracks 
revealing pycnidia (fungal fruiting structures). It  can be spread by water splash, and infect plants 
through wounds (Brown et al. 2012; Dale et al. 2021 ). Pruning provides opportunity for the pathogen 
to infect wounds and spread throughout an orchard o n contaminated equipment (Fucikovsky 1994; 
Brown et al. 2012; Popenoe et al. 2019). Cophinforma tumefaciens  infected wounded avocado nursey 
plants placed under trees infected with the pathoge n , while unwounded plants were not infected 
(Fucikovsky 1994). This suggests that wounds are ne cessary for infections to occur. Cophinforma 
tumefaciens can also be spread by the movement of infected plan ts (Blazquez and Hunt 1967) and 
contaminated pruning tools to new locations (Riding s and Marlatt 1975).  
Time to symptom development  
During pathogenicity tests, C. tumefaciens caused disease symptoms on different host plants 
(avocado, citrus and weeping bottlebrush), between about 2 – 24 weeks after inoculations (Marlatt 
and Ridings 1974; Rodriguez et al. 1985a; Rodriguez  et al. 1985b; Fucikovsky 1992). It caused 
swelling on at inoculation areas of Citrus spp. during pathogenicity tests after 12 days and t hey 
exhibited dieback symptoms two months after (Rodrig uez et al. 1985a). Knots were observed on 
Citrus medica  25 days after inoculation and decline of affected branch occurred after 60 days with 
mature pycnidia at the outer layer of the stem (epi dermis cortex) and the vascular tissues (Rodriguez 
et al. 1985b). 
Early gall formations were observed in Callistemon viminalis from 35 days of artificial inoculation.  
Galls increased rapidly in size between 42-126 days  after inoculation. On naturally infected trees, 
galls varied in size with older galls developing a “witches broom effect” (deformed of mass of twigs 
and branches) (Marlatt and Ridings 1974).  
Factors that influence symptom expression  
Cophinforma tumefaciens causes diseases symptoms such as galls that appears  to be related to 
water (Dale et al. 2021). Galls can generally girdl e branches and interrupt the flow of nutrient and 
water (University of Minnesota 2019). This makes th e plant more susceptible to drought stress and 
can lead dieback symptoms (University of Minnesota 2019). Dieback symptoms and death of woody 
ornamental plant species infected by C. tumefaciens  have been observed to be more in severe, warm 
and wet conditions followed by a period of drought (Dale et al. 2021).  
153 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.5.4  Likelihood of entry 
Cophinforma tumefaciens has been reported to be present in Iran, Mexico, Ja maica, and the United 
States of America (Table 5-8). It  caused galls on branches and young stems of avocado s (Fucikovsky 
1992; Fucikovsky 1994), and can be spread by the mo vement of infected plant stock (Blazquez and 
Hunt 1967). The fact that C. tumefaciens causes galls on branches of infected avocado plants  
(Fucikovsky 1994) suggests that it is unlikely that  budwood for nursery stock will be harvested from 
infected plant material. However, infections of pla nt material by C. tumefaciens  can occur through the 
use of contaminated pruning tools (Ridings and Marl att 1975) which means that avocado nursery 
stock (budwood) can be infected from pruning tools during preparation for export. As such, infected 
budwood might not be detected by visual inspection during preparation for export or during 
phytosanitary inspections on arrival to New Zealand .   
As part of commodity description, all imported avoc ado germplasm, will undergo a growing period of 
active growth with a minimum of three distinct phen ological growing events referred to as ‘shoot flush ’ 
in 3A PEQ. This period in 3A PEQ will impact the li kelihood of entry in the following manner: 
• Avocado seedings derived from infected avocado bud wood are likely to exhibit symptoms 
during the time spent in PEQ. During pathogenicity tests, C. tumefaciens was observed to 
cause symptoms between about 2 – 24 weeks after ino culations on different host plants 
including avocado (Marlatt and Ridings 1974; Rodrig uez et al. 1985a; Rodriguez et al. 1985b; 
Fucikovsky 1992) 
• swollen galls produced by C. tumefaciens infections can eventually crack, revealing pycnidia  
(fungal fruiting structures) which can be spread by  water splash (Brown et al. 2012; Dale et al. 
2021). However, this is unlikely to occur because r egular inspections at Level 3A PEQ are 
likely to detect galls. Additionally, there are mea sures in place to manage the risks associated 
with wastewater, waste, and accidental transfer (se e section 2.2), therefore viable C. 
tumefaciens propagules are highly unlikely to escape level 3A P EQ to infect a suitable host. 
• Searches of Google Scholar, CPC and Google using t he search terms ‘Sphaeropsis 
tumefaciens’, ‘Cophinforma tumefaciens endophytic i nfection’ found no evidence for 
asymptomatic S. tumefaciens infections or longer latent periods in avocado plan ts and other 
host plants.  
Therefore, if C. tumefaciens is imported on avocado budwood, the residual biosec urity risk is likely to 
be managed by the active growing period in 3A PEQ.  
Given the arguments and evidence above, that is:  
• established C. tumefaciens infections are highly likely to be detected, and in fected material 
removed or destroyed, during preparation for export , or in phytosanitary inspections pre-
export and on arrival in New Zealand 
• residual biosecurity risks from recent infections or contamination of the surface of avocado 
budwood are likely to be managed by the growing per iod of active growth with a minimum of 
three distinct phenological growing events referred  to as ‘shoot flush’ in 3A PEQ 
the likelihood of C. tumefaciens entering New Zealand associated with Persea americana  budwood is 
considered to be negligible , with low  uncertainty. 
5.5.5  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of C. tumefaciens entering New Zealand associated with Persea americana  
budwood (as described in the commodity description,  and taking into account the proposed 
growing period of active growth with a minimum of t hree distinct phenological growing events 
referred to as ‘shoot flush’ in 3A PEQ) is consider ed to be negligible with low uncertainty;  
• therefore, continuing the assessment was considere d unnecessary; and Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 154 the overall level of assessed risk to New Zealand f rom C. tumefaciens on imported Persea americana 
budwood (as in the commodity description) is consid ered to be negligible , with low  uncertainty. 
5.5.6  Management considerations 
Cophinforma tumefaciens causes galls and tumours that occurs on stems, bran ches, and trunks of 
infected plants (Naylor 1963; Fucikovsky 1992; Fuci kovsky 1994; Brown et al. 2012). Galls and 
tumours vary in size reaching up to 8cm in diameter  and can occur in large numbers (Fucikovsky 
1992). They can lead to death of affected twigs (Fu cikovsky 1994; Baker et al. 2008) and in severe 
cases result in the death of the entire plant (Fuci kovsky 1994).  
C. tumefaciens is unlikely to persist as an asymptomatic infection  on host plant or plant material. 
Symptoms are likely to become visible between 2 - 1 8 weeks of infection. This suggests that 
symptoms of pre-existing infections are likely to b e detected within the period of level 3A PEQ.   
Infections caused by C. tumefaciens appears to be related to water stress. Dieback symp toms and 
plant death have been observed to be more severe in  warm and wet conditions followed by a period 
of drought (Dale et al. 2021).   
Disease caused by C. tumefaciens can be controlled by ensuring that uninfected nurse ry plants are  
not be kept in close proximity to or placed under t ress infected with C. tumefaciensi  (Fucikovsky 
1994). 
5.5.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Cophinforma tumefaciens causes galls on stems, branches, and trunks of infe cted plants (Naylor 
1963; Fucikovsky 1992; Fucikovsky 1994; Brown et al . 2012). Multiple galls can occur on the bark of 
twigs and can girdle affected part leading to death  (Fucikovsky 1994; Baker et al. 2008). In severe 
cases, it can result in the death of the entire pla nt (Fucikovsky 1994; Baker et al. 2008). It caused 
galls of different sizes (up to 8cm in diameter) an d shapes on branches and young stems of avocado 
plants in Mexico (Fucikovsky 1992). 
o What are the known environmental conditions conduci ve to symptom expression? 
Infections caused by C. tumefaciens appear to be related to water stress. Dieback sympt oms and 
plant death have been observed to be more severe in  warm and wet conditions followed by a period 
of drought (Dale et al. 2021). 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Cophinforma tumefaciens is unlikely to persist as an asymptomatic infection  on host plant or plant 
material because infections have been observed to o ccur mainly through wounds (Marlatt and Ridings 
1974; Rodriguez et al. 1985a; Rodriguez et al. 1985 b). Recently infected material (cut budwood) as a 
result of contamination during preparation is likel y to exhibit symptoms within the PEQ period.  
o What is the optimum season for conducting detection  testing? 
Optimum season for conducting testing has not been specified.  
155 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.5.8  References 
Baker, R; Caffier, D; Choiseul, J W; Clercq, P D; D ormannsne-Simon, E; Gerowitt, B, et al. (2008) 
Pest risk assessment made by France on Sphaeropsis tumefaciens  Hedges considered by France as 
harmful in French overseas departments of French Gu iana, Guadeloupe and Martinique ‐Scientific 
opinion of the panel on plant health. EFSA Journal 677: 1-14. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Blazquez, C; Hunt, P (1967) Sphaeropsis Knot: a new  disease of rough lemon rootstock. In 
Proceedings of the Florida State Horticultural Soci ety  (Vol. 80, pp. 46-46). 
Brown, S P; Ingram, D L; Barrick, W E (2012) Hollie s at a glance. EDIS 2012(3). 
Dale, A; Harlow, E; Harmon, C; Marble, C (2021) Gal ling damage to woody ornamentals: diagnosis 
and potential causes. EDIS 2021(1): 6-6. 
Farr, D F; Bills, G F; Chamuris, G P; Rossman, A Y (1989) Fungi on plants and plant products in the 
United States . APS press. 
Farr, D F; Rossman, A Y (2021) Fungal databases, U.  S. National Fungus Collections. https://nt.ars-
grin.gov/fungaldatabases/  Accessed Septemeber 27, 2021 
Fucikovsky, L (1992) Sphaeropsis tumor of avocado. In Proceedings of the Second World Avocado 
Congress  (pp. 129-132). 
Fucikovsky, L (1994) Tumour caused by Sphaeropsis tumefaciens  on avocado. Revista Mexicana de 
Micología 10: 181-185. 
Hedges, F; Tenny, L S (1912) Knot of citrus trees c aused by Sphaeropsis tumefaciens . 
Index Fungorum (2022) Index Fungorum. http://www.indexfungorum.org/names/Names.asp   
Marlatt, R; Ridings, W (1979) Sphaeropsis gall of S chinus terebinthifolius, a new host. Plant Disease 
Reporter 63(9): 786-787. 
Marlatt, R B; Ridings, W H (1974) Sphaeropsis gall of bottlebrush tree, Callistemon viminalis , a new 
host. Phytopathology 64(7): 1001-1003. 
Naylor, A G (1963) Sphaeropsis knot disease of citr us in Jamaica.  Caribbean Food Crops Society . 
St. Croix, U. S. Virgin Islands. 
Nazerian, E; Mirabolfathy, M; Alian, Y (2006) Incid ence of citrus knot disease in northern Iran. Iranian 
Journal of Plant Pathology 42(3): 509-519. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 156 Popenoe, J; Warwick, C R; Bourdon, J; Felter, L A ( 2019) Key plant, key pests: Holly ( Ilex  sp.). In E H 
Department (Ed.). 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Ridings, W; Marlatt, R (1975) Sphaeropsis gall of bottlebrush .  
Rodriguez, S D; Rodriguez, R; Melendez, P L (1985a)  Suitability of citrus species as hosts of 
Sphaeropsis tumefaciens  Hedges. The Journal of Agriculture of the University of Pue rto Rico 69(1): 
57-61. 
Rodriguez, S D; Rodríguez, R; Melendez, P L (1985b)  Histopathology of citron (Citrus medica) 
infected with Sphaeropsis tumefaciens. The Journal of Agriculture of the University of Pue rto Rico 
69(3): 397-400. 
University of Minnesota (2019) Crown galls. https://extension.umn.edu/plant-diseases/crown-gall  
Accessed 31/01/2022 
Van de Kerckhove, G; Smither-Kopperl, M; Kistler, H  (2002) First report of Sphaeropsis tumefaciens  
on an endangered St. John's-Wort in Florida. Plant Disease 86(10): 1177-1177. 
Yuan, Z Q (1998) Stem canker diseases of eucalypts in Tasmania.  thesis; University of Tasmania,  
Zhao, P; Crous, P; Hou, L; Duan, W; Cai, L; Ma, Z, et al. (2021) Fungi of quarantine concern for 
China I: Dothideomycetes. Persoonia-Molecular Phylogeny and Evolution of Fung i 47(1): 45-105. 
 
  
157 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.6  Diaporthe perseae 
Diaporthe perseae is a fungal plant pathogen that causes stem-end rot  (postharvest) disease in 
avocado. 
5.6.1  Taxonomic description 
Scientific name: Diaporthe perseae (Zerova) Gomes et al. (2013)  
Order/Family: Diaporthales/Diaporthaceae  
Other names include : Phomopsis perseae  Zerova (1940) 
Taxonomic notes:  Diaporthe perseae  was also referred to as Phomopsis perseae (known as the 
asexual state). Historically it was commonly referr ed to as Phomopsis perseae , but for the purpose of 
this PRA, it will be referred to as Diaporthe perseae . 
5.6.2  Hazard identification 
Diaporthe perseae is not known to be present in New Zealand. However,  two Phomosis spp. (asexual 
stage of Diaporthe ) were reported by Hartill and Everett (2002) to be  associated with avocado in New 
Zealand. Neither of these were confirmed as Diaporthe perseae.  
o Diaporthe perseae  is not listed in PPIN (2021) 
o Diaporthe perseae  is recorded as absent from New Zealand in Biota NZ  (2022) 
o Diaporthe perseae  is a regulated pest for New Zealand, has unwanted status but is 
not a notifiable organism (ONZPR 2021) 
Diaporthe perseae has the potential to establish (and spread) in New Zealand because: 
• The host plant, avocado is grown commercially, and  in home gardens in some parts of New 
Zealand.  
• It is an endophytic pathogenic fungus, that has be en isolated from twigs, branches and trunks 
not showing diseased symptoms. It can be present on  all parts of an infected tree (Zerova 
1940; Darvas and Kotze 1987).  
• Climate is unlikely to be a barrier to its establi shment and spread in New Zealand because it 
is reported to occur in places such as  Australia a nd South Africa, which have a similar 
climate (CMI) ≥ 0.7 to New Zealand (Phillips et al. 2018).  
• Diaporthe perseae can spread naturally by wind and rain or by human m ovement of infected 
nursery stock and movement of infected fruits to av ocado growing areas.  
Diaporthe perseae  has the potential to cause harm to New Zealand bec ause: 
• Diaporthe perseae  has been associated with and shown to cause postha rvest (stem-end) rot 
disease in avocado (Darvas and Kotzé 1981; Darvas a nd Kotze 1987; Korsten et al. 1994).  
• Diaporthe perseae can cause cankerous lesions on trunks of avocado tr ees in South Africa 
(Van der Merwe and Kotzé 1991). 
• Postharvest rot diseases caused by D. perseae can affect the marketability of avocado crops 
in New Zealand. It is an important commercial crop in New Zealand worth up to $110 million 
in international sales and up to 56.6 million in do mestic sales (Plant & Food Research 2020).  
Diaporthe perseae  is associated with P. americana  budwood because: 
• Persea americana  is a known host of Diaporthe perseae (Darvas and Kotzé 1981; Darvas 
and Kotze 1987; Darvas and Wehner 1987); 
• Diaporthe perseae can occur endophytically on all parts of a tree (Da rvas and Kotze 1987). It 
can occur on twigs, branches and pedicels of avocad o plants. From the pedicel, it can Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 158 eventually colonise the inflorescence of the stem-e nd tissue and cause stem-end rot (Hartill 
and Everett 2002).  
Given the arguments and evidence above, D. perseae  meets the criteria to be a hazard on Persea 
americana  budwood (as per the commodity description) importe d to New Zealand. 
5.6.3  Risk assessment 
Biology and epidemiology of Diaporthe perseae 
Biology and host range 
Diaporthe perseae is an endophytic (can inhabit plant tissues without  causing disease) and 
pathogenic fungus (Wilson 1995) that is known to ca use stem-end rot disease (Darvas and Kotze 
1987). Depending on the host and the health of the host plants, some species of Diaporthe can exist 
as harmless endophytes or as pathogens (Udayanga et  al. 2011). Some are host specific as is the 
case of Diaporthe perseae  (Farr et al. 2002), which has mostly been reported  as a pathogen of 
Persea americana (avocado). 
Diaporthe perseae  was originally described when conidiospores (asexu al spores) from the branches 
of dying trees and leaves of avocado Persea gratissima (americana ) were observed and isolated in 
Russia (Zerova 1940; Uecker 1988). It has since bee n reported to cause postharvest disease of 
avocado in Australia (Peterson 1978; Muirhead et al . 1982) and South Africa (Darvas and Kotze 
1987) and has been isolated from young avocado frui ts in the Netherlands (Gomes et al. 2013). It is, 
however, unclear if D. perseae is still present in Australia. It had been reported  to be associated with 
avocado by Peterson (1978) in Australia in the late  1970’s and there is no information on its present 
status in Australia. Lim et al. (2019) recently rep orted D. perseae  as one of the fungi observed in 
stem-end rot disease of mangoes in Malaysia. It was  also recently reported to be isolated along with 
other Diaporthe on healthy leaves of Citrus grandis in China (Dong et al. 2020) and from Camellia 
sinensis  (tea leaves) in Taiwan (Ariyawansa et al. 2021) (T able 5-9). 
Diaporthe perseae can occur endophytically on all parts of a tree (Da rvas and Kotze 1987). It can 
occur in twigs, branches and pedicels of avocado pl ants. From the pedicel, it can eventually colonise 
the inflorescence of the stem-end tissue and cause stem-end rot (Hartill and Everett 2002). However, 
infection can remain latent (not show symptoms) pri or to harvest with symptoms becoming apparent 
after harvest (Peterson 1978). Immature fruits are more vulnerable to stem-end rot infections than 
mature fruits (Kotzé and Darvas 1985). 
Stem-end rot is often reported to be caused by seve ral fungal pathogens (Darvas and Kotze 1987; 
Korsten et al. 1994; Guarnaccia et al. 2016). Patho genicity tests using several pathogens that cause 
stem-end rot disease found that D. perseae appeared to be a weak pathogen of stem-end rot dise ase 
in avocado (Peterson 1978; Darvas and Kotzé 1981; M enge and Ploetz 2003). Korsten et al. (1994) 
also found that D. perseae was less frequently isolated from diseased avocado fruits than other 
postharvest rot causing fungi. It was observed to c ause less severe disease symptoms than other 
pathogens (Darvas and Wehner 1987).  However, it is important to note that some pathogen ic fungi 
such as Lasiodiplodia theobromae might be isolated at low frequency but are destruct ive wound 
pathogens of avocado.   
Table 5-9: Plant host range and disease cause by Diaporthe perseae  
Continent Country  Host plant Symptoms /disease CMI* Reference  
Africa South Africa Persea americana (Avocado) Stem-end rot 0.5–0.9 (Darvas and Kotze 
1987; Darvas and 
Wehner 1987) 
Asia China Citrus grandis  Asymptomatic  0.4-0.8 Dong et al. (2020) 
Malaysia Mangifera indica (Mango)  Stem-end rot  0.4-0.5 Lim et al. (2019) 
Taiwan  Camellia sinensis  (tea leaves) Asymptomatic  0.4–0.5 Ariyawansa et al. 
(2021)  
159 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Continent Country  Host plant Symptoms /disease CMI* Reference  
Europe  Netherlands  Persea americana (Avocado)  Fruit rot 0.9 Gomes et al. (2013) 
Russia Persea americana (Avocado)  Dieback disease 0.3-0.8 (Zerova 1940; Uecker 
1988) 
Oceania  Australia  Persea americana (Avocado)  Post-harvest disease 0.4-0.9 (Peterson 1978; 
Muirhead et al. 1982) 
*(Phillips et al. 2018)  
Reproduction and spread 
Under field conditions, spores are generally produc ed when tissues (on twigs, branches and stems) 
are dead (Darvas and Kotze 1987; Uecker 1988; Menge  and Ploetz 2003; Gomes et al. 2013), then 
grey, white or creamy colonies containing conidioma ta appear (Gomes et al. 2013). This can usually 
serve as a source of primary infection (Dann et al.  2013), can be transferred to open wounds on the 
plant, the pedicel, and fruits, and can potentially  be spread by rain splashes or wind (Menge and 
Ploetz 2003).  
Most stem-end rot infections occur during harvest t hrough the pedicel, pedicel scars or wounds 
(Darvas and Wehner 1987). Infections can occur thro ugh wounds on the bark of the tree (which can 
also be a source of infection) or wounds created th rough picking of fruit in the field (Kotzé and Darv as 
1985; Hartill and Everett 2002). It can also be spr ead by the use of the same cutting implement from 
an infected plant to a non-infected plant (Hartill and Everett 2002).  
Diaporthe perseae,  in its endophytic phase, can be latent or dormant without showing any symptoms 
(Dann et al. 2013; Dong et al. 2020). This means th at symptomless cuttings of avocado infected with 
D. perseae can be transmitted and spread through grafting espe cially in commercial avocado plant 
nurseries. Under unfavourable environmental conditi ons such as drought, frost or hail, plants 
colonised by D. perseae can become stressed and begin to exhibit symptoms ( Udayanga et al. 2011). 
Infection and spread of D. perseae (as well as other pathogenic fungi associated with avocado) 
occurs mostly during prolonged wet periods of rain and high humidity. Peterson (1978) found that 
natural infection of fruits did not occur in dry co nditions but occurred after four or more conservati ve 
days of rainfall.  
Symptoms 
Pathogenic fungi such as D. perseae  that are endophytic usually have a latent or dorma nt phase 
within the plant tissues (Wilson 1995).  They can b e present throughout the life cycle of infected 
plants without showing visible symptoms. Symptoms o f D. perseae such as lesions and rot, tend to 
only occur after harvest (Peterson 1978). This mean s that in its latent phase, it can occur in healthy  
looking avocado twigs and stems, with no visible sy mptoms.   
In its pathogenic form, D. perseae  colonises the xylem and the phloem at the stem-end  of the fruit. It 
eventually becomes necrotrophic (secretes enzymes t hat kill the host tissues while living on the 
nutrients from the dead tissues), causing stem-end rot by colonising the fruit pulp (Karunanayake and 
Adikaram 2020).  
Symptoms develop after harvest, at the onset of fru it ripening (Karunanayake and Adikaram 2020). 
Visible symptoms begin as brownish or black rot at the fruit pedicel which progresses internally 
causing discolouration and decay. Internal decay ma y extend on the external part of the fruit leading 
to brown or black discolouration (Darvas and Wehner  1987; Karunanayake and Adikaram 2020). 
Mycelium and abundant spores might be observed on t he abscission scar of infected fruit and can 
eventually cover the fruit as ripening progresses, leading to softening and shrivelling of the entire fruit 
(Menge and Ploetz 2003).  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 160 Conditions for symptom development 
Symptom development of stem-end rot disease varies with pathogens and can be slower or faster 
depending on the pathogen (Karunanayake and Adikara m 2020) as well as the environmental 
conditions. For example, cool temperature is though t to promote D. perseae infection. Additionally 
water stress appears to generally stimulate latent infections by several fungi (Menge and Ploetz 
2003), suggesting that colonised plants are likely to exhibit pathogenic effects of D. perseae  in dry 
conditions.  
By inoculating avocado (Martin Grande) seedlings un der artificial condition, (Van der Merwe and 
Kotzé 1991) found that  D. perseae caused lesions on cuttings and within cambium tissu es (phloem 
and xylem tissues) ten days after inoculation at 26 ° C- 28° C.  Within 20 days, inoculated plants 
completely dried out and died (Van der Merwe and Ko tzé 1991) . The same inoculation method 
resulted in no symptom development on “Duke 7” avoc ado variety, suggesting D. perseae might 
affect some avocado varieties and not others (Van d er Merwe and Kotzé 1991).  
Diaporthe perseae  was observed to cause fruit rot after eight to ele ven days in artificial post-harvest 
inoculations in Fuerte, Edranol, and Hass varieties  but no rot was observed in the Ryan variety 
(Darvas and Kotzé 1981). 
5.6.4  Likelihood of entry 
Diaporthe perseae has been reported to be present in seven countries.  It has been reported to be 
associated with avocado in South Africa, Russia, Au stralia and the Netherlands (Peterson 1978; 
Muirhead et al. 1982; Darvas and Kotze 1987; Uecker  1988; Gomes et al. 2013).  It is, however, 
unclear if D. perseae is still present in Australia. It was reported to b e associated with avocado by 
Peterson (1978) in Australia in the late 1970’s and  there is no information on its present status in 
Australia.  
In its endophytic phase, it can be present  on leafless and rootless avocado budwood without sh owing 
visible symptoms. Therefore, it is likely to that i t will not be detected during export preparation an d 
pre-export phytosanitary inspection to New Zealand or on arrival to New Zealand. Given that it has 
been reported to be present in at least seven count ries, D. perseae  can be associated with the 
commodity when it arrives in Post Entry Quarantine (PEQ). 
All imported avocado germplasm will undergo PEQ at level 3A, during which the budwood will 
undergo a minimum of three distinct phenological pe riods of active growth. The period in Level 3A 
PEQ is not likely to impact the likelihood of entry  of D. perseae . This is because infected budwood 
that is grafted in PEQ level 3A is not likely to sh ow any visible symptoms within the time in PEQ if t he 
fungus is in a latent phase. However, symptoms such  as dead twigs and sporulation of the grafted 
plants can develop if the plants become subjected t o stress (such as drought). Spores are generally 
produced when tissues (on twigs, branches and stems ) are dead (Darvas and Kotze 1987; Uecker 
1988). It therefore highly unlikely that spores wil l be produced on imported budwood and escape from 
PEQ without being detected.  
Disease symptoms (stem-end rot) associated with D. perseae occur mostly on the fruit after harvest. 
This cannot be detected in PEQ level 3A because gra fted budwood will not be in PEQ long enough to 
produce suitably mature fruit. As such, infected pl ants are likely to remain undetected unless 
molecular diagnostic testing for D. perseae  is carried out on infected tissue. 
Given the arguments and evidence above, that is:  
• Diaporthe perseae has been reported to be present in seven countries  
• it can be present  on leafless and rootless avocado budwood without sh owing visible symptom 
• Infected budwood that is grafted in PEQ level 3A i s not likely to show any visible symptoms 
within the time in PEQ if the fungus is in a latent  phase. 
• Infected plants are likely to remain undetected un less molecular diagnostic testing for D. 
perseae  is carried out on infected tissue.  
161 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand the likelihood of D. perseae  entering New Zealand associated with Persea americana  budwood is 
considered to be high, with low uncertainty. 
5.6.5  Likelihood of exposure 
This assessment is made on the basis that D. perseae  has entered New Zealand undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for D. perseae .   
If avocado plants are infected with D. perseae  at the time of their release from post entry quara ntine, 
they will be planted in New Zealand or used to prop agate new plants for planting (see section 2.3 for 
additional information about exposure).  
Given the arguments and evidence above, the likelih ood of exposure of D. perseae  in New Zealand 
from Persea americana  budwood is considered high, with low uncertainty. 
5.6.6  Likelihood of establishment 
This assessment is made on the basis that D. perseae  has been successfully exposed to a suitable 
host plant in the New Zealand environment. 
Diaporthe perseae is recorded to be present in parts of Australia, So uth Africa, the Netherlands and 
Russia which have a CMI range of between 0.4 - 0.9.  CMI of ≥ 0.7 indicates a similar climate to the 
whole of New Zealand (Phillips et al. 2018).  As su ch, the conditions in some parts of New Zealand 
are likely to be suitable for D . perseae to occur and spread. Therefore, climate would not b e a barrier 
to the establishment of D. perseae in New Zealand.  
Avocado plants are widely grown in some parts of Ne w Zealand commercially in orchards and in-
home gardens mostly in the North Island and some pa rts of the South Island (Chapter 2), therefore 
suitable hosts are available in those areas. D. perseae can spread by the movement of infected 
nursery stock for planting. However, its spread mig ht be limited because it is generally believed to b e 
specific to avocado (Darvas and Kotze 1987; Darvas and Wehner 1987; Uecker 1988). However, it 
was recently reported to be associated with stem-en d in mangoes in Malaysia (Lim et al. 2019), 
isolated from healthy citrus leaves in China (Dong et al. 2020) and from tea plants in Taiwan 
(Ariyawansa et al. 2021). These recent molecular st udies are indicating that many Diaporthe species 
have wider host ranges that historically reported ( Lim et al. 2019; Dong et al. 2020; Ariyawansa et al . 
2021). Therefore, although it is likely that D. perseae will spread in avocado growing areas of 
New Zealand, there is moderate uncertainty because it may be able to infect other hosts. 
Spores of D. perseae  can  be present on infected fruit (Menge and Ploetz 2003 ) and can be a source 
of infection if infected fruit is discarded near av ocado plants. Therefore D. perseae can be spread to 
new areas by human movement of infected fruit. 
Given the arguments and evidence above, that is: 
• The climatic conditions in some parts of New Zeala nd are likely to be suitable for D . perseae 
to occur and spread. 
• Suitable avocado host plants are available in orch ards and in-home gardens mostly in the 
North Island and some parts of the South Island. D. perseae can spread by the movement of 
infected nursery stock for planting. 
• Spores of D. perseae can be present on infected fruit and can be spread to new areas by 
human movement of infected fruit. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 162 the likelihood of D. perseae  establishing in New Zealand is considered high, wi th low-moderate 
uncertainty. 
5.6.7  Impacts in New Zealand 
Diaporthe perseae  is reported as present in seven countries (Table 5- 9). It causes stem-end rot 
(postharvest) disease in mostly avocado (Darvas and  Wehner 1987) and have been reported to 
cause stem-end rot in mangos (Lim et al. 2019). It can be spread by the use of the same cutting 
implement from an infected plant to a non-infected plant (Hartill and Everett 2002), and spores 
produced on infected plants can be spread by water splash and infect plants through wounds created 
through picking of fruit in the field (Kotzé and Da rvas 1985; Hartill and Everett 2002). 
Economic impacts 
Diaporthe perseae causes stem-end rot disease symptoms that can go un noticed and mainly become 
apparent after harvest. Diseased symptoms of stem-e nd rot become apparent at the onset of fruit 
ripening (Karunanayake and Adikaram 2020). Infected  fruits can mask symptoms in certain storage 
conditions such as low temperatures (Darvas 1982) w ith rot symptoms becoming apparent later 
outside those conditions. Muirhead et al. (1982) re ports D. perseae as a less important pathogen of 
stem-end rot disease than other stem-end rot causin g fungi such as Dothiorella aromatica in 
Queensland Australia. Stem-end rot caused by Colletotrichum  gloeosporioides and Phomopsis  spp. 
are also common in New Zealand (Hartill and Everett  2002).This suggests that while D. perseae  can 
result in some postharvest losses of avocado fruits , overall losses may not differ from current levels  of 
stem-end rot diseases.  
Infections by D. perseae could affect market access of exports of avocado to  other parts of the world 
where D. perseae is not reported to be present. Because D. perseae is reported to cause diseases in 
avocado in few countries including Australia (Table  5-9). The fact that it is recorded as present in 
Australia, which is New Zealand’s major export mark et, suggests it is not likely to have a significant  
impact on export. But its presence in New Zealand c an potentially result in trade barriers to countrie s 
other countries where it is has not been reported t o be present.  
Pathogenicity testing using different stem-end rot pathogens showed that some avocado cultivars 
were more susceptible to stem-end rot infections th an others. The Hass variety was observed to be 
less susceptible to stem-end rot disease caused by D. perseae than Fuerte, Edranol and the Ryan 
varieties (Darvas 1982).  D. perseae is likely to infect and cause diseases in New Zeala nd. This might 
however be limited in New Zealand because the Hass variety is the main avocado presently grown 
(Chapter 2). However, its impact will likely be hig her if more susceptible varieties of avocado are 
grown in the future.  
Given the arguments and evidence above, that is: 
• D. perseae  can result in some postharvest losses of avocado, overall losses may not 
differ from current levels of stem-end rot disease in New Zealand. 
• Current methods of control of other stem-end rot c ausing pathogens in New Zealand may 
also be effective for controlling diseases caused b y D. persea . 
• Infection by D. perseae could affect market access of exports of avocado to  other parts of 
the world where D. perseae is not reported to be present. 
• Infection caused by D. perseae might be limited in New Zealand because the Hass 
variety which is the main avocado is recorded to be  less susceptible to stem-end rot 
disease. 
the economic impact of D. perseae  to New Zealand is considered to be low, with moder ate 
uncertainty. 
Environmental impacts 
Diaporthe perseae has been reported to infect mainly avocado with onl y one recent association with 
mangoes by Lim et al. (2019). Diaporthe perseae is also asymptomatic in Camellia and Citrus (Table  
163 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5-9). Five indigenous New Zealand plant species bel ong to the family Lauraceae, the same family as 
avocado ( Perseae americana ) (NZPCN 2021).  Searches from Google, Google scholar, U.S. National 
Fungus Collections Fungus-Host Distributions Databa se, CABI and EPPO using the search term 
‘Diaporthe perseae and the environment’ and ‘ Phomopsis perseae and the environment’ found no 
record of D. perseae infecting other plants species outside the Persea  genus except for recent report 
of its association to mangoes and asymptomatic infe ctions in Camellia and Citrus . This suggests that 
D. perseae is relatively host specific and is not likely to af fect native plants and the environment.  
Given the arguments and evidence above, the impact on the environment from the establishment of 
D. perseae  in New Zealand is considered to be low, with low u ncertainty. 
Health impacts 
Searches using the search term ‘ Diaporthe perseae impacts on health’ and ‘ Phomopsis perseae 
impact on health’ from Google, Google scholar, CABI  and Pubmed found no record of D. perseae 
causing any health impact on humans and animals. 
Given the arguments and evidence above, the health impact of D. perseae  to New Zealand is 
considered to be negligible, with low uncertainty. 
Sociocultural impacts 
Avocado has become popular and is widely consumed i n New Zealand. It is commonly grown in 
home gardens in some parts of the country. Stem-end  rot disease causes rot in avocado and makes 
the fruit inedible and can cause scarcity in local markets.  
Given the arguments and evidence above, the sociocu ltural impact of D. perseae to New Zealand is 
considered to be low, with low uncertainty. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, health and society is considered to be 
low, with low uncertainty. 
5.6.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is high with low uncertain ty, 
• assuming entry, the likelihood of exposure is high  with low uncertainty, 
• assuming successful exposure, the likelihood of es tablishment is high with low-moderate 
uncertainty, 
• the overall impact on the New Zealand economy, env ironment, health and society is 
considered to be low with low uncertainty. 
the overall level of assessed risk to New Zealand f rom D. perseae  on imported Persea americana 
budwood (as in the commodity description) is consid ered to be low , with moderate  uncertainty. 
5.6.9  Management considerations 
Symptoms caused by D. perseae are not likely to be expressed during the growing p eriod in PEQ. 
Diaporthe perseae  can occur in healthy looking avocado twigs and ste ms and be present throughout 
the life cycle of infected plants without showing v isible symptoms; stem-end rot symptoms only 
develop after fruit harvest (Peterson 1978). 
In general pathogenic endophytes such as D. perseae can exhibit symptoms under environmental 
stresses such as drought, hail or frost (Udayanga e t al. 2011), but the specific conditions for sympto m 
expressions for D. perseae are not well described.  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 164 Samples can be taken for testing from any part of t he avocado leafless budwood and testing different 
parts of the budwood might be required. This is bec ause D. perseae can occur in healthy looking 
avocado twigs and stems and be present throughout t he life cycle of infected plants without showing 
visible symptoms (Peterson 1978). However, it is no t clear if the pathogen will be evenly distributed or 
not throughout an infected avocado budwood and that  the right bit will be tested.   Optimum season or 
conditions for conducting detection testing has not  been specified.  
5.6.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Symptoms caused by D. perseae is not likely to be expressed during the growing pe riod in PEQ. It 
can occur in healthy looking avocado twigs and stem s and be present throughout the life cycle of 
infected plants without showing visible symptoms wi th stem-end rot symptoms developing after fruit 
harvest (Peterson 1978). 
o What are the known environmental conditions conduci ve to symptom expression? 
In general, pathogenic endophytes such as D. perseae can exhibit symptoms under environmental 
stresses such as drought, hail or frost (Udayanga e t al. 2011), but the specific conditions for sympto m 
expressions for D. perseae are not well described.  
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Samples can be taken for testing from any part of t he avocado leafless budwood and testing different 
parts of the budwood might be required. This is bec ause D. perseae can occur in healthy looking 
avocado twigs and stems and be present throughout t he life cycle of infected plants without showing 
visible symptoms (Peterson 1978). It is not clear i f it will be evenly distributed or throughout an 
infected avocado budwood; therefore, there is a hig h chance of false negatives.  
o What is the optimum season for conducting detection  testing? 
An optimum season or conditions for conducting dete ction testing has not been identified from the 
literature.  
5.6.11  References 
Ariyawansa, H A; Tsai, I; Wang, J-Y; Withee, P; Tan jira, M; Lin, S-R, et al. (2021) Molecular 
Phylogenetic Diversity and Biological Characterizat ion of Diaporthe Species Associated with Leaf 
Spots of Camellia sinensis in Taiwan. Plants 10(7): 1434. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Dann, E; Ploetz, R; Coates, L; Pegg, K (2013) 13 Fo liar, Fruit and Soilborne Diseases. The avocado: 
botany, production and uses : 380. 
Darvas, J; Kotze, J (1987) Fungi associated with pr e-and postharvest diseases of avocado fruit at 
Westfalia Estate, South Africa. Phytophylactica 19(1): 83-86.  
165 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Darvas, J; Kotzé, J (1981) Post-harvest diseases of  avocados. South African Avocado Grower’s 
Association Year Book 4: 63 66. 
Darvas, J, Kotze, JM; Wehner, F (1987) Pathogenicit y of fungi causing pre-and postharvest diseases 
of avocado fruit. Phytophylactica 19(4): 489-494. 
Darvas, J M (1982) Etiology and control of some fru it diseases of avocado (Persea americana Mill.) at 
Westfalia Estate. DSc (Agric) thesis, University of Pretoria . 
Dong, Z; Manawasinghe, I S; Huang, Y; Shu, Y; Phill ips, A J L; Dissanayake, A J, et al. (2020) 
Endophytic Diaporthe associated with Citrus grandis cv tomentosa in China. Frontiers in Microbiology 
11: 3621. 
Farr, D F; Castlebury, L A; Rossman, A Y (2002) Mor phological and molecular characterization of 
Phomopsis vaccinii and additional isolates of Phomo psis from blueberry and cranberry in the eastern 
United States. Mycologia 94(3): 494-504. 
Gomes, R; Glienke, C; Videira, S; Lombard, L; Groen ewald, J; Crous, P (2013) Diaporthe: a genus of 
endophytic, saprobic and plant pathogenic fungi. Persoonia: Molecular Phylogeny and Evolution of 
Fungi 31: 1. 
Guarnaccia, V; Vitale, A; Cirvilleri, G; Aiello, D;  Susca, A; Epifani, F, et al. (2016) Characterisati on and 
pathogenicity of fungal species associated with bra nch cankers and stem-end rot of avocado in Italy. 
European Journal of Plant Pathology 146(4): 963-976. 
Hartill, W F T; Everett, K R (2002) Inoculum source s and infection pathways of pathogens causing 
stem ‐end rots of ‘Hass’ avocado ( Persea americana ). New Zealand Journal of Crop and Horticultural 
Science 30(4): 249-260. 
Karunanayake, K; Adikaram, N (2020) Stem-end rot in  major tropical and sub-tropical fruit species. 
Ceylon Journal of Science 49(5). 
Korsten, L; Sanders, G M; Grosse-Weischede, E (1994 ) Isolation and pathogenicity of avocado post-
harvest pathogens from Westfalia and other avocado producing areas. South African Avocado 
Growers’ Association Year book 17: 46-48. 
Kotzé, J; Darvas, J (1985) Symptoms and causes. SA Avocado Growers' Assoc Yrb 8: 29-33. 
Lim, L; Mohd, M H; Zakaria, L (2019) Identification  and pathogenicity of Diaporthe species associated 
with stem-end rot of mango (Mangifera indica L.). European Journal of Plant Pathology 155(2): 687-
696. 
Menge, J A; Ploetz, R C (2003) Diseases of avocado.  Diseases of Tropical Fruit Crops. RC Ploetz, 
ed. CABI Publishing, Wallingford, UK : 35-71. 
Muirhead, I; Fitzell, R; Davis, R; Peterson, R (198 2) Post-harvest control of anthracnose and stem-
end rots of Fuerte avocados with prochloraz and oth er fungicides. Australian Journal of Experimental 
Agriculture 22(119): 441-446. 
NZPCN (2021) New Zealand Plant Conservation Network . https://www.nzpcn.org.nz/  Accessed June 
2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Peterson, R (1978) Susceptibility of Fuerte avocado  fruit at various stages of growth, to infection by  
anthracnose and stem end rot fungi. Australian Journal of Experimental Agriculture 18(90): 158-160. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 166 Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Udayanga, D; Liu, X; McKenzie, E H; Chukeatirote, E ; Bahkali, A H; Hyde, K D (2011) The genus 
Phomopsis : biology, applications, species concepts and names  of common phytopathogens. Fungal 
Diversity 50(1): 189-225. 
Uecker, F (1988) A world list of Phomopsis names wi th notes on nomenclature, morphology and 
biology. Mycologia memoir (13). 
Van der Merwe, M d V; Kotzé, J (1991) PHOMOPSIS PER SEAE THE CAUSE OF TRUNK CANKER 
OF MARTIN GRANDE AVOCADO ROOTSTOCKS IN SOUTH AFRICA . (14:85-86 ). 
Wilson, D (1995) Endophyte: the evolution of a term , and clarification of its use and definition. Oikos 
73: 274-276. 
Zerova, M (1940) Some Phomopsis species new for the  USSR. Botanichnii Zhurnal 1(2): 305-312. 
 
  
167 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.7  Diaporthe sterilis 
Diaporthe sterilis  is a fungus that has relatively recently been isol ated from branch cankers on 
avocado orchard plants in Italy. 
5.7.1  Taxonomic description 
Scientific name: Diaporthe sterilis L. Lombard, G. Polizzi & Crous (2014) 
Order/Family: Diaporthales/Diaporthaceae  
5.7.2  Hazard identification 
Diaporthe sterilis  is not known to be present in New Zealand: 
• Diaporthe sterilis  is not listed in NZOR (2021), Biota NZ (2022) or P PIN (2021) 
• Diaporthe sterilis  is not listed in ONZPR (2021) 
Diaporthe sterilis  has the potential to establish (and spread) in New  Zealand because: 
• The host plant, avocado, is grown commercially, an d in home gardens in some parts of New 
Zealand.  
• Vaccinium corymbosum (blueberry) is also a known host (Lombard et al. 20 14) of D. sterilis  
and it is grown commercially in both the North and South Island of New Zealand. 
• It is an endophytic pathogenic fungus that can be present on twigs, branches and trunks not 
showing diseased symptoms (Udayanga et al. 2011).  
• Climate is unlikely to be a barrier to its establi shment and spread in New Zealand, having 
been reported to occur in Italy which has a similar  climate (CMI ≥ 0.7) to New Zealand 
(Phillips et al. 2018).  
• Diaporthe sterilis can spread by human movement of infected nursery st ock and movement of 
infected fruits to avocado growing areas.  
Diaporthe sterilis  has the potential to cause harm to New Zealand bec ause: 
• Persea americana  is a known host of D. sterilis (Guarnaccia et al. 2016) as well as V. 
corymbosum (blueberry)  
• Diaporthe sterilis can occur endophytically on plant parts (Lombard et  al. 2014). Diaporthe 
spp. can occur on twigs, branches and pedicels of a vocado plants. From the pedicel, they can 
eventually colonise the inflorescence of the stem-e nd tissue and cause stem-end rot (Hartill 
and Everett 2002). 
• Avocados are an important commercial crop in New Z ealand. In the 2019–2020 financial 
year, export sales of fresh avocados earned NZ$112. 3 million and domestic sales earned 
NZ$50.6 million (Plant & Food Research 2020). 
Diaporthe sterilis  is associated with P. americana  budwood because: 
• Diaporthe sterilis was isolated from diseased avocado tissues that wer e showing symptoms of 
shoot and branch cankers from orchards in Italy and  caused stem-end rot disease in fruits 
during pathogenicity tests (Guarnaccia et al. 2016) .  
Given the arguments and evidence above, D. sterilis  meets the criteria to be a hazard on P. 
americana  budwood (as in the commodity description) imported  to New Zealand. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 168 5.7.3  Risk assessment 
Biology and epidemiology of Diaporthe sterilis 
Biology and host range 
Diaporthe sterilis was first described when it was isolated from V. corymbosum (blueberry)  in Italy 
where it was observed in association with trunk can kers (Lombard et al. 2014). It was associated with 
avocado in Italy after being isolated from diseased  avocado tissues showing symptoms such as shoot 
and branch cankers as well as stem-end rot disease in fruits from orchards (Guarnaccia et al. 2016). 
From 94 fungal isolates sampled from avocado orchar ds in Italy, six pathogenic fungi were identified, 
and D. sterilis  was isolated the least frequently (13%). The fungu s has also been isolated from dead 
aerial branches of the flowering plant Cytisus  sp.  in Italy (Dissanayake et al. 2017). Having been 
recently described, there is limited information ab out D. sterilis and at present it is only known to be 
associated with three plant species (in three plant  families) and reported only in three provinces in 
Italy (Table 5-10)  
Table 5-10: Known distribution and hosts of Diaport he sterilis. 
Continent  Country  State/Region  Host plant  CMI*  Reference  
Europe Italy Catania Province, 
Sicily  Persea americana (avocado)  0.8 Guarnaccia et al. (2016) 
Vaccinium corymbosum 
(blueberry)  (Ericaceae)  0.8 Lombard et al. (2014) 
Forli-Cesena 
Province Cytisus sp. (Fabaceae) 0.8–0.9 Dissanayake et al. (2017) 
*(Phillips et al. 2018) 
Depending on the host and the health of the host pl ants, most species of Diaporthe can exist as 
harmless endophytes or as pathogens (Udayanga et al . 2011). Diaporthe sterilis has been isolated 
(along with other Diaporthe spp.) from both symptomatic and asymptomatic Vaccinium spp. plant 
materials in Italy (Lombard et al. 2014). 
Symptoms 
Diaporthe sterilis was observed to cause cankers in branches of avocad o plants and has been 
isolated from cankered shoots and branches (Guarnac cia et al. 2016). While D. sterilis was not 
isolated from diseased fruits collected, it was obs erved to cause stem-end rot disease of fruits when a 
pathogenicity test was carried out to satisfy Koch’ s postulates (Guarnaccia et al. 2016). During 
pathogenicity tests, internal tissues of avocado st ems infected with D. sterilis were examined after 
three months and tissue discolouration was observed  (Guarnaccia et al. 2016). However, isolates of 
Diaporthe spp. including D. sterilis caused less severe symptoms (shoot cankers and stem -end rot) 
than other fungal species in avocado. This indicate s that it is not as virulent as some other pathogen ic 
fungi that cause cankers and stem-end rot diseases (Guarnaccia et al. 2016).  
Infected fruits developed brown to dark brown margi ns at the stem end after 10 days incubation at 
25° C. The flesh of the fruit showed discoloured int ernal vascular bundles and as the rot progressed 
during fruit ripening, the fruits , became brown an d shrivelled (Guarnaccia et al. 2016).  
Diaporthe sterilis is also known to cause disease symptoms on V. corymbosum (Lombard et al. 2014).  
It caused cankers at the base of a trunk, green ste ms and twigs resulting in the development of brown 
lesions and twig blight. Cankers present at the cro wn of the plant resulted in mortality  (Lombard et al. 
2014). Cankerous stems were also observed to have i nternal discolouration of the vascular tissues. 
Red to brown spots were also observed on the leaves  (Lombard et al. 2014). 
Transmission and spread  
Members of the genus Diaporthe in their endophytic phase can have a latent or dorm ant phase 
without showing any symptoms (Dann et al. 2013; Don g et al. 2020). This means that, potentially,  
169 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand symptomless cuttings of avocado can be infected wit h the fungus. They may be transmitted and 
spread through grafting especially in commercial av ocado plant nurseries. Under unfavourable 
environmental conditions such as drought, frost or hail, colonised plants can become stressed and 
begin to exhibit symptoms (Udayanga et al. 2011). 
Avocado fruits can be systemically infected with st em-end rot disease caused by pathogenic fungi 
from the genus Diaporthe.  However, Guarnaccia et al. (2016) found that D. sterilis did not infect 
avocado fruits with stem-end rot systemically. Duri ng the study, D. sterilis was not isolated from 
infected fruits (with stem-end rot symptoms) from t he orchard but it caused stem-end rot disease 
when infected artificially during pathogenicity tes ts (Guarnaccia et al. 2016). Under field conditions , 
fruits can get infected during harvest through the pedicel, pedicel scars or wounds (Darvas and 
Wehner 1987) and can be spread by the use of infect ed cutting implements during fruit harvest (Hartill  
and Everett 2002). 
Conditions for symptom development 
Specific conditions for symptom development of D. sterilis has not been specified. 
5.7.4  Likelihood of entry 
Diaporthe sterilis has so far been reported in association with avocad o only in the island of Sicily 
(Guarnaccia et al. 2016), and a very limited distri bution on other hosts on mainland Italy (Lombard et  
al. 2014; Guarnaccia et al. 2016). 
Members of the genus Diaporthe  are known to be present  on leafless and rootless avocado budwood 
without showing visible symptoms (Udayanga et al. 2 011). Given many Diaporthe species share 
similar characteristics such as asymptomatic infect ion, it is possible that D. sterilis  may not be 
detected during export preparation and pre-export p hytosanitary inspection to New Zealand or on 
arrival to New Zealand. Therefore, D. sterilis  has the potential to be associated with the commod ity 
when it arrives in Post Entry Quarantine (PEQ). 
All imported avocado germplasm will undergo PEQ at level 3A, during which the budwood will 
undergo a minimum of three distinct phenological pe riods of active growth. However, it is unclear if D. 
sterilis is likely to show symptoms and be detected in Level  3A PEQ. This is because conditions for 
symptom development of infection by D. sterilis have not been specifically described. However, from  
pathogenicity test, internal tissues of avocado ste ms were examined after three months and tissue 
discolouration was observed. Infected fruits develo ped brown to dark brown margin at the stem end 
after 10 days incubation at 25° C (Guarnaccia et al.  2016). The fact that D. sterilis has not been 
observed to produce conidia in culture (Guarnaccia et al. 2016) suggests it is possible that spores 
might not be produced on seedlings derived from inf ected budwood in PEQ, but can develop 
symptoms during the PEQ period. However, molecular diagnostic test might be required to detect 
asymptomatic infections.  
Given the arguments and evidence above, that is:  
• Diaporthe sterilis has the potential to be present on imported leafles s/rootless avocado 
budwood and may not show visible symptoms. 
• Infected budwood may exhibit symptoms during level  3A PEQ. However, this is uncertain 
because only a single study has been conducted, whi ch found that inoculated avocado plants 
showed discolouration of internal stem after three months.   
• Many Diaporthe species share similar characteristics such as asymp tomatic infection, so D. 
sterilis may be present  on leafless and rootless avocado budwood without sh owing visible 
symptoms. Molecular diagnostic testing may be requi red to detect asymptomatic infections.  
the likelihood of D. sterilis  entering New Zealand associated with Persea americana  budwood is 
considered to be high, with moderate  uncertainty. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 170 5.7.5  Likelihood of exposure 
This assessment is made on the basis that D. sterilis  has entered New Zealand undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for D. sterilis .   
If avocado plants are infected with D. sterilis  at the time of their release from Post Entry Quara ntine 
they will be planted in New Zealand or used to prop agate new plants for planting (see section 2.3 for 
additional information about exposure).  
Given the arguments and evidence above, the likelih ood of exposure of D. sterilis  in New Zealand 
from Persea americana  budwood is considered high , with moderate  uncertainty. The uncertainty is 
due to the little information available about this species.  
5.7.6  Likelihood of establishment 
This assessment is made on the basis that D. sterilis  has been successfully exposed to a suitable 
host plant in the New Zealand environment. 
Diaporthe sterilis is recorded to be present in regions of Italy that have a CMI range of between 0.8-
0.9. CMI, suggesting that the conditions in most pa rts of New Zealand are likely to be suitable for D . 
sterilis to occur and spread. Therefore, climate is not expe cted to be a barrier to the establishment of 
D. sterilis in New Zealand. 
Avocado plants are widely grown in some parts of Ne w Zealand commercially in orchards and in-
home gardens mostly in the North Island and some pa rts of the South Island (Chapter 2). Blueberries 
are grown in parts of the North and South Island of  New Zealand (Coriolis 2020), Therefore, suitable 
hosts are available in both the North and South Isl and of New Zealand for D. sterilis to establish.  
Given the arguments and evidence above, that is: 
• The climatic conditions in most parts of New Zeala nd are likely to be suitable for D . sterilis to 
establish. 
• Suitable host plants (avocado and blueberry) are a vailable in the North and South Island of 
New Zealand. 
• Uncertain why D . sterilis hasn’t yet spread to different parts of Europe wher e hosts plants are 
available and there are limited controls on plant m ovement. 
the likelihood of D. sterilis  establishing in New Zealand is considered moderate , with moderate 
uncertainty. The uncertainty is due to the little i nformation available about this species. 
5.7.7  Impacts in New Zealand 
Diaporthe sterilis  has so far been reported to be present in Italy in  association with avocado, blueberry 
and Cytisus  sp. (Lombard et al. 2014; Guarnaccia et al. 2016).  It was isolated from cankers on 
avocado branches on one occasion (Guarnaccia et al.  2016). It was also reported to cause cankers 
on trunks, twigs and stems of blueberry plants in I taly (Lombard et al. 2014). 
Diaporthe sterilis  is likely to be spread by the movement of infected  nursery stock for planting. 
Avocado plants are widely grown in some parts of Ne w Zealand commercially in orchards and in-
home gardens mostly in the North Island and some pa rts of the South Island (New Zealand Avocado 
2021). Blueberries are grown in parts of the North and South Island of New Zealand (Coriolis 2020), 
Therefore, suitable hosts are available in both the  North and South Island of New Zealand for D. 
sterilis  to spread.  
171 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Economic impacts 
Diaporthe species including D. sterilis was observed to cause stem/shoot cankers of avocado  in Italy 
(Guarnaccia et al. 2016), however, It was one of th e least frequent and virulent fungus obtained from 
diseased trunks and shoots (Guarnaccia et al. 2016) . Reports of this fungus affecting avocado fruits 
by causing stem-end-rot, have come from artificial infection i.e., pathogenicity tests (Guarnaccia et al. 
2016), but there are no reports of this D. sterilis  naturally infecting avocado fruits. D. sterilis  is likely to 
cause less severe disease symptoms in avocado compa red to other fungal pathogens such as 
Colletotrichum  gloeosporioides, and Phomopsis  spp. that are already present and common in New 
Zealand (Hartill and Everett 2002). This suggests t hat while D. sterilis  can result in some postharvest 
losses of avocado fruits, overall losses may not di ffer from current levels of stem-end rot diseases i n 
New Zealand.  
Infections by D. sterilis may affect market access of exports of avocado to o ther parts of the world 
where D. sterilis is not reported to be present. Because D. sterilis is reported to cause diseases in 
avocado in only one country, its presence in New Ze aland can potentially result in trade barriers to 
countries where it is has not been reported to be p resent.  
Diaporthe sterilis causes disease symptoms on blueberries;  it caused cankers at the base and brown 
lesions on stems resulting in twig blight (Lombard et al. 2014). The blueberry industry is a growing 
industry in New Zealand with an estimate of NZ$70-8 0 million in both domestic and international trade 
in 2020 (Coriolis 2020). While D. sterilis  has the potential to affect blueberry production i n New 
Zealand and can lead to reduced yield, its overall impact on blueberry production has not been 
quantified. 
Given the arguments and evidence above, that is: 
• D. sterilis can cause trunk cankers and potentially result in s ome postharvest losses of 
avocado. Overall losses may not differ from current  levels of losses caused by other 
pathogenic fungi on avocado already present in New Zealand. 
• Vaccinium corymbosum is a known host of D. sterilis. The potential impacts on blueberry 
production have not been assessed and quantified bu t could potentially affect blueberry 
production in New Zealand and lead to reduced yield . In 2020, blueberry industry in New 
Zealand was estimated to be worth between NZ$70-80 million in both domestic and 
international trade. 
the economic impact of D. sterilis  to New Zealand is considered to be very  low  with moderate  
uncertainty. 
Environmental impacts 
Infection by D. sterilis has only been demonstrated to be associated with av ocados, blueberries and  
Cytisus sp. so far (Lombard et al. 2014; Guarnaccia et al. 2016). Although it has only been recorded 
in three host plants, it is likely it can infect ot her plants. Having been associated with Cytisus sp. in 
Italy (Dissanayake et al. 2017), it can potentially  infect and be an inoculum source (that can infect 
other plant species) in the two similar weed specie s ( Cytisus scoparius  and Genista monspessulana ) 
which have naturalised and are widely spread in New  Zealand (Weedbusters 2022).   
Searches from Google, Google scholar, U.S. National Fungus Collections Fungus-Host 
Distributions Database, CABI and EPPO using the search term ‘ Diaporthe sterilis and the 
environment’ found no record of D. sterilis causing environmental impacts. 
Given the arguments and evidence above, the impact on the environment from the establishment of 
D. sterilis  in New Zealand is considered to be very  low , with moderate uncertainty. 
Human health impacts 
Searches using the search term ‘ Diaporthe sterilis impacts on health’ from Google, Google scholar, 
CABI and Pubmed found no record of D. sterilis causing any health impact on humans and animals. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 172 Given the arguments and evidence above, the human h ealth impact of Diaporthe sterilis to 
New Zealand is considered to be negligible with low  uncertainty. 
Sociocultural impacts 
Avocado has become popular and is widely consumed i n New Zealand. It is commonly grown in 
home gardens in some parts of the country. Diaporthe sterilis can potentially cause diseases such as 
stem-end rot disease. This can result in rot of avo cado fruits making them inedible and can lead to 
reduced yield for home gardeners and scarcity in lo cal markets. Blueberry is also grown in 
commercial quantities and widely consumed in New Ze aland. The impact of D. sterilis on avocado  
has not been assessed and quantified.  
Given the arguments and evidence above, the sociocu ltural impact of D. sterilis to New Zealand is 
considered to be very  low , with low  uncertainty. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, human health and society is 
considered to very low  with moderate uncertainty. 
5.7.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is high , with moderate  uncertainty 
• assuming entry, the likelihood of exposure is high , with moderate  uncertainty 
• assuming successful exposure, the likelihood of es tablishment is moderate , with 
moderate uncertainty. 
• the overall impact on the New Zealand economy, env ironment, human health and society 
is considered to be very  low , with moderate  uncertainty. 
the overall level of assessed risk to New Zealand f rom D. sterilis  on imported P. americana budwood 
(as in the commodity description) is considered to be low , with moderate  uncertainty. 
5.7.9  Management considerations 
Diaporthe sterilis  was observed in association with cankers in branch es of avocado plants when it 
was isolated along with other fungi on cankered sho ots and branches. It was not isolated from 
diseased fruits collected during this study, but it  caused stem-end rot disease of fruits when a 
pathogenicity test was carried out to satisfy Koch’ s postulates (Guarnaccia et al. 2016). 
Infected fruits developed brown to dark brown margi ns at the stem end after 10 days incubation at 
25° C. The flesh of the fruit showed discoloured vas cular bundles and the rot progressed as the fruit 
ripened, it generally became brown and shrivelled ( Guarnaccia et al. 2016). 
Environmental conditions conducive for development of trunk cankers caused by  D. sterilis have not 
been specified. During pathogenicity test, fruits i nfected with D. sterilis  developed dark to brown 
margins at the stem end after 10 days incubation at  25° C (Guarnaccia et al. 2016).  
Samples can be taken for testing from any part of t he avocado leafless budwood and testing different 
parts of the budwood might be required. Because, li ke other Diaporthe species,  it can be present on 
twigs, branches and trunks not showing diseased sym ptoms (Udayanga et al. 2011). 
Optimum season for conducting detection has not bee n specified.   
173 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.7.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
D. sterilis  was isolated along with other fungi from cankered shoots and branches of avocado plants. 
It was not isolated from diseased fruits collected during this study, but it caused stem-end rot disea se 
of fruits when a pathogenicity test was carried out  to satisfy Koch’s postulates (Guarnaccia et al. 
2016). 
o What are the known environmental conditions conduci ve to symptom expression? 
Environmental conditions conducive for development of trunk cankers caused by  D. sterilis have not 
been specified. During pathogenicity test, fruits i nfected with D. sterilis  developed brown to dark 
brown margin at the stem end after 10 days incubati on at 25° C (Guarnaccia et al. 2016).  
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections? 
Samples can be taken for testing from any part of t he avocado leafless budwood and testing different 
parts of the budwood might be required. Because lik e other Diaporthe’s it can be present on twigs, 
branches and trunks not showing diseased symptoms ( Udayanga et al. 2011). 
o What is the optimum season for conducting detection  testing? 
Optimum season for conducting detection has not bee n specified.  
5.7.11  References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Coriolis (2020) Opportunities in the New Zealand Blueberry Industry . 
https://www.mbie.govt.nz/dmsdocument/11670-opportun ities-in-the-new-zealand-blueberries-industry  
Dann, E; Ploetz, R; Coates, L; Pegg, K (2013) Folia r, fruit and soliborne diseases. In B Schaffer; B 
Wolstenholme; A Whiley (eds) The avocado: botany, production and uses. 2nd ed. CABI: London, 
UK. 
Darvas, J, Kotze, JM; Wehner, F (1987) Pathogenicit y of fungi causing pre-and postharvest diseases 
of avocado fruit. Phytophylactica 19(4): 489-494. 
Dissanayake, A J; Camporesi, E; Hyde, K D; Zhang, W ; Yan, J Y; Li, X H (2017) Molecular 
phylogenetic analysis reveals seven new Diaporthe  species from Italy.  . Mycosphere 8: 853–877. 
Dong, Z; Manawasinghe, I S; Huang, Y; Shu, Y; Phill ips, A J L; Dissanayake, A J, et al. (2020) 
Endophytic Diaporthe associated with Citrus grandis cv tomentosa in China. Frontiers in Microbiology 
11: 3621. 
Guarnaccia, V; Vitale, A; Cirvilleri, G; Aiello, D;  Susca, A; Epifani, F, et al. (2016) Characterisati on and 
pathogenicity of fungal species associated with bra nch cankers and stem-end rot of avocado in Italy. 
European Journal of Plant Pathology 146(4): 963-976. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 174 Hartill, W F T; Everett, K R (2002) Inoculum source s and infection pathways of pathogens causing 
stem ‐end rots of ‘Hass’ avocado ( Persea americana ). New Zealand Journal of Crop and Horticultural 
Science 30(4): 249-260. 
Lombard, L; van Leeuwen, G; Guarnaccia, V; Polizzi,  G; van Rijswick, P; Rosedahl, K, et al. (2014) 
Diaporthe  species associated with Vaccinium , with specific reference to Europe. Phytopathologia 
Mediterranea 53(2): 287-299. 
New Zealand Avocado (2021) General questions. https://industry.nzavocado.co.nz/contact/faq-and-
help/faq-and-help-guide/   
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Udayanga, D; Liu, X; McKenzie, E H; Chukeatirote, E ; Bahkali, A H; Hyde, K D (2011) The genus 
Phomopsis : biology, applications, species concepts and names  of common phytopathogens. Fungal 
Diversity 50(1): 189-225. 
Weedbusters (2022) Weed List. Cytisus . https://www.weedbusters.org.nz/what-are-weeds/weed-
list/?weed-search=Cytisus + Accessed 28/02/2022 
 
  
175 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.8  Dothiorella aromatica 
Dothiorella aromatica is a fungal plant pathogen that causes stem-end rot  (postharvest) disease in 
avocado. It has also been associated with stem-end rot disease in mangos. 
5.8.1  Taxonomic description 
Scientific name: Dothiorella aromatica  (Sacc.) Petr. & Syd. (1927)   
Order/Family: Botryosphaeriales/ Botryosphaeriaceae  
Other names include : Macrophoma aromatica  Sacc. (1915) 
5.8.2  Hazard identification 
Dothiorella aromatica is not known to be present in New Zealand.  
o Dothiorella aromatica is not listed in PPIN (2021) 
o Dothiorella aromatica is recorded as absent from New Zealand in Biota NZ (2022) 
o Dothiorella aromatica is a regulated pest for New Zealand, has unwanted s tatus but is 
not a notifiable organism in ONZPR (2021). 
Dothiorella aromatica has the potential to establish (and spread) in New Zealand because: 
• the host plant, avocado is grown commercially, and  in home gardens in some parts of 
New Zealand.  
• it is an endophytic pathogenic fungus, which has b een isolated from twigs, stems, and 
inflorescence of asymptomatic avocado plants. It ca n be present on all parts of an infected 
tree (Johnson et al. 1992).   
• climate is unlikely to be a barrier to its establi shment and spread in New Zealand because it 
occurs in Australia and South Africa, which have a similar climate (CMI) ≥ 0.7 to New Zealand 
(Phillips et al. 2018).  
• Dothiorella aromatica can spread naturally by wind and rain or by human m ovement of 
infected nursery stock and movement of infected fru its to avocado growing areas.  
Dothiorella aromatica has the potential to cause harm to New Zealand beca use: 
• Dothiorella aromatica has been associated with and shown to cause posthar vest (stem-end) 
rot disease in avocado (Darvas and Kotzé 1981; Darv as and Kotze 1987b; Korsten et al. 
1994).  
• postharvest rot diseases caused by D. aromatica can affect the marketability of avocado 
crops in New Zealand. It is an important commercial  crop in New Zealand worth up to $110 
million in domestic sales and up to 56.6 million in  domestic sales (Plant & Food Research 
2019).  
Dothiorella aromatica is associated with P. americana  budwood because: 
• Persea americana  is a known host of D. aromatica (Peterson 1978; Darvas and Kotzé 1981; 
Darvas and Kotze 1987b; Darvas and Wehner 1987); 
• Dothiorella aromatica can occur endophytically on twigs, branches and ped icels of and 
infected avocado plant  (Darvas and Kotze 1987b). I t can eventually colonise the 
inflorescence from the pedicel of the stem-end tiss ue and cause stem-end rot (Hartill and 
Everett 2002). 
Given the arguments and evidence above, D. aromatica  meets the criteria to be a hazard on Persea 
americana  budwood (as per the commodity description) importe d to New Zealand. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 176 5.8.3  Risk assessment 
Biology and epidemiology of Dothiorella aromatica 
Biology and host range 
Depending on the host and the health of the host pl ants, species from the family Botryosphaeriaceae  
can exist as harmless endophytes or as pathogens (U dayanga et al. 2011). Dothiorella aromatica can 
be an endophytic (can inhabit plant tissues without  showing visible symptoms) and pathogenic fungus 
(Johnson et al. 1992; Wilson 1995) that is known to  cause stem-end rot disease and post-harvest rot 
(Kotzé and Darvas 1985; Darvas and Kotze 1987b). Dothiorella aromatica can occur on twigs, 
branches and pedicels of avocado plants (Darvas and  Kotze 1987b; Johnson et al. 1992). From the 
pedicel, it can eventually colonise the inflorescen ce (flowers) of the of the stem-end tissue and caus e 
stem-end rot (Hartill and Everett 2002).  
Stem-end rot is often reported to be caused by seve ral fungal pathogens (Darvas and Kotze 1987b; 
Korsten et al. 1994; Guarnaccia et al. 2016). Dothiorella aromatica was one of the most frequently 
isolated pathogens from avocado exhibiting stem-end  rot disease symptoms collected from avocado 
producing areas in South Africa (Korsten et al. 199 4) (Table 5-11).   
Table 5-11: Dothiorella aromatica  host and geographic range, and disease symptoms 
Continent Country  State/Region Host plants Symptoms 
/disease CMI* Reference  
Oceania  Australia  Queensland  Persea americana 
(avocado)  Stem-end rot  0.7  (Peterson 1978)  
Magnifera indica (Mango)  Stem-end rot 0.6 - 0.9 (Johnson et al. 1992) 
Africa South Africa   Persea americana 
(avocado)  Stem-end rot  0.6 - 0.8  (Darvas and Kotzé 
1978; Darvas and 
Kotze 1987a)  
*(Phillips et al. 2018) 
Reproduction and spread 
Fruiting bodies of D. aromatica  are rarely seen on twigs and branches of avocado p lants, but have 
been observed in abundance on fallen fruits on the ground and can also be observed on dead 
branches or barks (Darvas and Kotze 1987b). These f allen fruiting bodies usually can serve as a 
source of primary infection (Dann et al. 2013) and can be transferred to open wounds on plants, the 
pedicel, and fruits, and can potentially be spread by rain splashes or wind (Menge and Ploetz 2003). 
Most stem-end rot infections occur during harvest t hrough the pedicel, pedicel scars or wounds 
(Darvas and Wehner 1987). Infections can occur thro ugh wounds on the bark of the tree or wounds 
created through picking of fruit in the field (Kotz é and Darvas 1985; Hartill and Everett 2002). It ca n 
also be spread by the use of the same cutting imple ment from an infected plant to a non-infected 
plant (Hartill and Everett 2002).  
Dothiorella aromatica,  in its endophytic phase, can be latent or dormant without showing any 
symptoms (Johnson et al. 1992). This means that sym ptomless cuttings of avocado plants infected 
with D. aromatica can be transmitted and spread through grafting espe cially in commercial avocado 
plant nurseries.  
Infection and spread of D. aromatica (as well as other pathogenic fungi associated with avocado) 
occurs mostly during prolonged wet periods of rain and high humidity (Darvas and Kotzé 1978; 
Peterson 1978; Darvas et al. 1987). Peterson (1978)  found that natural infection of fruits did not occ ur 
in dry conditions but occurred after four or more c onservative days of rainfall.   
177 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Symptoms 
Dothiorella aromatica  can have a latent or dormant phase of infection wi thin the plant tissues (Wilson 
1995). Hence, it can be present throughout the life  cycle of infected plants without showing visible 
symptoms. Symptoms of D. aromatica such as lesions and rot, which produces spores, ten d to only 
occur after harvest (Darvas and Kotzé 1978; Peterso n 1978). This means that in its latent phase, D. 
aromatica  can occur in healthy looking avocado twigs and ste ms, with no visible symptoms.   
In its pathogenic phase, D. aromatica  colonises the xylem and the phloem at the stem-end  of the fruit 
(Karunanayake and Adikaram 2020). Dothiorella aromatica eventually becomes necrotrophic 
(secretes enzymes that kill the host tissues while living on the nutrients from the dead tissues), 
causing stem-end rot by colonising the fruit pulp ( Karunanayake and Adikaram 2020).  Infection can 
remain latent (not show symptoms) prior to harvest with symptoms only becoming apparent after 
harvest (Peterson 1978). Immature fruits are more v ulnerable to stem-end rot infections than mature 
fruits (Kotzé and Darvas 1985). 
Stem-end rot symptoms develop after harvest, at the  onset of fruit ripening (Darvas and Kotzé 1978; 
Darvas et al. 1987; Karunanayake and Adikaram 2020) . Visible symptoms begin as brownish or black 
rot at the fruit pedicel which progresses internall y causing discolouration and decay. Internal decay 
may extend on the external part of the fruit leadin g to brown or black discolouration (Darvas and 
Wehner 1987; Karunanayake and Adikaram 2020). Mycel ium and abundant spores might be 
observed on the abscission scar of infected fruit a nd can eventually cover the fruit as ripening 
progresses, leading to softening and shrivelling of  the entire fruit (Menge and Ploetz 2003).  
Pathogenicity tests using avocado fruits showed tha t all artificially infected fruits developed sympto ms 
(lesions) 10 days post inoculation (Peterson 1978; Kotzé and Darvas 1985). 
Conditions for symptom development 
Infection and spread of D. aromatica (as well as other pathogenic fungi associated with avocado) 
occurs mostly during prolonged wet periods of rain and high humidity (Darvas and Kotzé 1978; 
Peterson 1978; Darvas et al. 1987). Peterson (1978)  found that natural infection of fruits did not occ ur 
in dry conditions but occurred after four or more c onservative days of rainfall. Under laboratory 
conditions, temperature was observed to affect spor e germination of D. aromatica , with the minimum 
and maximum temperature limits of 10-35° C (Denner e t al. 1986) and an optimum growth 
temperature of 25° C (Schoeman 2005).   
5.8.4  Likelihood of entry 
Dothiorella aromatica  has been reported to be associated with avocado in  South Africa and Australia 
and is associated with mangos in Australia (Darvas and Kotzé 1978; Peterson 1978; Johnson et al. 
1992).  
In its endophytic phase, it can be present  inside leafless and rootless avocado budwood withou t 
showing visible symptoms (Johnson et al. 1992). The refore, it is likely it will not be detected during  
export preparation and pre-export phytosanitary ins pection to New Zealand or on arrival to 
New Zealand. 
All imported avocado germplasm will undergo PEQ at level 3A, during which the budwood will 
undergo a minimum of three distinct phenological pe riods of active growth. The period in Level 3A 
PEQ is not likely to impact the likelihood of entry  of D. aromatica . Seedlings derived from infected 
budwood grafted in PEQ level 3A are not likely to s how visible symptoms within the time in PEQ. This 
is because D. aromatica  has only been reported to cause symptoms (stem-end  rot disease) on 
avocado fruits (Peterson 1978; Darvas et al. 1987),  therefore unlikely to produce visible symptoms. 
Fruiting bodies of D. aromatica  are rarely seen on twigs and branches of avocado p lants, but have 
been observed in abundance on fallen fruits on the ground and can also be observed on dead 
branches or barks (Darvas et al. 1987). It is, high ly unlikely that spores will be produced on seedlin gs 
derived from infected imported budwood and escape f rom PEQ without being detected. As such, Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 178 infected seedlings are likely to remain undetected unless molecular diagnostic testing for D. aromatica  
is carried out. 
Given the arguments and evidence above, that is:  
• it can be present  on leafless and rootless avocado budwood without sh owing visible symptom  
• infected budwood that is grafted in PEQ level 3A i s not likely to show any visible symptoms 
within the time in PEQ if the fungus is in a latent  phase. 
• infected plants are likely to remain undetected un less molecular diagnostic testing for D. 
aromatica  is carried out. 
the likelihood of D. aromatica  entering New Zealand associated with Persea americana  budwood is 
considered to be high, with low uncertainty. 
5.8.5  Likelihood of exposure 
This assessment is made on the basis that D. aromatica  has entered New Zealand undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for D. aromatica . 
If avocado plants are infected with D. aromatica  at the time of their release from post entry 
quarantine, they will be planted in New Zealand or used to propagate new plants for planting (see 
section 2.3 for additional information about exposu re).  
Given the arguments and evidence above, the likelih ood of exposure of D. aromatica  in New Zealand 
from Persea americana  budwood is considered high, with low uncertainty. 
5.8.6  Likelihood of establishment 
This assessment is made on the basis that D. aromatica  has been successfully exposed to a suitable 
host plant in the New Zealand environment. 
Dothiorella aromatica  is recorded to be present in Australia (Queensland ) and South Africa which 
have a Composite match index (CMI) range of between  0.6-0.8. A CMI of ≥ 0.7 indicates a similar 
climate to the whole of New Zealand (Phillips et al . 2018). As such, the conditions in some parts of 
New Zealand are likely to be suitable for D. aromatica to occur and spread. Therefore, climate is not 
considered to be a barrier to the establishment of D. aromatica in New Zealand.  
Avocado plants are widely grown in some parts of Ne w Zealand commercially in orchards and in-
home gardens mostly in the North Island and some pa rts of the South Island (New Zealand Avocado 
2021), therefore suitable hosts are available in th ose areas. Dothiorella aromatica can spread by the 
movement of infected nursery stock for planting. Ho wever, its spread might be limited by host 
availability because it has only been recorded to b e associated with avocado (Darvas and Kotzé 
1978) and mangoes (Peterson 1978; Johnson et al. 19 92). However, mangos are not grown in New 
Zealand; therefore, it is likely that D. aromatica will be restricted to avocado growing areas of New 
Zealand.  
Spores of D. aromatica are usually produced on rotting fruits and have bee n observed in abundance 
on fallen fruits on the ground (Darvas et al. 1987) . This suggests that infected fruit that is discard ed 
near avocado plants could be a source of inoculum. Therefore, D. aromatica could be spread to new 
areas by human movement of infected fruit. 
Given the arguments and evidence above, that is:  
179 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • the climatic conditions in some parts of New Zeala nd are likely to be suitable for D . aromatica 
to occur and spread. 
• suitable avocado host plants are available in orch ards and in-home gardens mostly in the 
North Island and some parts of the South Island. D. aromatica can spread by the movement 
of infected nursery stock for planting. 
• spores of D. aromatica can be present on infected fruit and can be spread to new areas by 
human movement of infected fruit. 
the likelihood of D. aromatica establishing in New Zealand is considered high, wit h low-moderate 
uncertainty. 
5.8.7  Impacts in New Zealand 
Dothiorella aromatica have been reported to be asso ciated with avocado and mangoes, causing 
stem-end rot (postharvest) disease (Darvas and Wehn er 1987; Johnson et al. 1992).  Dothiorella 
aromatica  can occur in plant tissue without showing symptoms  (Johnson et al. 1992). As such, 
symptomless cuttings of avocado plants infected wit h D. aromatica can be transmitted and spread 
through grafting especially in commercial avocado p lant nurseries. Fruiting bodies of D. aromatica  
have been observed in abundance on fallen fruits on  the ground and on dead branches or barks 
(Darvas and Kotze 1987b). These fallen fruiting bod ies usually can serve as a source of primary 
infection (Dann et al. 2013) and can be transferred  to open wounds on plants, the pedicel, and fruits,  
and can potentially be spread by rain splashes or w ind (Menge and Ploetz 2003). 
Economic impacts 
Dothiorella aromatica causes stem-end rot disease symptoms that can go un noticed and mainly 
become apparent after harvest. Stem-end rot symptom s become apparent at the onset of fruit 
ripening (Karunanayake and Adikaram 2020). Low temp eratures can mask symptoms on infected fruit 
(Darvas 1982), rot symptoms can become apparent out side those stem-end rot caused by 
Colletotrichum  gloeosporioides and Phomopsis  spp. are also common in New Zealand (Hartill and 
Everett 2002). This suggests that while D. aromatica  can result in some postharvest losses of 
avocado fruits, it is likely to be managed by prese nt practices in place for managing stem-end rot 
disease in New Zealand.  Post-harvest disease cause d by D. aromatica can be controlled to an extent 
by pre-harvest fungicide sprays such as benomyl, ca ptafol, Cu-oxychloride and Cu-hydroxide (Darvas 
and Kotze 1987a). Post-harvest disease caused by D. aromatica can be controlled to an extent by 
pre-harvest fungicide sprays such as benomyl, capta fol, Cu-oxychloride and Cu-hydroxide (Darvas 
and Kotze 1987a). Overall losses may not differ fro m current levels of stem-end rot diseases.    
Infections by D. aromatica can affect market access of exports of avocado to o ther parts of the world 
where D. aromatica is not reported to be present (Table 5-11). The fac t that it is recorded as present 
in Australia, which is New Zealand’s major export m arket, suggests it is not likely to have a signific ant 
impact on export. But its presence in New Zealand c an potentially result in trade barriers to other 
countries where it is has not been reported to be p resent.  
Given the arguments and evidence above, that is: 
• Dothiorella aromatica can result in some postharvest losses of avocado, b ut overall 
losses may not differ from current levels of stem-e nd rot disease in New Zealand. 
• current methods of control of other stem-end rot c ausing pathogens in New Zealand may 
also be effective for controlling disease caused by  D. aromatica . 
• the establishment of D. aromatica is not likely to affect market access of export of 
avocado to Australia (which is one of New Zealand’s  major export market) but could 
potentially affect market access of export to other  parts of the world where it is not 
reported to be present.   
the economic impact of D. aromatica to New Zealand is considered to be low , with low  
uncertainty. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 180 Environmental impacts 
Dothiorella aromatica has been reported to infect avocado and mangos (Dar vas and Kotzé 1978; 
Peterson 1978; Johnson et al. 1992). Searches from Google, Google scholar, U.S. National Fungus 
Collections Fungus-Host Distributions Database, CAB I and EPPO using the search term ‘ Dothiorella 
aromatica and the environment’ found no record of D. aromatica infecting other plants. This suggests 
that D. aromatica is not likely to affect native plants and the envir onment.  
Given the arguments and evidence above, the impact on the environment from the establishment of 
D. aromatica  in New Zealand is considered to be very low, with low uncertainty.  
Human health impacts 
Searches using the term ‘ Dothiorella aromatica impacts on health’ from Google, Google scholar, CAB I 
and Pubmed found no record of D. aromatica causing any health impact on humans and animals. 
Given the arguments and evidence above, the health impact of D. aromatica  to New Zealand is 
considered to be negligible, with low uncertainty. 
Sociocultural impacts  
Avocado has become popular and is widely consumed i n New Zealand. It is commonly grown in 
home gardens in some parts of the country. Stem-end  rot disease causes rot in avocado and makes 
the fruit inedible and can cause scarcity in local markets.  
Given the arguments and evidence above, the sociocu ltural impact of D. aromatica to New Zealand is 
considered to be low, with low uncertainty. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, health and society is considered to be 
low, with low uncertainty. 
5.8.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is high with low uncertain ty, 
• assuming entry, the likelihood of exposure is high  with low uncertainty, 
• assuming successful exposure, the likelihood of es tablishment is high with low-moderate 
uncertainty, 
• the overall impact on the New Zealand economy, env ironment, health and society is 
considered to be low with low uncertainty. 
the overall level of assessed risk to New Zealand f rom D. aromatica  on imported Persea americana 
budwood (as in the commodity description) is consid ered to be low , with moderate  uncertainty. 
5.8.9  Management considerations 
Symptoms caused by D. aromatica are not likely to be expressed during the growing p eriod in PEQ.  It  
can occur in healthy looking avocado twigs and stem s and be present throughout the life cycle of 
infected plants without showing visible symptoms; s tem-end rot symptoms only develop after fruit 
harvest (Peterson 1978). 
Infection and spread of D. aromatica (as well as other pathogenic fungi associated with avocado) 
occurs mostly during prolonged wet periods of rain and high humidity (Darvas and Kotzé 1978; 
Peterson 1978; Darvas et al. 1987). Peterson (1978)  found that natural infection of fruits did not occ ur 
in dry conditions but occurred after four or more c onservative days of rainfall. Under laboratory  
181 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand conditions, germination of D. aromatica  spore were affected by temperature, with a suitabl e growing 
range of 10-35° C (Denner et al. 1986) and an optimu m growth temperature of 25° C (Schoeman 
2005).   
Infection and spread of D. aromatica (as well as other pathogenic fungi associated with avocado) 
occurs mostly during prolonged wet periods of rain and high humidity (Darvas and Kotzé 1978; 
Peterson 1978; Darvas et al. 1987). Peterson (1978)  found that natural infection of fruits did not occ ur 
in dry conditions but occurred after four or more c onservative days of rainfall.  
Samples can be taken for testing from any part of t he avocado leafless budwood and testing different 
parts of the budwood might be required. This is bec ause D. aromatica can occur in healthy looking 
avocado twigs and stems and be present throughout t he life cycle of infected plants without showing 
visible symptoms (Peterson 1978). However, it is no t clear if the pathogen will be evenly distributed or 
not throughout an infected avocado budwood and that  the right bit will be tested.  
Post-harvest disease caused by D. aromatica can be controlled to an extent by pre-harvest fungi cide 
sprays such as benomyl, captafol, Cu-oxychloride an d Cu-hydroxide (Darvas and Kotze 1987a). 
Optimum season or conditions for conducting detecti on testing has not been specified.   
5.8.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Symptoms caused by D. aromatica are unlikely to be expressed during the growing per iod in PEQ. 
Dothiorella aromatica can occur in healthy looking avocado twigs and stem s and can be present 
throughout the life cycle of infected plants withou t showing visible symptoms, with stem-end rot 
symptoms (which is the only symptom it has been rep orted to cause) developing in immature fruit on 
the tree and ripening fruit post-harvest (Peterson 1978; Darvas and Wehner 1987). 
o What are the known environmental conditions conduci ve to symptom expression? 
In general, pathogenic endophytic fungi can exhibit  symptoms under environmental stresses such as 
drought, hail or frost (Udayanga et al. 2011). Howe ver, because D. aromatica causes postharvest rot 
which only develops during fruit ripening (Darvas a nd Kotzé 1978; Darvas and Kotze 1987a), 
conditions conducive for symptom expression in avoc ado seedlings derived from budwood infected 
with D. aromatica have not been specified. This is because they are n ot likely to express symptoms 
within the level 3A PEQ period. However, under labo ratory conditions, germination of D. aromatica  
spores occur within a range of 10-35° C (Denner et a l. 1986) and optimum growth occurs at 25° C 
(Schoeman 2005).   
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Samples can be taken for testing from any part of t he avocado leafless budwood and testing different 
parts of the budwood might be required. This is bec ause D. aromatica can occur in healthy looking 
avocado twigs and stems and be present throughout t he life cycle of infected plants without showing 
visible symptoms (Peterson 1978). It is not clear i f it will be evenly distributed throughout an infec ted 
avocado budwood; therefore, there is a high chance of false negatives.  
o What is the optimum season for conducting detection  testing? 
An optimum season or conditions for conducting dete ction testing has not been identified from the 
literature.  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 182 5.8.11  References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Dann, E R; Ploetz, R C; Coates, L M; Pegg, K G (201 3) 13 Foliar, fruit and soilborne diseases. The 
avocado botany, production and uses.  
Darvas, J (1982) Etiology and control of some fruit diseases of avoc ado (Persea americana Mill) at 
Westfalia Estate.  thesis; University of Pretoria, South Africa., Sou th Africa. Retrieved from 
http://www.avocadosource.com/papers/SouthAfrica_Pap ers/DarvasJozsef1982/THESIS_JOE%20DA 
RVAS_TITLE%20PAGE.pdf   
Darvas, J; Kotze, J (1987a) Avocado fruit diseases and their control in South Africa. South African 
Avocado Growers' Association Yearbook 10: 117-119. 
Darvas, J; Kotze, J (1987b) Fungi associated with p re-and postharvest diseases of avocado fruit at 
Westfalia Estate, South Africa. Phytophylactica 19(1): 83-86. 
Darvas, J; Kotzé, J (1978) Stem-end rot and other p ost-harvest diseases. South African Avocado 
Growers’ Association Yearbook 2: 49-51. 
Darvas, J; Kotzé, J (1981) Post-harvest diseases of  avocados. South African Avocado Grower’s 
Association Year Book 4: 63 66. 
Darvas, J; Kotze, J; Wehner, F (1987) Field occurre nce and control of fungi causing postharvest 
decay of avocados. Phytophylactica 19(4): 453-456. 
Darvas, J, Kotze, JM; Wehner, F (1987) Pathogenicit y of fungi causing pre-and postharvest diseases 
of avocado fruit. Phytophylactica 19(4): 489-494. 
Denner, F; Kotzé, J; Putterill, J (1986) The effect  of temperature on spore germination, growth and 
appressorium formation of Colletotrichum gloeospori oides and Dothiorella aromatica. South Arican 
Avocado Growers’ Association Yearbook 9: 19-22. 
Guarnaccia, V; Vitale, A; Cirvilleri, G; Aiello, D;  Susca, A; Epifani, F, et al. (2016) Characterisati on and 
pathogenicity of fungal species associated with bra nch cankers and stem-end rot of avocado in Italy. 
European Journal of Plant Pathology 146(4): 963-976. 
Hartill, W F T; Everett, K R (2002) Inoculum source s and infection pathways of pathogens causing 
stem ‐end rots of ‘Hass’ avocado ( Persea americana ). New Zealand Journal of Crop and Horticultural 
Science 30(4): 249-260. 
Johnson, G; Mead, A; Cooke, A; Dean, J (1992) Mango  stem end rot pathogens ‐fruit infection by 
endophytic colonisation of the inflorescence and pe dicel. Annals of Applied Biology 120(2): 225-234. 
Karunanayake, K; Adikaram, N (2020) Stem-end rot in  major tropical and sub-tropical fruit species. 
Ceylon J Sci 49(5): 327-336. 
Korsten, L; Sanders, G M; Grosse-Weischede, E (1994 ) Isolation and pathogenicity of avocado post-
harvest pathogens from Westfalia and other avocado producing areas. South African Avocado 
Growers’ Association Year book 17: 46-48. 
Kotzé, J; Darvas, J (1985) Symptoms and causes. SA Avocado Growers' Assoc Yrb 8: 29-33. 
Menge, J A; Ploetz, R C (2003) Diseases of avocado.  Diseases of Tropical Fruit Crops. RC Ploetz, 
ed. CABI Publishing, Wallingford, UK : 35-71.  
183 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand New Zealand Avocado (2021) General questions. https://industry.nzavocado.co.nz/contact/faq-and-
help/faq-and-help-guide/   
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Peterson, R (1978) Susceptibility of Fuerte avocado  fruit at various stages of growth, to infection by  
anthracnose and stem end rot fungi. Australian Journal of Experimental Agriculture 18(90): 158-160. 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2019) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2019. pdf  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Schoeman, M V (2005) Comparative studies of Dothiorella on avocado.  thesis; University of Pretoria,  
Udayanga, D; Liu, X; McKenzie, E H; Chukeatirote, E ; Bahkali, A H; Hyde, K D (2011) The genus 
Phomopsis : biology, applications, species concepts and names  of common phytopathogens. Fungal 
Diversity 50(1): 189-225. 
Wilson, D (1995) Endophyte: the evolution of a term , and clarification of its use and definition. Oikos 
73: 274-276. 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 184 5.9  Elsinoe perseae  (avocado scab) 
Elsinoe perseae (avocado scab) is a fungal pathogen that causes bro wn scabby lesions on fruit, 
leaves and stems of avocado plants. It can reduce a vocado fruit yield, quality and marketability. 
5.9.1  Taxonomic description 
Scientific name: Elsinoe perseae  (Jenkins) Rossman & W.C. Allen (2016)  
Order/Family: Myriangiales/ Elsinoaceae 
Other names include : Sphaceloma perseae  Jenkins (1934), avocado scab 
Taxonomic notes: Elsinoe perseae  was originally confused with E. fawcettii , the causal agent of 
citrus scab. However, Jenkins (1934) showed it to b e a distinct species and demonstrated in 
pathogenicity tests that E. perseae  does not infect citrus. 
5.9.2  Hazard identification 
Elsinoe perseae  is not known to be present in New Zealand: 
• however in the past Sphaceloma perseae  (a synonym of E. perseae ) was recorded in error 
(NZFungi2 2021). For example, Hartill (1991) miside ntified E. perseae  as a postharvest 
disease on avocado, and that work was cited recentl y by Fan et al. (2017). It is not listed in 
PPIN (2021) under either name.  
• Elsinoe perseae  is a regulated pest for New Zealand (ONZPR 2021), however it is listed in 
ONZPR under the synonym Sphaceloma perseae . 
Elsinoe perseae  has the potential to establish (and spread) in New  Zealand because: 
• Hosts are likely to be available, at least in some  areas of New Zealand. The reported host of 
E. perseae  is avocado ( Persea americana ) and other Persea  spp., and avocado plants are 
commonly grown in New Zealand, in home gardens and commercial production, mainly in the 
north of the North Island. 
• The climate is unlikely to limit its development a nd spread:  Elsinoe perseae  is found in some 
areas such as Rio Grande do Sul, Brazil and parts o f Argentina and South Africa (CABI 2021; 
EPPO 2021) which have a Climate Match Index (CMI) ≥ 0.7 indicating a similar climate to the 
whole of New Zealand (Phillips et al. 2018). 
Elsinoe perseae  has the potential to cause harm to New Zealand bec ause: 
• It causes scabby lesions on avocado fruit, reducin g their marketability and value, and 
sometimes causing loss of yield due to premature fr uit drop (Stevens and Piper 1941; Ploetz 
et al. 2011; Everett and Siebert 2018).  
• Avocados are an important commercial crop in New Z ealand. In the 2018–2019 financial 
year, export sales of fresh avocados earned NZ$110 million and domestic sales earned NZ$ 
56.5 million (Plant & Food Research 2019). 
Elsinoe perseae  is associated with Persea americana  budwood because: 
• avocado ( P. americana ) is commonly reported as the host of E. perseae  (CABI 2021; EPPO 
2021); 
• Elsinoe perseae  causes lesions on avocado shoots and twigs appeara nce (Jenkins 1934; 
Stevens and Piper 1941).  
185 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Given the arguments and evidence above, E. perseae  meets the criteria to be a hazard on Persea 
americana  budwood (as in the commodity description) imported  to New Zealand. 
5.9.3  Risk assessment 
Biology and epidemiology of Elsinoe perseae  
Table 5-12. The geographical distribution of Elsinoe perseae  (CPC 2021; EPPO 2021) 
Region Country State/Province  (if recorded) CMI range* 
Africa Guinea  0.4–0.5 
Morocco  0.5– 0.8  
South Africa  0.5– 0.9  
Zambia  0.5–0.6 
Zimbabwe  0.5– 0.7  
Asia Philippines  0.3–0.4 
Taiwan  0.4– 0.8  
North America and 
the Caribbean Barbados  0.3–0.6 
Bermuda  Not determined 
Costa Rica  0.4–0.5 
Cuba  0.5–0.6 
Dominica  Not determined 
Dominican Republic  0.5– 0.7  
El Salvador  0.3–0.5 
Guadeloupe  Not determined 
Guatemala  0.3–0.6 
Haiti  0.5 
Honduras  0.4–0.6 
Jamaica  0.5–0.6 
Mexico  0.4– 0.8  
Nicaragua  0.4–0.6 
Panama  0.5–0.6 
Puerto Rico  0.5– 0.8  
USA (restricted distribution) Florida 0.5– 0.8  
Texas 0.6– 0.8  
South America Argentina (restricted distribution) Jujuy (Aguirre 2003) 0.6– 0.8  
Tucumán 0.6– 0.9  
Brazil (restricted distribution) Espirito Santo 0.5–0.6 
Rio Grande do Sul 0.7–0.9 
Guyana  0.4–0.5 
Peru  0.4– 0.8  
Venezuela  0.4– 0.8  
* Climate Match Index (CMI) with all of New Zealand  (Phillips et al. 2018). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 186 Hosts 
Elsinoe perseae  is widely reported as a pathogen of Persea  species, mainly Persea americana  (e.g. 
CPC 2021; EPPO 2021 and other references cited in t his PRA). Specimens recorded as ‘ Elsinoe 
perseae ’ or ‘ Sphaceloma perseae ’ in the Kew Royal Botanic Gardens collection are m ainly from P. 
americana , with some records from Persea drymifolia  or Persea gratissima (HerbIMI 2021), which are 
synonyms of P. americana . Farr and Rossman (2021) record P. americana , P. gratissima  and a 
Persea  sp. as hosts. The USDA fungal collection records n umerous specimens collected from P. 
americana , two specimens from P. drymifolia  and several specimens collected from Persea  spp. (Farr 
and Rossman 2021). All the E. perseae  or S. perseae  specimens in the Kew and USDA collections 
were collected from Persea  species. 
Elsinoe perseae  causes severe scab disease in some avocado cultiva rs, while others are less 
affected (Stevens and Piper 1941; Ploetz et al. 201 1). For example, the Lula cultivar is now seldom 
planted in Florida because it is extremely sensitiv e to E. perseae , and the Hass and Fuerte cultivars 
are moderately susceptible (Ploetz et al. 2011). 
Searches found a single record of E. perseae  on pineapple ( Ananas comosus ) in the USDA fungal 
database (Farr and Rossman 2021). However, this is highly likely to be a mistaken identification, 
given that there are no other records of E. perseae  or S. perseae  from pineapple or other plant hosts 
apart from Persea  species. 
Geographical distribution 
The recorded distribution of E. perseae is shown in Table 5-12. 
Symptoms 
Elsinoe perseae  infects young leaves, stems and fruit of avocado, causing scab like lesions up to 3 
mm in diameter (Jenkins 1934). Scab lesions may be isolated, or many spots may coalesce (Stevens 
and Piper 1941; Ploetz et al. 2011). Leaves may bec ome stunted, crinkled and distorted (Ploetz et al. 
2011). 
Lesions on young leaves begin as dark red spots tha t become brown to almost black as the leaf ages 
(Jenkins 1934). The tissue at the centre of older l eaf spots is dry and dead and may fall out, leaving  
holes in the leaves (Jenkins 1934).   
On the skin of fruit, E. perseae  causes dark brown, raised oval spots or lesions (J enkins 1934). 
Severe infections cause leaf-curling and distort tw igs and fruit (Stevens and Piper 1941). In severe 
infections, spots may merge to form irregular areas  of hard tissue over most of the fruit surface 
(Stevens and Piper 1941) ( Error! Reference source not found. ). As the size of the fruit increases, 
cracks and fissures may develop in the affected are as (Stevens and Piper 1941). 
On green bark of twigs and petioles, the spots are raised, darker purple and have a smoother surface 
(Stevens and Piper 1941).  
187 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand  
Figure 5-2 Scab lesions on avocado fruit  (Fructibu s, CC0, via Wikimedia Commons; 
https://commons.wikimedia.org/wiki/File:3_x_Avocado _scab_2017_A.jpg; accessed 22/6/2021)  
Reproduction and transmission 
Conidiophores (asexual spore-bearing structures) of  E. perseae  are produced in acervuli (open 
saucer-shaped fruiting structures that rupture the epidermis of host organs) in lesions on leaves, fru it 
or stems (Jenkins 1934; Stevens and Piper 1941). Je nkins (1934) observed that the abundant 
conidiophores and conidia formed a dense velvety ol ive to brown covering over the lesions, which 
gradually weathered away, until only occasional con idiophores remained in lesions on four-month-old 
fruit.  
Under cool moist weather conditions, abundant conid ia are produced in scab lesions (Stevens and 
Piper 1941). The optimum temperature for release of  conidia is from 8 to 28 ° C, and fewer conidia 
were found in the environment at temperatures below  8 ° C (Marroquín-Pimentel 1999). The optimum 
conditions for lesion development are a relative hu midity higher than 80% and a temperature between 
10 – 26 ° C (Marroquín-Pimentel 1999). The number of  new lesions decreases at temperatures below 
8 ° C or above 30 ° C (Marroquín-Pimentel 1999). Spor es may be produced repeatedly in old lesions 
when environmental conditions are suitable (Stevens  and Piper 1941). Scab lesions on old leaves, 
twigs or fruit remaining on the tree provide inocul um for infection in the following year (Stevens and  
Piper 1941; Ploetz et al. 2011).  
Mature leaves and fruit are not susceptible to new infections with E. perseae  (Stevens and Piper 
1941).  Leaves become resistant to infection when t he leaf hardens (Stevens and Piper 1941), 
approximately one month after they emerge (Ploetz e t al. 2011). The upper surface of the avocado 
leaf is more highly susceptible to infection by E. perseae  than the lower surface (Jenkins 1934). Fruit 
become resistant at between a third and half their final size (Stevens and Piper 1941; Ploetz et al. 
2011). 
Injuries caused by thrips provide entry wounds for E. perseae  (Ploetz et al. 2011). In Mexico, damage 
by thrips (most commonly Scirtothrips  and Frankliniella  spp.) and the appearance of E. perseae  scab 
symptoms on young avocado fruit are closely correla ted, if environmental conditions are also suitable,  
because wounds caused by thrips provide infection s ites for the fungus (Marroquín-Pimentel 1999; 
Avila-Quezada et al. 2002; Avila-Quezada et al. 200 3) 
Several other Elsinoe  species have a sexual reproductive stage (teleomor ph) in which airborne 
ascospores are produced (Hyde et al. 2013; Fan et a l. 2017). However, searches of CAB abstracts 
and Google using the search terms ‘ Elsinoe perseae ’ and ‘asci’ or ‘ascospores’ found no reports of 
the sexual stage of E. perseae . Jenkins (1934) reported that the sexual (perfect)  ascospore-producing 
stage of Sphaceloma perseae  had not been found, although she had once observed  what appeared 
to be immature Elsinoe  asci in avocado leaf lesions.  
Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 188 Time to symptom development 
In field trials, the time to symptom development is  7–10 days once spores are applied to susceptible 
avocado tissues in suitable environmental condition s (Stevens and Piper 1941). This has been 
replicated in many inoculation experiments on susce ptible avocado tissues, including leaves, stems 
and fruit (Stevens and Piper 1941). For example, yo ung unfolding avocado leaves (0.7 to 2 cm in 
length) were inoculated by securing filter paper or  cotton wool soaked with conidia to the leaf with w ax 
paper and a rubber band (Jenkins 1934). The inoculu m was removed after 1–2 days. The progression 
of symptoms was: 
• Initial symptoms (minute reddish spots) took appro ximately 7 days to develop (Jenkins 1934); 
• By the tenth day the lesions had increased to a di ameter of 0.7 mm and were 'dragon's blood 
red' on the upper surface and ‘light lobelia violet ’ on the lower surface of the leaf (Jenkins 
1934); 
• Over the following week, the lesions developed a y ellowish border and the epidermis blistered 
and ruptured (Jenkins 1934);  
• The circular perforation at the centre of the blis tered area later expanded to expose the 
necrotic leaf tissue underneath (Jenkins 1934). 
5.9.4  Likelihood of entry 
Elsinoe perseae  causes scablike lesions on avocado stems, therefor e it can be associated with 
leafless, rootless avocado budwood cuttings. Ploetz  et al. (2011) speculated that E. perseae  could be 
moved to new areas in infected scion material (i.e.  shoot cuttings such as budwood) but is more 
easily moved on infected fruit. In addition, ungerm inated conidia of E. perseae  could be present on 
the surface of the budwood and would be unlikely to  be detected by visual inspection without 
magnification. 
The geographic distribution is shown in Table X. Elsinoe perseae  has been reported in many parts of 
North America and the Caribbean and the Caribbean, as well as some parts of South America, Africa 
and Asia. 
Given that E. perseae  can be present on leafless, rootless avocado budwo od cuttings and is widely 
reported in avocado growing countries, it can be as sociated with the commodity at the time of export. 
However, if avocado budwood cuttings have an establ ished E. perseae  infection, it is highly likely that 
lesions will be detected, and infected material rem oved or destroyed, during preparation for export, o r 
in phytosanitary inspections pre-export or on arriv al in New Zealand. 
As part of the commodity description, all imported avocado germplasm, will undergo a growing period 
of active growth with a minimum of three distinct p henological growing events referred to as ‘shoot 
flush’ in 3A PEQ. This period in 3A PEQ will impact  on likelihood of entry in the following manner: 
• Ungerminated E. perseae  conidia are highly unlikely to remain viable (aliv e and still capable 
of infecting the plant) on the surface of avocado b udwood during preparation of the material 
for export, transit to New Zealand, surface disinfe ction (cuttings dipped in 1% sodium 
hypochlorite for 2 minutes) upon arrival in PEQ and  subsequent grafting of the buds onto new 
rootstock.  
• Furthermore, if viable conidia remain on a bud onc e it is grafted, infection is likely to occur 
once the bud breaks dormancy to form young unfoldin g leaves. In this case, visible lesions 
are likely to develop within 10 days (see above), a nd to be detected during routine 
inspections. 
• Searches of Google Scholar, CAB abstracts, CPC and  Google using the search terms 
‘Elsinoe perseae’, ‘Sphaceloma perseae’ or ‘avocado  scab’ found no evidence for 
asymptomatic E. perseae  infections or longer latent periods in avocado pla nts46. Budwood or 
grafted plants infected with E. perseae  are therefore almost certain to develop symptoms a nd 
be detected and destroyed before they are released from PEQ.  
 
46 Spanish and Portuguese references were also chec ked when they were found in searches on the species  names.  
189 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • Conidia are spread by watersplash, windborne rain and insects (thrips) (Stevens and Piper 
1941; Ploetz 2003). Level 3A PEQ has measures in pl ace to manage the risks associated 
with insects, wastewater, waste and accidental tran sfer (see section 2.2), therefore viable E. 
perseae  propagules are highly unlikely to escape level 3A PEQ to infect a suitable host. 
Therefore, if E. perseae  is imported on avocado, the residual biosecurity r isks are likely to be 
managed by the growing period of active growth with  a minimum of three distinct phenological 
growing events referred to as ‘shoot flush’ in 3A P EQ. 
Given the arguments and evidence above, that is:  
• established E. perseae  infections are highly likely to be detected, and i nfected material 
removed or destroyed, during preparation for export , or in phytosanitary inspections pre-
export or on arrival in New Zealand; 
• residual biosecurity risks from recent infections or ungerminated conidia on the surface of 
avocado budwood are likely to be managed by the gro wing period of active growth with a 
minimum of three distinct phenological growing even ts referred to as ‘shoot flush’ in 3A PEQ; 
the likelihood of E. perseae  entering New Zealand associated with Persea americana  budwood is 
considered to be negligible, with low uncertainty.  
Therefore, further assessment is considered unneces sary at this time; and likelihoods of exposure 
and establishment and impacts to New Zealand were n ot assessed. 
5.9.5  Overall level of assessed risk to New Zealand 
Based on the assessment of likelihood above, that:  
• the likelihood of E. perseae  entering New Zealand associated with Persea americana  
budwood (as described in the commodity description,  and taking into account the proposed 
growing period of active growth with a minimum of t hree distinct phenological growing events 
referred to as ‘shoot flush’ in 3A PEQ) is consider ed to be negligible with low uncertainty;  
• therefore, continuing the assessment was considere d unnecessary; and 
the overall level of risk to New Zealand from E. perseae  on imported Persea americana budwood is 
considered to be negligible, with low uncertainty.  
5.9.6  Management considerations 
Elsinoe perseae  causes lesions up to 3 mm in diameter on young lea ves and stems (Jenkins 1934). 
New lesions on leaves may initially appear as tiny dark red spots (Jenkins 1934). Lesions are likely t o 
occur on the upper surface of leaves (Jenkins 1934) . Older lesions (and therefore lesions on older 
stems, leaves and fruit) have a brown to black scab by appearance (Jenkins 1934; Stevens and Piper 
1941). Symptoms become visible in 7 ─ 10 days following infection. This suggests that sy mptoms of 
pre-existing E. perseae infections are highly likely to be detected by visu al inspection during 
preparation for export or on arrival in New Zealand . The number of new lesions decreases at 
temperatures below 8 ° C or above 30 ° C (Marroquín-P imentel 1999), so symptoms may be slower to 
develop if the budwood is stored and transported at  temperatures below 8 ° C. Nevertheless, E. 
perseae  is highly unlikely to persist as an asymptomatic i nfection on susceptible tissues.  
Ungerminated conidia may remain on older unsuscepti ble plant parts or dormant buds. If viable 
conidia have remained on the surface of buds, infec tions are likely to develop when the plants break 
dormancy and produce new shoots. Infection occurs a t moderate temperatures (between 10 – 26° C) 
and during periods of relative humidity above 80% ( Marroquín-Pimentel 1999) (e.g. periods of rain, 
overhead irrigation, or heavy morning dew). Therefo re, temperatures in PEQ are likely to favour 
infection, but there may not be enough water on the  surface of the plant to allow conidia to germinate  
and infect susceptible tissues. Nevertheless, conid ia are highly unlikely to remain viable on P. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 190 americana  budwood through pre- and post-export handling and the PEQ period. Therefore, 
prophylactic testing in the absence of visible lesi ons is unnecessary. 
Everett et al. (2011) developed primers to detect a nd identify E. perseae in PCR testing of DNA 
extracted from scab lesions on avocado skins, and i t is likely that this test can be used for diagnost ic 
testing in budwood. 
5.9.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit?  
Elsinoe perseae  causes lesions up to 3 mm in diameter on young lea ves and stems (Jenkins 1934). 
New lesions on leaves may initially appear as tiny dark red spots (Jenkins 1934). Lesions are likely t o 
occur on the upper surface of leaves (Jenkins 1934) . Older lesions (and therefore lesions on older 
stems, leaves and fruit) have a brown to black scab by appearance (Jenkins 1934; Stevens and Piper 
1941). 
o What are the known environmental conditions conduci ve to symptom expression? 
Infection occurs during periods of relative humidit y above 80% (Marroquín-Pimentel 1999) (e.g. 
periods of rain, overhead irrigation, or heavy morn ing dew). Moderate temperatures (between 10 – 
26° C) favour infection (Marroquín-Pimentel 1999). S ymptoms become visible in 7 ─ 10 days following 
infection (Stevens and Piper 1941). The number of n ew lesions decreases at temperatures below 8 
° C or above 30 ° C (Marroquín-Pimentel 1999). 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Elsinoe perseae  is highly unlikely to persist as an asymptomatic i nfection on susceptible tissues, 
although ungerminated conidia may remain on older u nsusceptible plant parts or dormant buds. If 
viable conidia have remained on the surface of buds , infections are likely to develop when the plants 
break dormancy and produce new shoots. Conidia are unlikely to remain viable on unsusceptible 
plant parts through the PEQ period so prophylactic testing in the absence of visible lesions is 
unnecessary 
o What is the optimum season for conducting detection  testing? 
Not applicable. 
5.9.8  References 
Avila-Quezada, G D; Teliz-Ortiz, D; Gonzalez-Hernan dez, H; Vaquera-Huerta, H; Tijerina-Chavez, L; 
Johansen-Naime, R, et al. (2002) Dinamica espacio-t emporal de la rona ( Elsinoe perseae ), el dano 
asociado a trips y antracnosis ( Glomerella cingulata ) del aguacate en Michoacan, Mexico. [Spatial-
temporal dynamics of scab ( Elsinoe perseae ), damage associated to thrips and anthracnose 
(Glomerella cingulata ) of avocado in Michoacan, Mexico]. Revista Mexicana de Fitopatolgia 20(1): 77-
87. 
Avila-Quezada, G D; Teliz-Ortiz, D; Mora-Aguilera, G; Vaquera-Huerta, H; Tijerina-Chavez, L (2003) 
Spatial and temporal dynamic of scab ( Sphaceloma perseae Jenk.) on avocado ( Persea americana  
Mill.). Revista Mexicana de Fitopatologia 21(2): 152-160.  
191 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand CABI (2021) Crop Protection Compendium. https://www.cabi.org/cpc  Accessed December 2021 
EPPO (2021) European and Mediterranean Plant Protec tion Organization (EPPO) Global Database. 
https://gd.eppo.int/  Accessed May 2021 
Everett, K R; Rees-George, J; Pushparajah, I P S; M anning, M A; Fullerton, R A (2011) Molecular 
identification of Sphaceloma perseae  (avocado scab) and its absence in New Zealand. Journal of 
Phytopathology 159(2): 106-113. 
Everett, K R; Siebert, B (2018) Exotic plant diseas e threats to the New Zealand avocado industry and 
climatic suitability: a review. New Zealand Plant Protection 71: 25-38. 
Fan, X L; Barreto, R W; Groenewald, J Z; Bezerra, J  D P; Pereira, O L; Cheewangkoon, R, et al. 
(2017) Phylogeny and taxonomy of the scab and spot anthracnose fungus Elsinoë (Myriangiales, 
Dothideomycetes). Studies in Mycology 87: 1-41. 
Farr, D F; Rossman, A Y (2021) Fungal Databases, U.S. National Fungus Collections,  ARS, USDA.  
Hartill, W F T (1991) Post-harvest diseases of avoc ado fruits in New Zealand. New Zealand Journal of 
Crop and Horticultural Science 19(3): 297-304. 
HerbIMI (2021) Kew Royal Botanic Gardens Fungarium Catalogue (HerbIMI). 
http://www.herbimi.info/herbimi/home.htm  Accessed 17/05/2021 
Hyde, K D; Jones, E B G; Liu, J-K; Ariyawansa, H; B oehm, E; Boonmee, S, et al. (2013) Families of 
Dothideomycetes. Fungal Diversity 63(1): 1-313. 
Jenkins, A E (1934) Sphaceloma perseae  the cause of Avocado scab. Journal of Agricultural 
Research 49(10): 859-pp. 
Marroquín-Pimentel, F J (1999) Factores que favorec en la incidencia de roña ( Sphaceloma perseae  
Jenk.) en el cultivo del aguacate ( Persea americana  Mill.) "Hass", en tres regiones agroclimáticas de 
Michoacán, México. Revista Chapingo Serie Horticultura 5: 309-312. 
NZFungi2 (2021) New Zealand Fungi and Bacteria (NZF UNGI). 
https://nzfungi2.landcareresearch.co.nz/  Accessed September 2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2019) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2019. pdf  
Ploetz, R C (2003) Diseases of Tropical Fruit Crops . CABI Pub. 
Ploetz, R C; Dann, E; Pegg, K; Eskalen, A; Ochoa, S ; Campbell, A (2011) Pathogen exclusion: 
options and implementation. VII World Avocado Congress 2011 (VII Congreso Mundi al del Aguacate 
2011).  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Stevens, H E; Piper, R B (1941) Avocado diseases in  Florida. Circular. United States Department of 
Agriculture (582): 46-pp .Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 192 5.10  Gliocladiopsis forsbergii , Gliocladiopsis peggii  and Gliocladiopsis whileyi  
Gliocladiopsis  is a genus of soilborne fungi found mostly in trop ical and sub-tropical regions of the 
world. Species of this genus are regarded as second ary plant pathogens or saprobes. Gliocladiopsis 
forsbergii, G. peggii and  G. whileyi  have been isolated frequently from necrotic roots of avocado trees, 
but pathogenicity studies have so far only been don e for one strain of G. peggii . Genus level 
information is being used where necessary as limite d information about the ecology of these fungi is 
available. 
5.10.1  Taxonomic description 
Scientific name: Gliocladiopsis forsbergii L.E. Parkinson, E.K. Dann & R.G. Shivas (2016)  
Scientific name: Gliocladiopsis peggii L.E. Parkinson, E.K. Dann & R.G. Shivas (2016)  
Scientific name: Gliocladiopsis whileyi L.E. Parkinson, E.K. Dann & R.G. Shivas (2016)  
Order/Family: Hypocreales/Nectriaceae  
5.10.2  Hazard identification 
Gliocladiopsis forsbergii, G. peggii and  G. whileyi  are not known to be present in New Zealand: 
• Gliocladiopsis forsbergii, G. peggii and  G. whileyi  are not listed in either Biota NZ (2022) or 
PPIN (2021), and 
• Gliocladiopsis forsbergii, G. peggii and  G. whileyi  are not listed in ONZPR (2021) and their 
regulatory status has not been assessed (ONZPR 2021 ). 
Gliocladiopsis forsbergii, G. peggii and  G. whileyi  have the potential to establish (and spread) in 
New Zealand because: 
• their natural host ( P. americana ) is available for its establishment (NZPCN 2021), and 
• other Gliocladiopsis  species, such as G. tenuis  and G. curvata , have established and are 
present in New Zealand (NZOR 2021; Biota NZ 2022), and 
• suitable climate is available for their establishm ent (Phillips et al. 2018). 
Gliocladiopsis forsbergii, G. peggii and  G. whileyi  have the potential to cause harm to New Zealand 
because: 
• Gliocladiopsis forsbergii, G. peggii and  G. whileyi  are likely secondary plant pathogens that 
could contribute to avocado tree decline, root rot,  reduced tree vigour and predisposed trees 
to infection by other pathogens (Parkinson et al. 2 017a).  
Gliocladiopsis forsbergii, G. peggii and  G. whileyi  are associated with P. americana  budwood 
because: 
• Persea americana  is a known host of G. forsbergii, G. peggii and  G. whileyi (Parkinson et al. 
2017a); 
• Gliocladiopsis species are mostly soilborne but have also been rec overed as endophytes 
from flowers, stems, leaves and seeds (Refaei et al . 2011; Liu and Cai 2013; Gordillo and 
Decock 2019), roots (as Glionectria  in Hakizimana et al. (2011)), and from stem lesion s 
(Parkinson et al. 2017a). 
Given the arguments and evidence above, G. forsbergii, G. peggii and  G. whileyi fulfil the criteria to 
be a hazard on P. americana  budwood (as in the commodity description) imported  to New Zealand.  
193 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.10.3  Risk assessment 
Biology and epidemiology of Gliocladiopsis forsbergii , Gliocladiopsis peggii and 
Gliocladiopsis whileyi  
Host range 
Gliocladiopsis species are considered soilborne (Parkinson et al. 2017b) and many isolates have 
been collected from soil (Lombard and Crous 2012). However, some Gliocladiopsis isolates have 
been collected from diverse symptomatic terrestrial  plant material including P. americana  (in Ecuador, 
Australia), Syzygium aromaticum (Indonesia), Archontophoenix purpurea (New Zealand), 
Chamaedorea elegans (USA), Araucaria sp. (Malaysia), Vanilla sp. (Indonesia), Indigofera sp. 
(Indonesia) (Lombard and Crous 2012), from leaf lit ter (Lombard and Crous 2012), and decaying 
wood submerged in forest freshwater in China (Liu a nd Cai 2013). Although their host range is not 
well studied, G. forsbergii, G. peggii and  G. whileyi have all been isolated from diseased  P. americana  
stems or roots (Lombard and Crous 2012; Parkinson e t al. 2017b).  
Symptoms and biology 
There are limited pathogenicity studies on Gliocladiopsis  species (Dann et al. 2012; Parkinson et al. 
2017b). Parkinson et al. (2017b) fulfilled Koch’s p ostulates, i.e. re-isolation of an isolate of G.  peggii 
that had been isolated from necrotic avocado roots.  Parkinson et al. (2017b) could not demonstrate 
pathogenicity at least for the tested isolate of G. peggii  after 5 weeks. However, G. forsbergii, G. 
peggii and  G. whileyi  have been frequently isolated from necrotic roots of avocado (black root rot) and 
stem lesions in Australia and Ecuador (Parkinson et  al. 2017b) either together with other fungi or 
alone. This suggests a weak or secondary pathogenic  life mode (Dann, pers. comm). So far, only one 
strain of G. peggii has been tested for pathogenicity in a glasshouse s tudy (Dann et al. 2012; 
Parkinson et al. 2017b), i.e., only for seedlings, in limited environmental conditions and for a limit ed 
period of time. However, considering the frequent i solation from symptomatic plant material (Crous 
and Wingfield 1993; Lombard and Crous 2012; Liu and  Cai 2013), this PRA considers the species G. 
forsbergii, G. peggii and  G. whileyi to be secondary or opportunistic pathogens (Ramírez -Gil and 
Morales 2019; Solís-García et al. 2021).  
Transmission 
There is limited information about the transmission  and spread of Gliocladiopsis  species. Crous and 
Wingfield (1993) consider this group soilborne fung i. Spread is exacerbated by frequent irrigation (an d 
over-irrigation), crowded seedling arrangements and  poor nursery hygiene practices (Crous and 
Wingfield 1993). Desiccation and unfavourable envir onmental conditions for fungal growth have little 
effect on the primary survival of spores of nectria ceous fungi, as these highly resistant resting 
structures can survive for several years, infesting  soil and host debris, and will germinate or sporul ate 
when conditions become favourable (Parkinson 2017).  Uncertainty of the transmission mode arises 
from Gliocladiopsis  species recovered as endophytes from flowers, root s, stems, leaves and seeds 
(Liu and Cai 2013). This suggests a possible endoph ytic life mode for at least some species within the  
genus. 
Symptom development and symptom expression 
Symptom development of Gliocladiopsis  species is not well understood. Likely factors inf luencing 
symptom expression depend on a variety of biotic an d abiotic conditions. Co-infection with other 
pathogens, such as with Botryosphaeriaceae fungi, i s thought to accelerate symptom expression 
(Parkinson 2017). For example, the co-infection dis ease pathway tends to begin with initial infection of 
rootstock cuttings at the graft union with Botryosp haeriaceae fungi. Infection is spread during 
propagation, followed by root infection with nectri aceous fungi in soil. As a result, the reported 
nectriaceous pathogens disrupt root function, while  botryosphaeriaceeous pathogens attack the xylem 
(Parkinson 2017). Some studies suggest synergistic effects of Gliocladiopsis  species with root 
pathogens such as Phytophthora  spp (Parkinson 2017; Ramírez-Gil and Morales 2019;  Solís-García 
et al. 2021). Other studies indicate no pathogenici ty of Gliocladiopsis  species but an endophytic life 
mode such as growth promotion (Parkinson 2017) and antagonistic effects to other fungi (Pecundo et 
al. 2021).  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 194 5.10.4  Likelihood of entry 
This assessment is made on the basis that G. forsbergii, G. peggii and  G. whileyi  are present in the 
countries where avocado budwood is being imported f rom. Gliocladiopsis forsbergii, G. peggii and  G. 
whileyi  have been reported from diseased avocado trees in Australia (Parkinson 2017) and from 
Ecuador (as Gliocladiopsis  sp., Liu and Cai (2013)).  
The mode of infection is unknown but likely occurs over roots and wounds. The limited amount of 
information available suggests that Gliocladiopsis  species are likely soilborne (Lombard and Crous 
2012; Parkinson et al. 2017b). However, Gliocladiopsis  spp have been isolated from stem lesions of 
avocado (Parkinson et al. 2017a; Parkinson et al. 2 017b). Gliocladiopsis  species have also been 
isolated as endophytes (Liu and Cai 2013). As a res ult, it cannot be ruled out that Gliocladiopsis  
species are associated with P. americana  budwood internally and surface sterilisation (as i n the 
commodity description) would not affect the fungus.  
Symptom expression and time to symptom development is not well understood for Gliocladiopsis  
species. In case of symptom expression during PEQ, the most likely observed symptoms would be 
black root rot or less likely stem lesions (Parkins on 2017). However, as with most secondary 
pathogens, it seems more likely that Gliocladiopsis  species would remain asymptomatic or endophytic 
during PEQ until favourable conditions or co-infect ion with other pathogens. Therefore, Gliocladiopsis  
species could pass undetected during PEQ without mo lecular testing. 
Given the arguments and evidence above, that is:  
• limited information suggests that Gliocladiopsis  species are likely soilborne (Crous and 
Wingfield 1993; Lombard and Crous 2012), and 
• some Gliocladiopsis  species have also been isolated as endophytes (Liu  and Cai 2013), and 
• Gliocladiopsis  species could remain asymptomatic or endophytic du ring PEQ (Parkinson 
2017) 
the likelihood of G. forsbergii, G. peggii and  G. whileyi entering New Zealand associated with P. 
americana  budwood is considered to be low, with high uncerta inty. 
5.10.5  Likelihood of exposure 
This assessment is made on the basis that G. forsbergii, G. peggii and  G. whileyi  have entered 
New Zealand undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is known to be a suitable host for G. 
forsbergii, G. peggii and  G. whileyi (Parkinson et al. 2017a).   
If avocado plants are infected with G. forsbergii, G. peggii and  G. whileyi  at the time of their release 
from PEQ they will be planted in New Zealand or use d to propagate new plants for planting (see 
section 2.3 for additional information about exposu re).  
Given the arguments and evidence above, the likelih ood of exposure of G. forsbergii, G. peggii and  G. 
whileyi  in New Zealand from P. americana  budwood is considered high, with low uncertainty. 
5.10.6  Likelihood of establishment 
This assessment is made on the basis that G. forsbergii, G. peggii and  G. whileyi  has been 
successfully exposed to a suitable host plant in th e New Zealand environment.  
195 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand The natural host range of G. forsbergii, G. peggii and  G. whileyi is unknown but they have all been 
isolated from P. americana (Parkinson et al. 2017a). This host in the form of cultivated avocados is 
available for its establishment in the North Island  (see section 2.3). A saprobic life mode of these f ungi 
seems also likely (Lombard and Crous 2012; Liu and Cai 2013). 
Some avocado growing regions, such as East Australi a (from where the species have been 
described), have a similar climate to the whole of New Zealand, as well as to the Auckland and 
Northland regions, as indicated by a climate match index of ≥0.7 (Phillips et al. 2018). Therefore, 
climate suitable for the establishment of G. forsbergii, G. peggii and  G. whileyi  is readily available. In 
addition, climate suitability is supported by the f act that other Gliocladiopsis  species have already 
established in New Zealand (Biota NZ 2022). 
Given the arguments and evidence above, that is: 
• their natural host ( P. americana ) is available for its establishment (NZPCN 2021), and 
• a saprophytic life mode is supported, and 
• other Gliocladiopsis  species, such as G. tenuis  and G. curvata , have established and are 
present in New Zealand (NZOR 2021; Biota NZ 2022), and 
• suitable climate is available for their establishm ent (Phillips et al. 2018) 
the likelihood of G. forsbergii, G. peggii and  G. whileyi establishing in New Zealand is considered 
high, with low uncertainty. 
5.10.7  Impacts in New Zealand 
Gliocladiopsis  species are considered soilborne and spread is exa cerbated by frequent irrigation (and 
over-irrigation), crowded seedling arrangements and  poor nursery hygiene practices (Crous and 
Wingfield 1993). Unfavourable environmental conditi ons for fungal growth have little effect on the 
primary survival of spores of nectriaceous fungi, a s these highly resistant resting structures can 
survive for several years, infesting soil and host debris, and will germinate or sporulate when 
conditions become favourable (Parkinson 2017). Othe r Gliocladiopsis  species have been recovered 
as endophytes from flowers, roots, stems, leaves an d seeds (Liu and Cai 2013). This suggests a 
possible endophytic life mode for at least some spe cies within the genus. 
Economic impacts 
There is very little evidence for economic impacts of G. forsbergii, G. peggii and  G. whileyi . Although 
frequently isolated from necrotic avocado roots in Australia, limited pathogenicity tests are availabl e. It 
seems likely that G. forsbergii, G. peggii and  G. whileyi are secondary plant pathogens that could 
contribute to avocado tree decline, root rot, reduc ed tree vigour and predisposed trees to infection b y 
other pathogens (Parkinson et al. 2017a). However, their economic impact has not been 
demonstrated as multiple biotic and abiotic factors  are likely to be involved in disease expression. T he 
limited evidence suggest that this group of fungi i s not a severe pathogen (Dann et al. 2012; 
Parkinson et al. 2017b), and that existing orchard management practises would manage the impact of 
these fungi (Dann, pers. comm). 
Given the arguments and evidence above, that is: 
• Gliocladiopsis forsbergii, G. peggii and  G. whileyi are likely secondary pathogens that 
should be managed by existing orchard management pr actises 
the economic impact of G. forsbergii, G. peggii and  G. whileyi on New Zealand is considered to be 
very low, with moderate uncertainty. 
Environmental impacts 
There are no reports of environmental impacts of Gliocladiopsis species (google scholar search terms 
["wild plants" AND "  Gliocladiopsis "] and ["reservoir plants" AND "  Gliocladiopsis "] and 
[" Gliocladiopsis " AND "natural environments"]). There is one report o f G. forsbergii isolated from a Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 196 Grevillea sp (Parkinson et al. 2017a). Other than this report , G. forsbergii, G. peggii and  G. whileyi  
have so far only been isolated from avocado (Farr a nd Rossman 2021). 
Given the arguments and evidence above, the impact on the environment from the establishment of 
G. forsbergii, G. peggii and  G. whileyi in New Zealand is considered to be negligible, with  low 
uncertainty. 
Human health impacts 
There are no known human health impacts associated with Gliocladiopsis  species (google scholar 
search terms ["human health" AND "  Gliocladiopsis "] and ["toxin" AND "  Gliocladiopsis "]). 
Given the arguments and evidence above, the human h ealth impact of G. forsbergii, G. peggii and  G. 
whileyi on New Zealand is considered to be negligible, with  low uncertainty. 
Sociocultural impacts 
A response to an outbreak of Gliocladiopsis  could involve the removal of infected or exposed a vocado 
trees growing on residential properties. This is li kely to cause distress to affected residents, howev er, 
this impact is likely to be localised and short-liv ed. Moreover, a response seems unlikely given that 
severe pathogenicity has never been reported for Gliocladiopsis . 
Given the arguments and evidence above, the sociocu ltural impact of G. forsbergii, G. peggii and  G. 
whileyi  on New Zealand is considered to be negligible, wit h low uncertainty. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, human health and society is 
considered to be very low, with moderate uncertaint y. 
5.10.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is low 
• assuming entry, the likelihood of exposure is high  
• assuming successful exposure, the likelihood of es tablishment is high 
• the overall impact on the New Zealand economy, env ironment, human health and society 
is considered to be very low 
the overall level of assessed risk to New Zealand f rom G. forsbergii, G. peggii and  G. whileyi  on 
imported P. americana budwood (as in the commodity description) is consid ered to be very low, with 
moderate uncertainty. 
5.10.9  Management considerations 
The economic impact of Gliocladiopsis forsbergii, G. peggii and  G. whileyi  has not been demonstrated 
as multiple biotic and abiotic factors are likely t o be involved in disease expression. The limited 
evidence suggest that this group of fungi on avocad o is not a severe pathogen (Dann et al. 2012; 
Parkinson et al. 2017b), and that existing orchard management practises would manage the impact of 
these fungi (Dann, pers. comm). 
5.10.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ?  
197 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand o What symptoms will the pest or disease exhibit? 
Gliocladiopsis species can remain asymptomatic or endophytic durin g PEQ (Lombard and Crous 
2012). In case of symptom expression black root rot  is the most likely symptom to develop (Parkinson 
2017). Stem lesions are less likely to develop (Par kinson 2017). 
o What are the known environmental conditions conduci ve to symptom expression? 
There is no information available about what enviro nmental conditions favour symptom expression or 
a pathogenic life stage of Gliocladiopsis species (Liu and Cai 2013). However, it has been su ggested 
that co-infection with other pathogens could favour  symptom expression (Refaei et al. 2011; Solís-
García et al. 2021). 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
There is little information available about asympto matic infection. However, a strain of Gliocladiopsis 
peggii  has been isolated from asymptomatic roots (Dann et  al. 2012). Usually, infected root samples 
or stem lesions are taken for sampling (Parkinson 2 017; Parkinson et al. 2017b).  
o What is the optimum season for conducting detection  testing? 
There is no information available about the optimum  season for conducting testing. 
5.10.11  References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Crous, P; Wingfield, M (1993) A re-evaluation of Cylindrocladiella , and a comparison with 
morphologically similar genera. Mycological Research 97(4): 433-448. 
Dann, E K; Cooke, A W; Forsberg, L I; Pegg, K G; Ta n, Y P; Shivas, R G (2012) Pathogenicity studies 
in avocado with three nectriaceous fungi, Calonectr ia ilicicola, Gliocladiopsis sp. and Ilyonectria 
liriodendri. Plant Pathology 61(5): 896-902. 
Farr, D F; Rossman, A Y (2021) Fungal Databases, U.S. National Fungus Collections,  ARS, USDA.  
Gordillo, A; Decock, C (2019) Multigene phylogeneti c and morphological evidence for seven new 
species of Aquanectria and Gliocladiopsis (Ascomycota, Hypocreales) from tropical areas. Mycologia 
111(2): 299-318. 
Hakizimana, J; Gryzenhout, M; Coutinho, T; Van den Berg, N (2011) Endophytic diversity in Persea 
americana  (avocado) trees and their ability to display bioco ntrol activity against Phytophthora 
cinnamomi . In Proceedings VII world avocado congress  (pp. 1-10). 
Liu, F; Cai, L (2013) A novel species of Gliocladiopsis from freshwater habitat in China. Cryptogamie, 
Mycologie 34(3): 233-241. 
Lombard, L; Crous, P W (2012) Phylogeny and taxonom y of the genus Gliocladiopsis . Persoonia - 
Molecular Phylogeny and Evolution of Fungi 28(1): 25-33. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
NZPCN (2021) New Zealand Plant Conservation Network . https://www.nzpcn.org.nz/  Accessed June 
2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 198 Parkinson, L E (2017) Investigating soilborne nectriaceous fungi impactin g avocado tree 
establishment in Australia.  thesis; The Univeristy of Queensland,  
Parkinson, L E; Shivas, R G; Dann, E K (2017a) Nove l species of Gliocladiopsis (Nectriaceae, 
Hypocreales, Ascomycota) from avocado roots (Persea  americana) in Australia. mycoscience 58(2): 
95-102. 
Parkinson, L E; Shivas, R G; Dann, E K (2017b) Path ogenicity of Nectriaceous Fungi on Avocado in 
Australia. Phytopathology 107(12): 1479-1485. 
Pecundo, M H; Dela Cruz, T E E; Chen, T; Notarte, K  I; Ren, H; Li, N (2021) Diversity, Phylogeny and 
Antagonistic Activity of Fungal Endophytes Associat ed with Endemic Species of Cycas (Cycadales) in 
China. Journal of Fungi 7(7): 572. 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX ‘match climates regional’  
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Ramírez-Gil, J G; Morales, J G (2019) Polyphasic id entification of preharvest pathologies and 
disorders in avocado cv. Hass. Agronomía Colombiana 37(3): 213-227. 
Refaei, J; Jones, E; Sakayaroj, J; Santhanam, J J M  (2011) Endophytic fungi from Rafflesia cantleyi : 
species diversity and antimicrobial activity. Mycosphere 2(4): 429-447. 
Solís-García, I A; Ceballos-Luna, O; Cortazar-Muril lo, E M; Desgarennes, D; Garay-Serrano, E; 
Patiño-Conde, V, et al. (2021) Phytophthora root ro t modifies the composition of the avocado 
rhizosphere microbiome and increases the abundance of opportunistic fungal pathogens. 11: 3484. 
 
  
199 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.11  Grovesinia moricola  (zonate leaf spot) 
Grovesinia moricola  (zonate leaf spot) is a fungal pathogen that produ ces characteristic target-shaped 
necrotic rings leading to leaf blight and defoliati on in a broad range of host species. The disease ha s 
been reported infecting Persea americana  (avocado) in the USA and Brazil, causing round lea f 
lesions with dark margins. It has the potential to infect a number of economically significant hosts i n 
New Zealand.  
5.11.1  Taxonomic description 
Scientific name: Grovesinia moricola  (I. Hino) Redhead  
Order/Family: Helotiales/ Schlerotiniaceae 
Other names include: Grovesinia pyramidialis, Botrytis moricola, Cristul ariella moricola, Cristulariella 
pyramidalis, Hinomyces moricola 
Taxonomic notes: 
This fungus was first described under the name Botrytis moricola (Narumi-Saito et al. 2006). Previous 
anamorphic synonyms are C. moricola  and H. moricola  and other taxonomic synonyms are G. 
pyramidalis and  C. pyramidalis (Robert et al. 2005; Johnston et al. 2014). 
5.11.2  Hazard identification 
Grovesinia moricola  is not known to be present in New Zealand: 
• Grovesinia moricola, or any of the synonyms listed above, are not listed  in NZOR (2021), 
Biota NZ (2022) or PPIN (2021).  
• Grovesinia moricola  is not listed in ONZPR (2021). Grovesinia pyramidalis is listed as 
regulated in ONZPR (2021), and Cristulariella moricola  is listed as ‘not assessed’.  
Grovesinia moricola  has the potential to establish (and spread) in New  Zealand because: 
• Many reported hosts of G. moricola  are present in New Zealand, including avocado, app le, 
tomato and grapevine. 
• The climate is unlikely to limit its development a nd spread: G. moricola  has been reported in 
USA (southeastern states), South Korea, Taiwan, and  Japan. These regions have a CMI 
ranging from 0.6-0.8, indicating a similar climate to many parts of New Zealand (Phillips et al. 
2018). The fungus is also reported in regions of In dia and Brazil which have a CMI ranging 
from 0.4-0.6. This suggests a relatively broad rang e of climatic tolerance for this species. 
Latham (1974) reports that growth is favoured by hi gh humity and moderate to cool 
temperatures, suggesting the New Zealand climate is  likely to be favourable for the 
establishment of this fungus species 
Grovesinia moricola  has the potential to cause harm to New Zealand bec ause: 
• It is reported to cause leaf lesions and defoliati on of a large number of host species, which 
may reduce the productivity of economically importa nt species such as avocado, apple, 
tomato and grapevine. Infections in tomatoes were r eported to result in a 50% reduction in 
yield (Dillard et al. 1995). Loss of productivity t o this degree would have significant economic 
impacts.  
Grovesinia moricola  is associated with P. americana budwood because: Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 200 • The fungus has been reported infecting the leaves of avocados in Brazil (Bezerra et al. 2008). 
Because green budwood may include some leaf tissue within the buds, there is the potential 
for this fungus to be associated with the commodity . Also, while this fungus is predominantly 
reported as a foliar pathogen, it has been reported  infecting the stems of potato (Trolinger et 
al. 1978) and tomato (Dillard et al. 1995), suggest ing that the fungus may infect the stems or 
leaf buds of avocado budwood.  
Given the arguments and evidence above, Grovesinia moricola  meets the criteria to be a hazard on 
P. americana  budwood (as in the commodity description) imported  to New Zealand. 
5.11.3  Risk assessment 
Biology and epidemiology of G. moricola  
Host range 
Grovesinia moricola  has been reported infecting a wide range of host p lants in many different plant 
families. A survey of literature found that at leas t 100 species, belonging to 42 plant families, are 
naturally infected by this fungus (Appendix 3). The re were two reports found of infection of avocado 
with G. moricola ; one in USA (Trolinger et al. 1978) and one in Bra zil (Bezerra et al. 2008). There are 
three other hosts of G. moricola reported in the Lauraceae family; Cinnamomum kanehirae 
(camphor), Lindera benzoin (spicebush) and Sassafras albidum (sassafras) (Trolinger et al. 1978; Fu 
and Lin 2012).  
Distribution 
Grovesinia moricola  has been reported from the regions and countries l isted in Table 5-13. 
Table 5-13: The geographical distribution of Groves inia moricola.  
Region  Country (Location)  Reference  CMI 
Asia South Korea (Gimcheon, Goseong, 
Chuncheon and Yeongdong) Cho et al. (2012); Cho et al. (2013); Cho et 
al. (2017); Shin et al. (2019); Park et al. 
(2020) 0.6-0.7 
India (Jabalpur and Khargone) Vyas et al. (1982) 0. 4-0.5 
Taiwan (Taipei and Wulai) Su and Leu (1983); Hu et al. (2002); Fu and 
Lin (2012) 0.6-0.7 
Japan (Akita Province) Trolinger et al. (1978); Takahashi and Tanba 
(1980) 0.7-0.8 
North America USA (Georgia, Louisiana, North 
Carolina, South Carolina, Alabama, 
Maryland, Illinois, West Virginia, 
Arkansas, New York) Cline et al. (1983); Colyer et al. (1992); 
Brenneman et al. (1993); Holcomb (1994); 
Dillard et al. (1995); Grand and Vernia 
(2004); Blake et al. (2015); Aubrey et al. 
(2017) 0.7-0.8 
South America Brazil (Bahia) Bezerra et al. (2008) 0.5-0.6 
Symptoms 
Symptoms of G. moricola  are often reported as small round lesions with dar k margins that grow larger 
and eventually coalesce, leading to leaf blight and  defoliation. Lesions are frequently described as 
zonated or target-shaped rings. In avocado the symp toms are described as greyish-brown, round to 
irregular leaf lesions with dark margins, less than  1cm broad (Bezerra et al. 2008). Symptoms on 
Cinnamomum kanehirae  (also in the family Lauraceae) are reported as bro wn lesions on the leaves 
that fuse as they become larger, causing leaf bligh t and eventual defoliation (Fu and Lin 2012). No 
evidence was found in the literature of asymptomati c infection occurring in any host species.   
201 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand On many hosts the development of symptoms of G. moricola infection develop rapidly (Leahy 1995). 
Inoculation experiments have frequently reported th e development of symptoms within 2 to 4 days 
(Hu et al. 2002; Cho et al. 2012; Fu and Lin 2012; Cho et al. 2013; Cho et al. 2017; Shin et al. 2019) . 
Holcomb (1994) reported that symptoms developed on Halesia diptera (silverbell) within 24 hours of 
inoculation.  
Optimal conditions for growth and symptom developme nt 
It is frequently reported that outbreaks of G. moricola  occur during periods of heavy or extended 
rainfall (Vyas et al. 1982; Aubrey et al. 2017). Nu merous inoculation experiment have successfully 
demonstrated pathogenicity in a range of host speci es at incubation temperatures ranging from 15 - 
30° C (Brenneman et al. 1993; Holcomb 1994; Hu et al . 2002; Shin et al. 2019). Latham (1974) 
investigated the impacts of temperature and moistur e on this fungus and found that lessions 
developed at all humidities tested, but fruiting bo dies did not develop below 96% relative humidity. 
Maximum growth occurred when inoculated leaves are wet and is favoured by moderate to cool 
temperatures (9-24° C).   
Reproduction and transmission 
Transmission of spores is thought to occur by splas hing of water (Bezerra et al. 2008). This fungus 
also readily produces sclerotia on artificial mediu m within two weeks, and on artificially inoculated 
leaves within four weeks (Shin et al. 2019). These sclerotia are believed to be important for 
overwintering of the fungus (Trolinger et al. 1978;  Cline et al. 1983).  
5.11.4  Likelihood of entry 
Grovesinia moricola has been reported to be present in six countries (T able 5-13), affecting a wide 
variety of host plants. It  has been reported infecting the leaves of avocados in Brazil (Bezerra et al. 
2008), while the symptoms of an infection on avocad o in USA are not stated (Trolinger et al. 1978). 
While this fungus is predominantly reported as a fo liar pathogen, it has been reported infecting the 
stems of potato (Trolinger et al. 1978) and tomato (Dillard et al. 1995), suggesting that the fungus h as 
the potential to be present on plant stems. Also, g reen budwood may include some leaf tissue within 
the buds. Therefore, there is potential for G. moricola  to be imported into PEQ on P. americana  
budwood.  
Grovesinia moricola infections appear on the surface of leaves and stem s, so it is expected that 
disinfection of budwood entering PEQ (1% sodium hyp ochlorite dip for 2 minutes) would be effective 
in elimating any infection on the surface. Although , it is uncertain if the fungus may persist in smal l 
crevices within the leaf buds. 
If G. moricola is imported into New Zeland, and disinfection were not suffient to remove the pathogen, 
it is very likely that it would produce visible sym ptoms in PEQ. There are no results of inoculation 
experiments available for avocado to determine the period to develop symptoms or the potential to be 
asymptomatic on this host. However, there are numer ous inoculation studies of other host species 
that demonstrate rapid symptom development and asym ptomatic infection has not been reported in 
any host species. Most inoculation studies show sym ptom development on leaf material within 2 to 4 
days of inoculation (Hu et al. 2002; Cho et al. 201 2; Cho et al. 2013; Cho et al. 2017; Shin et al. 
2019), including another Lauraceae species, Cinnamomum kanehirae  (Fu and Lin 2012). This 
suggests that if G. moricola  was present on avocado budwood imported to New Zea land, it is highly 
likely that symptoms would develop within the perio d of growth in PEQ. 
Based on the mode of reproduction and transmission,  there is no evidence available to suggest that 
G. moricola  would not be successfully contained within Level 3 A PEQ conditions.  
Given the arguments and evidence above, that is: 
• there is limited potential for the association of G. moricola  with avocado budwood cuttings, 
and Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 202 • infection by G. moricola  is highly likely to be detected during the period of growth in Level 3A 
PEQ; 
the likelihood of G. moricola entering New Zealand associated with P. americana budwood is 
considered to be negligible, with low uncertainty. Therefore, further assessment is considered 
unnecessary at this time; likelihoods of exposure a nd establishment and impacts to New Zealand are 
not further assessed.  
5.11.5  Overall level of associated risk to New Zealand 
Based on the assessment of likelihood above, that: 
• the likelihood of G. moricola  entering New Zealand associated with P. americana  budwood 
(as described in the commodity description, and tak ing into account the proposed growing 
period of active growth with a minimum of three dis tinct phenological growing events referred 
to as ‘shoot flush’ in 3A PEQ) is considered neglig ible, with low uncertainty; 
the overall level of risk to New Zealand from G. moricola on imported P. americana  bedwood is 
considered to be negligible, with low uncertainty.  
5.11.6  Management considerations 
Grovesinia moricola  is frequently reported producing rapidly developin g and highly visible symptoms 
on the foliage of a wide range of host species. The re is only a single source reporting the symptoms 
of G. moricola in avocado. Bezerra et al. (2008) reported the dise ase causing greyish-brown, round to 
irregular leaf lesions with dark margins, less than  1cm broad. This appears to be consistent with the 
symptoms reported in many other host species. There  was no evidence found of asymptomatic 
infections on any host species.  
It is frequently reported that outbreaks of G. moricola  on a variety of hosts occur during periods of 
heavy or extended rainfall (Vyas et al. 1982; Aubre y et al. 2017). Relative humity greater than 96% is  
required for the development of fruiting bodies (La tham 1974). Maximum growth occurs when 
inoculated leaves are wet and is favoured by modera te to cool temperatures (9-24° C).  Leahy (1995) 
reports that optimum conditions for disease develop ment are cool and wet weather during mid to late 
summer. 
Grovesinia moricola  appears to be readily isolated in many hosts from leaf samples exhibiting 
symptoms. The fungus may occur on either side of th e leaves (Leahy 1995), and may also be present 
on plant stems (Trolinger et al. 1978; Dillard et a l. 1995). This fungus can be identified based on th e 
distinctive conidial morphology, or sequencing of t he internal transcribed spacer (ITS) region of the 
ribosomal DNA using PCR primers ITS1 and ITS4 (Aubr ey et al. 2017; Shin et al. 2019). 
5.11.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
In avocado, G. moricola has been reported causing greyish-brown, round to i rregular leaf lesions with 
dark margins, less than 1cm broad (Bezerra et al. 2 008). These symptoms are consistent with those 
that have been observed in many other host species.   
o What are the known environmental conditions conduci ve to symptom expression?  
203 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand It is frequently reported that outbreaks of G. moricola  on many hosts occur during periods of heavy or 
extended rainfall (Vyas et al. 1982; Aubrey et al. 2017). Relative humity greater than 96% is required  
for the development of fruiting bodies, but lession s still develop at lower humidity (Latham 1974). 
Maximum growth occurs when inoculated leaves are we t and is favoured by moderate to cool 
temperatures (9-24° C).   
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Grovesinia moricola  appears to be readily isolated from leaf samples e xhibiting symptoms. There was 
no evidence found of asymptomatic infection occurri ng in any host species. The fungus may occur on 
either side of the leaves (Leahy 1995).  
o What is the optimum season for conducting detection  testing? 
Leahy (1995) reports that optimum conditions for di sease development are cool and wet weather 
during mid to late summer. Maximum growth occurs wh en inoculated leaves are wet and is favoured 
by moderate to cool temperatures (9-24 degrees Cels ius) (Latham 1974). Relative humity greater 
than 96% is required for the development of fruitin g bodies. 
5.11.8  References  
Aubrey, D P; Fraedrich, S W; Harrington, T C; Olati nwo, R (2017) Cristulariella moricola associated 
with foliar blight of Camden white gum ( Eucalyptus benthamii ), a bioenergy crop. Biomass and 
Bioenergy 105: 464-469. 
Bezerra, J; Luz, E; Gramacho, K; De Figueirêdo, V; Bezerra, K J P P (2008) Occurrence of 
Grovesinia pyramidalis  on soursop and avocado in Brazil. 57(2). 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Blake, J; Williamson, M; Ellington, K (2015) Index of plant diseases in South Carolina  (3rd ed.). 
Brenneman, T B; Hadden, J F; Ruter, J M (1993) Firs t report of Cristulariella moricola  causing zonate 
leaf spot on muscadine grape. Plant Disease 77(7). 
Cho, S E; Hong, S B; Choi, I Y; Oh, H T; Shin, H D (2017) First report of zonate leaf spot caused by 
Grovesinia moricola  on adzuki bean in Korea. Plant Disease 101(9): 1677-1677. 
Cho, S E; Park, J H; Choi, J K; Shin, H D (2012) Fi rst report of zonate leaf spot of Glycine max  
caused by Cristulariella moricola  in Korea. Plant Dis 96(6): 906. 
Cho, S E; Park, J H; Hong, S H; Shin, H D (2013) Fi rst report of zonate leaf spot caused by 
Hinomyces moricola  on japanese hop in Korea. Plant Disease 97(8): 1117-1117. 
Cline, M N; Crane, J L; Cline, S D (1983) The teleo morph of Cristulariella moricola . Mycologia 75(6): 
988-994. 
Colyer, P; VERNON, P; CALDWELL, W (1992) Zonate lea f-spot of kenaf caused by Cristulariella 
moricola . 76(8): 861-861. 
Dillard, H; Cobb, A; Garman, W; Brewer, R (1995) Fi rst report of zonate leaf spot on tomato, caused 
by Cristulariella moricola , in New York. Plant Disease 79(3): 319. 
Fu, C H; Lin, F Y (2012) First report of zonate lea f spot of Cinnamomum kanehirae  caused by 
Hinomyces moricola  in Taiwan. Plant Disease 96(8): 1226. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 204 Grand, L E; Vernia, C S (2004) Fungi on Plants in N orth Carolina. 
https://projects.ncsu.edu/cals/course/pp318/North_C arolina_index.html  Accessed 08/12/2021 
Holcomb, G (1994) First report of zonate leaf spot on silverbell tree caused by Cristulariella moricola . 
Plant Disease 78(12). 
Hu, B; Hsiao, W; Fu, C (2002) First report of zonat e leaf spot of Artocarpus altilis  caused by 
Cristulariella moricola  in Taiwan. Plant Disease 86(10): 1179-1179. 
Johnston, P R; Seifert, K A; Stone, J K; Rossman, A  Y; Marvanová, L (2014) Recommendations on 
generic names competing for use in Leotiomycetes (A scomycota). IMA Fungus 5(1): 91-120. 
Latham, A (1974) Effect of temperature and moisture  on Cristulariella pyramidalis . Phytopathology 
64(5): 635-639. 
Leahy, R M (1995) Cristulariella leaf spot on Florida ornamentals. Florida Department of Agriculture & 
Consumer Services. Plant Pathology Circular No. 370. 
Narumi-Saito, T; Hosoya, T; Sano, T; Harada, Y (200 6) Nervostroma , gen. nov. in the 
Sclerotiniaceae, the teleomorph of Cristulariella , and Hinomyces  anam. gen. nov. to accommodate 
the anamorph of Grovesinia : reassessment of the genus Cristulariella . Mycoscience 47: 351-359. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Park, J-H; Jung, B-N; Lee, S-H; Shin, H-D (2020) Id entification of Grovesinia moricola  causing zonate 
leaf spots on Lespedeza cyrtobotrya  in Korea. The Korean Journal of Mycology 48(1): 69-74. 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Robert, V; Stegehuis, G; Stalpers, J (2005) The Myc oBank engine and related databases. 
https://www.mycobank.org/  Accessed October 2021 
Shin, H-D; Choi, Y J; Hong, S H; Lee, Y-h (2019) Grovesinia moricola  occurring on Parthenocissus 
tricuspidata . The Korean Journal of Mycology 47: 271-274. 
Su, H; Leu, S (1983) Zonate leaf spot of Indian juj ube caused by Cristulariella moricola . Plant Disease 
67(8): 915-916. 
Takahashi, S; Tanba, J (1980) Occurrence of grape Cristulariella  leaf spot ( Cristulariella pyramidalis 
Waterman and Marshall) in Akita prefecture. Annual Report of the Society of Plant Protection of  North 
Japan (Japan) . 
Trolinger, J; Elliott, E; Young, R (1978) Host rang e of Cristulariella pyramidalis . Plant Disease 
Reporter 62(8): 710. 
Vyas, S; Prasad, K; Varna, R; Jain, A (1982) Zonate  leafspot of groundnut caused by Cristulariella 
pyramidalis . Plant protection bulletin 30(3/4): 158. 
  
205 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.12  Lasiodiplodia pseudotheobromae 
Lasiodiplodia pseudotheobromae  is a fungal plant pathogen that has been reported to cause dieback, 
cankers and postharvest diseases (stem-end rot and fruit rot disease) in many woody plant species 
which includes avocado.  
5.12.1  Taxonomic description 
Scientific name: Lasiodiplodia pseudotheobromae A.J.L. Phillips, A. Alves & Crous 2008 
Order/Family: Botryosphaeriales/Botryosphaeriaceae  
Other names include : None found 
Taxonomic notes:  Lasiodiplodia pseudotheobromae  was initially identified as a cryptic species of L. 
theobromae (Alves et al. 2008). This is because they have simi lar colony features. However, L. 
pseudotheobromae was discovered to be a different species with a lar ger and a different conidia 
shape (Munirah et al. 2017).  
5.12.2  Hazard identification 
Lasiodiplodia pseudotheobromae  is not known to be present in New Zealand: 
o L. pseudotheobromae  is not listed in PPIN (2021) 
o L. pseudotheobromae  is recorded as absent from New Zealand in Biota NZ  (2022)  
o Lasiodiplodia pseudotheobromae  is not listed in ONZPR (2021). 
Lasiodiplodia pseudotheobromae  has the potential to establish (and spread) in New  Zealand 
because: 
• host plants are grown commercially and in home gar dens in most parts of New Zealand 
(Table 5-14). 
• climate is unlikely to be a barrier to its establi shment and spread in New Zealand as it 
reported to occur in different parts of the world ( Table 5-14) which have similar climates (CMI 
≥ 7) to New Zealand (Phillips et al. 2018).  
• It has been associated with a wide range of host p lants commonly grown commercially and in 
home gardens such as, several Citrus  spp., and Vitis vinifera  (grapevine) (Table 5-14). 
• Lasiodiplodia pseudotheobromae  can spread by human movement of infected nursery s tock 
and movement of infected fruits. 
Lasiodiplodia pseudotheobromae has the potential to cause harm to New Zealand beca use: 
• Lasiodiplodia pseudotheobromae causes pre and postharvest diseases such as branch 
cankers, dieback and fruit rot. Such diseases can a ffect the marketability of host crops in New 
Zealand. It is an important commercial crop in New Zealand worth up to $110 million in 
domestic sales and up to 56.6 million in domestic s ales (Plant & Food Research 2020). 
Lasiodiplodia pseudotheobromae can be associated with Persea americana  budwood because: 
• Persea americana  is a known host of Lasiodiplodia pseudotheobromae (Bragard et al. 2021; 
Liang et al. 2021; Rodríguez-Gálvez et al. 2021) 
• Lasiodiplodia pseudotheobromae  infects avocado stems (Onaebi et al. 2020; Liang e t al. 
2021; Rodríguez-Gálvez et al. 2021). 
Given the arguments and evidence above, L. pseudotheobromae  meets the criteria to be a hazard on 
P. americana  budwood (as in the commodity description) imported  to New Zealand. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 206 5.12.3  Risk assessment 
Biology and epidemiology of Lasiodiplodia pseudothe obromae 
Biology and host range 
Lasiodiplodia pseudotheobromae is a pathogenic fungus from the Botryosphaeriaceae family (Alves 
et al. 2008; Trakunyingcharoen et al. 2015; Serrato -Diaz et al. 2020). Like most fungi from the 
Botryosphaeriaceae family, it can occur as an endop hyte or a latent opportunistic pathogen that 
causes symptoms when the host plant becomes stresse d (Slippers and Wingfield 2007; Burgess et al. 
2019; Liang et al. 2021). However, there are few pu blished studies that have tested asymptomatic 
tissues to determine if members of the genus Lasiodiplodia have an asymptomatic phase on plants 
they infect (Johnson et al. 1992). So far, the few reported studies of asymptomatic infection by L. 
pseudotheobromae have been from asymptomatic native non-crop plant s pecies in Australia, 
Thailand, China and India (Kapoor and Saxena 2014; Aramsirirujiwet et al. 2016; Burgess et al. 2019; 
de Silva et al. 2019). It was also recently isolate d from dead leaves of Magnolia spp. in China, 
indicating that it can be saprobic (de Silva et al.  2019).  
Lasiodiplodia pseudotheobromae  infects a broad range of host crop plants over a b road geographical 
distribution (Table 1). It is a common pathogen of many woody plant species including Citrus, Coffee, 
Gmelina, Rosa  and Acacia  species(Alves et al. 2008). It is associated with diseases such as cankers, 
dieback, fruit rot and stem-end rot many host plant  species in different parts of the world (Table 5-1 4). 
Most Lasiodiplodia spp. are pathogens that are common in tropical and subtropical areas. They 
generally have an optimal growth temperature of abo ut 30° C (Burgess et al. 2019). However, L. 
pseudotheobromae , unlike other members of the genus, can grow at temp eratures as low as 10° C 
(Slippers et al. 2004; Liang et al. 2021).  
Lasiodiplodia  pseudotheobromae  has been reported to be one of the most virulent o f Lasiodiplodia 
that can cause stem cankers, dieback of branches, s tem-end rot and fruit rot in different host plants in 
different parts of the world (Table 5-14) (Alves et  al. 2008; Ismail et al. 2012; Rodríguez-Gálvez et al. 
2017; Liang et al. 2021). It is one of the main pat hogens that can cause diseases such as blight, 
dieback disease, stem-end rot and fruit rot in avoc ado (Trakunyingcharoen et al. 2015; Onaebi et al. 
2020; Bragard et al. 2021; Liang et al. 2021; Rodrí guez-Gálvez et al. 2021).  In severe cases these 
disease symptoms that lead to death of infected tre es (Slippers and Wingfield 2007; Ismail et al. 
2012). 
Table 5-14: The distribution, hosts and diseases ca use by Lasiodiplodia pseudotheobromae  
(Countries in bold  are where Lasiodiplodia pseudotheobromae has been reported on P. americana 
(avocado). (–) in blank cells indicates information  was not available)  
Continent Country  State/Region Host plant Symptoms 
/Diseases CMI* Reference  
Africa Cameroon Mbalmayo and 
Nkoemvone Terminala spp. 
and Theobroma 
cacao (Cacao) Dieback (in 
Cocoa) 0.5 (Boyogueno et al. 
2012) 
Nigeria Enugu Persea americana 
(Avocado) Fruit rot 0.4 (Onaebi et al. 2020) 
Zaire (DRC)  unknown Coffea sp. - 0.5-0.6 (Alves et al. 2008) 
Egypt  - Mangifera indica 
(Mango)  Cankers and 
dieback 0.4-0.6 (Ismail et al. 2012) 
Asia Bangladesh Rajshahi  Citrus  sp. Stem-end rot 0.4 (Sultana et al. 2018) 
China Guangxi, Hubei, 
Zhejiang, Hunan, 
Jiangxi, Fujiang, 
Guangdong Citrus spp. Fruit rot 0.6-0.7 (Chen et al. 2021)  
207 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Continent Country  State/Region Host plant Symptoms 
/Diseases CMI* Reference  
China Shandong Province Malus pumila  
(Apple)  Canker and 
Shoot dieback 0.7 (Xue et al. 2019) 
China Hainan Plukenetia 
volubilis (sacha 
peanut) Branch cankers 0.5 (Wang and Song 
2021) 
China Hubei, Jiangsu Vitis vinifera  
(grapevine)  Pedicel and 
peduncle 
discolouration 0.7 (Dissanayake et al. 
2015) 
China Shuyang, Jiangsu 
Province Celtis sinensis 
(Chinese 
hackberry) Stem cankers 0.7 (Liang et al. 2020) 
China Guangzhou, 
Guangdong  Ormosia pinnata Dieback 0.5-0.6 (Li et al. 2020) 
China Unknown  Pteridium 
aquilinum  (Eagle 
fern)  - 0.4-0.8 (Alves et al. 2008; 
Rodríguez-Gálvez 
et al. 2021) 
China Yunnan Magnolia spp. Asymptomatic/ 
saprobic  0.6-0.8 (de Silva et al. 
2019) 
India Manipur Mangifera indica 
(Mango)  Fruit rot 0.5-0.6 (Bui et al. 2018) 
India  Yelandur Karnataka Aegle marmelos Asymptomatic 0.5 (Kapoor and 
Saxena 2014) 
Indonesia Sulawesi Cocoa Dieback and 
stem cankers 0.4-0.6 (Asman et al. 2020) 
Malaysia Throughout the 
peninsular  Mangifera indica 
(Mango)  Fruit rot 0.4-0.5 (Munirah et al. 
2017) 
Malaysia Kelantan, Pahang, 
Perak, Sabah, 
Sarawak, Selangor  Sansevieria 
trifasciata  (snake 
plant)  Leaf blight  0.4–0.5 (Kee et al. 2019) 
Thailand Lamphun Province Dimocarpus 
longan  (Logan 
fruit)  Fruit rot 0.5 (Pipattanapuckdee 
et al. 2019) 
Thailand Chiang Mai 
Province Persea americana 
(Avocado)  Fruit rot (stem-
end rot, mid-
section rot), 
stem cankers 0.5 (Trakunyingcharoen 
et al. 2015) 
Thailand Chiang Mai 
Province Hevea brasiliensis 
(Para rubber)  Stem cankers 0.5 (Trakunyingcharoen 
et al. 2015) 
Thailand Bangkok Hottuynia cordata 
(Plookao) Asymptomatic   0.4 (Aramsirirujiwet et 
al. 2016) 
Thailand Chiang Rai Cynometra 
malaccensis Leaf spot 0.4 (Gomdola et al. 
2020) 
Taiwan Southern cities, 
Tainan, Chaiyi Persea americana 
(Avocado)  Branch canker 
and fruit rot 0.4-0.8 (Liang et al. 2021) 
Europe Netherlands Unknown Rosa sp. - 0.9 (Alves et al. 2008) 
Europe-
Asia Turkey Mersin province 
Cukurova Citrus limon 
(Lemon) Postharvest fruit 
rot 0.5-0.9 (Awan et al. 2016) 
Central 
America  Costa Rica  Unknown  Gmelina arborea 
- 0.4-0.6 (Alves et al. 2008) Acacia mangium Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 208 Continent Country  State/Region Host plant Symptoms 
/Diseases CMI* Reference  
Middle 
East 
(Asia) Iran Northern and 
Southern Province Citrus spp. Dieback, 
cankers and 
fruit rot 0.4-0.8 (Abdollahzadeh et 
al. 2009) 
Israel - Persea americana 
(Avocado)  Branch dieback, 
branch wilting, 
mortality of 
young plants, 
stem-end rot. 0.5-0.7 (Bragard et al. 
2021) 
North 
America Mexico Puebla and 
Veracruz Citrus latifolia 
(Persian lime) Gummosis, 
stem canker, 
branch dieback 0.5-0.8 (Bautista-Cruz et al. 
2019) 
USA Puerto Rico Perseae 
americana 
(avocado)  Branch cankers 0.5-0.6  
USA Puerto Rico Citrus  sp. 
(tangerine)  Branch dieback 0.5-0.6 (Serrato-Diaz et al. 
2020) 
Oceania Australia  Northern Western 
Australia Mangifera indica 
(Mango), 
Macadamia  Cankers, 
dieback, and 
stem-end rot 0.4 (Sakalidis et al. 
2011; Burgess et al. 
2019; Jeff-Ego and 
Akinsanmi 2019) 
Australia Western Australia Vitis vinifera Cankers and 
dieback 0.4 (Burgess et al. 
2019) 
South 
America Brazil Rio Grande do 
Norte, Paraíba Carica papaya  
(papaya) Stem-end rot 0.5-0.6 (Netto et al. 2014) 
Brazil Minas Gerais, Bahia Annona 
crassiflora  
(marolo)  Dieback 0.5-0.7 (Machado et al. 
2019) 
Brazil Minas Gerais, Bahia Annona muricata  
(soursop)  Dieback 0.5-0.7 (Machado et al. 
2019) 
Brazil Minas Gerais, Bahia Annona 
squamosa  (sugar 
apple)  Dieback 0.5-0.7 (Machado et al. 
2019) 
Brazil Minas Gerais, Bahia Annona atemoya  
(atemoya)  Dieback 0.5-0.7 (Machado et al. 
2019) 
Brazil São Francisco, 
Assú and Siriji 
Valleys (North-
eastern Brazil) Vitis vinifera 
(Table grapes)  Decline 
symptoms 0.4-0.6 (Correia et al. 2013) 
Brazil  Minas Gerais and 
the Espirito Santo Jatropha curcas 
(Purging nut) Wilt, leaf fall, 
root/collar rot 0.5-0.6 (Machado et al. 
2014; Bautista-Cruz 
et al. 2019) 
Brazil Sao Paulo State  Diospyros kaki 
(Persimmon) Fruit rot 0.6-0.7 (Júnior et al. 2017) 
Peru Lambayeque, Lima, 
Piura, La Libertad 
regions. Persea americana 
(Avocado) Dieback 0.4-0.8 (Rodríguez-Gálvez 
et al. 2021) 
Peru Piura  Mangifera indica 
(Mango) Dieback  0.4-0.7 (Rodríguez-Gálvez 
et al. 2017) 
Suriname - Citrus 
auranitacum  - 0.4-0.5 (Alves et al. 2008)  
209 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Continent Country  State/Region Host plant Symptoms 
/Diseases CMI* Reference  
Uruguay Entire country Myrcianthes 
pungens - 0.7-0.9 (Pérez et al. 2010) 
Venezuela  Monagas State Acacia mangium Trunk cankers 0.5 (Castro-Medina et 
al. 2014) 
*(Phillips et al. 2018)  
Reproduction and spread 
Healthy plants can be infected through natural open ings and wounds such as pruning wounds 
(Slippers and Wingfield 2007; Rodríguez-Gálvez et a l. 2021). The fungi can be transmitted by 
contaminated tools during grafting and pruning. Inf ections have been observed to begin at pruning 
wounds suggesting that it is an important path thro ugh which the fungus enters the plant (Liang et al.  
2021). Propagation of infected bud wood and seedlin gs can also be a source of transmission.  
Spores on infected symptomatic avocado stems appear  as white powder from black lesions 
(Rodríguez-Gálvez et al. 2021). Spores can be prese nt all year round on infected twigs and in the soil  
but are mostly spread during the summer months (Lia ng et al. 2020). They can be spread by wind, 
rain and insects (Xiaoqin et al. 2001).  
Symptoms 
Lasiodiplodia pseudotheobromae causes dieback, branch cankers and fruit rot. The s pecies has been 
identified and isolated from symptomatic avocado pl ants and fruits (Onaebi et al. 2020; Liang et al. 
2021; Rodríguez-Gálvez et al. 2021).   
Under field conditions, necrosis was observed on th e stems of infected young avocado plants (Liang 
et al. 2021). Small necrotic spots can be observed around infected openings which can extend into 
the internal tissues (Rodríguez-Gálvez et al. 2021) . This can proceed into dieback symptoms that 
begins on the branch of the tree (Liang et al. 2021 ; Rodríguez-Gálvez et al. 2021), and can lead to 
defoliation of the infected branch. Infection can p rogress to other branches and the entire tree 
(Rodríguez-Gálvez et al. 2021). 
In pathogenicity tests, avocado stems inoculated wi th L. pseudotheobromae developed black lesions 
that excreted white powder (spores) (Liang et al. 2 021; Rodríguez-Gálvez et al. 2021). Lesions 
appeared 10 days after inoculation (Rodríguez-Gálve z et al. 2021), and expanded by 1.1 cm over two 
to four weeks. Tissues underneath the lesion turned  brown along the vascular bundle of the stems 
(Liang et al. 2021). After 10 days of incubation of  inoculated avocado stems, necrotic lesion followed  
by the development of dark spores with white aerial  mycelium were observed (Rodríguez-Gálvez et 
al. 2021).   
Lasiodiplodia pseudotheobromae caused black lesions on both wounded and unwounded avocado 
fruits. External lesions became visible after two d ays of inoculation and lesions grew larger as time 
progressed (2-4 weeks). Fruit pulp of infected avoc ado turned soft, water-soaked, and black 
underneath the lesions (Liang et al. 2021). 
Optimal growth conditions 
Optimal temperature for mycelial growth of L. pseudotheobromae isolates under laboratory conditions 
was  30° C with a range of 10-35° C (Liang et al. 202 1).  
5.12.4  Likelihood of entry 
Lasiodiplodia pseudotheobromae has been reported to be present in 23 countries aff ecting a wide 
variety of host plants, including multiple records of it being isolated from avocado (Table 5-14). It  has 
been isolated multiple times from aerial parts (ste ms, branches and fruits) of avocado plants Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 210 indicating that it can be associated with leafless avocado budwood  (Trakunyingcharoen et al. 2015; 
Onaebi et al. 2020; Bragard et al. 2021; Liang et a l. 2021; Rodríguez-Gálvez et al. 2021).   
Under field conditions, necrosis was observed on st ems of young avocado plants infected by L.  
pseudotheobromae  (Liang et al. 2021). Avocado budwoods with establi shed L.  pseudotheobromae  
infection are likely to exhibit symptoms such as ne crotic lesions and discolouration of internal tissu es. 
As such, infected budwoods could be detected and de stroyed during preparation for export, on 
phytosanitary inspection pre-export (if this occurs ), or on arrival in New Zealand.  
Species from the family Botryosphaeriaceae can occu r as latent opportunistic pathogens that do not 
cause disease symptoms (asymptomatic) on host plant s. They can eventually become pathogenic 
and express symptoms when the host plant is stresse d. Very few published studies have tested 
asymptomatic tissues to determine if Lasiodiplodia spp. might have an asymptomatic phase. One 
study found L.  theobromae to occur endophytically in the stem tissue of mango  trees (Johnson et al. 
1992). There is no evidence that L.  pseudotheobromae occurs as a latent and asymptomatic phase 
on cultivated crop plants such as avocado. However,  like other endophytic latent pathogens in its 
family, it is  possible that it can occur on asymptomatic leafless , rootless avocado budwood that might 
not be the detected during preparation for export o r on arrival in New Zealand.  
Studies that have carried out pathogenicity tests f ound that symptoms were expressed within 10 days 
(Liang et al. 2021). Avocado stems infected with L.  pseudotheobromae were observed to excrete 
white powder and form black lesions at the inoculat ion site during pathogenicity tests (Liang et al. 
2021; Rodríguez-Gálvez et al. 2021). The active gro wing period at level 3A PEQ (a minimum of three 
distinct phenological growing events) will likely r esult in expression of symptoms.  
Given the arguments and evidence above, that is:  
• Lasiodiplodia pseudotheobromae has been reported to be present in 23 countries. 
• Lasiodiplodia pseudotheobromae has been isolated from avocado plants (stems, branc hes 
and fruits) and can be associated with leafless avo cado budwood. 
• avocado budwood with established L.  pseudotheobromae  infection can exhibit symptoms 
such as necrotic lesions and discolouration of inte rnal tissues that would be detected during 
preparation for export or on arrival in New Zealand .  
• Lasiodiplodia pseudotheobromae can potentially be present on asymptomatic leafless , 
rootless avocado budwood and might not be the detec ted during preparation for export or on 
arrival in New Zealand, with high uncertainty. 
• if L.  pseudotheobromae is imported on leafless avocado budwood, the active  growing period 
at level 3A PEQ (a minimum of three distinct phenol ogical growing events) will likely result in 
expression of symptoms. 
the likelihood of L. pseudotheobromae  entering New Zealand associated with Persea americana  
budwood is considered to be low , with moderate  uncertainty. 
5.12.5  Likelihood of exposure 
This assessment is made on the basis that L. pseudotheobromae has entered New Zealand 
undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for L. 
pseudotheobromae .   
If avocado plants are infected with L. pseudotheobromae at the time of their release from post entry 
quarantine, they will be planted in New Zealand or used to propagate new plants for planting (see 
section 2.3 for additional information about exposu re).    
211 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Given the arguments and evidence above, the likelih ood of exposure of Lasiodiplodia 
pseudotheobromae  in New Zealand from Persea americana  budwood is considered high , with  
moderate  uncertainty. 
5.12.6  Likelihood of establishment 
This assessment is made on the basis that Lasiodiplodia pseudotheobromae has been successfully 
exposed to a suitable host plant in the New Zealand  environment. 
Lasiodiplodia pseudotheobromae is recorded to be present in 23 countries covering five continents 
(Table 5-14). Countries where it has been recorded have CMI ranges of between 0.4 - 0.9. A CMI of ≥ 
0.7, indicates a similar climate to the whole of Ne w Zealand (Phillips et al. 2018).  Although it is 
common in tropical areas with warmer temperatures ( Burgess et al. 2019), L. pseudotheobromae  is 
the only species in the genus that is observed to g row at temperatures as low as 10° C, with an 
optimum growth temperature of 30° C, in laboratory c onditions (Slippers et al. 2004; Liang et al. 2021) . 
This suggests that the climatic conditions in some parts of New Zealand are likely to be suitable for it 
to establish, especially the North Island where cli matic conditions are warmer. Therefore, climate is 
not likely to be a barrier for the establishment of  L. pseudotheobromae  in New Zealand, especially the 
north of the North Island.  
Lasiodiplodia pseudotheobromae is known to infect a wide range of host plants (Tab le 5-14) including 
some economic important crop plants such as Vitis vinifera  (grapevine), Citrus  spp. and P. americana 
(avocado) (Dissanayake et al. 2015; Bragard et al. 2021; Chen et al. 2021; Liang et al. 2021). These 
plants are grown commercially in different parts of  New Zealand. For example, avocado plants are 
widely grown commercially in orchards and in-home g ardens mostly in the North Island and some 
parts of the South Island (Chapter 2). Vitis vinifera  (grapes) is grown commercially in parts of the 
North and South Island and Citrus  spp. are grown both commercially and in home garde ns all around 
New Zealand. Therefore, suitable hosts are availabl e for L. pseudotheobromae  to establish and 
spread in all parts of New Zealand.  
Lasiodiplodia pseudotheobromae can spread by the movement of infected nursery stoc k for planting 
and the use of contaminated tools used for grafting  and pruning, and soil. Spores can be present all 
year round on infected twigs and in the soil, but a re mostly spread during the summer months (Liang 
et al. 2020). These can be a source of infection an d can be spread by wind, rain (Liang et al. 2020). 
Spread of the pathogen can also be enhanced by inse cts. For example, the insect pest Sahlbergella 
singularis  (Mirid bug) was observed to feed on cocoa pods res ulting in wounds which served as 
access points for infection by Lasiodiplodia spp. (Anikwe and Otuonye 2015). There are about six  
introduced bugs from the same family (Miridae) in N ew Zealand, three of which are pests feeding on 
buds, flowers, developing fruits and young shoots o f economic significant crops in New Zealand 
(Eyles 1999). It is possible that mirid bugs presen t in New Zealand can play are role in enhancing the  
spread of opportunistic pathogenic fungus such as L. pseudotheobromae .  
Given the arguments and evidence above, that is: 
• Lasiodiplodia pseudotheobromae  has been reported to be present in countries with a similar 
climate to New Zealand (parts of Australia, China, Netherland, and Uruguay). The climatic 
conditions in some parts of New Zealand are likely to be suitable for it to occur and spread, 
especially the North Island where climatic conditio ns are warmer 
• it is known to affect a wide range of host plants (Table 5-14), some of which are widely grown 
commercially in orchards and in home gardens in par ts of both the North and South Island of 
New Zealand. 
• spores of L. pseudotheobromae can be present all year round on infected twigs and  in the soil 
and can be spread through the human movement of inf ected nursery stock, fruits, 
contaminated soil and pruning material.  
the likelihood of Lasiodiplodia pseudotheobromae establishing in New Zealand is considered to be 
high , with moderate uncertainty. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 212 5.12.7  Impacts in New Zealand 
Lasiodiplodia pseudotheobromae  have been reported to be associated with avocado a nd a wide 
range of host plants, including economic important crops such as grapevine, citrus and persimmons 
(Table 1). It can cause branch cankers, dieback sym ptoms and postharvest rot diseases (Onaebi et 
al. 2020; Liang et al. 2021; Rodríguez-Gálvez et al . 2021). The fungus can be transmitted by the use 
of contaminated tools during grafting and pruning ( Liang et al. 2021). Propagation of infected bud 
wood and seedlings can also be a source of transmis sion. Spores of L. pseudotheobromae  on 
infected symptomatic avocado plants can be spread b y wind, rain and insects (Xiaoqin et al. 2001).  
Economic impacts 
Species from the genus Lasiodiplodia  are aggressive pathogens, affecting a wide range o f woody 
plant species, that lead to the decrease in orchard  productivity of economically important crops such 
as avocado (Valencia et al. 2019). In severe cases they can cause disease symptoms that lead to 
death of infected trees (Slippers and Wingfield 200 7; Ismail et al. 2012), resulting in significant 
economic loss.  
Lasiodiplodia pseudotheobromea is an aggressive pathogen of avocado and thus, it c an potentially 
cause severe diseases and lead to economic loss in the avocado industry (Rodríguez-Gálvez et al. 
2021). Avocado is increasingly becoming a significa nt horticultural crop in New Zealand. At the end of  
the 2020 financial year, 39,078 tonnes of avocado p roduced in New Zealand and earning up to 
NZ$56 million and NZ$110 million in domestic and in ternational sales respectively (Plant & Food 
Research 2020). Therefore, infections by L. pseudotheobromea can potentially result in yield loss 
which will have an impact on both the domestic and international market.  
Infections by L. pseudotheobromea could affect market access of exports of avocado to  other parts of 
the world where L. pseudotheobromea is not reported to be present. Its presence in New Zealand 
could potentially result in trade barriers to count ries where it is has not been reported to be presen t.  
Lasiodiplodia pseudotheobromea has been reported to cause disease in other economi cally important 
host plants causing symptoms such as post-harvest r ot, dieback, and tree/branch cankers. As such 
economic impact caused by L. pseudotheobromea is not limited to avocado. It can cause up to 10% 
yield loss in some crop plants (Awan et al. 2016; J únior et al. 2017), as well as lead to reduced 
productivity and longevity of the plants. For examp le: 
• it has been reported as one of the most virulent p athogens responsible for causing necrotic 
lesions and gum exudes of Persian limes in Mexico, post-harvest rot of Lemon in Turkey, tree 
cankers in orchards of Citrus reticulata and stem/trunk cankers, stem-end rot and fruit rot of 
Citrus  spp.  in Pakistan (Awan et al. 2016; Bautista-Cruz et al.  2019; Ahmed et al. 2020).  
These disease symptoms can result in reduced yields  and affect the marketability of infected 
crops. Citrus  spp. are crops of economic value in New Zealand bo th domestically and 
internationally. From pathogenicity tests, L. pseudotheobromea was observed to cause 
damage in 40-50% of fruit surface of lemons after f ive days (Awan et al. 2016). In 2019, 
limes, lemons and mandarins had a domestic value of  NZ$41 million, with lemons and 
mandarins having export values of NZ$8 million (Pla nt & Food Research 2020). 
• it has been associated with dieback symptoms and p edicel/peduncle discolouration in grapes 
in Brazil and China respectively (Dissanayake et al . 2015; Correia et al. 2016). Such 
symptoms are increasingly significant in reducing l ongevity of grapevines leading to reduced 
productivity. Reduction in crop yield and losses ca n potentially have a significant economic 
consequence for New Zealand because wine is the sec ond most valuable horticultural 
exports of New Zealand account to for up to NZ $1.9  billion (Plant & Food Research 2020). 
• it has been found to cause shoot and branch diebac k and cankers of apple trees in China 
(Xue et al. 2019). This can potentially lead to red uced productivity and reduced yield of 
infected trees. Apples are one of the most signific ant horticulture export crops for 
New Zealand worth up to NZ$876 million in export in  2020 (Plant & Food Research 2020).  
• it was found to cause post-harvest rot of persimmo ns in Brazil resulting in an estimated 10% 
loss in crop yield. Persimmons are grown in New Zea land with a value of NZ$1.3 million and  
213 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand NZ$10.7 million in domestic and export market respe ctively in 2020 (Plant & Food Research 
2020). 
While it is known that severe outbreaks of L. pseudotheobromea  can result in significant yield loss 
of infected orchards, it might also require the com plete removal of severely infected productive 
trees (avocado, citrus, persimmons, and grapevine) known to require years six to eight years to 
reach full production. Outbreaks can be triggered b y environmental stresses such as drought, hail 
or frost and trigger outbreaks (Udayanga et al. 201 1; Liang et al. 2021). This is likely to occur on a  
localized scale and causing significant economic on  a localized scale.   
Given the arguments and evidence above, that is: 
• L. pseudotheobromea  has been reported to be an aggressive pathogen of avocado that 
can potentially result in reduced productivity and yield loss. This can have an impact on 
both the domestic and international market.  
• infections by L. pseudotheobromea can affect market access of exports of avocado to 
other parts of the world where L. pseudotheobromea is not reported to be present  
• because L. pseudotheobromea affects other economic important h osts plants, it can lead 
to reduced productivity and longevity of the plants  such as grapevine, apples and 
persimmons resulting in additional economic loss.  
• There is moderate uncertainty that infection outbr eaks are likely to be sporadic and on a 
localized scale. 
the economic impact of Lasiodiplodia pseudotheobromea  to New Zealand is considered to be 
moderate-high, with moderate uncertainty.  
Environmental impacts  
There is little evidence of L. pseudotheobromea  impacting on non-crop plant species. It has mostly  
been reported to cause diseases in cultivated crop plant species (Table 5-14). Although, in a recent 
study in Australia, a closely related species L. theobromea  was reported to cause disease in some 
Australian native plant species ( Adansonia spp.) (Burgess et al. 2019). Lasiodiplodia theobromea is a 
related species that is already in New Zealand and it has so far not been reported to infect native 
species in New Zealand. In the same study, L. pseudotheobromea was isolated from asymptomatic 
tissues of Adansonia gregorii  (Burgess et al. 2019). It has also been isolated f rom an asymptomatic 
native perennial herb Houttuynia cordata in Thailand (Aramsirirujiwet et al. 2016) and from a 
deciduous shrub Aegle marmelos in India (Kapoor and Saxena 2014). This indicates t hat it might 
occur as an endophyte on non-crop species and proba bly be a source of infection for crop plants that 
might be grown in close proximity (Burgess et al. 2 019). For example Boyogueno et al. (2012) 
isolated L. pseudotheobromea from asymptomatic bark and branches of native speci es of Terminalia 
spp. growing in close proximity to symptomatic Theobroma cacao plants in Cameroon. Therefore, L. 
pseudotheobromea is likely to have a low impact on New Zealand’s env ironment. 
Given the arguments and evidence above, the impact on the environment from the establishment of 
Lasiodiplodia pseudotheobromea in New Zealand is considered to be low, with low un certainty. 
Human health impacts 
Google and google scholar searches using the search  term ‘ Lasiodiplodia pseudotheobromea  on 
health’ found only one study where L. pseudotheobromea  was isolated from an eye infection 
(keratitis) of a mango farmer after a traumatic eye  injury that is thought to be the result of inocula tion 
of the fungus from a mango tree branch when the inj ury occurred (Vanam et al. 2019). Lasiodiplodia 
pseudotheobromea is reported to cause rot in mangoes and can be pres ent on mango tree branches 
in a latent endophytic infection (Ismail et al. 201 2; Rodríguez-Gálvez et al. 2017). Reports of human 
infection by Lasiodiplodia spp. has involved closely related species L. theobromea (Maslen et al. 
1996; Summerbell et al. 2004) which is known to be present in New Zealand. There has been no 
report so far that it has affected human health in New Zealand.   
Given the arguments and evidence above, the health impact of L. pseudotheobromea  to New Zealand 
is considered to be very low, with low-moderate unc ertainty. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 214 Sociocultural impacts 
Diseases caused by L. pseudotheobromea  can potentially lead to reduced productivity and r ender 
fruits of avocado and other host plants inedible. T his can cause scarcity in local markets.  Avocado 
has become popular and is widely consumed in New Ze aland. It is commonly grown in home gardens 
in some parts of the country.  Other host plants su ch as Citrus  spp. are commonly grown in home 
gardens around New Zealand. 
Given the arguments and evidence above, the sociocu ltural impact of L. pseudotheobromea  to 
New Zealand is considered to be moderate, with low uncertainty. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, health and society is considered to be 
moderate-high, with moderate uncertainty. 
5.12.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is low with moderate uncer tainty 
• assuming entry, the likelihood of exposure high wi th moderate uncertainty 
• assuming successful exposure, the likelihood of es tablishment is high with moderate 
uncertainty 
• the overall impact on the New Zealand economy, env ironment, health and society is 
considered to be moderate-high with moderate uncert ainty 
the overall level of assessed risk to New Zealand f rom L. pseudotheobromea  on imported P. 
americana budwood (as in the commodity description) is consid ered to be moderate-high, with 
moderate uncertainty. 
5.12.9  Management considerations 
Under field conditions, L. pseudotheobromea causes necrosis on the stems of infected young plan ts 
(Liang et al. 2021). Small necrotic spots were obse rved around infected openings extending into the 
internal tissues (Rodríguez-Gálvez et al. 2021). Ov er time, this can proceed into dieback symptoms 
that begins on the branch of the tree (Liang et al.  2021; Rodríguez-Gálvez et al. 2021), and can lead 
to defoliation of the infected branch. Infection ca n progress to other branches and the entire tree 
(Rodríguez-Gálvez et al. 2021).  
Chemical fungicides and biocontrol agents (other mi croorganisms) have been used in controlling 
Lasiodiplodia species (Khanzada et al. 2005; Kotze et al. 2011). Fungicides were demonstrated to be 
effective for managing disease symptoms caused by L. pseudotheobromea in cocoa growing areas in 
Indonesia (Asman and Rosmana 2021). 
In general, pathogenic endophytes such as L. pseudotheobromae  can exhibit symptoms under 
environmental stresses such as drought, hail or fro st (Udayanga et al. 2011; Liang et al. 2021), but 
the specific conditions for symptom expressions for  L. pseudotheobromae  are not well understood 
and have not been described.  
PCR test can be used to detect the presence of L. pseudotheobromae  (Alves et al. 2008). Samples 
can be taken from any part of the avocado leafless budwood and testing different parts of the 
budwood might be required. However, it is not clear  if the pathogen will be evenly distributed 
throughout an infected avocado budwood and that the  right bit will be tested.    
There is no specified optimum season for conducting  testing for L. pseudotheobromae  
215 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.12.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Under field conditions, necrosis was observed on th e stems of infected young avocado plants (Liang 
et al. 2021). When plants get infected, small necro tic spots can be observed around infected openings 
which can extend into the internal tissues (Rodrígu ez-Gálvez et al. 2021). This can proceed into 
dieback symptoms that begins on the branch of the t ree (Liang et al. 2021; Rodríguez-Gálvez et al. 
2021)., and can lead to defoliation of the infected  branch. Infection can progress to other branches 
and the entire tree (Rodríguez-Gálvez et al. 2021).  
o What are the known environmental conditions conduci ve to symptom expression? 
In general, pathogenic endophytes such as L. pseudotheobromae  can exhibit symptoms under 
environmental stresses such as drought, hail or fro st (Udayanga et al. 2011; Liang et al. 2021), but 
the specific conditions for symptom expression for L. pseudotheobromae  are not well understood and 
have not been described.  
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Samples can be taken from any part of the budwood a nd testing different parts of the budwood might 
be required. However, it is not clear if it will be  evenly distributed throughout an infected avocado 
budwood and that the right part will be tested. 
o What is the optimum season for conducting detection  testing? 
There is no specified optimum season for conducting  testing for L. pseudotheobromae . 
5.12.11  References 
Abdollahzadeh, J; Goltapeh, E M; Javadi, A; Shams-B akhsh, M; Zare, R; Phillips, A (2009) Barriopsis 
iraniana  and Phaeobotryon cupressi : two new species of the Botryosphaeriaceae from tr ees in Iran. 
Persoonia 23: 1. 
Ahmed, M Z; Shafique, M S; Anwaar, H A; Sarfraz, S;  Tufail, M R; Fayyaz, A, et al. (2020) First report  
of Lasiodiplodia pseudotheobromae  causing trunk cankers in Citrus reticulata  in Pakistan. Plant 
Disease 104(9): 2522. 
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 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 220 5.13  Mycosphaerella perseae 
Mycosphaerella perseae is a fungal plant pathogen that causes silver spot disease in Persea 
americana (avocado). Silver spot disease causes lesions on th e leaves of the plant. 
5.13.1  Taxonomic description 
Scientific name: Mycosphaerella perseae  Miles 1917  
Order/Family: Mycosphaerellales / Mycosphaerellaceae (Robert et a l. 2005)  
Other names include : Sphaerella perseae  (Miles) Trotter 1928 
Taxonomic notes: A Septoria sp. is considered the anamorph and M. perseae  is the teleomorph. 
Mycosphaerella perseae  is the preferred name (Robert et al. 2005). 
5.13.2  Hazard identification 
Mycosphaerella perseae  is not known to be present in New Zealand: 
• Mycosphaerella perseae is not listed in NZOR (2021), Biota NZ (2022) or PP IN (2021). 
• Mycosphaerella perseae is not listed in ONZPR (2021). 
Mycosphaerella perseae  has the potential to establish (and spread) in New  Zealand because: 
• Persea americana  (avocado) is a known host (Zentmyer 1961; Ploetz 2 003) that is widely 
grown in New Zealand, in home gardens and commercia l production, mainly in the north of 
the North Island. 
• Mycosphaerella perseae causes leaf spot disease in tropical and subtropica l countries 
including Mexico and Central America (Ploetz 2003; Ploetz 2007). Some regions in these 
areas have a climate match index (CMI) ≥ 0.7 indicating a similar climate to the whole of N ew 
Zealand (Phillips et al. 2018).  
Mycosphaerella perseae  has the potential to cause harm to New Zealand bec ause: 
• it causes leaf spot on avocado (Ploetz 2003; Serme no et al. 2005). When leaves are heavily 
infected, necrotic lesions may encompass the entire  leaf (Ploetz 2003). Defoliation may occur, 
but this tends to be restricted to older leaves (Pl oetz 2003). 
• avocados are an important commercial crop in New Z ealand. In the 2019–2020 financial year, 
export sales of fresh avocados earned NZ$112.3 mill ion and domestic sales earned NZ$50.6 
million (Plant & Food Research 2020). 
Mycosphaerella perseae  is associated with Persea americana  budwood because: 
• Persea americana  is a known host of M. perseae  (Seaver and Chardon 1926; Ploetz 2003; 
Sermeno et al. 2005). 
• Mycosphaerella perseae causes leaf spots and seems to strictly parasitize leaves; however, 
in favourable climates and severe cases, the fungus  has been recorded to cause defoliation 
and invade the stem (Sermeno et al. 2005). 
Given the arguments and evidence above, Mycosphaerella perseae  meets the criteria to be a hazard 
on Persea americana  budwood (as in the commodity description) imported  to New Zealand.  
221 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.13.3  Risk assessment 
Biology and epidemiology of Mycosphaerella perseae 
Hosts and geographical distribution 
Mycosphaerella perseae is the causative agent of silver spot disease in Persea americana (avocado) 
(Ploetz 2003). Silver spot is considered a minor pr oblem in avocado orchards and there has been no 
record of this disease reducing yields (Ploetz 2003 ; Sermeno et al. 2005).  
Mycosphaerella perseae  has a distinct host range and has only been record ed on avocado (Seaver 
and Chardon 1926; Spaulding 1961; Ploetz 2003). It has been recorded on avocado from Puerto Rico 
(Seaver and Chardon 1926; Spaulding 1961), Mexico ( Spaulding 1961; Ploetz 2003) and Florida, 
USA (Spaulding 1961). 
Symptoms 
Mycosphaerella perseae causes light brown to silver spots or lesions on th e upper surface of leaves 
and darker brown spots on the lower surface of leav es (Ploetz 2003; Sermeno et al. 2005). A dark 
brown to black border often surrounds the spots and  leaf spots are slightly depressed on the surface 
of leaves (Ploetz 2003). Leaf spots can vary in siz e but can grow to a diameter of 1-2 cm (Sermeno et 
al. 2005). The disease is usually first observed in  the lower foliage and progresses up the tree 
(Sermeno et al. 2005). 
Necrotic lesions spread across the surface of the l eaves in heavily infected cases. Defoliation may 
occur, but tends to be restricted to older leaves ( Ploetz 2003). In severe cases, M. perseae may 
invade the stem (Sermeno et al. 2005). 
Reproduction and transmission 
Mycosphaerella perseae produces ascospores (i.e., sexual spores of Ascomyc ota). Ascospores 
produced in infected and dead leaves can infect you ng leaves through wind, rain and insects (Ploetz 
2003). The anamorph (i.e. asexual stage) of M. perseae , which was previously known as a Septoria 
sp., produces pycnidia (i.e. asexual fruiting bodie s). Conidia (i.e. asexual spores) are released from  
pycnidia and secondary spread can occur via conidia  from older leaves or dead twigs (Sermeno et al. 
2005). In both sexual and asexual transmission, rai n, fog and humid conditions favour disease 
development, especially during the spring season (P loetz 2003; Sermeno et al. 2005). 
Mycosphaerella perseae requires sufficient moisture to produce infection a nd grows optimally at 
temperatures between 10-27° C (Sermeno et al. 2005).  
In-field management 
Pruning of trees to reduce humidity is one type of management that controls the disease in avocado 
production. In addition, removing infected fallen l eaves (i.e. source of fungal inoculum) from the 
orchard is another form of disease management (Ploe tz 2003). Three applications of maneb, captan 
or copper fungicides at 30-day intervals have been successful in treating symptoms in orchards 
(Ploetz 2003).  
5.13.4  Likelihood of entry 
Mycosphaerella perseae  causes leaf spots on avocado leaves but in severe cases it has been 
reported to infect stems (Sermeno et al. 2005); the refore, the fungus could be associated with 
leafless, rootless avocado budwood cuttings. Howeve r, there is only limited evidence to support this 
association, based on a single technical document f rom El Salvador, with no primary records to verify 
this. However, M. perseae is more likely to produce ascospores and conidia on  older leaves or dying 
and dead material (Ploetz 2003; Sermeno et al. 2005 ) and thus removing leaves and importing clean 
rootless budwood would considerably reduce the like lihood of entry on this pathway. Conidia and 
ascospores of other Mycosphaerella species (e.g. M. ligulicola and M. musicola ) do not seem to 
survive for more than a few weeks (Blakeman and Hor nby 1966; Thammaiah et al. 2007). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 222 If avocado budwood cuttings have an established M. perseae  infection, it is highly likely that lesions 
will be detected, and infected material removed or destroyed, during phytosanitary inspections on 
arrival in New Zealand. 
As part of the commodity description, all imported avocado germplasm will undergo a growing period 
of active growth with a minimum of three distinct p henological growing events referred to as ‘shoot 
flush’ in 3A PEQ. This period in 3A PEQ will impact  on likelihood of entry in the following manner: 
• any ungerminated M. perseae  conidia on the surface of avocado budwood are high ly unlikely 
to remain viable (alive and still capable of infect ing the plant) on the assumption of 
survivability of conidia of M. ligulicola  (Blakeman and Hornby 1966) during preparation of t he 
material for export, transit to New Zealand, surfac e disinfection (cuttings dipped in 1% sodium 
hypochlorite for 2 minutes) upon arrival in PEQ and  subsequent grafting of the buds onto new 
rootstock.  
• if viable conidia remain on a bud once the bud is grafted, infection is likely to occur once the 
bud breaks dormancy to form young unfolding leaves.  In this case, visible lesions are likely to 
develop assuming the following conditions occurs, t emperatures between 10–27° C and high 
humidity, and thus, be detected during routine insp ections. 
• Searches of Google Scholar, CAB abstracts, CPC and  Google using the search terms 
‘Mycosphaerella perseae ’, ‘ Sphaerella perseae ’ and ‘asymptomatic’ found no evidence for 
asymptomatic M. perseae  infections or longer latent periods in avocado pla nts47. Budwood or 
grafted plants infected with M. perseae  are therefore almost certain to develop symptoms a nd 
be detected and destroyed before they are released from PEQ.  
• Conidia are spread by watersplash, windborne rain and insects (Ploetz 2003). Level 3A PEQ 
has measures in place to manage the risks associate d with insects, wastewater, waste and 
accidental transfer (see section 2.2), therefore vi able M. perseae  propagules are highly 
unlikely to escape level 3A PEQ to infect a suitabl e host. 
Therefore, if M. perseae  is imported on avocado, the residual biosecurity r isks are likely to be 
managed by the growing period of active growth with  a minimum of three distinct phenological 
growing events referred to as ‘shoot flush’ in 3A P EQ. 
Given the arguments and evidence above, that is:  
• there is very limited evidence for a potential ass ociation of M. perseae with leafless, rootless 
avocado budwood cuttings; 
• established M. perseae  infections are highly likely to be detected, and i nfected material 
removed or destroyed, during preparation for export , in phytosanitary inspections pre-export 
or on arrival in New Zealand; 
• residual biosecurity risks from recent infections or ungerminated conidia on the surface of 
avocado budwood are likely to be managed by the gro wing period of active growth with a 
minimum of three distinct phenological growing even ts referred to as ‘shoot flush’ in 3A PEQ; 
the likelihood of Mycosphaerella perseae  entering New Zealand associated with Persea americana  
budwood is considered to be negligible, with low un certainty. 
Therefore, further assessment is considered unneces sary at this time; and likelihoods of exposure 
and establishment and impacts to New Zealand were n ot assessed. 
5.13.5  Overall level of assessed risk to New Zealand 
Based on the assessment of likelihood above, that:  
• the likelihood of M. perseae  entering New Zealand associated with Persea americana  
budwood (as described in the commodity description,  and taking into account the proposed 
growing period of active growth with a minimum of t hree distinct phenological growing events 
referred to as ‘shoot flush’ in 3A PEQ) is consider ed to be negligible with low uncertainty;  
 
47  Spanish and Portuguese references were also checke d when they were found in searches on the species n ames.  
223 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • therefore, continuing the assessment was considere d unnecessary; and 
the overall level of risk to New Zealand from M. perseae  on imported Persea americana budwood is 
considered to be negligible, with low uncertainty.  
5.13.6  Management considerations 
Mycosphaerella perseae  produces visible lesions on leaves (see above) and  searches on the species 
name found no evidence for asymptomatic infection o f leaves or stem tissues. Therefore, M. perseae  
is highly unlikely to persist as an asymptomatic in fection on susceptible tissues. 
There is no information on time to development of s ymptoms, but high humidity and moisture 
conditions, at temperatures between 10-27° C are kno wn to induce symptoms (Ploetz 2003; Sermeno 
et al. 2005). Ascospores and conidia are more likel y to sporulate on older leaves or dying and dead 
material (Ploetz 2003; Sermeno et al. 2005) and thi s suggests that symptoms of pre-existing M. 
perseae infections are highly likely to be detected by visu al inspection during preparation for export or 
on arrival in New Zealand.  
If viable conidia have remained on the surface of b uds, infections are likely to develop when the 
plants break dormancy and produce new shoots. Given  the conditions described above, temperatures 
in PEQ are likely to favour infection, but there ma y not be enough water on the surface of the plant t o 
allow conidia to germinate and infect susceptible t issues. Nevertheless, conidia are highly unlikely t o 
remain viable on P. americana  budwood through pre- and post-export handling and the PEQ period. 
Therefore, prophylactic testing in the absence of v isible lesions is unnecessary.  
Mycospharella spp. specific primers for nested polymerase chain r eaction (PCR) have been 
developed, however, this was developed for Eucalyptus leaves (Glen et al. 2007). Other studies have 
demonstrated Mycospharella specific primers in other hosts (Guo et al. 2006) s uggesting PCR 
techniques could be developed for diagnostic testin g of M. perseae  in avocado if symptoms are 
detected in PEQ.  
5.13.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Mycosphaerella perseae  causes lesions on leaves which can measure up to 2 cm in diameter 
(Sermeno et al. 2005). Lesions can coalesce into la rger lesions as infection spreads (Ploetz 2003). 
Lesions are light brown to silver on the upper surf ace of leaves and darker brown spots on the lower 
surface of leaves (Ploetz 2003; Sermeno et al. 2005 ). A dark brown to black border often surrounds 
the spots and leaf spots are slightly depressed on the surface of leaves (Ploetz 2003).  
o What are the known environmental conditions conduci ve to symptom expression? 
Optimal growth occurs in high humidity and moisture  conditions at temperatures between 10-27° C 
(Sermeno et al. 2005). The use of overhead irrigati on to simulate rainfall could induce symptom 
expression of M. perseae , however, it would increase the risk of the diseas e spreading among plants. 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 224 There is no information that M. perseae  causes asymptomatic infections and thus, there is no 
information on which plant part should be tested to  maximise the detection of M. perseae  in the case 
of asymptomatic infection. 
o What is the optimum season for conducting detection  testing? 
Rain, fog and humid conditions in the spring favour  silver spot disease development (Ploetz 2003). 
5.13.8  References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Blakeman, J P; Hornby, D (1966) The persistence of Colletotrichum coccodes  and Mycosphaerella 
ligulicola  in soil, with special reference to sclerotia and c onidia. Transactions of the British Mycological 
Society 49: 227-240. 
Glen, M; Smith, A H; Langrell, S R H; Mohammed, C L  (2007) Development of nested polymerase 
chain reaction detection of Mycosphaerella  spp. and its application to the study of leaf dise ase in 
Eucalyptus  plantations. Phytopathology® 97(2): 132-144. 
Guo, J-R; Schnieder, F; Verreet, J-A (2006) Presymp tomatic and quantitative detection of 
Mycosphaerella graminicola development in wheat using a real-time PCR assay. FEMS Microbiology 
Letters 262(2): 223-229. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
Ploetz, R C (2003) Diseases of Tropical Fruit Crops . CABI Pub. 
Ploetz, R C (2007) Diseases of tropical perennial c rops: challenging problems in diverse 
environments. Plant Disease 91(6): 644-663. 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Robert, V; Stegehuis, G; Stalpers, J (2005) The Myc oBank engine and related databases. 
https://www.mycobank.org/  Accessed October 2021 
Seaver, F J; Chardon, C E (1926) Scientific survey of Porto Rico and the Virgin Isla nds  (Vol. 3). New 
York Academy of Sciences. 
Sermeno, J M; Rivas, A W; Mengjivar, R A (2005) Guia tecnica de las principales plagas artropodas y  
enfermedades de los frutales . Ministerio de Agricultura y Ganaderia, El Salvado r.  
Spaulding, P (1961) Foreign diseases of forest trees of the world: an a nnotated list . US Department of 
Agriculture, USA.  
Thammaiah, N; Kulkarni, M S; Kulkarni, S (2007) Sur vival of Mycospharella musicola ascospores in 
banana leaves. The Asian Journal of Horticulture 2: 78-79.  
225 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Zentmyer, G A (1961) Avocado diseases in the Americ as. CEIBA 9(2): 61-79. 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 226 5.14  Neocosmospora perseae 
Neocosmospora perseae  is a fungal pathogen reported to cause avocado tru nk cankers and is 
probably an opportunistic pathogen infecting the pl ant via wounds.  
5.14.1  Taxonomic description 
Scientific name: Neocosmospora perseae  Sand.-Den. & Guarnaccia (2018)  
Order/Family: Hypocreales/Nectriaceae 
Other names include : Fusarium perseae  (Sand.-Den. & Guarnaccia) O'Donnell, Geiser & T. A oki 
(2020) 
Taxonomic notes: Neocosmospora perseae is a recently described member of the Fusarium solani  
species complex (FSSC). Members of this complex ten d to be very similar morphologically. For this 
reason, members of the FSSC were historically refer red to as mating strains or formae speciales  
(groups of races and biotypes of a pathogen species  that can only infect plants within a certain host 
genus or species) of the species Fusarium solani.  However, recent studies estimate that the F. solani 
complex includes at least 60 phylogenetically disti nct species (Aoki et al. 2014). Even recently, the 
fungus causing a disease outbreak has often been cl assified as Fusarium solani or a member of the 
FSSC because of the difficulty of identifying FSSC members to species level based on morphological 
features. In the absence of specific studies on N. perseae, this assessment relies on historic 
information about the epidemiology of F. solani  sensu lato  (that is, used in its historic sense to 
encompass the whole species complex) and studies re ferring to F. solani  that probably relate to 
different species within the complex. Neocosmospora perseae is in clade 3 of the FSSC, along with 
species such as N. falciformis, N. keratoplastica, N. petroliphila and N. solani  sensu stricto  which are 
ubiquitous in soil and decaying plants. 
There is debate in the literature as to whether spe cies in the FSSC should remain part of Fusarium  or 
should be placed in the genus Neocosmospora (Aoki et al. 2019; Sandoval-Denis et al. 2019; Lynn  et 
al. 2020; O'Donnell et al. 2020; Geiser et al. 2021 ; Lynn et al. 2021). Discussion of fungal 
phylogenetics (taxonomy based on molecular sequence s and biological characteristics) is beyond the 
scope of this PRA. A name change is highly unlikely  to affect the conclusions of the PRA (unless it 
were to synonomise an ambrosia Fusarium complex (AF C) species with a species that is present in 
New Zealand). Although Species Fungorum gives the c urrent legitimate name as Fusarium perseae , 
EPPO (2021), Farr and Rossman (2021) and Mycobank ( Robert et al. 2005) favour Neocosmospora 
perseae . In addition, although there is no record of N. perseae in Biota NZ (2022) , this database 
records Neocosmospora  as a valid genus including N. solani replacing F. solani sensu stricto . To 
align with this, the species name Neocosmospora perseae has been used in this PRA. 
5.14.2  Hazard identification 
Neocosmospora perseae  is not known to be present in New Zealand: 
• Neither N. perseae nor its synonym F. perseae  are listed in either Biota NZ (2022) or PPIN 
(2021). While there is no record of N. perseae  in New Zealand (PPIN 2021; Biota NZ 2022), 
Fusarium solani  (sensu lato  i.e., the species complex) is present in New Zeala nd (Biota NZ 
2022) and recently described species within the com plex such as N. perseae  could previously 
have been identified as F. solani . The Manaaki Whenua – Landcare Research collection  
records a single isolate of N. solani  (ICMP 10680, identified as F. solani , and in clade 3, the 
same clade as N. perseae ) from P. americana  in Gisborne. However, DNA sequence of this 
New Zealand isolate (MG857354) is different from N. perseae (Ho, pers. comm.). 
• Neocosmospora perseae  is not listed in ONZPR (2021). 
Neocosmospora perseae  has the potential to establish (and spread) in New  Zealand because:  
227 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • it is recorded from areas with a Climate Match Ind ex (CMI) ≥0.7 indicating a similar climate to 
the whole of New Zealand (Phillips et al. 2018); 
• avocado is a host and is commonly grown in norther n parts of New Zealand, both 
commercially and domestically; 
• transmission of N. perseae  is likely to be similar to other species in the FS SC (that is N. solani  
in the historic broad sense). This group are soilbo rne fungi that opportunistically infect 
susceptible hosts, often through wounds, or lesions  caused by other fungi (Smith 2007; Marek 
et al. 2013). Conidia (asexual spores) of N. solani are produced on plant debris on the soil 
surface and dispersed by water splash (Meyers and C ook 1972). Some FSSC species also 
produce airborne ascospores (Smith 2007). Therefore , Neocosmospora perseae can also be 
transmitted by contaminated soil and tools. 
Neocosmospora perseae  has the potential to cause harm to New Zealand bec ause: 
• it causes trunk cankers on mature avocado trees, r educing their productivity (Guarnaccia et 
al. 2018); 
• avocados are an important commercial crop in New Z ealand. In the 2019–2020 financial year, 
export sales of fresh avocados earned NZ$100 millio n and domestic sales earned NZ$50.5 
million (Plant & Food Research 2019). 
Neocosmospora perseae  is associated with Persea americana  budwood because: 
• avocado ( P. americana ) is a known host of N. perseae ; 
• Neocosmospora perseae  was isolated from trunk cankers and caused cankers  on shoots of 
avocado seedlings that were at a similar developmen tal stage to the plant material used for 
commercial budwood.  
Given the arguments and evidence above, N. perseae  meets the criteria to be a hazard on Persea 
americana  budwood (as in the commodity description) imported  to New Zealand. 
5.14.3  Risk assessment 
Biology and epidemiology of Neocosmospora perseae 
Host range and distribution 
Neocosmospora perseae  was first described as a pathogen of avocado in It aly (Guarnaccia et al. 
2018) and more recently in Greece (Guarnaccia et al . 2021). It has also been reported from trees in 
São Paulo, Brazil (Contato et al. 2021),  but in th is study, the host species and symptoms were not 
reported (Table 5-15).  
Although formae speciales  of F. solani (current name N. solani ) have historically been characterised 
according to host, recent phylogenetic studies have  shown that some have diverse host ranges 
(Sandoval-Denis et al. 2019). Therefore, given that  N. perseae is only recently described, it cannot be 
assumed that it is specific to avocado. Furthermore , there are many historic records of Fusarium 
solani in avocado (see below), although only one relating to trunk cankers was found in searches. 
Table 5-15. Geographical distribution of Neocosmospora perseae  
Region Country Locality, State/Province  (if recorded) CMI* Host plant Reference 
Europe Italy San Leonardello, Catania 0.8  P. americana Guarnaccia et al. (2018) 
Greece Chania, Crete 0.7 P. americana Guarnaccia et al. (2021) 
South 
America Brazil Ribeirão Preto, São Paulo 0.6 Tree (species 
not recorded) Contato et al. (2021) 
* Climate Match Index (CMI) with all of New Zealand  (Phillips et al. 2018). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 228 Searches of Google scholar, CAB abstracts, CPC and Google using the search terms 
“Neocosmospora perseae ” and “ Fusarium perseae ” (with quote marks to restrict search results to 
these species names) found only three primary repor ts (Table 5-15) and a few other records, mainly 
taxonomic studies, referring to Guarnaccia et al. ( 2018) or including N.  perseae sequences in 
molecular phylogenies.   
Symptoms 
Neocosmospora perseae  was isolated from trunk cankers on mature (14-year -old) avocado plants 
(Guarnaccia et al. 2018). Infected bark appeared cr acked, darkly discoloured and/or slightly sunken. 
Reddish-brown discolouration within the canker exte nded into the xylem (Guarnaccia et al. 2018). 
Occasionally, a sugar exudate was present on the su rface (Guarnaccia et al. 2018). Approximately 
10% of plants showed disease symptoms (Guarnaccia e t al. 2018). Fusarium -like fungi were the only 
isolates obtained from symptomatic avocado trees an d all five of the characterised strains were 
considered to be the newly described species N. perseae (Guarnaccia et al. 2018).   
Transmission  
Guarnaccia et al. (2018) considered that transmissi on of N. perseae  is likely to rely on soil 
contamination and plant-associated reservoirs. Gene ral information about the life cycle of members of 
Fusarium solani  sensu lato  (i.e. the FSSC) is therefore relevant. Fusarium solani  is a ubiquitous soil 
fungus (Coleman 2016; Aoki et al. 2019; Sandoval-De nis et al. 2019; Lynn et al. 2020; Geiser et al. 
2021; Lynn et al. 2021). These reviews and taxonomi c treatments, and the results from Google 
Scholar and CABI searches on the term “ Fusarium solani ” and “ Neocosmospora solani ”, indicate that 
the FSSC is extremely widely reported as a cause of  foot and root rots, diebacks, seedling blights, 
branch and trunk cankers and stem and fruit rots, a s well as an endophyte and saprophyte in a 
diverse range of hosts and environments. Fusarium solani  opportunistically infects susceptible hosts, 
often through wounds, or lesions caused by other fu ngi (Marek et al. 2013). 
Conidia (asexual spores) of F. solani may be produced in lesions on stems and roots or pl ant debris 
on the soil surface and are dispersed by water spla sh (Meyers and Cook 1972; Roy 1997). When 
nutrients are depleted, germinated F. solani  conidia may form chlamydospores (resting spores) w hich 
can survive in the soil for long periods (Meyers an d Cook 1972), usually in, or on the surface of plan t 
residues (Smith 2007). Chlamydospores germinate if there is a source of organic nitrogen and sugar 
(Meyers and Cook 1972; Smith 2007), for example nut rients from roots or tubers of a nearby host 
plant. Germinating chlamydospores contain enough en ergy for the developing hyphae to grow a short 
distance but if they do not reach a suitable host, they lyse and die (Smith 2007). If the developing 
hyphae reach a suitable host they may colonise the cortex (the layer of cells between the epidermis 
and the vascular tissues of stems and roots) (Smith  2007). Some FSSC species can colonise the 
plant systemically following root infection. For ex ample, F. solani  was reisolated from stem tissues 
following root inoculation in cannabis plants (Punj a et al. 2021),  soybeans (Gai et al. 2012) and 
mandarin seedlings (Kurt et al. 2020).  
Some members of the FSSC produce airborne ascospore s (sexual spores), often in wounds or 
cankers on woody branches. These species can be hom othallic (a single isolate can produce 
ascospores, without the need for an isolate of anot her mating type) or heterothallic (a second mating 
type is required for fertilisation). 
It is likely that N. perseae  can be transmitted by grafting, as this is reporte d as a means of 
transmission in other FSSC species. For example, F. solani disease lesions on the trunks of almond 
and apple nursery plants were localised around or a bove graft unions implying that these fungi may 
have gained access to trees during grafting (Marek et al. 2013).  
Some species in the FSSC are reported to be spread by insects, for example the ambrosia fusarium 
clade (AFC) species are farmed by ambrosia beetles (see PRA on Fusarium dieback caused by AFC 
species (section 5.2)). However Guarnaccia et al. ( 2018) found no evidence that N. perseae  was 
associated with any vector, as there were no beetle  galleries or other sign of insect infestation in t rees 
infected with N. perseae .  
229 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Growth conditions and time to symptom development  
In natural infections, canker-causing pathogens suc h as N. perseae  may gain entry to the plant due to 
frost damage or mechanical injuries such as pruning  wounds (Guarnaccia et al. 2018). Cankers 
caused by N. perseae  have been observed in branches of 5-year-old avoca do plants and trunks of 
14-year-old avocado plants. However, the only infor mation about symptom development in N. 
perseae  comes from pathogenicity testing in 6-month-old (G uarnaccia et al. 2018) or two-year-old P. 
americana  seedlings (Guarnaccia et al. 2021). Stems of these  plants are likely to be similar in age to 
stems of budwood cuttings and shoots of newly graft ed plants.    
Symptoms of N. perseae  developed one month after inoculation in young avo cado  seedlings grown at 
25  ± 1 ° C (Guarnaccia et al. 2018; Guarnaccia et al. 202 1) and 95 % relative humidity under a 12-h 
fluorescent light/dark regime (Guarnaccia et al. 20 18).  After three months, all the inoculated avocad o 
seedlings showed disease symptoms, with serious sym ptoms leading to plant death (and N. perseae 
could be reisolated from these diseased seedlings) (Guarnaccia et al. 2018).  
In culture (on agar plates), the temperature range for growth of N. perseae was 9 –36 ° C, with an 
optimum of 27–30 ° C (Guarnaccia et al. 2018).  
Potential for latent infections in stems 
There are only two reports of N. perseae  from avocado plants (Guarnaccia et al. 2018; Guarn accia et 
al. 2021). Since those plants showed symptoms, ther e is no specific evidence that N. perseae  can be 
latent in plant stems for long periods without show ing symptoms. However, there is evidence in the 
literature that Neocosmospora  species can be endophytes in plant hosts (Sandoval -Denis et al. 2019) 
or can switch between an endophytic and pathogenic lifecycle in response to environmental stresses. 
For example: 
• a strain of N.  solani  isolated from the roots of a wetland plant ( Phragmites australis ) was a 
weak mutualist promoting root growth at medium sali nity in rice, Oryza sativa , roots and 
beneficial to survival at moderate salinity but was  associated with a negative effect on root 
length at medium high salinity (Eydoux and Farrer 2 020).  
• Fusarium solani  was among the species isolated from canker lesions  in dormant cold stored 
apple and almond ( Prunus dulcis ) seedlings (Marek et al. 2013). Symptoms included white, 
pink, and orange sporulation on the surface of the bark, emerging through lenticels (pores in 
the bark), directly over or adjacent to internal ne crosis of the inner bark and cambium. These 
symptoms developed in the seedlings after they were  left outside on pallets for approximately 
7 to 14 days and became desiccated. Marek et al. (2 013) considered it likely that Fusarium  
spp. were endophytically associated with the apple and almond scions (grafted budwood) as 
latent or asymptomatic infections.  
• Fusarium solani was isolated as an endophyte from healthy Persian o ak (Quercus brantii ) 
trees (as well as from declining trees) and did not  produce symptoms within three months in 
pathogenicity testing (Alidadi et al. 2019).  
Other reports of Neocosmospora solani (i.e. FSSC sp ecies, reported as Fusarium solani) in 
Persea americana 
Avocado has historically been reported as a host of  N. solani . Since N. perseae is likely to have been 
reported historically as F. solani, these records may provide insight into its biology and epidemiology .  
Neocosmospora solani  (along with Fusarium and Phytophthora spp.) was isolated  from trunk cankers 
on P. americana  in Michoacán Mexico (Torres et al. 2000). Canker s ymptoms showed as cracks in 
the bark and as dark discoloured wood with white po wder on the surface (Torres et al. 2000). 
Irrigated, heavily shaded groves favoured disease d evelopment. When a conidial solution was 
sprayed onto small wounds at the base of stems of a vocado seedlings (2 cm in diameter), N. solani  
caused a faint necrosis with white granular powder on the exterior of the stem. Small red lesions 
under the bark did not extend deeper into the wood,  suggesting that N. solani was a secondary 
parasite in this instance. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 230 Neocosmospora solani  has been reported from post-harvest stem end rot l esions of avocado fruit in 
Cameroon (Djeugap et al. 2015), Kenya (Wanjiku et a l. 2020; Wanjiku et al. 2021) and South Africa 
(Darvas and Kotze 1987; Darvas et al. 1987; Korsten  et al. 1995).  
In Michoacán, Mexico, N. solani  was isolated from root rots of avocado plants with  stunted leaves, 
leaf yellowing, interrupted growth during vegetativ e flushes, and premature abscission of leaves 
(Olalde-Lira et al. 2020). In 4-month-old avocado p lants, symptoms of N. solani  took 51–56 days to 
develop when a conidial suspension of each isolate was added near the roots, without damaging 
them.  
The Manaaki Whenua – Landcare Research database has  many records of N. solani (as F. solani ) in 
New Zealand, but only one is from avocado and there  is no record of the plant part the fungus was 
collected from. This isolate was collected from P. americana  in Gisborne in 1977 and is in Clade 3, 
the same clade of the FSSC as N. perseae ) but has been confirmed as being different from N. 
perseae based on a DNA sequence analysis 
(https://scd.landcareresearch.co.nz/specimen/ICMP_10 680; Ho, pers. comm.). 
5.14.4  Likelihood of entry 
Neocosmospora perseae  has only been recorded from branches and trunks of  avocado plants (5 or 
15 years old) in naturally occurring infections wit h visible canker symptoms. Although N. perseae  
caused disease symptoms within one month in pathoge nicity testing on young avocado  seedlings (i.e. 
in stems of a similar developmental stage to avocad o budwood), another species in the FSSC 
(reported as F. solani ) has been reported in budwood of other woody hosts , possibly with a latent 
period before external symptoms developed (see abov e). Based on current evidence, there is a low 
likelihood that N. perseae  can be present in or on P.  americana  budwood, and that it can escape 
detection during preparation for export, or in phyt osanitary inspections prior to export or on arrival  in 
New Zealand. Surface disinfection (cuttings dipped in 1% sodium hypochlorite for 2 minutes) upon 
arrival in PEQ is likely to kill any ungerminated s pores on the surface of the cutting but is highly 
unlikely to eliminate an existing infection. There is moderate uncertainty about the likelihood of N. 
perseae being associated with avocado budwood, since this s pecies is only recently described and 
there is no specific evidence for natural infection  of very young stem tissues. At the time of writing , no 
published studies have investigated the possibility  of asymptomatic N. perseae infections but other 
Neocosmospora  species can be endophytes or latent pathogens in p lant hosts (see section 0).  
Assuming that N. perseae  can be present in/on the commodity as described (l eafless, rootless 
avocado budwood cuttings), and given that it is rep orted in at least three avocado growing countries 
(Italy, Greece and Brazil), it can be associated wi th the commodity at the time of export. If so, it i s 
likely it can be transmitted by grafting to plants for planting generated from budwood. However, 
infected avocado budwood with externally visible ca nkers or lesions of N. perseae will almost certainly 
be removed or destroyed during preparation for expo rt, or in phytosanitary inspections pre-export or 
on arrival in New Zealand. Therefore, only material  with latent asymptomatic infections (or with mild 
internal symptoms that were not noticed at the time  of grafting) is likely to enter PEQ. 
As part of the commodity description all imported a vocado germplasm will undergo a growing period 
of active growth with a minimum of three distinct p henological growing events, referred to as ‘shoot 
flush’ in 3A PEQ. This period in 3A PEQ will impact  on likelihood of entry in the following manner: 
In young (6-month-old) avocado  seedlings inoculated with N. perseae and maintained at 
approximately 25 ° C and 95 % relative humidity, can ker and internal discolouration symptoms 
developed within one month (Guarnaccia et al. 2018) . These environmental conditions may not be 
met during the PEQ period. In addition, pathogenici ty tests involved inserting a mycelium plug (a 
colonised agar plug) into a wound formed by cutting  between two nodes (Guarnaccia et al. 2018). In 
nature, FSSC species are often reported as infectin g via wounds or disease lesions, so introduction of  
inoculum by wounding the plant mimics a natural inf ection route. However, a mycelium plug 
introduces much higher levels of inoculum than graf t transmission or water-splash infection of wounds 
with N. perseae spores, and the agar provides an initial energy sou rce for the pathogen (Bhunjun et 
al. 2021). Therefore, although symptoms of N. perseae developed rapidly in pathogenicity tests, 
natural conditions with less inoculum may not favou r rapid symptom development.   
231 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Neocosmospora solani (historically reported as F. solani ) infections are sometimes detected in 
nursery stock of woody species during routine inspe ctions in Post-Entry Quarantine (MPI 
interceptions records, accessed 2021), suggesting t hat symptomatic N. perseae infections  will usually 
be detected. For example, N. solani  (not identified to forma specialis  or variety level) was isolated 
from localised lesions at the nodes of cold-stored almond scions, and Marek et al. (2013) considered 
that these lesions developed either from spores tra pped on the buds, or from endophytic inoculum 
present in the scion.  Even when there were no exte rnal symptoms, internal necrosis caused by 
N. solani  in grafted almond nursery stock could still be obs erved on stems with light-brown or green 
bark (Marek et al. 2013).  However internal lesions  of N. solani  were difficult to detect in grafted 
almond nursery stock when the bark was dark brown, resulting in infected trees being supplied to 
growers. Therefore, it is likely that any symptoms caused by N. perseae  will be detected in PEQ, but 
latent infections or internal symptoms may be misse d. 
Given the arguments and evidence above, that is:  
• there is a documented association of N. perseae with trunks and branches of P. americana;  
• the association with P.  americana  budwood (i.e. young stem tissues) is moderately un certain 
because it is based on pathogenicity tests and info rmation about related fungal species; 
• estimates of time to symptom development are based  on pathogenicity tests and suggest 
symptoms of N. perseae will usually develop and be detected prior to expor t or within the 
PEQ period. However, the method used for pathogenic ity testing is likely to favour rapid 
infection and symptom development;  
• there is evidence that FSSC species similar to N. perseae sometimes remain latent for long 
periods and may only develop symptoms when the host  plant is stressed; 
• internal necrosis caused by N. perseae may not be detected in routine inspections of plant s in 
PEQ; 
the likelihood of N. perseae entering New Zealand associated with Persea americana  budwood is 
considered to be very low with moderate uncertainty . 
5.14.5  Likelihood of exposure 
This assessment is made on the basis that N. perseae has entered New Zealand undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for N. perseae.  
If avocado plants are infected with N. perseae at the time of their release from Post Entry Quaran tine 
they will be planted in New Zealand or used to prop agate new plants for planting (see section 2.3 for 
additional information about exposure).  
Given the arguments and evidence above, the likelih ood of exposure of N. perseae in New Zealand 
from Persea americana  budwood is considered high, with low uncertainty. 
5.14.6  Likelihood of establishment 
This assessment is made on the basis that N. perseae  has been successfully exposed to a suitable 
host plant in the New Zealand environment. 
The reported distribution and host range of N. perseae is shown in Table 5-15, and includes 
San Leonardello, Catania, Italy (Guarnaccia et al. 2018) and, areas with a CMI of 0.7 indicating that 
they have a similar climate to the whole of New Zea land (Phillips et al. 2018). Currently the only 
reported host is avocado ( P. americana ) which is grown commercially and in home gardens, 
particularly in northern regions of New Zealand (se e section 2.3). Therefore, the climate in New Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 232 Zealand is unlikely to limit the establishment of N. perseae  and hosts are likely to be available, at 
least in avocado growing regions.   
On culture medium, N. perseae  produced both conidia (asexual spores) and chlamyd ospores (resting 
spores that develop from conidia and facilitate sur vival/overwintering in the soil) (Guarnaccia et al.  
2018). Guarnaccia et al. (2018) therefore considere d it likely that N. perseae  is transmitted to new 
hosts via soil contamination and plant-associated r eservoirs. Conidia (asexual spores) of FSSC 
species such as  N. perseae are typically produced on plant debris on the soil surface and dispersed 
by soil water or water splash to infect roots or ab ove ground tissues of suitable hosts. Propagules of  
N. perseae could also be carried to new areas within New Zeala nd by movement of infected plant 
material or contaminated soil, and possibly by wind  or windborne rain. Therefore, it is likely that 
N. perseae would spread easily within and between areas where avocado is grown.  
Given the arguments and evidence above, the likelih ood of N. perseae  establishing in New Zealand is 
considered high, with low uncertainty. 
5.14.7  Impacts in New Zealand 
Neocosmospora persea is a recently described species of the Fusarium solani  species complex 
(FSSC) that causes trunk cankers in avocado (Guarna ccia et al. 2018). Members of this complex, 
specifically Fusarium solani , are ubiquitous soil fungi (Coleman 2016; Aoki et al. 2019; Sandoval-
Denis et al. 2019; Lynn et al. 2020; Geiser et al. 2021; Lynn et al. 2021) and thus N. perseae  is most 
likely spread through soil contamination and plant- associated reservoirs (Guarnaccia et al. 2018). 
There are likely multiple ways this fungus can be s pread: N. perseae  can be transmitted by grafting, 
as this is reported as a means of transmission in o ther FSSC species (e.g. Marek et al. 2013). 
Canker-causing pathogens such as N. perseae  may gain entry to the plant due to frost damage or  
mechanical injuries such as pruning wounds (Guarnac cia et al. 2018).  
Symptoms of N. perseae may take years before they are observed (described below) and thus N. 
perseae may have the ability to switch between an endophyti c and pathogenic lifecycle in response to 
environmental stresses (based on evidence that Neocosmospora  species can be endophytes in plant 
hosts (Sandoval-Denis et al. 2019)). 
Economic impacts 
Neocosmospora perseae  is only recently described and its known impacts a re limited to two disease 
outbreaks, one causing trunk cankers in 10% of 14-y ears-old avocado trees in an orchard in Italy and 
another causing branch cankers in 40% of 5-year-old  avocado trees (cv. ‘Hass’) in a 2-ha orchard (2 
ha) in Greece. Based on this information, economic impacts of N. perseae  have been assessed only 
for avocado.  
Although historical outbreaks of N. perseae were probably attributed to N. solani (i.e. F. solani ), 
searches found only one other report of N. solani sensu lato from trunk cankers on avocado, which 
appeared to be an opportunistic secondary infection  (Torres et al. 2000). This suggests that severe 
trunk canker symptoms from N. perseae in avocado commercial production are likely to be r are and 
localised to a few orchards or, at worst, one growi ng region. Alternatively, the causal agent of trunk  
cankers may not always be identified. Since newly p lanted trees take six to eight years to reach full 
production ( https://industry.nzavocado.co.nz/grow/becoming-an-a vocado-grower/ , accessed 
19/10/2021), if rogueing (removal of infected or da maged plants) was necessary, production losses 
from an outbreak could persist for several years. I f there was a widespread and severe N. perseae 
outbreak in productive avocado plants in either the  Bay of Plenty or Northland, it could cause 
moderate economic impacts, but this is an unlikely scenario. However, given that reports of N. solani 
and more recently N. perseae causing impacts in avocado are sporadic, it is more  likely that impacts 
will be low, with sporadic outbreaks damaging avoca do trees over a smaller geographical area, 
impacting a small number of growers. 
Many FSSC species are pathogenic to a wide range of  plant, insect and marine animal hosts (Zhang 
et al. 2006; O’Donnell et al. 2016; Sandoval-Denis and Crous 2018) and although formae speciales  of 
N. solani (reported as F. solani ) were historically characterised and named accordi ng to plant hosts,  
233 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand recent phylogenetic studies have shown that some ha ve diverse host ranges (Sandoval-Denis et al. 
2019).  This means that there is moderate uncertain ty that economic impacts of N. perseae will be 
limited to avocado. Economic impacts of N. perseae may need to be reassessed in future if disease 
outbreaks in other economically important hosts are  reported.  
Given the arguments and evidence above, that is: 
• Neocosmospora perseae outbreaks are likely to be rare and sporadic but ca n cause 
unwanted impacts on avocado production in New Zeala nd by damaging some trees in some 
orchards or growing regions.  
• since N. perseae is only recently described: 
o there is moderate uncertainty that economic impact s of N. perseae on the avocado 
industry  would be low in all circumstances; and 
o there is moderate uncertainty that impacts of N. perseae in New Zealand would be 
limited to avocado, given that closely related spec ies have diverse host ranges; 
the economic impact of N. perseae to New Zealand is considered to be low with moderat e 
uncertainty. 
Environmental impacts 
Neocosmospora perseae is only recently described and searches (see above)  found no specific 
evidence of hosts other than avocado plants; theref ore, there is no evidence to suggest that it can 
have impacts in the New Zealand environment. Howeve r, there is moderate uncertainty since closely 
related FSSC species in the same clade, such as N. falciformis, N. keratoplastica, N. petroliphila  and 
N. solani sensu stricto  are pathogenic to a range of plant, insect and mar ine animal hosts (Zhang et 
al. 2006; O’Donnell et al. 2016; Sandoval-Denis and  Crous 2018). Environmental impacts of N. 
perseae may need to be reassessed in future if there are ne w reports that suggest that its host range 
is similarly broad.  
Given the arguments and evidence above, the impact on the environment from the establishment of 
N. perseae in New Zealand is considered to be very low, with m oderate uncertainty. 
Health impacts 
Neocosmospora perseae is only recently described and searches (see sectio n 0) found no specific 
evidence that it causes human disease or produces m ycotoxins that can harm human health. 
However, N. perseae  is in the FSSC, and species in this complex cause approximately two thirds of 
fusarium infections in humans and other animals (Zh ang et al. 2006; Chehri et al. 2015). Clade 3 
FSSC species such as N. falciformis, N. keratoplastica, N. petroliphila  and N. solani sensu stricto  are 
ubiquitous in soil and decaying plants and this cla de is most often reported as human pathogens, 
causing skin and eye infections as well as more sev ere internal infections in immune compromised 
patients (Zhang et al. 2006; Mehl and Epstein 2007;  Chehri et al. 2015). Neocosmospora perseae  is 
also in clade 3 (Sandoval-Denis et al. 2019) and cl usters near  N. petroliphila  in a molecular 
phylogeny (Guarnaccia et al. 2018). Although N. perseae has not been recorded as a human 
pathogen, it is likely that it can cause opportunis tic infections in humans, particularly if they are 
immunocompromised. However, given that such opportu nistic infections are rare, and the known 
human FSSC pathogens N. petroliphila  and  N. solani  s.s. are already present in New Zealand (Biota 
NZ 2022), the additional health impact of N. perseae, if any,  is considered to be very low. 
Members of the FSSC are not usually considered to p roduce significant levels of mycotoxin in crops 
(Munkvold et al. 2021). However, N. solani  strains have been reported to produce several diff erent 
mycotoxins in culture (Shi et al. 2016; Hoque et al . 2018; Rabaaoui et al. 2021). However, even if 
N. perseae produces mycotoxins in avocados, the resulting heal th impacts for avocado consumers 
are likely to be very low. There is moderate uncert ainty in this conclusion, due to the lack of 
information about effects of mycotoxins produced by  FSSC species.   
Given the arguments and evidence above, the health impact of N. perseae to New Zealand is 
considered to be very low, with moderate uncertaint y.  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 234 Sociocultural impacts 
Neocosmospora perseae is only recently described and searches (see above)  found no specific 
evidence of hosts other than avocado plants. Avocad o is widely consumed in New Zealand. In some 
parts of the country avocados are common in home ga rdens, and trunk cankers caused by 
N. perseae may lead to decreased productivity or death in some  domestic trees. Neocosmospora 
perseae may lead to small reductions in commercial avocado fruit production but is unlikely to cause 
scarcity for New Zealand consumers.  
Given the arguments and evidence above, the sociocu ltural impact of N. perseae to New Zealand is 
considered to be very low, with moderate uncertaint y. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, health and society is considered to be 
low, with moderate uncertainty. 
5.14.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is very low 
• assuming entry, the likelihood of exposure is high  
• assuming successful exposure, the likelihood of es tablishment is high 
• the overall impact on the New Zealand economy, env ironment, health and society is 
considered to be low 
the overall level of assessed risk to New Zealand f rom N. perseae  on imported P. americana 
budwood (as in the commodity description) is consid ered to be low, with moderate uncertainty. 
5.14.9  Management considerations 
Neocosmospora perseae  causes cankers (areas of dark or discoloured necro tic tissue) on stems and 
trunks, possibly with bleeding and a white powdery fungal growth. In pathogenicity tests, symptoms 
developed within one month, and it is therefore lik ely that visible symptoms of N. perseae  will develop 
early in the PEQ period. If necrosis only affects t he internal tissues, they are still likely to be de tected 
by visual inspection on green stems, but may be mis sed on stems with darker bark.   
There is high uncertainty about whether latent asym ptomatic  N.  perseae infections occur in avocado 
budwood, although some Neocosmospora species have been reported as symptomless endophyte s 
or can be latent for long periods in other hosts (s ee biology and epidemiology section 5.14.3).  
Characterisation of N. perseae  was based on EF-1 α, ITS, LSU, and  RPB2 sequences (Guarnaccia et 
al. 2018) and this may be useful for diagnostic tes ting (if needed).     
5.14.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Neocosmospora perseae causes cankers (areas of dark or discoloured necrot ic tissue) on stems and 
trunks, possibly with bleeding and white powdery fu ngal growth. If necrosis only affects the internal 
tissues, they are still likely to be detected on gr een stems but may be missed on stems with darker 
bark.   
235 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand o What are the known environmental conditions conduci ve to symptom expression? 
Other related Neocosmospora species have been reported to switch from an endoph ytic to 
pathogenic lifestyle when plants are stressed, for example, by drought.  Neocosmospora perseae is 
only recently described and searches (see below) fo und no specific information about environmental 
conditions favouring symptom expression in natural infection. 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Assuming that N.  perseae can infect avocado budwood asymptomatically, it wou ld presumably be 
systemic in stem tissues or, if it accessed the bud wood at the time of collection, it would be 
concentrated at or near the cut end(s) of the budwo od. 
o What is the optimum season for conducting detection  testing? 
No relevant information was found. However, since t he pathogen causes stem cankers, the pathogen 
should be easier to detect during October and Novem ber after foliage is shed (Chapter 2). 
5.14.11  References 
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Chehri, K; Salleh, B; Zakaria, L (2015) Morphologic al and phylogenetic analysis of Fusarium solani  
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Coleman, J J (2016) The Fusarium solani species complex: ubiquitous pathogens of agricultur al 
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contemporary species concepts. Annual Review of Phytopathology 59: 373-402. 
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Neocosmospora . Persoonia 43: 90-185. 
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239 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.15  Neofusicoccum nonquaesitum 
Neofusicoccum nonquaesitum  is a pathogenic fungi from the family Botryoshaeri aceae. It  can cause 
diseases such as stem/branch cankers, necrosis and dieback in several woody crop plant species 
(grapevine, avocado, and apples) and non-crop plant  species.  
5.15.1  Taxonomic description 
Scientific name: Neofusicoccum nonquaesitum Inderb., Trouillas, R.M. Bostock & Michailides (201 0)  
Order/Family: Botryosphaeriales/ Botryosphaeriaceae 
5.15.2  Hazard identification 
Neofusicoccum nonquaesitum  is not known to be present in New Zealand: 
• Neofusicoccum nonquaesitum  is not listed in either Biota NZ (2022), PPIN (202 1) or NZOR 
(2021) 
• Neofusicoccum nonquaesitum  is not recorded in ONZPR (2021)  
Neofusicoccum nonquaesitum  has the potential to establish (and spread) in New  Zealand because: 
• host plants (avocado) are grown commercially and i n home gardens in some parts of New 
Zealand.  Neofusicoccum nonquaesitum  is associated with hosts plants such as avocado, 
blueberry, grapevine and apples that are grown comm ercially and in home gardens in 
different parts of New Zealand  
• Climate is unlikely to be a barrier to their estab lishment and spread in New Zealand because 
they are reported to occur in places (Table 5-16), which have a similar climate (CMI) ≥ 0.7 to 
New Zealand (Phillips et al. 2018)  
• Neofusicoccum nonquaesitum  can be spread by human movement of infected nurser y stock 
to avocado growing areas.  
Neofusicoccum nonquaesitum  has the potential to cause harm to New Zealand bec ause: 
• Neofusicoccum nonquaesitum  can cause cankerous lesions, necrosis and dieback symptoms 
on trunks of avocado trees (Carrillo et al. 2016; G uarnaccia et al. 2020).  
• Diseases caused by N. nonquaesitum  can reduce the productibility and yield of avocado  trees 
in New Zealand as well as other economic host plant s such as blueberry, grapevine and 
apples. 
Neofusicoccum nonquaesitum  is associated with Persea americana  budwood because: 
• Persea americana  are a known host of N. nonquaesitum  (Carrillo et al. 2016; Guarnaccia et 
al. 2020); 
• Neofusicoccum nonquaesitum  has been associated with avocado and have been rep orted to 
cause  stem/branch cankers and dieback disease  (Ca rrillo et al. 2016; Guarnaccia et al. 
2020). 
Given the arguments and evidence above, N. nonquaesitum  meets the criteria to be a hazard on 
Persea americana  budwood (as in the commodity description) imported  to New Zealand. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 240 5.15.3  Risk assessment 
Biology and epidemiology of Neofusicoccum nonquaesi tum 
General Biology  
Neofusicoccum nonquaesitum  is a pathogenic fungi from the family Botryoshaeri aceae (Inderbitzin et 
al. 2010; Yang et al. 2017). Like most fungi from t he family Botryoshaeriaceae, it is likely to occur as 
an endophyte (inhabit plant tissues without showing  visible symptoms) on plant tissue or as latent 
opportunistic pathogen that cause disease symptoms when the host plant is subjected to 
physiological stress (Wilson 1995; Phillips et al. 2013). For example, incidences of disease symptoms 
(such as cankers and dieback) caused by Botryoshaer iaceae species were observed to coincide with 
severe drought in avocado production area in Chile (Valencia et al. 2019). 
The family Botryoshaeriaceae is made up of morpholo gically diverse fungi that occur worldwide and 
are known to cause diseases such as cankers, necros is, dieback and fruit rot on several woody plant 
species (Slippers and Wingfield 2007; Twizeyimana e t al. 2013). They can infect fruit trees through 
wounds such as pruning wounds (Kotze et al. 2011). 
Several members of the genus Neofusicoccum  have been reported as pathogens of several perenni al 
crop plants (McDonald and Eskalen 2011; Phillips et  al. 2013). Neofusicoccum nonquaesitum  has 
been reported to be associated with several perenni al crop plants such as apples, avocado, almonds, 
grapevine, olives, and non-crop plant species (Tabl e 5-16).  
Symptoms  
Neofusicoccum nonquaesitum has been reported to cause branch cankers and dieba ck in avocado in 
California, Chile, and Greece (Carrillo et al. 2016 ; Valencia et al. 2019; Guarnaccia et al. 2020). 
Branch dieback occurs when the fungus colonises the  vascular tissue and affects the transport of 
water and nutrients causing blockage. This causes d ecay and weakens the infected plant and can 
result in reduced productivity of the plant (McDona ld and Eskalen 2011).  
Neofusicoccum nonquaesitum  caused branch cankers, and branch dieback symptoms  in avocado. 
Infected avocado branches exhibited branch dieback with dry brittle bark, powdery exudates with 
large cankers beneath the bark (Carrillo et al. 201 6). It was one of the most virulent isolates among 
three others that was observed to cause severe dama ge in vascular tissues and stems of avocado 
resulting in dieback and branch cankers in avocados  in Chile (Valencia et al. 2019). 
Pathogenicity tests using avocado seedlings showed that N. nonquaesitum caused necrosis and 
lesions in the vascular system within 3-5 weeks (Ca rrillo et al. 2016; Valencia et al. 2019), fruiting  
bodies were observed on inoculated stems (Valencia et al. 2019). 
Time to symptom development 
Under laboratory conditions, N. nonquaesitum  has been observed to cause disease symptoms on 
infected crop plants between 1 -5 weeks after inocu lation (Rooney-Latham and Soriano 2016; 
Valencia et al. 2019; Guarnaccia et al. 2020).  Pathogenicity tests using isolates of N. nonquaesitum 
inoculated on wounded  one-year old avocado seedlin g using a mycelial plug , showed that symptoms 
(brown gum exudate and necrosis in the vascular sys tem) were observed three weeks after 
inoculations (Valencia et al. 2019). In apples, sym ptoms became visible  seven days post inoculation 
(Rooney-Latham and Soriano 2016). 
Neofusicoccum nonquaesitum  was used to inoculate a non-crop plant (two-three year old branches of 
Umbellularia californica ) in its native environment and it exhibited sympto ms (large necrotic lesions) 
12 and18 months after inoculation (Lawrence et al. 2017).   
241 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Transmission and spread  
Pathogens from the family Botryoshaeriaceae can inf ect plants through wounds caused by machines, 
pruning practices and through natural openings (McD onald and Eskalen 2011). Under field conditions, 
N. nonquaesitum was isolated from infected symptomatic (powdery exu dates from cankered branches 
and stems) avocado plants (Carrillo et al. 2016; Gu arnaccia et al. 2020), and they produced fruiting 
bodies on inoculated stems during pathogenicity tes ts (Valencia et al. 2019). Species from the family 
Botryoshaeriaceae spread by water splash, wind and the use of infected material (Whiteman 2004; 
Amponsah et al. 2009). As such, N. nonquaesitum can potentially be spread by water splash, wind, 
and the use of infected pruning material.  
Conditions for symptom development  
Infections in orchards affected by branch canker an d dieback diseases caused by 
Botryosphaeriaceae species can remain dormant until  environmental conditions become favourable 
for the pathogens (Menge and Ploetz 2003). This is because they are generally known to cause 
symptoms when an infected plant is subjected to phy siological stress such as water stress (Udayanga 
et al. 2011).  
Optimal growth Conditions 
Isolate of N. nonquaesitum was collected (along with other pathogenic fungi) i n spring from 
symptomatic and asymptomatic avocado orchards in Ch ile  (Valencia et al. 2019).  Under laboratory 
conditions, mycelial growth of isolates of N. nonquaesitum were observed to grow in culture within  
temperature range of 5°  to 35° C with optimal growth  of 25° C in culture (Valencia et al. 2019). 
Table 5-16: Plant host range and diseases caused by  Neofusicoccum nonquaesitum  
Continent Country  State/Region Host plants Symptoms /disease CMI* Reference  
South 
America Chile Araucaria Araucaria araucana  
(Molina)  Branch dieback, 
cankers, and decline  0.8 (Pérez et al. 
2018) 
Illapel and 
Peumo Perseae americana 
(avocado) Branch dieback and 
Cankers 0.8 (Valencia et al. 
2019) 
Panguipulli 
and Teodoro 
Schmidt Vaccinium 
corymbosum 
(blueberry)  Cankers and twig 
dieback  0.8 (Pérez F et al. 
2014) 
North 
America United 
States California Persea americana 
(avocado)  Branch dieback 0.5-0.8 (Carrillo et al. 
2016) 
California Lithocarpus densiflora  
(tanoak)  Bleeding bole cankers 0.5-0.8 (Rooney-Latham 
et al. 2012) 
California Malus domestica 
(apples)  Branch cankers and 
dieback 0.5-0.8 (Rooney-Latham 
and Soriano 
2016) 
 Prunus dulcis 
(almonds)  Branch cankers 0.5-0.8 (Inderbitzin et al. 
2010) 
California Sequoiadendron 
gigantea (Giant 
sequoia) Branch cankers  0.5-0.8 (Rooney-Latham 
et al. 2012) 
California Sequoia 
sempervirens  (coast 
redwood)  Branch cankers 0.5-0.8 (Rooney-Latham 
et al. 2012) 
California  Umbelluria californica 
(California bay)  Dieback and cankers 0.5-0.8 (Lawrence et al. 
2017) 
* (Phillips et al. 2018) Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 242 5.15.4  Likelihood of entry 
Neofusicoccum nonquaesitum is known to affect a wide variety of host plants, i ncluding avocado 
(Table 5-16). Neofusicoccum nonquaesitum has been isolated from avocado branches indicating that 
they can be associated with leafless avocado budwoo d (Carrillo et al. 2016; Valencia et al. 2019; 
Guarnaccia et al. 2020). 
Under field conditions, N. nonquaesitum caused branch cankers and dieback symptoms on avoca do 
seedlings (Carrillo et al. 2016; Valencia et al. 20 19; Guarnaccia et al. 2020). Avocado budwood with 
established N. nonquaesitum infections can potentially exhibit symptoms such as  cankers and 
dieback of tissues. As such, infected budwood could  be detected and destroyed during preparation for 
export, on phytosanitary inspection pre-export (if this occurs), or on arrival in New Zealand. 
Species from the family Botryosphaeriaceae can occu r as latent opportunistic pathogens that do not 
cause disease symptoms (asymptomatic) on host plant s (Menge and Ploetz 2003). They can cause 
symptoms when an infected plant is subjected to phy siological stress such as water stress (Wilson 
1995; Udayanga et al. 2011). Like other endophytic latent pathogens in their family, it is  possible that 
N. nonquaesitum can occur on asymptomatic leafless, rootless avocad o budwood, and therefore 
might not be the detected by visual inspection duri ng preparation for export or on arrival in New 
Zealand.  
Pathogenicity tests using isolates (mycelial plug) of N. nonquaesitum inoculated on wounded 
seedlings and young plants (avocado and apples) fou nd that symptoms were expressed within 1 -5 
weeks (Rooney-Latham and Soriano 2016; Valencia et al. 2019; Guarnaccia et al. 2020). A non-crop 
plant (2-3 year old branches of Umbellularia californica ) inoculated in its native environment exhibited 
symptoms 12-18 months after inoculation. As such, t he active growing period at level 3A PEQ (a 
minimum of three distinct phenological growing even ts) will likely result in expression of symptoms. 
However, it is uncertain how long it will take for symptoms to be expressed in crop plant species in 
natural infection where inoculum might be at much l ower concentrations.   
Given the arguments and evidence above, that is:  
• Neofusicoccum nonquaesitum has been isolated from stems and branches of avocad o plants 
and can be associated with leafless avocado budwood . 
• avocado budwood with established N. nonquaesitum can exhibit symptoms such as cankers 
on plant tissue that can be detected during prepara tion for export or on arrival in 
New Zealand. 
• Neofusicoccum nonquaesitum can potentially be present on asymptomatic leafless  avocado 
budwood and might not be detected by visual inspect ion during preparation for export and 
upon arrival in New Zealand, with high uncertainty.  
• if N. nonquaesitum is imported on leafless avocado budwood, the active  growing period at 
level 3A PEQ (a minimum of three distinct phenologi cal growing events) will likely result in 
expression of symptoms. 
The likelihood of N. nonquaesitum entering New Zealand associated with Persea americana  budwood 
is considered to be low , with moderate  uncertainty. The uncertainty is because much of th e evidence 
is based on characteristics of the family rather th an on the species themselves. 
5.15.5  Likelihood of exposure 
This assessment is made on the basis that N. nonquaesitum has entered New Zealand undetected. 
When a pest or disease arrives in a new area, it us ually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for N. 
nonquaesitum .    
243 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand If avocado plants are infected with N. nonquaesitum at the time of their release from Post Entry 
Quarantine they will be planted in New Zealand or u sed to propagate new plants for planting (see 
section 2.3 for additional information about exposu re).  
Given the arguments and evidence above, the likelih ood of exposure of N. nonquaesitum in 
New Zealand from Persea americana  budwood is considered high , with low uncertainty. 
5.15.6  Likelihood of establishment 
This assessment is made on the basis that N. nonquaesitum has been successfully exposed to a 
suitable host plant in the New Zealand environment.  
Neofusicoccum nonquaesitum  is recorded to be present in a number of countries . Countries where 
both species have been recorded have CMI ranges of between 0.5-0.8 (Table 5-16). A CMI of ≥ 0.7, 
indicates a similar climate to the whole of New Zea land (Phillips et al. 2018). This suggests that the  
climatic conditions in some parts of New Zealand ar e likely to be suitable for them to establish, 
especially the North Island where climatic conditio ns are warmer. Therefore, climate is not likely to be 
a barrier for the establishment of N. nonquaesitum in New Zealand, especially the north of the North 
Island. 
Neofusicoccum nonquaesitum  is known to infect several host plants (Table 5-16 ) including crop plants 
such as apples, avocado and blueberry. These crop p lant species are commercially grown in different 
parts of New Zealand. For example, avocado plants a re widely grown commercially in orchards and 
in-home gardens mostly in the North Island and some  parts of the South Island (Chapter 2). 
Neofusicoccum nonquaesitum has also been associated with widespread amenity pl ants such as oak 
tree species (Table 5-16), which are commonly grown  in gardens and parks . Therefore, suitable hosts 
are available for N. nonquaesitum to establish and spread in all parts of New Zealand . 
Species like N. nonquaesitum  can spread by the movement of infected nursery sto ck for planting and 
the use of contaminated tools used for grafting and  pruning (Whiteman 2004). Under field conditions, 
powdery exudates from cankered branches and stems w ere observed on avocado plants infected 
with N. nonquaesitum (Carrillo et al. 2016; Guarnaccia et al. 2020), and  they produced fruiting bodies 
on inoculated stems during pathogenicity tests (Val encia et al. 2019). These fruiting bodies can be a 
source of infection and can be spread to uninfected  plants by water splash, wind, and the use of 
infected pruning material. 
Given the arguments and evidence above, that is: 
• Neofusicoccum nonquaesitum is reported to be present some areas which have sim ilar 
climate to New Zealand (Table 5-16). The climatic c onditions in some parts of New Zealand 
are likely to be suitable for them to occur and spr ead, especially the North Island where 
climatic conditions are warmer 
• Neofusicoccum nonquaesitum is associated with a range of crop and non-crop hos t plants 
(Table 5-16) that are widespread and available in N ew Zealand.  
• Neofusicoccum nonquaesitum can be spread through the human movement of infecte d 
nursery stock and contaminated pruning material. 
the likelihood of Neofusicoccum nonquaesitum establishing in New Zealand is considered high , with 
low  uncertainty. 
5.15.7  Impacts in New Zealand 
Neofusicoccum nonquaesitum  has been reported to be associated with several pe rennial crop plants 
such as apples, avocado, almonds and some non-crop plant species (Table 5-16). They can cause 
branch cankers and dieback symptoms in avocado (Car rillo et al. 2016; Valencia et al. 2019; 
Guarnaccia et al. 2020) and other perennial crops ( Table 5-16). Branch dieback and dieback 
symptoms causes decay and weakens the infected plan t and can affect the productivity of the plant 
(McDonald and Eskalen 2011). Neofusicoccum nonquaesitum  can be spread by the movement of Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 244 infected nursery stock for planting and the use of contaminated tools used for grafting and pruning 
and water splash (Whiteman 2004; Amponsah et al. 20 09). 
Economic impacts 
Neofusicoccum nonquaesitum  can cause branch cankers and dieback symptoms in a vocado. This 
can affect productivity and yield of avocado, leadi ng to economic loss in the avocado industry (Carril lo 
et al. 2016; Valencia et al. 2019; Guarnaccia et al . 2020). Avocado is increasingly becoming a 
significant horticultural crop in New Zealand. At t he end of the 2020 financial year, 39,078 tonnes of  
avocado produced in New Zealand and earning up to N Z$56 million and NZ$110 million in domestic 
and international sales respectively (Plant & Food Research 2020). Therefore, infections by N.  
nonquaesitum  can potentially result in yield loss which will ha ve an impact on both the domestic and 
international market.  
Neofusicoccum nonquaesitum  has been reported to affect other economically imp ortant host plants 
by causing symptoms such as dieback and tree/branch  cankers. As such economic impact caused by 
N.  nonquaesitum  is not limited to avocado. They can lead to reduce d productivity of other perennial 
crop plants. For example:  
• Neofusicoccum nonquaesitum  can cause necrosis in apples in (Rooney-Latham and  Soriano 
2016).This can potentially lead to reduced producti vity and reduced yield of infected trees. 
Apples are one of the most significant horticulture  export crops for New Zealand worth up to 
NZ$876 million in export in 2020 (Plant & Food Rese arch 2020).  
• Neofusicoccum nonquaesitum has been reported to be associated with blueberry i n Chile 
(Pérez et al. 2018). Botryosphaeriaceae species are  known to be important pathogens that 
affect blueberries worldwide (Burgess et al. 2019; Scarlett et al. 2019). If N. nonquaesitum  
establishes in New Zealand; it can potentially lead  to reduced productivity and reduced yield 
of infected plants. Blueberries are increasingly be coming important economic plant in 
New Zealand worth about NZ$44.4 million in both dom estic and export in 2020 (Plant & Food 
Research 2020). 
Given the arguments and evidence above, that is: 
• Neofusicoccum nonquaesitum  has been reported to be a pathogen of avocado that  can 
potentially result in reduced productivity and yiel d loss. This can have an impact on both 
the domestic and international marketability of avo cado  
• Neofusicoccum nonquaesitum can cause disease and result in reduced yields of o ther 
economic important host plants such as apples and b lueberries resulting in additional 
economic loss. 
the economic impact of N.  nonquaesitum  to New Zealand is considered to be moderate , with 
moderate  uncertainty. 
Environmental impacts 
Neofusicoccum nonquaesitum  has been reported to cause branch dieback and decl ine diseases in 
woody plant species such as oak trees and native co nifers in Chile and the United States (Table 
5-16).  For example, in California, Neofusicoccum nonquaesitum have caused cankers and dieback 
disease in native plants (Giant sequoia, coast redw ood, and coast redwood) (Rooney-Latham et al. 
2012). However, it is uncertain as to whether redwo od species in New Zealand would be susceptible 
to infection by N.  nonquaesitum . Neofusicoccum parvum  which is a closely related species to N.  
nonquaesitum  has been reported to infect Araucaria sp. , Populus nigra and Tibouchina lepidota in 
New Zealand (Sakalidis et al. 2013). As such, if N.  nonquaesitum  establishes in New Zealand, they 
can possibly infect other non-crop species. Such in fected plants can be a source of infection 
(inoculum) of crop plant that might be grown in clo se proximity (Inderbitzin et al. 2010; Burgess et a l. 
2019). 
Given the arguments and evidence above, the impact on the environment from the establishment of 
N.  nonquaesitum  in New Zealand is considered to be low, with low u ncertainty.    
245 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Human health impacts 
Searches using the search term ‘ Neofusicoccum  nonquaesitum  impacts on health’ from Google, 
Google scholar, CABI and Pubmed found no record of N.  nonquaesitum  causing any health impact on 
humans and animals. 
Given the arguments and evidence above, the human h ealth impact of N.  nonquaesitum  to 
New Zealand is considered to be negligible , with low  uncertainty. 
Sociocultural impacts 
Avocado has become popular and is widely consumed i n New Zealand. It is commonly grown in 
home gardens in some parts of the country. Diseases  caused by N. nonquaesitum can potentially 
lead to reduced productivity of avocado trees which  can cause scarcity of avocado for consumers.  
Some oak species in New Zealand are amenity species , some of which are planted as landscaping 
plants in towns.  
Given the arguments and evidence above, the sociocu ltural impact of N. nonquaesitum  to New 
Zealand is considered to be low, with low  uncertainty. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, human health and society is 
considered to be moderate , with moderate  uncertainty.  
5.15.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry  low , with moderate  uncertainty. 
• assuming entry, the likelihood of exposure high , with low  uncertainty  
• assuming successful exposure, the likelihood of es tablishment high , with low  uncertainty. 
• the overall impact on the New Zealand economy, env ironment, human health and society 
is considered to be moderate , with moderate  uncertainty. 
the overall level of assessed risk to New Zealand f rom N. nonquaesitum on imported Persea 
americana budwood (as in the commodity description) is consid ered to be moderate , with moderate  
uncertainty. 
5.15.9  Management considerations 
Neofusicoccum nonquaesitum causes branch cankers and dieback in avocado (Carri llo et al. 2016; 
Valencia et al. 2019; Guarnaccia et al. 2020). Avoc ado branches infected with N. nonquaesitum  
exhibited branch dieback with dry brittle bark, pow dery exudates and large cankers beneath the bark 
(Carrillo et al. 2016). 
In general, Botryoshaeriaceae species can cause dis ease symptoms which can develop when plants 
are subjected to physiological stress (Phillips et al. 2013). In avocado production areas in Chile, 
incidence of disease symptoms (cankers and dieback)  caused by Botryoshaeriaceae species such as 
N. nonquaesitum  was observed to coincide with severe drought (Vale ncia et al. 2019; Agustí-Brisach 
et al. 2020). This suggests symptoms on seedlings d erived from infected budwood are likely to be 
expressed in dry conditions. 
Samples can be taken for testing from any part of t he avocado leafless budwood and testing different 
parts of the budwood might be required. This is bec ause N. nonquaesitum  can be present on plant 
tissues without causing symptoms (Twizeyimana et al . 2013), and can cause disease symptoms 
which can develop when plants are subjected to phys iological stress (Phillips et al. 2013).  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 246 Molecular techniques (PCR) can be used to confirm i f avocado budwood or seedlings derived from 
budwood are infected with N. nonquaesitum  (Inderbitzin et al. 2010). However, it is not clea r if it will 
be evenly distributed or throughout an infected avo cado budwood; therefore, there is a high chance of 
false negatives.  
An optimum season or conditions for conducting N. nonquaesitum  detection testing has not been 
specified from the literature.  
Similar species from the genus Neofusicoccum  such as N. parvum,  and N. australe are recorded as 
present in New Zealand and have been associated wit h perennial crop plants such as grapevine 
causing dieback disease (Amponsah et al. 2009; Tenn akoon et al. 2018). Measures used to manage 
diseases caused by N. parvum are likely to manage diseases caused by N. nonquaesitum .  
5.15.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Neofusicoccum nonquaesitum causes branch cankers and dieback in avocado (Carri llo et al. 2016; 
Valencia et al. 2019; Guarnaccia et al. 2020). Avoc ado branches infected with N. nonquaesitum  
exhibited branch dieback with dry brittle bark, pow dery exudates and large cankers beneath the bark 
(Carrillo et al. 2016).  
o What are the known environmental conditions conduci ve to symptom expression? 
In general, Botryoshaeriaceae species can cause dis ease symptoms which can develop when plants 
are subjected to physiological stress (Phillips et al. 2013). In avocado production areas in Chile, 
incidence of disease symptoms (cankers and dieback)  caused by Botryoshaeriaceae species such as 
N. nonquaesitum  was observed to coincide with severe drought (Vale ncia et al. 2019; Agustí-Brisach 
et al. 2020). This suggest that in dry conditions, seedlings derived from infected budwood are likely to 
be stressed and could express symptoms. 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Samples can be taken for testing from any part of t he avocado leafless budwood and testing different 
parts of the budwood might be required. This is bec ause species such as N. nonquaesitum  survive on 
plant tissues without causing symptoms (Menge and P loetz 2003) and cause disease symptoms 
which can develop when plants are subjected to phys iological stress (Phillips et al. 2013). However, i t 
is not clear if the fungi will be evenly distribute d throughout an infected avocado budwood; therefore , 
there is a high chance of false negatives. Molecula r techniques (PCR), can be used to confirm if 
avocado budwood or seedlings derived from budwood a re infected with N. nonquaesitum  (Inderbitzin 
et al. 2010). 
o What is the optimum season for conducting detection  testing? 
An optimum season or conditions for conducting N. nonquaesitum  detection testing has not been 
specified from the literature.  
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Disease 97(12): 1580-1584. 
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Phomopsis: biology, applications, species concepts and names of common phytopathogens. Fungal 
Diversity 50(1): 189-225. 
Valencia, A L; Gil, P M; Latorre, B A; Rosales, I M  (2019) Characterization and pathogenicity of 
Botryosphaeriaceae species obtained from avocado tr ees with branch canker and dieback and from 
avocado fruit with stem end rot in Chile. Plant Dis ease 103(5): 996-1005. 
Whiteman, S A (2004) Phaeomoniella chlamydospora: p otential inoculum sources in the grapevine 
propagation process. thesis; Lincoln University,  
Wilson, D (1995) Endophyte: the evolution of a term , and clarification of its use and definition. Oiko s 
73: 274-276. 
Yang, T; Groenewald, J Z; Cheewangkoon, R; Jami, F;  Abdollahzadeh, J; Lombard, L, et al. (2017) 
Families, genera, and species of Botryosphaeriales.  Fungal biology 121(4): 322-346.  
249 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.16  Pestalotiopsis longiseta 
Pestalotiopsis longiseta  has been reported to cause dieback disease in Persea americana (avocado) 
in China. 
5.16.1  Taxonomic description 
Scientific name: Pestalotiopsis longiseta (Speg.) K.Dia & Tak. Kobay (1990). 
Order/Family: Xylariales/Amphisphaeriaceae  
Other names include : Pestalotia longiseta (Dai et al. 1990). 
Taxonomic notes: The genus Pestalotiopsis was recently segregated into three different genera  
(Pestalotiopsis, Pseudopestalotiopsis and  Neopestalotiopsis ). This was derived based on DNA 
sequencing and morphological characteristics (Mahar achchikumbura et al. 2014).  
About 16 species from the genus Pestalotiopsis are recorded as present in New Zealand (Biota NZ 
2022). Pestalotiopsis clavispora and  P. versicolor have been isolated from Persea americana in New 
Zealand (Biota NZ 2022). Pestalotiopsis clavispora  has been reported to cause stem-end rot disease 
of avocado in Chile (Valencia et al. 2011) and P. versicolor  has also been reported to cause 
postharvest disease in avocado in South Africa (Dar vas and Wehner 1987). 
5.16.2  Hazard identification 
Pestalotiopsis longiseta is not known to be present in New Zealand: 
o Pestalotiopsis longiseta  is not listed in either Biota NZ (2022) or PPIN (2 021). 
o Pestalotiopsis longiseta is a regulated pest for New Zealand (ONZPR 2021)  
o Pestalotiopsis longiseta  has unwanted status and is a notifiable organism ( ONZPR 
2021)  
Pestalotiopsis longiseta has the potential to establish (and spread) in New Zealand because: 
• Avocado which is a known host plant is grown comme rcially and also in home gardens in 
most parts of New Zealand. 
• It is not likely to be restricted by climate becau se it occurs in both tropical and temperate 
climate and in countries with similar climate (CMI ≥ 0.7 (Phillips et al. 2018)) to most parts of 
New Zealand.   
• It  can spread by the human movement of infected nurser y stock for planting. 
Pestalotiopsis longiseta has the potential to cause harm to New Zealand beca use: 
• Having been recently associated with avocado, it c an potentially affect avocado crops and 
cause yield and economic loss. 
• It can infect other host plants and cause crop los s, for example, it was reported to cause 10-
20% loss of tea ( Camellia sinensis ) in India and Japan and up to 10% loss in crop yie ld of 
Persimmons ( Diospyros kaki ) in Brazil.  
Pestalotiopsis longiseta is associated with Persea americana  budwood because: 
• It is a known host of Pestalotiopsis longiseta  (Lin et al. 2018); 
• It was recently reported to cause dieback symptoms  in young avocado plants after it was 
isolated from an avocado plant nursery in China (Li n et al. 2018).  
Given the arguments and evidence above, Pestalotiopsis longiseta meets the criteria to be a hazard 
on Persea americana  budwood (as in the commodity description) imported  to New Zealand. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 250 5.16.3  Risk assessment 
Biology and epidemiology of Pestalotiopsis longiset a 
Biology  
Pestalotiopsis is a species rich genus known to cause plant diseas es (Kang et al. 1999). They have 
often been isolated as endophytes and are also know n to occur as saprobes (Watanabe et al. 2010; 
Maharachchikumbura et al. 2014). They are common in  both tropical and temperate ecosystems 
(Sutton 1980; Fail and Langenheim 1990). Species fr om this genus have received attention because 
they produce various antimicrobial active compounds  significant to pharmaceutical science (Uzma et 
al. 2018; Elkhateeb and Daba 2021).  
As pathogens, Pestalotiopsis species can cause a variety of diseases such as; ca nkers, shoot 
dieback, leaf spots, needle blight, grey blight, sc abby canker, chlorosis, fruit rot and other posthar vest 
diseases (Kang et al. 1999; Crous et al. 2011; Maha rachchikumbura et al. 2014). They are 
considered weak pathogens because they are not host  specific but opportunistic and are able to infect 
a wide range of host plants (Elliott 2006; Joshi et  al. 2009; Kamhawy et al. 2011). However, they have  
caused diseases that have resulted in reduced produ ctivity and resulted in economic loss crop plant 
species such as Camellia sinensis  (tea), Magnifera indica  (mango) and Cocos nucifera (Coconut) 
(Joshi et al. 2009; Ismail et al. 2013; Maharachchi kumbura et al. 2013).   
Pestalotiopsis spp. produce asexual spores (conidiospores) and lik e most endophytic pathogens, they 
have been demonstrated to inhabit tree barks and le aves without causing symptoms. Symptoms can 
eventually develop when the host plant is stressed or wounded (Maharachchikumbura et al. 2011).  
The conditions that can lead to expression of sympt oms are usually hard to predict. Some species 
can be present on leaves of their host plant all ye ar round and become an inoculum source on mature 
fruits which can eventually develop postharvest rot  (Ullasa and Rawal 1985). Spores also can survive 
harsh weather conditions and are able to cause infe ctions when they get transferred onto a suitable 
host plant (Maharachchikumbura et al. 2011). 
Host Range  
Pestalotiopsis longiseta was recently reported to cause dieback symptoms in young avocado plants 
after being isolated from an avocado plant nursery in China (Lin et al. 2018). It is known to cause 
diseases in other crops such as Diospyros kaki (Japanese persimmon), Camellia sinensis (tea) in 
Japan and Thailand and leaf spot in Actinidia deliciosa  (kiwifruit) in Iran (Table 5-17). 
Pestalotiopsis species have been associated with  Actinidia deliciosa (kiwi fruit) (Ushiyama et al. 1996; 
Erta ș and Karakaya 2018). Pestalotiopsis  longiseta among other Pestalotiopsis  species is reported to 
have been isolated from leaf spots on kiwi fruit le aves in orchards in Iran. In this study, only the 
morphological characteristics of the isolates were used for identification (Mousakhah et al. 2014). Th e 
taxonomy of members of the genus Pestalotiopsis is complex and difficult to classify. 
(Maharachchikumbura et al. 2011). Isolates of Pestalotiopsis species can have similar morphological 
characteristics with slight differences that makes them difficult to group (Keith et al. 2006). As suc h, a 
combination of both molecular techniques and morpho logical characteristics is more reliable for 
species identification (Maharachchikumbura et al. 2 011; Maharachchikumbura et al. 2012).  
Table 5-17 The distribution, hosts and diseases cau sed by Pestalotiopsis longiseta 
Continent  Country State/Region Host plant Symptoms/diseases CMI* References 
Asia China Hainan 
Province Persea americana 
(avocado)  Dieback 0.4-0.5 (Lin et al. 2018) 
Japan Torrori 
Prefecture Diospyros kaki 
(Japanese 
persimmon)  Lesions on leaves, 
ring spot on fruit 
calyxes  0.7 (Yasuda et al. 
2003)  
251 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Continent  Country State/Region Host plant Symptoms/diseases CMI* References 
Japan Shizuoka 
Plateau Camellia sinensis  
(Tea) Grey blight 0.7 (Omatsu et al. 
2012; Yamada et 
al. 2016) 
Thailand Chai Mai  Camellia sinensis  
(Tea) Grey blight 0.5 (Maharachchikum 
bura et al. 2013) 
Iran Guilan 
Province  Actinidia deliciosa 
(Kiwi fruit) Leaf spots 0.6-0.8 (Mousakhah et al. 
2014) 
India Arunachal 
Pradesh and 
Papum Pare Phrynium 
capitatum  Willd Endophytic 
(symptomless) 
infection  0.5-0.8 (Sharma et al. 
2020). 
* (Phillips et al. 2018)  
Transmission and Spread  
Pestalotiopsis longiseta can be transmitted and spread by both natural and a rtificial means through 
rain splash and from plucking tools and equipment ( Yamada et al. 2016). Natural transmission 
velocity estimates have shown that fungal spores di spersed by rain splash will normally land <1m 
from source (Fitt et al. 1989; Fitt et al. 2006). S pores carried by water splash (rain or irrigation) that 
happen to be deposited on plants with wounds are li kely to infect host plants (Yamada et al. 2016).  
Hand plucked tea farms were less susceptible to inf ection by P. longiseta as most infections occurred 
through wounds on leaves and stems caused by machin e plucking (Horikawa 1986). Pestalotiopsis 
species can occur in cuticles and intercellular spa ces of leaves and cause disease symptoms when it 
becomes damaged (Fail and Langenheim 1990).  
Wounds on plants appears to be necessary for transm ission of Petsalotiopsis species (Elliott 2006; 
Chen et al. 2018). For example during a pathogenici ty test on tea leaves, wounded leaves developed 
symptoms in contrast to unwounded leaves that exhib ited little or no symptoms (Chen et al. 2018). 
Wounds caused by insect damage have been reported t o enhance infection by Pestalotiopsis 
species. Insect damage was reported to be necessary  for disease development in Elaeis guineensis 
(Africa oil palm) (Elliott 2006).  
Symptoms on Persea americana (avocado)  
Nursery avocado plants infected by Pestalotiopsis longiseta exhibited blight on the green shoot 
initially, it progressed to necrotic lesions on the  stems and leaves. This eventually resulted in dieb ack 
symptoms of shoots and twigs. During pathogenicity testing, all inoculated 2-year old potted avocado 
plants started to blight and form necrotic lesions in seven days. The green shoots developed dieback 
symptoms by day 15 (Lin et al. 2018). 
Symptoms on other plant species  
Pestalotiopsis longiseta  caused ring spots on leaves and calyxes of young f ruits of persimmon. It also 
caused lesions that resulted in defoliation of leav es. During pathogenicity testing, it produced simil ar 
symptoms (large lesions on leaves) observed from na tural infection 15 days after inoculation (Yasuda 
et al. 2003). In tea growing areas in Japan, it cau sed severe lesions in tea crops causing leaves 
(Hamaya and Horikawa 1982) and shoots to wither, th ereby affecting the quality of the tea (Hamaya 
and Horikawa 1982; Ando et al. 1987). However susce ptibility varied among different tea cultivars 
(Takeda 2002). It has also been reported to cause l eafspots of kiwifruit plants (Mousakhah et al. 
2014). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 252 5.16.4  Likelihood of entry 
Pestalotiopsis longiseta has been reported to be present in five countries a nd is known to affect some 
crop plants including avocado (Table 5-17). It was recently reported to cause dieback symptoms in 
young avocado plants when it was isolated from an a vocado plant nursery in China (Lin et al. 2018).  
During pathogenicity test, 2-year old potted avocad o plants were inoculated with P. longiseta and in 
seven days all inoculated plants started to blight and form necrotic lesions. The green shoots 
developed dieback symptoms by day 15 (Lin et al. 20 18). In a pathogenic phase of infection, 
symptoms are likely to be expressed on infected avo cado budwood during the active growing period 
at level 3A PEQ (a minimum of three distinct phenol ogical growing events).  
Species from the genus Pestalotiopsis  have been demonstrated to inhabit tree barks and l eaves 
without causing symptoms (latent endophytic infecti on). They can eventually develop symptoms when 
the host plant is stressed or wounded (Maharachchik umbura et al. 2011). P. longiseta has been 
isolated as an endophyte from leaves, stems and roo ts of a wild plant species (Sharma et al. 2020).  
This suggests that it can potentially be present on  leafless avocado budwood and not exhibit 
symptoms during the growing period in PEQ. However,  there is no study that has investigated 
endophytic infection of P. longiseta in crop plant species.  
Given the arguments and evidence above, that is:  
• Pestalotiopsis longiseta is reported to be present in five countries and has  been associated 
with avocado and other plants. 
• In its pathogenic phase of infection, it is likely  to exhibit symptoms if infected budwood is 
grafted in PEQ level 3A.  
• It could be present on avocado budwood (in a laten t or endophytic phase) without exhibiting 
symptoms especially if the budwood are not physiolo gically stressed or wounded.  
the likelihood of P. longiseta entering New Zealand associated with P. americana  budwood is 
considered to be low , with moderate  uncertainty. 
5.16.5  Likelihood of exposure 
This assessment is made on the basis that P. longiseta has entered New Zealand undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for P. longiseta .     
If avocado plants are infected with P. longiseta at the time of their release from PEQ they will be 
planted in New Zealand or used to propagate new pla nts for planting (see section 2.3 for additional 
information about exposure).    
Given the arguments and evidence above, the likelih ood of exposure of P. longiseta in New Zealand 
from P. americana  budwood is considered high , with moderate  uncertainty.  
5.16.6  Likelihood of establishment 
This assessment is made on the basis that P. longiseta  has been successfully exposed to a suitable 
host plant in the New Zealand environment. 
Pestalotiopsis longiseta is recorded to be present mainly in Asia: China, In dia Japan, Thailand and 
Iran (Table 5-17). The countries where it has been recorded to be present have a CMI range of 0.4-
0.8. CMI of ≥ 0.7 indicates a similar climate to the whole of Ne w Zealand (Phillips et al. 2018). 
Species from the genus Pestalotiopsis are reported to be common in both tropical and temp erate  
253 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand regions (Sutton 1980; Fail and Langenheim 1990). Th is suggests that the climatic conditions in some 
parts of New Zealand are likely to be suitable for it to establish. About 16 species from the genus 
Pestalotiopsis are recorded to be present in New Zealand (Biota NZ  2022). This indicates that climate 
is likely not to be a barrier to the establishment of P. longiseta in New Zealand.  
Pestalotiopsis longiseta has been reported to infect and cause diseases in c rop plant species 
(avocado, Japanese persimmons,tea and kiwifruit). A vocado which is a known host plant is widely 
grown commercially in orchards and in home gardens in the North Island and some parts of the South 
Island of New Zealand (Chapter 2). Therefore, suita ble hosts are available for P. longiseta to establish 
and spread in New Zealand. Members of the genus Pestalotipsis are generally not host specific but 
opportunistic (Elliott 2006; Joshi et al. 2009; Kam hawy et al. 2011), P. longiseta  can potentially infect 
other host plants and establish in New Zealand. 
Most Pestalotiopsis  infections occur through wounds and natural openin gs on the host plant. Species 
of the genus Pestalotiopsis  can occur in cuticles and intercellular spaces of leaves and cause disease 
symptoms when leaves become damaged (Fail and Lange nheim 1990). Pestalotiopsis longiseta has 
been isolated as an endophyte from leaves, stems an d roots of wild native plants in India (Sharma et 
al. 2020; Shukla 2020). As such, it  can spread by the human movement of infected nurser y stock for 
planting..  
Given the arguments and evidence above, that is:  
• Pestalotiopsis longiseta has been reported in four countries, some of which have a similar 
climate to New Zealand. Climate in most parts of Ne w Zealand is suitable for it to occur and 
spread especially since about 16 species from the s ame genus are already known to be 
present in New Zealand. 
• Avocado, one of its known host plants, is widely g rown commercially and in home gardens in 
both the North and South Island of New Zealand. Add itionally, because it is not host specific, 
it can potentially infect other host plants and spr ead. 
• It  can spread by the human movement of infected nurser y stock for planting. 
the likelihood of P. longiseta  establishing in New Zealand is considered moderate , with moderate  
uncertainty. 
5.16.7  Impacts in New Zealand 
Pestalotiopsis longiseta  has been reported to cause disease symptoms (dieba ck, lesions, leaf spot 
and gery blight) in crops such as persimmon, tea, k iwifruit as well as young avocado plants (Table 
5-17). It  can be transmitted and spread through spores carrie d by water splash (rain or irrigation) that 
happen to be deposited on plants with wounds (Yamad a et al. 2016). Pestalotiopsis longiseta can 
establish and spread in New Zealand because avocado , kiwifruit and perssimons are grown 
commercially in orchards and in home gardens New Ze aland. Broad range chemical fungicides such 
as QoI are commonly can be used to control disease symptoms caused by Pestalotiopsis longiseta  
(Bartlett et al. 2002; Yamada et al. 2016).  
Economic impacts 
Pestalotiopsis longiseta was recently reported to cause dieback symptoms in young avocado plants 
after being isolated from an avocado plant nursery in China. It caused dieback symptoms in up to 
30% of young avocado plants in China (Lin et al. 20 18). This is the first report of P. longiseta infecting 
avocado plants. Because it is considered to be a we ak opportunistic pathogen, it is able to infect a 
wide range of crop plants (Maharachchikumbura et al . 2011). It’s association with avocado could have 
possibly been as a result of an opportunistic infec tion. The fact that P. longiseta  is known to affect 
mainly leaves and result in dieback symptoms (Yasud a et al. 2003; Yamada et al. 2016; Lin et al. 
2018) suggests that young plants might be more susc eptible to its pathogenic effect. It was observed 
to cause leaf spots that resulted in dieback sympto ms of the young avocado nursery plants in China 
(Lin et al. 2018). It is possible that young avocad o plants are more susceptible than mature 
established plants. Having been recently discovered  to be associated with avocado, the impact it 
might have on avocado crop yield has not been asses sed and quantified. However, the loss of 30% of Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 254 young plants would have a significant impact on a s ingle nursery grower who could be supplying 
several orchards.  
Pestalotiopsis longiseta and other Pestalotiopsis spp. having been reported to cause grey blight 
disease in tea was estimated to cause b etween 10-2 0% crop loss in Japan (Horikawa 1986) and 
17% crop loss in India (Joshi et al. 2009) as a res ult of the infection of young tea leaves. Although tea 
is widely consumed in New Zealand it is only grown on a small commercial scale in the Waikato 
region (zealong.com). If P. longiseta is to establish in New Zealand, the grower is likel y to suffer some 
economic loss. However, the economic impact on tea crop production in New Zealand is not likely to 
be significant.  
Pestalotiopsis longiseta has been reported to cause post-harvest rot in pers immons in Brazil resulting 
in an estimated 10% loss in crop yield. Persimmons are grown in New Zealand with a value of NZ$1.3 
million and NZ$10.7 million in domestic and export markets respectively (Plant & Food Research 
2020). It can potentially affect the crop yield of persimmons that might result in some economic impac t 
in New Zealand.  
About sixteen species from the genus Pestalotiopsis are reported to be present in New Zealand (Biota 
NZ 2022), two of which have been associated with av ocado in Chile (Valencia et al. 2011) and South 
Africa (Darvas and Wehner 1987). So far none of the  Pestalotipsis species present in New Zealand 
has been reported to cause crop loss or economic lo ss to crop planting in New Zealand.  
Given the arguments and evidence above, that is: 
• Pestalotiopsis longiseta is likely to result in the loss of young avocado nu rsery plants. 
Because it was only recently discovered to be assoc iated with avocado, the impact it 
might have on avocado crop yield has not been asses sed and quantified.  
• Although it caused 10-20% crop loss of tea in Indi a and Japan, tea crop has little 
economic significance in New Zealand as such not li kely to have a significant impact on 
the economy  
• It caused up to 10% loss in crop yield of Persimmo ns in Brazil. Persimmons have a value 
of NZ$12 million in domestic and export market.  
• Several species form the genus Pestalotiopsis are reported to be present in New Zealand 
and so far, none has been reported to cause crop lo ss or economic loss of or other 
economic crop plants present in New Zealand. 
the economic impact of P longiseta  to New Zealand is considered to be low , with moderate  
uncertainty. 
Environmental impacts 
There is no record of P. longiseta having a significant impact on native plants and th e environment. 
However, Pestalotiopsis species are ubiquitous and have been isolated as th e endophytes and as 
saprobes from soil, polluted water and from leaves,  bark and twigs (Maharachchikumbura et al. 
2011). The fact that species from the genus are not  host specific but mostly opportunistic (Elliott 20 06; 
Joshi et al. 2009; Kamhawy et al. 2011) suggests th at it can potentially infect plants in the 
environment. However, they are considered weak path ogen (Beresford and Mulholland 1982; Madar 
et al. 1991) therefore, their impact on the environ ment might not be significant. 
Given the arguments and evidence above, the impact on the environment from the establishment of 
P. longiseta  in New Zealand is considered to be low , with low  uncertainty. 
Human health impacts 
Species from the genus Pestalotiopsis are  commonly known plant pathogens that rarely cause hu man 
diseases (Borgohain et al. 2020). Few human infecti ons caused by Pestalotiopsis species have been 
reported. One report involved a gardener that devel oped keratitis (eye infection) after sweeping twigs  
and leaves on a windy day and Pestalotiopsis clavispora was identified as causative agent (Monden 
et al. 2013). Another report of Pestalotipsis species affecting human health involved some 
Pestalotiopsis spp. recovered from sinuses, fingernails, bronchi, scalp, foot and eye (associated with  
255 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand onychomycosis disease) of a few individuals working  in tea plantations in India. (Sutton 1999; 
Maharachchikumbura et al. 2011; Borgohain et al. 20 20). Infected individuals were exposed to 
pathogenic fungi such as Pestalotiopsis species present in the plantations (Borgohain et al . 2020).  
Sixteen Pestalotiopsis  species are reported as present in New Zealand (Bi ota NZ 2022). There has 
been no report on any of Pestalotiopsis  species infecting humans and causing health proble ms in 
New Zealand.  
Given the arguments and evidence above, the human h ealth impact of P. longiseta  to New Zealand is 
considered to be low , with low  uncertainty. 
Sociocultural impacts 
Avocado has become popular and is widely consumed i n New Zealand. It is commonly grown in 
home gardens in some parts of the country. The pote ntial impact of P. longiseta on avocado crop 
yield has not been assessed and quantified. However , 16 species from the same genus are reported 
as present in New Zealand, and two have been has be en associated with avocado. This suggests 
that P. longiseta is not likely to cause scarcity of avocado fruits i n local markets. 
Given the arguments and evidence above, the sociocu ltural impact of Pestalotiopsis longiseta to 
New Zealand and is considered to be negligible , with low  uncertainty. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, human health and society is 
considered to be low , with low  uncertainty. 
5.16.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is low  with moderate  uncertainty 
• assuming entry, the likelihood of exposure is high  with moderate  uncertainty 
• assuming successful exposure, the likelihood of es tablishment is moderate  with 
moderate  uncertainty  
• the overall impact on the New Zealand economy, env ironment, human health and society 
is considered to be low  with moderate uncertainty.  
the overall level of assessed risk to New Zealand f rom P. longiseta  on imported P. americana 
budwood (as in the commodity description) is consid ered to be low , with moderate uncertainty. 
5.16.9  Management considerations 
Plants infected by Pestalotiopsis longiseta can exhibit blight on the green shoot initially, wh ich can 
progress to form necrotic lesions on the stems and leaves. This can eventually result in dieback 
symptoms of shoots and twigs. During pathogenicity test, 2-year old potted avocado plants were 
inoculated with P. longiseta and in seven days all inoculated plants started to blight and form necrotic 
lesions. The green shoots developed dieback symptom s by day 15 (Lin et al. 2018).     
Under laboratory conditions, inoculated avocado pla nts were covered with plastic bags for 48 hours 
and kept under high humidity at 28° C and symptoms w ere observed to develop in seven days (Lin et 
al. 2018). However environmental conditions condusi ve for symptom development in field conditions 
has not been specified.  
Broad range chemical fungicides such as QoI are com monly used to control gray blight disease 
caused by Pestalotiopsis longiseta  (Bartlett et al. 2002; Yamada et al. 2016). Molecu lar techniques 
(genomic DNA using ITS1/ITS4) primers (Lin et al. 2 018) can be used to test for asymptomatic Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 256 infection and any part of the plant (budwood) can b e tested for asymptomatic infections.  Optimum 
conditions for conducting testing has not been spec ified.  
5.16.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Plants infected by Pestalotiopsis longiseta can exhibit blight on the green shoot, which can pr ogress 
to form necrotic lesions on the stems and leaves. T his can eventually result in dieback symptoms of 
shoots and twigs. During pathogenicity testing, 2-y ear old potted avocado plants were inoculated with 
P. longiseta and in seven days all inoculated plants started to blight and form necrotic lesions. The 
green shoots developed dieback symptoms by day 15 ( Lin et al. 2018). 
o What are the known environmental conditions conduci ve to symptom expression? 
Under field conditions, environmental conditions co ndusive for symptom development caused by P. 
longiseta have not been specified. However, under laboratory conditions, inoculated avocado plants 
were covered with plastic bags for 48 hours and kep t under high humidity at 28° C and symptoms 
were observed to develop in seven days (Lin et al. 2018).  
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?   
Any part of the plant (budwood) can be tested for a symptomatic infections. 
o What is the optimum season for conducting detection  testing? 
Optimum conditions for conducting testing have not been specified. 
5.16.11  References 
Ando, Y; Narisawa, N; Oniki, M (1987) Etiology of s hoot blight of tea plant occurred recently. 
Japanese Journal of Phytopathology 53(2): 258-261. 
Bartlett, D W; Clough, J M; Godwin, J R; Hall, A A;  Hamer, M; Parr ‐Dobrzanski, B (2002) The 
strobilurin fungicides. Pest Management Science: formerly Pesticide Science  58(7): 649-662. 
Beresford, R; Mulholland, R (1982) Susceptibility o f farm shelter cypresses to three fungi associated 
with cypress canker disease. New Zealand Journal of Forestry Science 12(1): 7-13. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Borgohain, P; Barua, P; Mahanta, J; Saikia, L R (20 20) Pestalotioid fungi: a rare agent of 
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 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 260 5.17  Phyllachora gratissima  (tar spot) 
Phyllachora gratissima  is a fungal leaf pathogen that causes tar spot on the leaves of Persea 
americana  (avocado). It is considered a minor pathogen that is more frequent in ‘Creole’ avocados. 
5.17.1  Taxonomic description 
Scientific name: Phyllachora gratissima Rehm (1892) 
Order/Family: Phyllachorales/Phyllachoraceae 
5.17.2  Hazard identification 
Phyllachora gratissima  is not known to be present in New Zealand: 
• Phyllachora gratissima  is listed as absent from New Zealand in Biota NZ ( 2022) and NZOR 
(2021)  
• Phyllachora gratissima is not listed in PPIN (2021) or ONZPR (2021)  
Phyllachora gratissima  has the potential to establish in New Zealand beca use: 
• Persea americana (avocado)  is a known host (Spaulding 1961; Molano 2007) that is widely 
grown in in New Zealand, in home gardens and commer cial production, mainly in the north of 
the North Island and the Hawkes Bay region. 
• Phyllachora gratissima  causes tar spot in avocado and is recorded in coun tries with a climate 
match index (CMI) ≥ 0.7 (e.g. Bolivia, Colombia, Ecuador, Mexico, Vene zuela) indicating a 
similar climate to the whole of New Zealand (Philli ps et al. 2018). 
Phyllachora gratissima  has the potential to cause harm to New Zealand bec ause: 
• Phyllachora gratissima causes tar spot in avocado which can sometimes caus e defoliation in 
trees (Spaulding 1961). 
• avocados are an important commercial crop in New Z ealand. In the 2019–2020 financial year, 
export sales of fresh avocados earned NZ$112.3 mill ion and domestic sales earned NZ$50.6 
million (Plant & Food Research 2020). 
Given the arguments and evidence above, Phyllachora gratissima  meets the criteria to be a hazard 
for New Zealand 
5.17.3  Risk assessment 
Biology and epidemiology of Phyllachora gratissima 
Hosts  
Phyllachora gratissima is specific to P. americana (avocado) (Spaulding 1961; Hodges 1969). 
Distribution  
Phyllachora gratissima  has been recorded in North, Central and South Amer ica (Table 5-18).  
261 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Table 5-18: Distribution of Phyllachora gratissima and the climate match index (CMI) of each country. 
Region Country CMI* Reference 
North America Mexico 0.3–0.8 Molano (2007) 
Central America 
and the 
Caribbean Costa Rica 0.3–0.6 Spaulding (1961) 
Guatemala 0.3–0.6 Spaulding (1961) 
Puerto Rico (USA) 0.5–0.6 Zentmyer (1961) 
South America Bolivia 0.4–0.8 Zentmyer (1961) 
Colombia 0.3–0.8 Spaulding (1961); Zentmyer (1961) 
Ecuador 0.4–0.8 Spaulding (1961); Zentmyer (1961) 
Venezuela 0.4–0.8 Spaulding (1961); Zentmyer (1961)  
*(Phillips et al. 2018)  
Symptoms  
This disease is readily visible as symptoms resembl e droplets of tar on leaf surfaces (Molano 2007; 
Thaung 2008). These spots look like small domes wit h a matte to shining black membrane (Thaung 
2008). The black spots are surrounded by a chloroti c halo (Molano 2007). The tar spots increase in 
size and turn a brown colour on both the upper and underside of the leaf (Molano 2007). Infection can 
sometimes cause defoliation (Spaulding 1961). 
Phyllachora  species are minor plant pathogens that rarely kill  host tissues (i.e. obligate biotrophs); 
however, the longevity of infection allows pathways  for secondary infection by other pathogens 
(Tamakaew et al. 2017). 
Time to symptom development  
There is limited information regarding time to symp tom development of P. gratissima  in avocado; 
however, Phyllachora tar spot of bamboo in India forms lesions after 7-9  days (Thaung 2008). Other 
tar spot pathogens such as P. maydis  form symptoms within 14 days and has a short laten t period in 
P. maydis  which ranges from 14 to 20 days post inoculation ( Valle-Torres et al. 2020). 
Conditions for symptom development have not been de scribed for P. gratissima . However, P. maydis  
develops symptoms between 10 to 20° C and developmen t decreases above 25° C (Thaung 2008). 
Reproduc tion and transmission 
There is limited information regarding reproduction  and transmission of P. gratissima and thus 
information is based on other Phyllachora species. Ascospores, of P. maydis , are released by wind or 
rainsplash on foliage during periods of moderate te mperature (16–23° C), leaf wetness duration of 
greater than 7 h per night and a relative humidity of 75% (Valle-Torres et al. 2020). 
5.17.4  Likelihood of entry: 
Phyllachora gratissima  has been recorded in tropical climates (Table 5-18 ) and is predominantly a 
foliar pathogen (Tamakaew et al. 2017). Green budwo od may include some leaf tissue within the 
buds and therefore, there is potential for P. gratissima  to be imported into post entry quarantine (PEQ) 
on P. americana  budwood.  
Phyllachora gratissima  appears to be a surface pathogen, so it is expecte d that disinfection of 
budwood entering PEQ (1% sodium hypochlorite dip fo r 2 minutes) would be effective in eliminating 
any infection on the surface. Although, it is uncer tain if the fungus may persist in small crevices wi thin 
the leaf buds. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 262 If P. gratissima is imported into New Zealand, and disinfection were  not suffient to remove the 
pathogen, it is very likely that it would produce v isible symptoms in PEQ. There are no results of 
inoculation experiments available for avocado to de termine the period to develop symptoms or the 
potential to be asymptomatic on this host. However,  other tar spot pathogens (i.e. P. maydis ) forms 
symptoms within 14 days (Valle-Torres et al. 2020).  This suggests that if P. gratissima  was present on 
avocado budwood imported to New Zealand, it is high ly likely that symptoms would develop within the 
period of growth in PEQ. 
Based on the mode of reproduction and transmission,  there is no evidence available to suggest that 
P. gratissima  would not be successfully contained within Level 3 A PEQ conditions.  
Given the arguments and evidence above, that is: 
• there is limited potential for the association of P. gratissima  with avocado budwood cuttings. 
• infection by P. gratissima  is highly likely to be detected during the period of growth in Level 3A 
PEQ. 
Given the arguments and evidence above, the likelih ood of Phyllachora gratissima  entering 
New Zealand associated with P. americana budwood is considered to be negligible, with low 
uncertainty. 
5.17.5  Overall level of associated risk to New Zealand 
Based on the assessment of likelihood above, that: 
• the likelihood of P. gratissima  entering New Zealand associated with P. americana  budwood 
(as described in the commodity description, and tak ing into account the proposed growing 
period of active growth with a minimum of three dis tinct phenological growing events referred 
to as ‘shoot flush’ in 3A PEQ) is considered neglig ible, with low uncertainty; 
the overall level of risk to New Zealand from P. gratissima  on imported P. americana  bedwood is 
considered to be negligible, with low uncertainty.  
5.17.6  Management considerations 
Phyllachora gratissima produces highly visible black spots on leaves of av ocado which appear within 
days of infection (Spaulding 1961; Molano 2007; Tha ung 2008). It is considered a minor pathogen 
which, in some cases, can cause defoliation (Spauld ing 1961). Literature searches on the species 
found no evidence for asymptomatic infection of lea ves or stem tissues. Therefore, P. gratissima  is 
highly unlikely to persist as an asymptomatic infec tion on susceptible tissues. 
Warm and humid conditions (16–23° C and 75% humidity ) are conducive to disease expression and 
ascospore release (Valle-Torres et al. 2020). Detec tion of Phyllachora species can be conducted 
using PCR primers ITS4 and ITS5 to sequence the ITS  region (i.e. common for many fungi) (Ruhl et 
al. 2016). However, given many Phyllachora species are obligate biotroiphs, they are considere d 
unculturable (Ruhl et al. 2016). 
5.17.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Phyllachora gratissima causes tar spot on the leaves of P. americana . Black dots (that resemble tar) 
appear on the surface of leaves surrounded by a chl orotic halo (Molano 2007; Thaung 2008). Spots  
263 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand increase in size and turn a brown colour that is se en on both the upper and underside of the leaf 
(Molano 2007). Infection may cause defoliation (Spa ulding 1961). 
o What are the known environmental conditions conduci ve to symptom expression? 
Moderate temperature between 10–25° C and 75% relati ve humidity seem to be conducive to 
symptom expression of Phyllachora species (Thaung 2008; Valle-Torres et al. 2020). 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested? 
Phyllachora gratissima  is a foliar pathogen and thus symptomatic leaves s hould be tested. There is 
evidence that this genus has a short latency period  suggesting that asymptomatic infection is unlikely  
(Valle-Torres et al. 2020). 
o What is the optimum season for conducting detection  testing? 
Seasons with moderate temperatures and relative hum idity (Thaung 2008; Valle-Torres et al. 2020) 
seem to be conducive to symptom expression and woul d be optimal for detection testing. 
5.17.8  References  
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Hodges, C S (1969) A new species of Phyllachora on Persea . Mycologia 61(4): 838. 
Molano, P J T (2007) Enfermedades del aguacate. Revista politécnica 3(4): 51-70. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX ‘match climates regional’  
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Ruhl, G; Romberg, M K; Bissonnette, S; Plewa, D; Cr eswell, T; Wise, K A (2016) First report of tar 
spot on corn caused by Phyllachora maydis  in the United States. Plant Disease 100(7): 1496. 
Spaulding, P (1961) Foreign diseases of forest trees of the world: an a nnotated list . US Department of 
Agriculture, USA.  
Tamakaew, N; Maharachchikumbura, S S N; Hyde, K D; Cheewangkoon, R (2017) Tar spot fungi 
from Thailand. Mycosphere 8: 1054-1058. 
Thaung, M M (2008) Pathologic and taxonomic analysi s of leaf spot and tar spot diseases in a tropical 
dry to wet monsoon ecosystem of lowland Burma. Australasian Plant Pathology 37(2): 180. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 264 Valle-Torres, J; Ross, T J; Plewa, D; Avellaneda, M  C; Check, J; Chilvers, M I, et al. (2020) Tar spot : 
an understudied disease threatening corn production  in the Americas. Plant Disease 104(10): 2541-
2550. 
Zentmyer, G A (1961) Avocado diseases in the Americ as. CEIBA 9(2): 61-79. 
 
  
265 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.18  Phyllosticta perseae  (leaf spot disease) 
Phyllosticta perseae  is a fungal pathogen known to cause leaf spot dise ase in multiple Persea  
species. Affected plants typically have dark spots in lesions at leaf edges and may lead to leaf death . 
5.18.1  Taxonomic description 
Scientific name: Phyllosticta perseae  Ellis and G. Martin 1885  
Order/Family: Botryosphaeriales/Phyllostictaceae 
Other names include: Phyllosticta micropuncta Cooke 1878 
Taxonomic notes: Phyllosticta perseae  and P. micropuncta  are often considered synonymous 
(Shetty et al. 2016; Farr and Rossman 2021; Ramirez  et al. 2021) but some databases consider them 
as different species (Robert et al. 2005; Index Fun gorum 2022). Phyllosticta perseae  and P. 
micropuncta  are likely considered synonymous by majority of li terature because the earliest 
specimens were observed to be the same (Ramirez et al. 2021). A recent taxonomic revision of the 
genus Phyllosticta  showed that they often occur as anamorphs of some Guignardia  species but no 
evidence was found to show that P. perseae  or P. micropuncta are anamorphs of any Guignardia 
species (Wulandari et al. 2013). There is very litt le information on P. micropuncta in the literature.  
5.18.2  Hazard identification 
Phyllosticta perseae  is not known to be present in New Zealand: 
• Phyllosticta perseae is not listed in NZOR (2021), Biota NZ (2022) or PP IN (2021). 
• Phyllosticta perseae is not listed in ONZPR (2021). 
Phyllosticta perseae  has the potential to establish (and spread) in New  Zealand because: 
• Persea americana  (avocado) is a known host (Zentmyer 1961; Rieuf an d Teasca 1970; Lara 
Vazquez 2019) that is widely grown in New Zealand, in home gardens and commercial 
production, mainly in the north of the North Island . 
• Phyllosticta perseae  causes leaf spot disease in tropical and subtropic al countries including 
Dominican Republic, India and South Africa (Doidge 1950; Zentmyer 1961; Das et al. 2005). 
Some regions in these areas have a climate match in dex (CMI) ≥ 0.7 indicating a similar 
climate to the whole of New Zealand (Phillips et al . 2018). 
Phyllosticta perseae  has the potential to cause harm to New Zealand bec ause: 
• it causes leaf spot on avocado (Blain 1931; Zentmy er 1961; Rieuf and Teasca 1970). The 
extent of leaf spot disease in avocado is still unk nown but Rieuf and Teasca (1970) observed 
the pathogen on dead leaf tissue of avocado indicat ing that infection could lead to leaf death. 
• avocados are an important commercial crop in New Z ealand. In the 2019–2020 financial year, 
export sales of fresh avocados earned NZ$112.3 mill ion and domestic sales earned NZ$50.6 
million (Plant & Food Research 2020). 
Phyllosticta perseae  is associated with Persea americana  budwood because: 
• Persea americana  is a known host of P. perseae  (Blain 1931; Zentmyer 1961; Rieuf and 
Teasca 1970). 
• Phyllosticta perseae causes leaf spots and seems to strictly parasitise leaves; although there 
is no evidence to assert that the pathogen also inf ects stems, it is likely that spores could 
contaminate the crevices around buds or the surface  of budwood . Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 266 Given the arguments and evidence above, Phyllosticta perseae  meets the criteria to be a hazard on 
Persea americana  budwood (as in the commodity description) imported  to New Zealand. 
5.18.3  Risk assessment 
Biology and epidemiology of Phyllosticta perseae 
Hosts and geographical distribution  
Phyllosticta perseae is the causative agent of leaf spot disease in Persea spp including Persea  
americana (avocado) (Blain 1931; Zentmyer 1961; Ohr et al. 20 03). Leaf spot is considered a minor 
problem in avocado orchards because it is an uncomm on disease and there has been no record of 
this disease reducing yield (Zentmyer 1961; USDA 20 16). Phyllosticta perseae  has also been isolated 
from dead leaves of avocado (Rieuf and Teasca 1970) .The pathogen has not been recorded to infect 
other plant genera. Phyllosticta perseae  is found in both tropical and subtropical regions of the world 
(Table 5-19). 
Table 5-19: Geopgraphic distribution of Phyllosticta perseae  
Region Country  CMI* Host References 
Asia India 0.2–0.9 Persea americana and  P. 
bombycina    (Rao 1965; Das et al. 2005; Chattopadhyay et 
al. 2014; Ray et al. 2019) 
Africa Morocco 0.5–0.9 P. americana (Rieuf and Teasca 1970) 
South Africa 0.6–0.9 P. americana (Doidge 1950) 
America USA 0.5–0.9 P. americana , P. carolinensis , 
P. borbonia, and Persea  sp. (Ellis and Martin 1885; Anderson 1919; Blain 
1931; Alfieri Jr 1984; Farr and Rossman 2021) 
Mexico 0.3–0.8 P. americana (Lara Vazquez 2019) 
Dominican 
Republic 0.5–0.7 P. americana (Zentmyer 1961) 
* Climate Match Index (CMI) with all of New Zealand  (Phillips et al. 2018). 
Symptoms  
There was no information regarding the severity of leaf spot disease caused by Phyllosticta perseae  
in Persea americana . Therefore, information on symptoms shown here is based on description of 
infection in Persea bombycina  which may be slightly different in Persea americana . 
Phyllosticta perseae causes brownish-gray spots around the edges of host  leaves on both the dorsal 
and ventral surfaces (Ellis and Martin 1885; Chatto padhyay et al. 2014; Ray et al. 2019). Older leaves  
are more likely to be infected with the pathogen (R ay et al. 2019). Necrotic lesions around the spots 
on the edges of leaves may result in the eventual d eath of leaves (Chattopadhyay et al. 2014; 
Ramirez et al. 2021). The percentage of necrotic le sions on Persea bombycina  leaves ranges 
between 19% – 47% of the surface area of the leaf ( Chattopadhyay et al. 2014). In experimental 
inoculations, more than 30% of all leaves on a 3-mo nth old Persea bombycine seedlings could be 
infected (Das et al. 2005). The total leaf infectio n in adult trees (8-10 year olds) may exceed 50% in  
severe cases (Chattopadhyay et al. 2014). 
Reproduction and transmission 
The sexual morph of Phyllosticta perseae  is yet to be identified (Chattopadhyay et al. 2014 ). Rieuf 
and Teasca (1970) noted that the anamorph (i.e. ase xual stage) of P. perseae produces pycnidia (i.e. 
asexual fruiting bodies). Typically, conidia (i.e. asexual spores) of Phyllosticta  species can spread 
from infected leaves to uninfected leaves through r ain or water splashes (Wikee et al. 2011). By 
spraying the leaves of 3-month old P. bomybcina seedlings with a concentrated solution containing P. 
perseae  conidia, leaves became infected suggesting the pat hogen can be transmitted by water (Das  
267 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand et al. 2005). Transmission and spread of the diseas e is favoured by rain, especially during the rainy 
season in India (Chattopadhyay et al. 2014). 
The optimal temperature for the development of P. persea  on avocado is unknown. However, the 
pathogen was shown to develop well on P. bombycina  at a temperature of 25 ° C (Das et al. 2005). 
The pathogen’s viability on dead leaves of Persea  spp is not known but Phyllosticta citricarpa,  which 
affects Citrus , is known to be viable on dying or dead plant tiss ues for up to 45 days (de Oliveira Silva 
et al. 2017). 
In-field management  
There is no known management practice of Phyllosticta perseae  in avocado orchards. However, 
management practice of P. perseae in P. bombycina  orchards involves application 0.1% Mancozeb (a 
broad spectrum fungicide) two times before the peak  rainy season (CMERTI 2021). 
5.18.4  Likelihood of entry 
Phyllosticta perseae  causes leaf spots on avocado leaves (Rieuf and Tea sca 1970) but has not been 
reported on stems. There is a possibility that P. perseae  spores could contaminate leaf buds or the 
surface of relatively wet, leafless, rootless avoca do budwood cuttings due to the transmission of 
spores through water or rain splash (Das et al. 200 5; Chattopadhyay et al. 2014). However, there is 
currently no evidence to support this association. Furthermore, P. perseae is more likely to produce 
conidia on older leaves or dying and dead material (Rieuf and Teasca 1970; Chattopadhyay et al. 
2014; Ray et al. 2019) and thus importing clean roo tless budwood would considerably reduce the 
likelihood of entry on this pathway.  
As part of the commodity description, all imported avocado germplasm will undergo a growing period 
of active growth with a minimum of three distinct p henological growing events referred to as ‘shoot 
flush’ in 3A PEQ. This period in 3A PEQ will impact  on likelihood of entry in the following manner: 
• any ungerminated P. perseae  conidia on the surface of avocado budwood are high ly unlikely 
to remain viable (alive and still capable of infect ing the plant), based on the assumption of the 
known conidial viability of P. citricarpa  (Korf et al. 2001; de Oliveira Silva et al. 2017),  during 
preparation of the material for export, transit to New Zealand, surface disinfection (cuttings 
dipped in 1% sodium hypochlorite for 2 minutes) upo n arrival in PEQ and subsequent grafting 
of the buds onto new rootstock.  
• if viable conidia remain on a bud once the bud is grafted, infection is likely to occur once the 
bud breaks dormancy to form leaves. In this case, v isible spots and lesions are likely to 
develop assuming the following conditions occurs, t emperatures close to 25 ° C and high 
humidity, and thus, be detected during routine insp ections. 
• Searches of Google Scholar, CAB abstracts, CPC and  Google using the search terms 
‘Phyllosticta perseae ’, ‘ Phyllosticta micropuncta ’ and ‘asymptomatic’ found no evidence for 
asymptomatic P. perseae  infections or longer latent periods in avocado pla nts 48 . Additionally, 
recent isolation of endophytic fungi of avocado tre es in Florida did not find P. perseae, 
suggesting this pathogen may be restricted to the s urface of leaves (Shetty et al. 2016). 
Budwood or grafted plants infected with P. perseae  are therefore almost certain to develop 
symptoms and be detected and destroyed before they are released from PEQ.  
• Conidia are spread by watersplash and rain (Wikee et al. 2011; CMERTI 2021). Level 3A 
PEQ has measures in place to manage the risks assoc iated with insects, wastewater, waste 
and accidental transfer (see section 2.3), therefor e viable P. perseae  propagules are highly 
unlikely to escape level 3A PEQ to infect a suitabl e host. 
Therefore, if P. perseae  is imported on avocado, the residual biosecurity r isks are likely to be 
managed by the growing period of active growth with  a minimum of three distinct phenological 
growing events referred to as ‘shoot flush’ in 3A P EQ. 
Given the arguments and evidence above, that is:  
 
48 Spanish and Portuguese references were also checked  when they were found in searches on the species na mes. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 268 • there is very limited evidence to suggest that P. perseae can be associated with leafless, 
rootless avocado budwood cuttings as the fungus is only known to be associated with leaves 
of host plants; 
• residual biosecurity risks from new infections or ungerminated conidia on the surface of 
avocado budwood are likely to be managed by the gro wing period of active growth with a 
minimum of three distinct phenological growing even ts referred to as ‘shoot flush’ in 3A PEQ; 
the likelihood of Phyllosticta perseae  entering New Zealand associated with Persea americana  
budwood is considered to be negligible, with low un certainty. 
Therefore, further assessment is considered unneces sary at this time; and likelihoods of exposure 
and establishment and impacts to New Zealand were n ot assessed. 
5.18.5  Overall level of assessed risk to New Zealand 
Based on the assessment of likelihood above, that:  
• the likelihood of P. perseae  entering New Zealand associated with P. americana  budwood (as 
described in the commodity description, and taking into account the proposed growing period 
of active growth with a minimum of three distinct p henological growing events referred to as 
‘shoot flush’ in 3A PEQ) is considered to be neglig ible with low uncertainty;  
• therefore, continuing the assessment was considere d unnecessary; and 
the overall level of risk to New Zealand from P. perseae  on imported P. americana budwood is 
considered to be negligible, with low uncertainty.  
5.18.6  Management considerations 
Phyllostica perseae  produces visible spots and lesions on leaves (Chat topadhyay et al. 2014; 
Ramirez et al. 2021). Searches on the species name found no evidence for asymptomatic infection of 
leaves or stem tissues. Therefore, P. perseae  is highly unlikely to persist as an asymptomatic 
infection on susceptible tissues.  
No information was found on the time to development  of symptoms on avocado, but high humidity 
and moisture conditions, and temperatures close to 25° C are known to induce symptoms in P. 
bombycina  (Das et al. 2005). Conidia are more likely to germ inate on older leaves or dying and dead 
material than new leaves (Rieuf and Teasca 1970; Ch attopadhyay et al. 2014) and this suggests that 
symptoms of pre-existing P. perseae infections are highly likely to be detected by visu al inspection 
during preparation for export or on arrival in New Zealand.  
If viable conidia have remained on the surface of b uds, infections are likely to develop when the plan t 
breaks dormancy and produces new shoots. Given the conditions described above, temperatures in 
PEQ are likely to favour infection, but given that there is no overhead watering in PEQ (MPI 2021), 
there may not be enough water on the surface of the  plant to allow conidia to germinate and infect 
susceptible tissues. Nevertheless, conidia are high ly unlikely to remain viable on P. americana  
budwood through pre- and post-export handling and t he PEQ period. Therefore, prophylactic testing 
in the absence of visible lesions is not considered  necessary.  
Phyllosticta spp. specific primers (Pca8/ITS4, GCM/GCMR, GCF2/GC R4) for nested polymerase 
chain reaction (PCR) have been developed, however, these were developed for Citrus leaves and 
fruits (Wang et al. 2012). This suggests that  PCR techniques could be developed for diagnostic 
testing of P. perseae  if symptoms are detected in PEQ.    
269 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.18.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Phyllosticta perseae  produces brownish-gray spots within small necrotic  lesions around the ends and 
sides of host plant leaves (Ellis and Martin 1885; Ramirez et al. 2021). The disease mostly affects le af 
quality and sometimes leads to leaf loss (Rieuf and  Teasca 1970; Das et al. 2005). 
o What are the known environmental conditions conduci ve to symptom expression? 
There is very little information about the conditio ns for symptom expression in P. americana  but in  P. 
bombycina , symptoms are best expressed in highly humid condi tions and at a temperature of 25 ° C 
(Das et al. 2005). Although, the pathogen was colle cted on leaves of P. carolinensis  during winter in 
Florida (Ellis and Martin 1885), it is important to  note that winter in Florida  is mild because the c limate 
ranges from tropical to subtropical. in Florida is largely tropical. In India, the pathogen is best 
transmitted and expressed during the rainy season, suggesting that wet and humid environmental 
conditions are most appropriate (Chattopadhyay et a l. 2014).  
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested? 
Phyllosticta perseae  is not known to cause asymptomatic infections. 
o What is the optimum season for conducting detection  testing? 
The pathogen is likely to develop and be expressed in the rainy season or warm, humid and wet 
conditions (Chattopadhyay et al. 2014). 
5.18.8  References  
Alfieri Jr, S (1984) Index of plant diseases in Flo rida. Florida Department of Agriculture & Consumer 
Services, Bulletin 11: 1-389. 
Anderson, P (1919) Index to American species of Phyllosticta . Mycologia 11(2): 66-79. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Blain, W (1931) A list of diseases of economic plan ts in Alabama. Mycologia 23(4): 300-304. 
Chattopadhyay, S; Sangma, C D; Tikader, A; Rajan, R  K; Bindroo, B B (2014) Assessment of som 
(Persea bombycina ) clones for resistance against Phyllosticta perseae . Tropical plant pathology 
39(3): 259-264. 
CMERTI (2021) Central Muga Eri Research and Trainin g Institute (CMER&TI) Frequently asked 
questions. https://cmerti.res.in/faq/   
Das, R; Das, K; Chakravorty, R (2005) Reaction of d ifferent cultivars of Persea bombycina  Kost 
towards leaf spot disease caused by Phyllosticta perseae  Ell. & Mart. Séricologia 45(3): 345-350. 
de Oliveira Silva, A; Savi, D C; Raiser, P H S; Gon çalves, F P; Kava, V; Galli-Terasawa, L V, et al. 
(2017) Epidemiological aspects of Phyllosticta citricarpa colonization and viability in Citrus sinensis . 
Journal of Plant Diseases and Protection 124(1): 73-80. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 270 Doidge, E M (1950) The South African fungi and lich ens to the end of 1945; host index. Bothalia 5: 
739-1032. 
Ellis, J; Martin, G (1885) New Florida fungi. The Journal of Mycology 1(8): 97-101. 
Farr, D F; Rossman, A Y (2021) Fungal databases, U.  S. National Fungus Collections. https://nt.ars-
grin.gov/fungaldatabases/  Accessed Septemeber 27, 2021 
Index Fungorum (2022) Index Fungorum. http://www.indexfungorum.org/names/Names.asp   
Korf, H; Schutte, G; Kotzé, J (2001) Effect of pack house procedures on the viability of Phyllosticta 
citricarpa , anamorph of the citrus black spot pathogen. African Plant Protection 7(2): 103-109. 
Lara Vazquez, F (2019) Spatial analysis of red spider (Olygonichus Punicae  Hirst) populations and its 
damage in avocado crops in Mexico state.  thesis; Autonomous Mexico State University, Mexico . 
Retrieved from http://ri.uaemex.mx/handle/20.500.11799/104645   
MPI (2021) Facility Standard: Post Entry Quarantine for Plants . Ministry for Primary Industries, 
https://www.mpi.govt.nz/dmsdocument/11368-Post-Entr y-Quarantine-forPlants-Facilities-Standard  
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
Ohr, H D; Coffer, M D; McMillan, R T, Jr. (2003) Di seases of avocado. 
https://www.apsnet.org/edcenter/resources/commonnam es/Pages/Avocado.aspx   
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Ramirez, J; Watson, K; Thiers, B; McMillin, L (2021 ) The New York Botanical Garden Herbarium (NY). 
Version 1.42. Occurrence dataset: Phyllosticta perseae . https://www.gbif.org/occurrence/1928844179   
Rao, V G (1965) The genus Phyllosticta  in India. Sydowia 19: 117-122. 
Ray, M K; Baruah, P K; Mishra, P K; Das, S (2019) A  comprehensive mycofloral diversity of 
pedosphere, phyllosphere and aerosphere of Som ( Persea bombycina Kost.) in lower Brahmaputra 
valley of Assam. Aerobiologia 35(3): 553-566. 
Rieuf, P; Teasca, G (1970) Fungi on avocado pear in  Morocco. Awamia 34: 47-90. 
Robert, V; Stegehuis, G; Stalpers, J (2005) The Myc oBank engine and related databases. 
https://www.mycobank.org/  Accessed October 2021 
Shetty, K G; Rivadeneira, D V; Jayachandran, K; Wal ker, D M (2016) Isolation and molecular 
characterization of the fungal endophytic microbiom e from conventionally and organically grown 
avocado trees in South Florida. Mycological Progress 15(9): 977-986. 
USDA (2016) Importation of Fresh Fruit of Avocado, Persea americana Miller var. ‘Hass’, into the 
Continental United States from Colombia: A Pathway- Initiated Risk Assessment. In U S D o A (USDA)  
271 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand (Ed.), (4 ed.): United States Department of Agricul ture (USDA), Animal and Plant Health Inspection 
Service (APHIS). 
Wang, X; Chen, G; Huang, F; Zhang, J; Hyde, K D; Li , H (2012) Phyllosticta  species associated with 
citrus diseases in China. Fungal Diversity 52(1): 209-224. 
Wikee, S; Udayanga, D; Crous, P W; Chukeatirote, E;  McKenzie, E H; Bahkali, A H, et al. (2011) 
Phyllosticta —an overview of current status of species recogniti on. Fungal Diversity 51(1): 43-61. 
Wulandari, N; Bhat, D; To-anun, C (2013) A modern a ccount of the genus Phyllosticta . Plant 
Pathology & Quarantine 3(2): 145-159. 
Zentmyer, G A (1961) Avocado diseases in the Americ as. CEIBA 9(2): 61-79. 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 272 5.19  Pleiocarpon algeriense  and Cylindrocladiella peruviana  
Pleiocarpon algeriense  and Cylindrocladiella peruviana  are causative agents of black-foot disease of 
grapevines which causes necrosis at the base of roo t stocks, reduced vigor of plants and occasional 
mortality. In avocado trees, both of these organism s cause stem and crown rot. 
5.19.1  Taxonomic description 
Scientific name: Pleiocarpon algeriense W. Aigoun-Mouhous, A. Cabral & A. Berraf-Tebbal (20 19) 
Order/Family: Hypocreales/Nectriaceae 
Scientific name: Cylindrocladiella peruviana (Bat., J.L. Bezerra & M. P. Herrera) Boesew. (1982)  
Other names: Cylindrocladium peruvianum Bat., J. L. Bezerra & M. P. Herrera (1965) 
Order/Family: Hypocreales/Nectriaceae 
5.19.2  Hazard identification 
Pleiocarpon algeriense  and Cylindrocladiella peruviana are not known to be present in New Zealand: 
• Pleiocarpon algeriense is not listed in Biota NZ (2022), NZOR (2021), PPIN  (2021) or ONZPR 
(2021). 
• Cylindrocladiella peruviana  is listed as absent from New Zealand in Biota NZ ( 2022) and 
NZOR (2021) and is not listed in PPIN (2021). 
• Cylindrocladiella peruviana is listed as regulated in ONZPR (2021). 
Pleiocarpon algeriense  and Cylindrocladiella peruviana have the potential to establish [and spread] in 
New Zealand because: 
• Persea americana (avocado) is a known host (Aiello et al. 2020) that  is widely grown in New 
Zealand, in home gardens and commercial production,  mainly in the north of the North Island 
and the Hawkes Bay region. 
• Eucalyptus spp. and Vitis spp. are also known hosts of C. peruviana  (Crous and Wingfield 
1993; van Coller et al. 2005) which are also widely  grown in New Zealand. 
• Pleiocarpon algeriense  and Cylindrocladiella peruviana have been recorded from countries 
(e.g. Italy) with a climate match index (CMI) ≥ 0.7 (Phillips et al. 2018) indicating a similar 
climate to the whole of New Zealand. 
Pleiocarpon algeriense  and Cylindrocladiella peruviana have the potential to cause harm to New 
Zealand because: 
• Pleiocarpon algeriense and Cylindrocladiella peruviana cause stem and crown rot in Persea 
americana plants which can result in the death of trees (Aiel lo et al. 2020). 
• avocados are an important commercial crop in New Z ealand. In the 2019–2020 financial year, 
export sales of fresh avocados earned NZ$112.3 mill ion and domestic sales earned NZ$50.6 
million (Plant & Food Research 2020). 
Given the arguments and evidence above, Pleiocarpon algeriense  and Cylindrocladiella peruviana 
meet the criteria to be a hazard for New Zealand  
273 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.19.3  Risk assessment 
Biology and e pidemiology of Pleiocarpon algeriense and Cylindroc ladiella peruviana 
Pleiocarpon algeriense is a recently described organism (Aigoun-Mouhous et  al. 2019) and was first 
isolated from the basal part of Vitis spp. rootstock in Algeria (Aigoun-Mouhous et al. 20 19). It has also 
been isolated from Persea americana  plants in Italy  (Aiello et al. 2020). 
Cylindrocladiella peruviana  is associated with root and cutting rot of Acacia mearnsii , Eucalyptus spp. 
and Vitis vinifera (van Coller et al. 2005) in addition to leaf spot i n Acacia spp. and Eucalytus spp. 
(Crous and Wingfield 1993). It has also been isolat ed from Persea americana  plants in Italy  (Aiello et 
al. 2020). 
Symptoms 
Both Pleiocarpon algeriense  and Cylindrocladiella peruviana cause wilting of avocado plants as a 
result of stem and crown rot (Aiello et al. 2020). Infected plants have stunted growth, general wiltin g 
and leaf chlorosis; the basal stem and crown of pla nts become dry, cracked and show external decay 
(Aiello et al. 2020). Tissue discolouration is obse rved internally (i.e. infection in the xylem) which  can 
result in the detachment of bark and/or roots from the stem (Aiello et al. 2020). In advanced stages o f 
infection, root rot is also observed (Aiello et al.  2020). 
An orchard in Italy, consisting of 2200 plants, sho wed 40% disease incidence (880 trees infected) 
where 800 plants had died (Aiello et al. 2020). Pleiocarpon algeriense was found co-occuring with 
Cylindrocladiella peruviana  and the symptoms observed could be the result of t he interaction between 
the two species; however, pathogenicity trials, whe re plants were inoculated with P. algeriense  or C. 
peruviana only, still produced visible symptoms and P. algeriense was more virulent than C. 
peruviana  (Aiello et al. 2020). 
Time and conditons to symptom development 
In vivo  pathogenicity trials in seedlings and young trees ( ≥3 years old) resulted in similar symptoms as 
described above (Aiello et al. 2020). Visible necro tic lesions were visible both externally and intern ally 
in the bark above the inoculation site and initial symptoms developed within 2 months after inoculatio n 
in seedlings (Aiello et al. 2020). After 4 months p ost inoculation symptoms in young trees were simila r 
to those as seen in the orchard (described above) ( Aiello et al. 2020). 
In in vivo experiments, plants were held in growth chambers wi th a 12 hour photoperiod and 
temperatures of 25° C ± 1° C (Aiello et al. 2020). Pl ants were also watered regularly (Aiello et al. 202 0). 
In culture, no growth of P. algeriense  was observed at 10° C; colonies started growing at 15° C and the 
optimal temperature for growth is 25–30° C (Aigoun-M ouhous et al. 2019). The minimum temperature 
requirements for growth of C. peruviana in culture is 5° C with a maximum of 35° C and an opt imum of 
25° C (Crous and Wingfield 1993). 
Reproduction and transmission 
Given the recent discovery of P. algeriense , there is limited information on the reproduction and 
transmission of this organism. Affected plants prod uced in nurseries could represent the primary 
pathway for the transmission of this pathogen (Aiel lo et al. 2020). Long lived spores such as 
chlamydospores are rarely seen in P. algeriense  (Aiello et al. 2020). 
Cylindrocladiella peruviana is dispersed through wind and rain splash from the soil surface or by 
contact with the ground (Department of Agriculture Fisheries and Forestry 2004). Chlamydospores 
are extensive and are observed in chains in Cylindrocladiella species (Crous and Wingfield 1993).  
In addition, Aiello et al. (2020) collected symptom atic plant material (sections of basal stem and cro wn 
tissue) which were then surface disinfected for 1 m in in 1.5% sodium hypotchorlite. Growth of P. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 274 algeriense  and C. peruviana  still occurred from surface disinfected material i ndicating this organism 
grows internally and would not be affected by surfa ce disinfection (Aiello et al. 2020). 
5.19.4  Likelihood of entry 
This assessment is made on the basis that Pleiocarpon algeriense and Cylindrocladiella peruviana  
are present in the countries where avocado budwood is being imported from. Pleiocarpon algeriense  
and Cylindrocladiella peruviana  have been reported on avocado in Italy (Aiello et al. 2020). 
Cylindrocladiella peruviana has been recorded on other host species in many oth er countries ( Error! 
Reference source not found. ).  
Infection by both cause stem and crown rot and infe ction is more commonly associated with the base 
of the plant (Aiello et al. 2020). Severe infection  can result in the base of the tree detatching from  the 
roots (Aiello et al. 2020). Infections were observe d in trees ≥3 years old, suggesting the pathogens 
may have a latency period (Aiello et al. 2020). Cylindrocladiella species are soil-borne fungi and 
regarded as saprotrophs and pathogens, suggesting t hey may remain latent in the environment (i.e. 
soil) (Lombard et al. 2012). The mode of infection of C. peruviana and P. algeriense  are most likely 
through roots and wounds as dispersal (particularly  for C. peruviana ) is through wind and rain splash 
from the soil surface (Crous and Wingfield 1993; De partment of Agriculture Fisheries and Forestry 
2004). 
Infection is most likely associated with the base o f stems near the surface of the soil; however, 
Cylindrocladiella peruviana  has caused root and cutting rot in other host spec ies (e.g. Acacia 
mearnsii , Eucalyptus spp. and Vitis vinifera ) (van Coller et al. 2005) suggesting a possibilili ty this 
pathogen could be associated with avocado budwood; however, given the recent observation of the 
association of C. peruviana  with avocado, there is no evidence of the associat ion of this pathogen on 
avocado budwood. It has been demonstrated through a rtificial inoculations that Pleiocarpon 
algeriense causes infection in grapevine cuttings (Aigoun-Mouh ous et al. 2019); however, similar to 
C. peruviana , there is no evidence of infection on avocado cutt ings. Therefore, there is high 
uncertainty regarding the possibility of infection in avocado budwood. 
Given the internal infection of both of these organ isms, the prescribed surface disinfection of budwoo d 
entering PEQ (1% sodium hypochlorite dip for 2 minu tes) would reduce surface populations of these 
fungi but would not reduce internal infections. 
Given the arguments and evidence above, that is: 
• Cylindrocladiella peruviana and P. algeriense  are likely soilborne (Lombard et al. 2012; Aiello 
et al. 2017; Aiello et al. 2020) 
• latent infections of C. peruviana and P. algeriense are observed in avocado orchards as 
disease has only been observed in 3 year old plants  (Aiello et al. 2020), 
• Cylindrocladiella peruviana and P. algeriense  infect cuttings of other host species (van Coller 
et al. 2005; Aigoun-Mouhous et al. 2019) 
• routine surface disinfection (1% sodium hypochorit e for 2 minutes) would not reduce internal 
infections 
the likelihood of Pleiocarpon algeriense  entering New Zealand associated with P. americana budwood 
is considered to be low, with high uncertainty. 
5.19.5  Likelihood of exposure 
This assessment is made on the basis that Cylindrocladiella peruviana and Pleiocarpon algeriense  
have entered New Zealand undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or   
275 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for C. peruviana and 
P. algeriense . 
If avocado plants are infected with C. peruviana and/or P. algeriense  at the time of their release from 
PEQ they will be planted in New Zealand or used to propagate new plants for planting (see section 
2.3 for additional information about exposure).  
Given the arguments and evidence above, the likelih ood of exposure of C. peruviana and P. 
algeriense  in New Zealand from P. americana  budwood is considered to be high, with low uncerta inty. 
5.19.6  Likelihood of establishment 
This assessment is made on the basis that Cylindrocladiella peruviana and Pleiocarpon algeriense  
have been successfully exposed to a suitable host p lant in the New Zealand environment. 
Pleiocarpon algeriense  has been recorded on Persea americana in Italy (Aiello et al. 2020) and on 
Vitis vinifera in Algeria (Aigoun-Mouhous et al. 2019). Algeria ha s a climate match index ranging 
between 0.3–0.8 (Phillips et al. 2018). Cylindrocladiella peruviana has a wider geographic and host 
range in comparison to P. algeriense  (Error! Reference source not found. ). Both species are found 
in countries that have a similar climate to the who le of New Zealand, as well as to the Auckland and 
Northland regions, as indicated by a climate match index of ≥0.7 (Phillips et al. 2018). Climate 
suitability is further supported by the fact that o ther Cylindrocladiella species have already established 
in New Zealand (Biota NZ 2022). 
Both species infect hosts that are either grown com mericially (e.g. grapes, avocado and Eucalyptus ) 
or as backyard plants in many home gardens. Therefo re, hosts for the establishment of C. peruviana 
and P. algeriense  are readily available. In addition, C. peruviana has commonly been isolated from 
soils (Table 5-20). 
Table 5-20: Geographic and host range of Cylindrocladiella peruviana . 
Region Country CMI* Host Reference 
Europe Spain 0.7–0.9 Vitis vinifera Agustí-Brisach et al. (2012) 
Italy 0.7–0.9 Persea americana Aiello et al. (2020) 
North America USA 0.5–0.8 Vitis vinifera Koike et al. (2016) 
Asia Taiwan 0.4–0.8 Eriobotrya japonica Tsai et al. (2012) 
Thailand 0.3–0.5 Soil van Coller et al. (2005) 
India 0.2–0.5 Oryza sativa van Coller et al. (2005) 
Japan 0.6–0.8 - Victor et al. (1998) 
Vietnam 0.4–0.5 Soil Pham et al. (2018) 
South America Peru 0.4–0.8 Ants van Coller et al. (2005) 
Brazil 0.3–0.9 Ants Victor et al. (1998) 
Piptadenia sp. Lombard et al. (2012) 
Psidium guajava Lombard et al. (2012) 
Not recorded  Soil van Coller et al. (2005) 
Africa South Africa 0.5–0.9 Acacia mearnsii Victor et al. (1998) 
Vitis vinifera van Coller et al. (2005) 
Eucalyptus sp. Victor et al. (1998) 
Leaf litter Victor et al. (1998) 
Pelargonium sp. Crous et al. (2019) 
Oceania Australia 0.4–1 Soil Lombard et al. (2012) Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 276 * Climate match index (CMI) ≥ 0.7 indicates countri es with a similar climate to the whole of the New Z ealand (Phillips et al. 
2018). 
Given the arguments and evidence above, that is: 
• hosts (in the form of cultivated avocados and othe r cultivated crops) are available for the 
establishment of Cylindrocladiella peruviana and Pleiocarpon algeriense . 
• suitable climate (Table 5-20) is available for the  establishment of Cylindrocladiella peruviana 
and Pleiocarpon algeriense   
the likelihood of C. peruviana and P. algeriense  establishing in New Zealand is considered high, wi th 
low uncertainty. 
5.19.7  Impacts in New Zealand: 
The co-occurance of Pleiocarpon algeriense and Cylindrocladiella peruviana  in Persea americana  has 
been recorded causing 40% disease incidence in orch ards with a high proportion of those causing 
death of the plant (Aiello et al. 2020). Both of th ese organisms have also been implicated in causing 
black-foot disease in grapevines (e.g. van Coller e t al. 2005; Aigoun-Mouhous et al. 2019). 
Other agents of black-foot disease are recorded as present in New Zealand (e.g. Ilyonectria spp., 
Cylindrocarpon  spp., Dactylonectria spp. and Cylindrocladiella parva ) and are managed through the 
use of fungicides (Bleach et al. 2013). Black-foot disease is particularly a problem in nurseries and 
new vineyards (Berlanas et al. 2020) and death is l ikely in vines less than 10 years old (Bleach et al . 
2021). Fungi causing black-foot disease can live as  latent pathogens within grapevine and may 
become pathogenic under specific conditions such as  waterlogging, water stress, nutrient deficiency 
or soil compaction (Berlanas et al. 2020). Diseased  vines need to be removed and fungal inoculum 
removed (Bleach et al. 2021).  
Given Pleiocarpon algeriense and Cylindrocladiella peruviana are soil-borne pathogens and that both 
can produce long lived chlamydospores, spread of th ese pathogens can occur through the movement 
of infected soils (Crous and Wingfield 1993). 
Economic impacts 
Pleiocarpon algeriense is likely to affect both the avocado and grape indu stry whereas 
Cylindrocladiella peruviana  is likely to affect avocado, grape and Eucalyptus spp. plantations ( Error! 
Reference source not found. ). 
In 2020, the export values for avocado was $112.3 m illion and the domestic value was $50.6 million 
(Plant & Food Research 2020). The export value for grapes for wine was $1.9 billion (Plant & Food 
Research 2020). Eucalyptus spp. were valued at $671 million in 2018 with an es timated planted area 
of 27, 298 ha (Radics et al. 2018). 
Incidence of these pathogens in vineyards and plant ations are lacking; however, given that other fungi  
that cause black-foot disease are present in New Ze aland and have been for awhile (Bleach et al. 
2013; Bleach et al. 2021), current management pract ices are likely to account for disease caused by 
P. algeriense and C. peruviana .  
Therefore, given these pathogens have the ability t o cause up to 40% disease incidence in avocado 
orchards, economic impacts are likely (Aiello et al . 2020). Furthermore, cost of plant and inoculum 
removal would also need to be incorporated into the  cost of management (Bleach et al. 2021). 
Given the arguments and evidence above, that is: 
• some species causing black-foot disease in grapevi nes are already present in New Zealand 
(Bleach et al. 2021), 
• management practices are used in New Zealand for Cylindrocladiella spp. and other black-
foot disease causing fungi (Bleach et al. 2013; Ble ach et al. 2021),  
277 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • the host range of P. algeriense and C. peruviana  indicates not only the avocado but also the 
grape and Eucalyptus industry could be affected which together are value d at $2.7 billion 
(sum of both domestic and export earnings), 
the economic impact of Pleiocarpon algeriense and Cylindrocladiella peruviana  to New Zealand is 
considered to be moderate, with moderate uncertaint y. 
Environmental impacts 
It is unknown if either Pleiocarpon algeriense and Cylindrocladiella peruviana  have known native New 
Zealand plant hosts. However, C. peruviana  is known to infect Acacia mearnsii which is present 
throughout New Zealand (NZPCN 2021). Cylindrocladiella peruviana is commonly found in the soil 
and has been associated with ants (species unknown)  in South America ( Error! Reference source 
not found. ). Ants may also act as a mode of dispersal for thi s fungus. 
Given the possibility of C. peruviana species living as pathogens or saprotrophs on plant s and in the 
soil (Lombard et al. 2012), this fungus has the pot ential wide range of environmental impacts. 
However, a related species C. parva is already present in New Zealand (Biota NZ 2022), suggesting 
impacts would not differentiate drastically. In con trast, Pleiocarpon algeriense  is newly described 
(Aigoun-Mouhous et al. 2019) and thus, environmenta l impacts are unknown. 
Given the arguments and evidence above, the impact on the environment from the establishment of 
Pleiocarpon algeriense and Cylindrocladiella peruviana  in New Zealand is considered to be very low, 
with moderate uncertainty. 
Health impacts 
There is no evidence that Pleiocarpon algeriense or Cylindrocladiella peruviana cause human health 
impacts. Search terms [ Cylindrocladiella  OR Pleiocarpon AND “human health”] were used in Google, 
Google Scholar and Web of Science with no results. 
Given the arguments and evidence above, the health impacts of Pleiocarpon algeriense and 
Cylindrocladiella peruviana to New Zealand is considered to be negligible, with  low uncertainty. 
Sociocultural impacts 
Both Pleiocarpon algeriense and Cylindrocladiella peruviana have the potential to cause death of 
plants in avocado orchards and vineyards (Aigoun-Mo uhous et al. 2019; Aiello et al. 2020). If left 
unmanaged, there could be a decline in fruits in ma rkets. Avocado, grapes (and wine) are popular 
and are widely consumed in New Zealand. They are co mmonly grown in home gardens in some parts 
of the country. 
Given the arguments and evidence above, the social/ cultural  impacts of Pleiocarpon algeriense and 
Cylindrocladiella peruviana to New Zealand is considered to be low, with low un certainty. 
5.19.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is low 
• assuming entry, the likelihood of exposure is high  
• assuming successful exposure, the likelihood of es tablishment is high 
• the overall impact on the New Zealand economy, env ironment, human health and society 
is considered to be moderate 
the overall level of assessed risk to New Zealand f rom Pleiocarpon algeriense and Cylindrocladiella 
peruviana  on imported Persea americana budwood (as in the commodity description) is consid ered to 
be moderate, with moderate uncertainty. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 278 5.19.9  Management considerations 
Cylindrocladiella peruviana and Pleiocarpon algeriense cause stem and crown rot in Persea 
americana (avocado). Infected plants have stunted growth, gen eral wilting and leaf chlorosis; the 
basal stem and crown of plants become dry, cracked and show external decay (Aiello et al. 2020). 
Tissue discolouration is observed internally (i.e. infection in the xylem) which can result in the 
detachment of bark and/or roots from the stem (Aiel lo et al. 2020). In advanced stages of infection, 
root rot is also observed (Aiello et al. 2020). 
Experimental conditions for symptom expression a 12  hour photoperiod and temperatures of 25° C ± 
1° C (Aiello et al. 2020). In the field, stem and cr own rots are exacerbated by specific conditions suc h 
as waterlogging, water stress, nutrient deficiency or soil compaction (Berlanas et al. 2020). 
Infection seems to be common around the base of tre es; however, there is evidence these species 
can infect cuttings in other host species (van Coll er et al. 2005; Aigoun-Mouhous et al. 2019). Thus, 
the possibility for association with avocado budwoo d can not be ruled out. Infections are within 
internal tissues of stems (with external symptoms v isible) and thus testing of tissue within stems 
would be necessary.  
PCR testing is available for both Cylindrocladiella peruviana and Pleiocarpon algeriense . To 
distinguish among organisms within the complex that  causes black-foot disease, multiple gene 
regions are sequenced to better resolve species ide ntification (Aigoun-Mouhous et al. 2019). Gene 
regions sequenced include the ITS, tub2 , tef1 , his3 and rpb2 gene regions (Aigoun-Mouhous et al. 
2019; Aiello et al. 2020).  
5.19.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Both Pleiocarpon algeriense  and Cylindrocladiella peruviana cause wilting of avocado plants as a 
result of stem and crown rot (Aiello et al. 2020). Infected plants have stunted growth, general wiltin g 
and leaf chlorosis; the basal stem and crown of pla nts become dry, cracked and show external decay 
(Aiello et al. 2020). Tissue discolouration is obse rved internally which can result in the detachment of 
bark and/or roots from the stem (Aiello et al. 2020 ). In advanced stages of infection, root rot is als o 
observed (Aiello et al. 2020). 
o What are the known environmental conditions conduci ve to symptom expression? 
Experimental conditions for symptom expression are 12 hour photoperiod and temperatures of 25° C ± 
1° C (Aiello et al. 2020). In the field, stem and cr own rots are exacerbated by specific conditions suc h 
as waterlogging, water stress, nutrient deficiency or soil compaction (Berlanas et al. 2020). 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested? 
Transverse and longitudinal sections from the graft ing point, basal part of the crown and middle part 
between grafting point and basal point have success fully had the pathogens isolated (Aigoun-
Mouhous et al. 2019). 
o What is the optimum season for conducting detection  testing? 
There is no optimum season for conducting detection  testing as specific environmental stressors 
(listed above) exacerbate symptom expression.  
279 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.19.11  References  
Agustí-Brisach, C; Alaniz, S; Gramaje, D; Pérez-Sie rra, A; Armengol, J; Landeras, E, et al. (2012) 
First report of Cylindrocladiella parva and C. peru viana associated with Black-foot Disease of 
grapevine in Spain. Plant Disease 96(9): 1381-1381.  
Aiello, D; Gusella, G; Vitale, A; Guarnaccia, V; Po lizzi, G (2020) Cylindrocladiella peruviana and 
Pleiocarpon algeriense causing stem and crown rot o n avocado (Persea americana). European 
Journal of Plant Pathology 158(2): 419-430. 
Aiello, D; Polizzi, G; Crous, P W; Lombard, L (2017 ) Pleiocarpon gen. nov. and a new species of 
Ilyonectria causing basal rot of Strelitzia reginae  in Italy. IMA Fungus 8(1): 65-76. 
Aigoun-Mouhous, W; Elena, G; Cabral, A; León, M; Sa baou, N; Armengol, J, et al. (2019) 
Characterization and pathogenicity of Cylindrocarpo n-like asexual morphs associated with black foot 
disease in Algerian grapevine nurseries, with the d escription of Pleiocarpon algeriense sp. nov. 
European Journal of Plant Pathology 154(4): 887-901 . 
Berlanas, C; Ojeda, S; López-Manzanares, B; Andrés- Sodupe, M; Bujanda, R; del Pilar Martínez-Diz, 
M, et al. (2020) Occurrence and diversity of Black- Foot Disease fungi in symptomless grapevine 
nursery stock in Spain. Plant Disease 104(1): 94-10 4. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Bleach, C; Jones, E; Ridgway, H; Jaspers, M (2013) Hot water treatment to reduce incidence of black 
foot pathogens in young grapevines grown in cool cl imates. Phytopathologia Mediterranea 52(2): 347-
358. 
Bleach, C; Ridgway, H J; Jaspers, M V; Jones, E E ( 2021) The relative susceptibility of grapevine 
rootstocks to black foot disease is dependent on in oculum pressure. New Zealand Plant Protection 
74(1): 62-69. 
Crous, P; Wingfield, M (1993) A re-evaluation of Cy lindrocladiella, and a comparison with 
morphologically similar genera. Mycological Researc h 97(4): 433-448. 
Crous, P W; Schumacher, R K; Akulov, A; Thangavel, R; Hernández-Restrepo, M; Carnegie, A J, et 
al. (2019) New and interesting fungi. 2. Fungal sys tematics and evolution 3(1): 57-134. 
Department of Agriculture Fisheries and Forestry (2 004) Longan and lychee fruit from the People's 
Republic of China and Thailand. Australian Governme nt, Canberra, ACT.  
Koike, S T; Bettiga, L J; Nguyen, T T; Gubler, W D (2016) First report of Cylindrocladiella lageniform is 
and C. peruviana as grapevine pathogens in Californ ia. Plant Disease 100(8): 1783. 
Lombard, L; Shivas, R G; To-Anun, C; Crous, P W (20 12) Phylogeny and taxonomy of the genus 
Cylindrocladiella. Mycological Progress 11(4): 835- 868. 
NZOR (2021) The New Zealand Organisms Register. htt p://nzor.org.nz Accessed 03/03/2021 
NZPCN (2021) New Zealand Plant Conservation Network . https://www.nzpcn.org.nz/ Accessed June 
2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/ Accessed 17 M arch 2021 
Pham, N Q; Barnes, I; Chen, S; Pham, T Q; Lombard, L; Crous, P W, et al. (2018) New species of 
Cylindrocladiella from plantation soils in south-ea st Asia. MycoKeys 32: 1-24. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 280 Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zeala nd Horticulture. Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Radics, R I; Withers, T M; Maeson, D F; Stovold, T;  Yao, R (2018) Economic impact of eucalyptus 
tortoise beetle (Paropsis charybdis) in New Zealand . Scion, Rotorua, New Zealand.  
Tsai, Y J; Chen, B Y; Huang, J W (2012) Identificat ion for the causal agent of loquat twig blight in 
Taiwan. Plant Pathology Bulletin 21(2): 79-89. 
van Coller, G J; Denman, S; Groenewald, J Z; Lampre cht, S C; Crous, P W (2005) Characterisation 
and pathogenicity of Cylindrocladiella spp. associa ted with root and cutting rot symptoms of 
grapevines in nurseries. Australasian Plant Patholo gy 34(4): 489-498. 
Victor, D; Crous, P W; Janse, B J H; Van Zyl, W H; Wingfield, M J; Alfenas, A C (1998) Systematic 
appraisal of species complexes within Cylindrocladi ella. Mycological Research 102(3): 273-279. 
Agustí-Brisach, C; Alaniz, S; Gramaje, D; Pérez-Sie rra, A; Armengol, J; Landeras, E, et al. (2012) 
First report of Cylindrocladiella parva  and C. peruviana  associated with Black-foot Disease of 
grapevine in Spain. Plant Disease 96(9): 1381-1381. 
Aiello, D; Gusella, G; Vitale, A; Guarnaccia, V; Po lizzi, G (2020) Cylindrocladiella peruviana and 
Pleiocarpon algeriense  causing stem and crown rot on avocado ( Persea americana ). European 
Journal of Plant Pathology 158(2): 419-430. 
Aiello, D; Polizzi, G; Crous, P W; Lombard, L (2017 ) Pleiocarpon  gen. nov. and a new species of 
Ilyonectria causing basal rot of Strelitzia reginae  in Italy. IMA Fungus 8(1): 65-76. 
Aigoun-Mouhous, W; Elena, G; Cabral, A; León, M; Sa baou, N; Armengol, J, et al. (2019) 
Characterization and pathogenicity of Cylindrocarpon -like asexual morphs associated with black foot 
disease in Algerian grapevine nurseries, with the d escription of Pleiocarpon algeriense  sp. nov. 
European Journal of Plant Pathology 154(4): 887-901. 
Berlanas, C; Ojeda, S; López-Manzanares, B; Andrés- Sodupe, M; Bujanda, R; del Pilar Martínez-Diz, 
M, et al. (2020) Occurrence and diversity of Black- Foot Disease fungi in symptomless grapevine 
nursery stock in Spain. Plant Disease 104(1): 94-104. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Bleach, C; Jones, E; Ridgway, H; Jaspers, M (2013) Hot water treatment to reduce incidence of black 
foot pathogens in young grapevines grown in cool cl imates. Phytopathologia Mediterranea 52(2): 347-
358. 
Bleach, C; Ridgway, H J; Jaspers, M V; Jones, E E ( 2021) The relative susceptibility of grapevine 
rootstocks to black foot disease is dependent on in oculum pressure. New Zealand Plant Protection 
74(1): 62-69. 
Crous, P; Wingfield, M (1993) A re-evaluation of Cylindrocladiella , and a comparison with 
morphologically similar genera. Mycological Research 97(4): 433-448. 
Crous, P W; Schumacher, R K; Akulov, A; Thangavel, R; Hernández-Restrepo, M; Carnegie, A J, et 
al. (2019) New and interesting fungi. 2. Fungal systematics and evolution 3(1): 57-134.  
281 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Department of Agriculture Fisheries and Forestry (2 004) Longan and lychee fruit from the People's 
Republic of China and Thailand . Australian Government, Canberra, ACT.  
Koike, S T; Bettiga, L J; Nguyen, T T; Gubler, W D (2016) First report of Cylindrocladiella lageniformis  
and C. peruviana  as grapevine pathogens in California. Plant Disease 100(8): 1783. 
Lombard, L; Shivas, R G; To-Anun, C; Crous, P W (20 12) Phylogeny and taxonomy of the genus 
Cylindrocladiella . Mycological Progress 11(4): 835-868. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
NZPCN (2021) New Zealand Plant Conservation Network . https://www.nzpcn.org.nz/  Accessed June 
2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Pham, N Q; Barnes, I; Chen, S; Pham, T Q; Lombard, L; Crous, P W, et al. (2018) New species of 
Cylindrocladiella  from plantation soils in south-east Asia. MycoKeys 32: 1-24. 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Radics, R I; Withers, T M; Maeson, D F; Stovold, T;  Yao, R (2018) Economic impact of eucalyptus 
tortoise beetle (Paropsis charybdis) in New Zealand . Scion, Rotorua, New Zealand.  
Tsai, Y J; Chen, B Y; Huang, J W (2012) Identificat ion for the causal agent of loquat twig blight in 
Taiwan. Plant Pathology Bulletin 21(2): 79-89. 
van Coller, G J; Denman, S; Groenewald, J Z; Lampre cht, S C; Crous, P W (2005) Characterisation 
and pathogenicity of Cylindrocladiella  spp. associated with root and cutting rot symptoms  of 
grapevines in nurseries. Australasian Plant Pathology 34(4): 489-498. 
Victor, D; Crous, P W; Janse, B J H; Van Zyl, W H; Wingfield, M J; Alfenas, A C (1998) Systematic 
appraisal of species complexes within Cylindrocladiella . Mycological Research 102(3): 273-279. 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 282 5.20  Podosphaera perseae-americanae 
Podosphaera perseae-americanae  is a fungus causing powdery mildew on leaves of Persea 
americana  (avocado) plants. 
5.20.1  Taxonomic description 
Scientific name:  Podosphaera perseae-americanae  Siahaan & S. Takam. 
Order/Family:  Erysiphales/Erysiphaceae 
Taxonomic notes:  Genus Podosphaera consists of two subsections Podosphaera  sect. 
Podosphaera  and Podosphaera  sect. Sphaerotheca . However, based on DNA sequences, 
Podosphaera perseae-americanae  seems to form an independent lineage, suggesting t hat this 
fungus may belong to an undescribed genus. Due to l acking sexual morph description, this fungus 
was tentatively assigned to genus Podosphaera  (Siahaan et al. 2016). Powdery mildew on avocado 
can also be caused by Pseudoidium perseae-americanae  (synonym Oidium perseae-americanae ), 
but these two fungi are distinguishable by morpholo gical characteristics, where Podosphaera  
produces conidia (asexual spores) in chains (catena te-type) while Pseudoidium  ( syn. Oidium ) 
produces non-catenate conidia (Siahaan et al. 2016) . 
5.20.2  Hazard identification 
Podosphaera perseae-americanae  is not known to be present in New Zealand as it is  not listed in 
Biota NZ (2022) or PPIN (2021). The regulatory stat us of Podosphaera perseae-americanae  has not 
been assessed (ONZPR 2021). 
Podosphaera perseae-americanae  has the potential to establish (and spread) in New  Zealand 
because: 
• Persea americana  (avocado) is a known host (Siahaan et al. 2016) th at is widely grown in 
New Zealand, in home gardens and commercial product ion, mainly in the north of the North 
Island. 
Podosphaera perseae-americanae  has the potential to cause harm to New Zealand bec ause: 
• Podosphaera perseae-americanae  causes powdery mildew on avocado (Siahaan et al. 
2016). 
Podosphaera perseae-americanae  is associated with Persea americana  budwood because: 
• Persea americana  is a known host of Podosphaera perseae-americanae  (Siahaan et al. 
2016); 
• Podosphaera perseae-americanae  was isolated from young leaves of Persea americana.  
Powdery mildew fungi stay dormant in buds of infect ed plants, as dormant mycelia (Glawe 
2008). Therefore, mycelium may be present on leafle ss budwood produced from an infected 
mother plant. 
Given the arguments and evidence above, Podosphaera perseae-americanae  meets the criteria to be 
a hazard on Persea americana  budwood (as in the commodity description) imported  to New Zealand.  
283 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.20.3  Risk assessment 
Biology and epidemiology of Podosphaera perseae-ame ricanae 
Host range  
The host range of Podosphaera perseae-americanae  is restricted to Persea americana  as it is so far 
the only host plant and locality recorded (Siahaan et al. 2016). Most other Podosphaera  species 
parasitise woody plants from Rosaceae  family, with the exception of species in Podosphaera  sect. 
Sphaerotheca  subsect. Magnicellulatae  with herbaceous host plants scattered among 40 pla nt 
families that do not include the Rosaceae . Some species in the genus Podosphaera  are plurivorous 
(with multiple host plants) such as Podosphaera xanthii  reported from plants in the families 
Asteraceae , Fabaceae , Cucurbitaceae  and  Solanaceae  (Pérez-García et al. 2009). Since 
Podosphaera perseae-americanae  was only reported from Persea americana  in one country, the 
known host range of Podosphaera perseae-americanae  is restricted to P. americana , although host 
plants may include other members of the Lauraceae f amily. The possibility that this species may not 
be in the genus Podosphaera  (Siahaan et al. 2016) further introduces uncertain ty associated with the 
assessments. 
Symptoms  
Powdery mildews in general are characterised by a f loury layer of mycelium with conidia (asexual 
spores) which covers affected leaves, buds, shoots and fruits.  Affected developing shoots and leaves 
may remain short, deformed and lesions and chloroti c spots can develop. Podosphaera perseae-
americanae  causes powdery mildew disease on Persea americana , although no detailed description 
of the symptoms is provided, the depicted symptoms include thick powdery cover on the underside of 
slightly discoloured and deformed young leaves (Sia haan et al. 2016). Generally, powdery mildew 
symptoms can become severe in warm, humid, shaded a reas such as nurseries. Rain can wash 
conidia from plant surfaces before they germinate, thus reducing symptom expression (Zentmyer 
1953; Glawe 2008). 
Life cycle and transmission  
Podosphaera perseae-americanae  was isolated from young avocado leaves and is like ly to only affect 
above ground tissues similarly to other powdery mil dews. Although, some species of the genus 
Podosphaera  can be endophytic (e.g. Podosphaera tridactyla  in buds and leaves of Eucalyptus  
(Miguel et al. 2019)), mycelium of Podosphaera perseae-americanae  has been described as 
ectophytic – affecting only the host cells on the s urface (Siahaan et al. 2016). Podosphaera perseae-
americanae  was isolated only in its asexual stage, producing large amounts of asexual spores 
(conidia) on avocado leaves. The conidia of Podosphaera perseae-americanae  are likely airborne and 
transmitted by wind or human activity as is the cas e of other Podosphaera  species and powdery 
mildew in general (Glawe 2008; Numminen and Laine 2 020). The complete life cycle of Podosphaera 
perseae-americanae  could involve an asexual stage as well as a sexual  stage, as is the case for 
other powdery mildews (Glawe 2008). Sexual spores m ay be released from dormant chasmothecia 
(sexual ascocarps – fruiting bodies) with spring ra ins. Powdery mildews are obligate parasites of 
vascular plants, that means they can survive unfavo urable conditions as dormant cleistothecia, 
endophytes or as dormant hyphae in buds of their ho st.  The latter is most likely in case of 
Podosphaera perseae-americanae  as the ascospores produced in chasmothecia have no t been 
observed in Podosphaera perseae-americanae  so far and mycelium of Podosphaera perseae-
americanae  has been described as ectophytic (Siahaan et al. 2 016).   
5.20.4  Likelihood of entry 
In plants, powdery mildews can colonise all metabol ically active above ground plant parts (i.e. stems,  
twigs, leaves, flowers, buds,  and fruit) as epiphy tes or endophytically (Glawe 2008). Podosphaera 
perseae-americanae  was isolated from young leaves and it is likely to  colonise dormant buds similar 
to other powdery mildews (Glawe 2008). Therefore, Podosphaera perseae-americanae  can be 
associated with avocado budwood. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 284 Avocado budwood is dipped in 1% sodium hypochlorite  for 2 minutes upon entry into the quarantine 
facility, which is likely to kill surface infection s, but may not penetrate into buds where dormant 
mycelium might be present. 
Although there is not much information specifically  related to Podosphaera perseae-americanae , 
based on related species of powdery mildew, conidia l production typically begins within several days 
of infecting the host (Glawe 2008). Although some Podosphaera  species are known to be endophytic, 
such as Podosphaera tridactyla  in the leaves of hybrid  Eucalyptus grandis X Eucalyptus urophyla 
(Miguel et al. 2019) , the only record of Podosphaera perseae-americanae  describes it as an epiphyte 
with ectophytic mycelium (Siahaan et al. 2016). 
Avocado plants in post entry quarantine L3A must be  inspected at least twice per week during periods 
of active growth and once per week during dormancy (MPI 2021). Podosphaera perseae-americanae  
produces cylindrical spores with a size of 24.5-33. 5 x 13.5-20 µm. In the event of rapid sporulation, 
typical of powdery mildews, airborne spores could e scape containment facilities of L3A PEQ through 
the vents which are screened with stainless steel i nsect-proof mesh with a maximum opening size of 
0.04 mm (40 µm) (MPI 2021). Powdery mildew spores a re typically airborne and spread better in low 
humidity, usually over short distances, although so me powdery mildew species other than 
Podosphaera  have been recorded to spread over hundreds of kilo metres (Glawe 2008). Due to 
limited information related to Podosphaera perseae-americanae  the uncertainty associated with this 
assessment is high. 
Given the arguments and evidence above, that is:  
• Podosphaera perseae-americanae  is likely to enter PEQ in dormant buds.  
• Podosphaera perseae-americanae  is not likely to survive as an epiphyte on avocado  
budwood without causing symptoms throughout the PEQ  period. In other words, the likelihood 
of Podosphaera perseae-americanae  entering New Zealand on avocado plants from PEQ 
undetected is negligible with moderate uncertainty.   
• If symptoms develop, rapid production of airborne spores may not be detected early enough 
for adequate containment and measures in PEQ L3A ma y not prevent spores escaping 
containment facilities. 
the likelihood of Podosphaera perseae-americanae  entering New Zealand associated with Persea 
americana  budwood is considered to be low, with moderate unc ertainty. 
5.20.5  Likelihood of exposure 
Since there is a negligible risk of avocado plants infected with Podosphaera perseae-americanae at 
the time of their release from Post Entry Quarantin e, this assessment is made on the basis that 
Podosphaera perseae-americanae has entered New Zealand undetected as airborne spor es.  
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. If suitable hosts were  present near the post-entry quarantine facilities,  for 
example, if the facility was located near avocado o rchards, private gardens with avocado trees or 
other native or naturalised plants from the Laurace ae family, the fungus could be exposed to suitable 
host material. However, the amount of inoculum like ly to escape is considered to be small, and the 
conidia would have to land on a suitable host under  suitable conditions to germinate and cause 
disease. Due to limited information related to Podosphaera perseae-americanae  the uncertainty 
associated with this assessment is moderate. 
Given the arguments and evidence above, the likelih ood of exposure of Podosphaera perseae-
americanae in New Zealand from Persea americana  budwood is considered low, with moderate 
uncertainty.  
285 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.20.6  Likelihood of establishment 
This assessment is made on the basis that Podosphaera perseae-americanae has been successfully 
exposed to a suitable host plant in the New Zealand  environment. 
If the host range of the pathogen is only Persea americana then hosts in the form of cultivated 
avocados will be available for their establishment in Aotearoa New Zealand and especially in the 
North Island (see section 2.3). If the host range i ncludes other members of the family Lauraceae then 
the number of potential host species available for the establishment of this fungus is greatly increas ed 
– there are five native and four introduced species  (in addition to Persea americana ) from the 
Lauraceae family found in New Zealand (NZPCN 2021).  
Podosphaera perseae-americanae  is reported from North Sumatra and West Java in In donesia 
(Siahaan et al. 2016). These two regions have a mor e tropical climate than the whole of New 
Zealand, or Auckland and Northland regions, as indi cated by a climate match index range of 0.3 – 0.6 
(Phillips et al. 2018). Therefore, climate consiste ntly suitable for the establishment of Podosphaera 
perseae-americanae  is not readily available. However, powdery mildews  generally require low 
humidity to spread (Glawe 2008), for example  Podosphaera xanthii  has spread in Korea with higher 
temperatures and low moisture (Lee 2012). Podosphaera perseae-americanae  is so far reported only 
from two regions in Indonesia, which may be due the  fact that the potential to establish has not yet 
been realised elsewhere. Due to limited information  related to Podosphaera perseae-americanae  the 
uncertainty associated with this assessment is high . 
Given the arguments and evidence above, that is: 
• hosts (in the form of cultivated avocados) amd pot ential hosts(in the form of native and 
introduced members of the Lauraceae family) are ava ilable for the establishment of 
Podosphaera perseae-americanae, and 
• climate suitable for the establishment of the Podosphaera perseae-americanae  is likely not 
readily available,  
the likelihood of Podosphaera perseae-americanae establishing in New Zealand is considered low, 
with moderate uncertainty. 
5.20.7  Impacts in New Zealand 
Podosphaera perseae-americanae  is a recently described species causing powdery mi ldew on 
avocado (Siahaan et al. 2016). Fungi related to Podosphaera perseae-americanae , causing powdery 
mildews, can produce airborne conidia in large amou nts, within a short space of time (3–7 days post 
infection under disease-promoting conditions). This  can cause rapid spread of the disease.  
Powdery mildew typically disperse by airborne conid ia over over short distances, although some 
powdery mildew species other than Podosphaera  have been recorded to spread over hundreds of 
kilometres (Glawe 2008). Rain can wash conidia from  plant surfaces before they germinate, thus 
reducing symptom expression or preventing spread (Z entmyer 1953; Glawe 2008). Podosphaera 
perseae-americanae  is so far reported to only infect avocado, so it’s  spread is highly likely to be 
limited to avocado growing regions due to host avai lability. 
Economic impacts 
Because avocados are so far the only known host of Podosphaera perseae-americanae  which are 
commercially produced in New Zealand, the assessmen t of economic impacts is limited to the 
avocado industry. 
There is no specific information on the economic im pacts of Podosphaera perseae-americanae 
currently available. However, powdery mildew infect ion may impact yields, as is the case with species 
in the genus Podosphaera , although yield losses may vary widely between spe cies. For example, 
Podosphaera macularis  (hop powdery mildew) caused complete loss of 810 h ectares of hops in 
Washington, USA worth 10,000,000 USD (Mahaffee et a l. 2003), whereas Podosphaera aphanis  on Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 286 strawberries may not even cause direct yield losses  if the powdery mildew symptoms occur after fruit 
harvest (Carisse and Bouchard 2010).  
If there were an outbreak of Podosphaera perseae-americanae  in one of the major avocado-
producing regions in New Zealand, the outbreak migh t not be contained to that region. Spread within 
and between regions could be quite rapid, especiall y if dry, windy conditions conductive for conidia 
dispersion were followed by rain or a humid period that would be favourable for germination of the 
conidia 
However, there is a wide range of control options f or powdery mildews which include synthetic 
fungicides, wettable sulphur or copper sprays (Maha ffee et al. 2003; Mburu et al. 2014), surfactants 
(Hislop and Clifford 1976) or cultural practices (M buru et al. 2014). Although there is no specific 
information on control of Podosphaera perseae-americanae , control measures used against other 
powdery mildews are likely applicable to control Podosphaera perseae-americanae . 
Given the arguments and evidence above, that is: 
• avocados are the only known host of Podosphaera perseae-americanae  commercially 
produced in New Zealand, 
• infection of avocado trees with Podosphaera perseae-americanae  could cause yield 
losses 
• an outbreak would likely spread quickly within and  between regions 
the economic impact of Podosphaera perseae- americanae to New Zealand is considered to be low, 
with high uncertainty. 
Environmental impacts 
Podosphaera  species have a wide range of hosts including culti vated and wild plants, and some 
species may cause significant disease in wild plant s or natural environments (Takamatsu et al. 2010). 
Podosphaera perseae-americanae  was isolated from avocado, but there is no informa tion available to 
confidently assume whether Podosphaera perseae-americanae  is a specialist only parasitising 
Persea americana  or whether it could be plurivorous (parasitising m ultiple host plants). The host 
range of Podosphaera perseae-americanae  may include other species of the family Lauraceae,  which 
include five native Lauraceae species ( Beilschmiedia taraire , Beilschmiedia tawa , Cassytha 
paniculate , Cassytha pubescens and Litsea calicaris ) found in Aotearoa New Zealand (NZPCN 2021). 
Some of these native species are endemic, however n one of these are threatened Aotearoa New 
Zealand (NZPCN 2021). 
Given the arguments and evidence above, the impact on the environment from the establishment of 
Podosphaera perseae-americanae in New Zealand is considered to be low, with high u ncertainty. 
Human health impacts 
There are no known human health impacts associated with Podosphaera perseae-americanae .  
Given the arguments and evidence above, the impact on human health from the establishment of 
Podosphaera perseae-americanae in New Zealand is considered to be negligible, with  low 
uncertainty. 
Sociocultural impacts 
An outbreak of Podosphaera perseae-americanae  may affect avocado plants grown in home gardens. 
However, as there is likely a wide range of control  options for powdery mildews, this impact is likely  to 
be very low. If native Lauraceae plants were suscep tible to the disease, an outbreak could affect 
sociocultural values especially since Beilschmiedia spp. and Litsea calicaris  are only found in 
Aotearoa New Zealand (NZPCN 2021).  
Given the arguments and evidence above, the sociocu ltural impact of Podosphaera perseae-
americanae to New Zealand is considered to be very low, with m oderate uncertainty.  
287 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, human health and society is 
considered to be low, with moderate uncertainty. 
5.20.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is low, 
• assuming entry, the likelihood of exposure is low,  
• assuming successful exposure, the likelihood of es tablishment is moderate, 
• the overall impact on the New Zealand economy, env ironment, human health and society 
is considered to be low,  
the overall level of assessed risk to New Zealand f rom Podosphaera perseae-americanae on imported 
Persea americana budwood (as in the commodity description) is consid ered to be very low, with 
moderate uncertainty. 
5.20.9  Management considerations 
The limited information on Podosphaera perseae-americanae  include thick powdery cover on the 
underside of slightly discoloured and deformed youn g leaves (Siahaan et al. 2016). Symptoms similar 
to those described from other powdery mildews could  develop after infection by Podosphaera 
perseae-americanae ; conidia can be produced quickly and in large amou nts (3–7 days post infection 
under disease-promoting conditions). White mycelium  can cover juvenile parts (inflorescence and 
leaves) causing damage and even necrosis. Old infec tion sites appear as conspicuous chlorotic areas 
with net-like markings (McMillan 1976). The pest mi ght not exhibit symptoms if it is present as 
dormant hyphae in buds of the host plant. 
Symptomatic Podosphaera perseae-americanae  was isolated from avocado plants in Indonesia in 
September 2013 and January 2015, where mean daily t emperatures were greater than 26 o C and 
monthly rainfall was between 50 and 300 mm ("Monthl y Climatic Data for the World September 2013"  
2013; "Monthly Climatic Data for the World January 2015"  2015). Generally, powdery mildew 
symptoms can become severe in warm, humid, shaded a reas such as nurseries. Rain can wash 
conidia from plant surfaces before they germinate, thus reducing the conductivity to symptom 
expression (Zentmyer 1953; Glawe 2008). However, po wdery mildews are usually synchronized with 
host life cycles, thus the conditions might depend more on the etiology of the host (Glawe 2008), such  
as development of young shoots and leaves. 
Powdery mildews can survive as dormant hyphae in bu ds of their host (Glawe 2008). In case dormant 
Podosphaera perseae-americanae  mycelia is unknowingly imported into PEQ, young le aves and 
shoots should be inspected regularly for developing  symptoms. Molecular diagnostics focusing on 
genetic marker regions 28S rRNA and ITS should be s ufficient to differentiate this pathogen from 
other powdery mildews or allow to test asymptomatic  plants (Siahaan et al. 2016). 
Symptoms of Podosphaera perseae-americana  were described in Indonesia which is a tropical 
country with relatively stable high humidity and te mperature. The symptoms were recorded in 
September and January. 
5.20.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 288 The limited information on Podosphaera perseae-americanae  include thick powdery cover on the 
underside of slightly discoloured and deformed youn g leaves (Siahaan et al. 2016). Symptoms similar 
to those described from other powdery mildews could  develop after infection by Podosphaera 
perseae-americanae ; conidia can be produced quickly and in large amou nts (3–7 days post infection 
under disease-promoting conditions). White mycelium  can cover juvenile parts (inflorescence and 
leaves) causing damage and even necrosis. Old infec tion sites could appear as conspicuous chlorotic 
areas with net-like markings (McMillan 1976). The p est might not exhibit symptoms if it is present as 
dormant hyphae in buds of the host plant. 
o What are the known environmental conditions conduci ve to symptom expression? 
Symptomatic Podosphaera perseae-americanae  was isolated from avocado plants in Indonesia in 
September 2013 and January 2015, where mean daily t emperatures were greater than 26 o C and 
monthly rainfall was between 50 and 300 mm ("Monthl y Climatic Data for the World September 2013"  
2013; "Monthly Climatic Data for the World January 2015"  2015). Generally, powdery mildew 
symptoms can become severe in warm, humid, shaded a reas such as nurseries. Rain can wash 
conidia from plant surfaces before they germinate, thus reducing symptom expression (Zentmyer 
1953; Glawe 2008). However, powdery mildews are usu ally synchronized with host life cycles, thus 
the conditions might depend more on the etiology of  the host (Glawe 2008), such as development of 
young shoots and leaves.  
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Powdery mildews can survive as dormant hyphae in bu ds of their host (Glawe 2008). In case dormant 
Podosphaera perseae-americanae  mycelia is unknowingly imported into PEQ, young le aves and 
shoots should be inspected regularly for developing  symptoms. 
o What is the optimum season for conducting detection  testing? 
Symptoms of Podosphaera perseae-americana  were described in Indonesia which is a tropical 
country with relatively stable high humidity and te mperature. The symptoms were described in 
September and January. This suggests that summer wo uld be the optimum season for detection 
testing in New Zealand. 
5.20.11  References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Carisse, O; Bouchard, J (2010) Age-related suscepti bility of strawberry leaves and berries to infectio n 
by Podosphaera aphanis . Crop Protection 29(9): 969-978. 
Glawe, D A (2008) The powdery mildews: a review of the world's most familiar (yet poorly known) 
plant pathogens. Annu Rev Phytopathol 46: 27-51. 
Hislop, E C; Clifford, D R (1976) Eradication of ap ple powdery mildew ( Podosphaera leucotricha ) with 
dormant season sprays of surface-active agents. Annals of Applied Biology 82(3): 557-568. 
Lee, H B (2012) Molecular phylogenetic status of Ko rean strain of Podosphaera xanthii , a causal 
pathogen of powdery mildew on Japanese thistle ( Cirsium japonicum ) in Korea. Journal of 
Microbiology 50(6): 1075-1080. 
Mahaffee, W F; Thomas, C S; Turechek, W W; Ocamb, C  M; Nelson, M E; Fox, A, et al. (2003) 
Responding to an introduced pathogen: Podosphaera macularis  (Hop Powdery Mildew) in the Pacific 
Northwest. Plant Health Progress 4(1): 21.  
289 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Mburu, S; Sakong, E; Otipa, M; Ndungu, J; Njoroge, C (2014) Powdery mildew in avocado. 
https://www.cabi.org/ISC/FullTextPDF/2016/201678006 14.pdf   
McMillan, R T J (1976) Disease of avocado. In J W S auls; R L Phillips; L K Jackson (Eds.), First 
international tropical fruit short course  (pp. 66-70). Gainesville, University of Florida: U niversity of 
Florida. 
Miguel, P S B; Miguel, F B; Moreira, B C; De Olivei ra, M N V; Delvaux, J C; De Souza Freitas, F, et al . 
(2019) Diversity of the endophytic filamentous fung al leaf community at different development stages 
of eucalyptus. Journal of Forestry Research 30(3): 1093-1103. 
Monthly Climatic Data for the World January 2015 (2 015). In N O a A Administration (Ed.), (Vol. 68, 
pp. 64). 
Monthly Climatic Data for the World September 2013 (2013). In N O a A Administration (Ed.), (Vol. 66, 
pp. 60). 
MPI (2021) Facility Standard: Post Entry Quarantine for Plants . Ministry for Primary Industries, 
https://www.mpi.govt.nz/dmsdocument/11368-Post-Entr y-Quarantine-forPlants-Facilities-Standard  
Numminen, E; Laine, A-L (2020) The spread of a wild  plant pathogen is driven by the road network. 
PLOS Computational Biology 16(3): e1007703. 
NZPCN (2021) New Zealand Plant Conservation Network . https://www.nzpcn.org.nz/  Accessed June 
2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Pérez-García, A; Romero, D; Fernández-Ortuño, D; Ló pez-Ruiz, F; De Vicente, A; Torés, J A (2009) 
The powdery mildew fungus Podosphaera fusca  (synonym Podosphaera xanthii ), a constant threat to 
cucurbits. Molecular Plant Pathology 10(2): 153-160. 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX ‘match climates regional’  
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Siahaan, S A; Hidayat, I; Kramadibrata, K; Meeboon,  J; Takamatsu, S (2016) Podosphaera perseae-
americanae , a new powdery mildew species on Persea americana  (avocado) from Indonesia. 
mycoscience 57(6): 417-421. 
Takamatsu, S; Niinomi, S; Harada, M; Havrylenko, M (2010) Molecular phylogenetic analyses reveal 
a close evolutionary relationship between Podosphaera  (Erysiphales: Erysiphaceae) and its 
rosaceous hosts. Persoonia 24: 38-48. 
Zentmyer, G A (1953) Diseases of the Avocado. United States Department of Agriculture. Washington  
D.C. Yearbook of Agriculture.  
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 290 5.21  Pseudocercospora purpurea  
Pseudocercospora purpurea  is a fungal plant pathogen causing Pseudocercospor a  spot disease 
resulting in leaf, stem, and fruit spot symptoms in  Persea  spp. including avocado ( P. americana ). The 
disease is a serious pre-harvest disease affecting all cultivars of avocado in warm, humid, and rainy 
climates. 
5.21.1  Taxonomic description 
Scientific name: Pseudocercospora purpurea (Cooke) Deighton 1976  
Order/Family: Capnodiales/Mycosphaerellaceae 
Other names include: Cercospora purpurea , Cercospora/Pseudocercospora spot; black spot; leaf 
spot: avocado; spot blotch of avocado; Cercospora s pot blotch; mancha angular de la hoja del 
aguacate (Spanish). 
Taxonomic notes: A review of  the previous scientific literature relating to the fungus was recently 
undertaken by Kallideen (2020) and mentions the his toric name for the fungus, Cercospora purpurea  
Cooke (1878) (stat. anam.) Kallideen (2020) referre d to a previous taxonomic revision of Cercospora  
and allied genera, and found the fungus was renamed  Pseudocercospora purpurea . 
5.21.2  Hazard identification 
Pseudocercospora purpurea  is not known to be present in New Zealand: 
o Pseudocercospora purpurea  is not listed in PPIN (2021) 
o Pseudocercospora purpurea  is recorded as ‘recorded in error’ in Biota NZ (20 22). 
The sole NZ collection has been redetermined as an unidentified coelomycete. 
o Pseudocercospora purpurea  is a regulated pest in New Zealand, has an unwante d 
status but is not notifiable (ONZPR 2021). 
Pseudocercospora purpurea  has the potential to establish (and spread) in New  Zealand because:  
• The reported host of Pseudocercospora purpurea is avocado ( Persea americana ) and other 
Persea spp. (California Department of Food & Agriculture 2 016). 
• Pseudocercospora purpurea  is found in subtropical and tropical regions (Cali fornia Department 
of Food & Agriculture 2016), some of which have a c limate match index (CMI) ≥ 0.7 (Table 
5-21) indicating a similar climate to New Zealand ( Phillips et al. 2018).  
Pseudocercospora purpurea  has the potential to cause harm to New Zealand bec ause: 
• It causes disease symptoms on leaves, stems, and f ruit (California Department of Food & 
Agriculture 2016).  
• Avocados are an important commercial crop in New Z ealand. Export sales in 2020 (fresh and 
oil) earned NZ$122 million. Domestic sales earned N Z$ 50.6 million in 2019/20 (Plant & Food 
Research 2020).  
• Pseudocercospora purpurea  has been reported to cause significant losses (48% ) in avocado 
production by decreasing fruit quality and making f ruits unacceptable for export (Reina-
Noreña et al. 2015; Rodríguez-Polanco et al. 2020).  
Pseudocercospora purpurea  is associated with Persea americana  budwood  because: 
• Persea americana  is a commonly reported host of Pseudocercospora purpurea (EPPO 2021).   
291 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • Pseudocercospora purpurea  occurs in association with leaves, stems, and frui t (Kallideen 
2020; USDA 2021). This disease can infect previousl y uninjured leaves, young stems, and 
fruit (McMillan 1976).  
• Pseudocercospora purpurea is known to infect all commercial cultivars of avoc ado. 
Given the arguments and evidence above, Pseudocercospora purpurea  meets the criteria to be a 
hazard on Persea americana  budwood (as in the commodity description) imported  to New Zealand. 
5.21.3  Risk assessment 
Biology and epidemiology of Pseudocercospora purpur ea 
Host range 
Pseudocercospora purpurea  has a limited known range of plant hosts. All are Persea  spp., in the 
family Lauraceae, namely, P. americana  (syn. P. gratissima , avocado), P. borbonia  (redbay) , P. 
drymifolia  (Mexican avocado) and  P. palustris  (swamp bay) (California Department of Food & 
Agriculture 2016). 
Host susceptibilities differ between Persea americana  cultivars. Late maturing avocado cultivars are 
more susceptible as they have longer period during which they can be infected (Menge and Ploetz 
2003). For example, Fuerte and Ryan cultivars were found to be considerably more susceptible to P. 
purpurea  than Edranol and Hass (Darvas and Kotze 1987). Has s avocados are known to be less 
susceptible to P. purpurea  (Willis and Mavuso 2007). In Florida, Waldin, Boot h 7 & 8, Taylor, Linda, 
Lula, Nabal, Trapp and Wagner are the most suscepti ble while Collinson, Fuchsia and Pollock are 
moderately susceptible (Darvas 1982). Cultivars may  also be considered less susceptible for several 
seasons but later become severely infected after P.  purpurea becomes firmly established in trees 
(Stevens and Piper 1941). If exposed to conidia ear ly in the critical period (when the climate is wet 
and warm) then fruit (such as later maturing fruit)  have significantly more P. purpurea  spots than fruit 
only exposed later (Darvas and Kotzé 1979). Avocado  fruit exposed to natural infection early in the 
critical period (when the climate is wet and warm) develop significantly more p. purpurea  spots than 
fruit exposed later  
All commercial cultivars of P. americana  are affected (Everett and Siebert 2018). However, there has 
been studies undertaken in Westfalia, South Africa to develop new disease resistant cultivars. 
Cultivars with a natural tolerance or resistance to  P. purpurea  have been identified but none have 
succeeded to commercial production due to other cha racteristics which were not desirable (Bruwer et 
al. 2015). As different cultivars vary in their sus ceptibility to P. purpurea  in different geographical 
regions it has been suggested by Menge and Ploetz ( 2003) that there may be different physiological 
races of this pathogen. 
Geographical distribution 
Pseudocercospora purpurea  is widely spread in subtropical and tropical count ries (Table 5-21). The 
fungus is widely reported in avocado growing countr ies and is considered one of the most common 
disease problems.  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 292 Table 5-21: Geographical distribution of Pseudocerc ospora purpurea (Dann et al. 2013; CABI 
2021) and climate similarity (CMI) to New Zealand. 
Region Country  State/Province  CMI* 
Asia India Sikkim 0.6- 0.7  
Japan   0.6- 0.8  
Philippines   0.3-0.4 
Africa  Cameroon   0.4-0.5 
Congo Democratic Republic   0.5- 0.8  
Cote d'Ivoire   0.5 
Guinea   0.4-0.5 
Kenya   0.4- 0.8  
South Africa   0.5-0.9 
North America USA Florida 0.5- 0.7  
Georgia, Mississippi 0.7- 0.8  
Bermuda   Not determined 
Mexico   0.4- 0.8 
Central America & 
Caribbean Dominica   Not determined 
El Salvador   0.4-0.5 
Honduras   0.3-0.6 
Jamaica   0.5-0.6 
Nicaragua   0.4-0.5 
Panama   0.3-0.5 
Puerto Rico   0.5-0.6 
Trinidad and Tobago   0.5 
U.S. Virgin Islands   Not determined 
South America  Colombia Northern Tolima 0.3-0.8  
0.5-0.8  
Argentina   0.6- 0.9  
Bolivia   0.4- 0.8  
Brazil Sao Paulo 0.3-0.9  
0.7 
Chile   0.5 -0.9 
Guyana   0.4-0.5 
Peru   0.4- 0.8  
Venezuela   0.3- 0.7  
Oceania Palau Belau Not determined 
Australia Queensland 0.4- 0.8  
Europe Spain   0.4 -0.8  
Note: Dann et al. (2013) lists West Indies, Atherton (Ta blelands), Queensland, Australia, and Spain. CABI 
(2021) does not list Spain. 
*(Phillips et al. 2018)   
293 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Symptoms 
Pseudocercospora purpurea  can infect the leaves, stem, and fruit of Persea americana  at any time 
during  the growing season (Schoeman and Kallideen 2018). On leaves, the fungus causes small 
lesions (1-6mm) that are angular, purple-purplish b rown, and look like flecks, or spots, near the leaf  
margin (Perez-Jimenez 2008; California Department o f Food & Agriculture 2016; Kallideen 2020). The 
angular appearance of the lesions is highly diagnos tic for the disease (Marais 2004). After the 
appearance of lesions, chlorotic halos become visib le around older spots (Schoeman and Kallideen 
2018). Eventually, lesions are seen on both leaf su rfaces (Schoeman and Kallideen 2018). The 
infection may progress up the stems (Perez-Jimenez 2008). The pathogen survives on old lesions. In 
high humidity conditions, sporulation causes a grey , felty mycelium growth in the centre of lesion. 
Large areas of infection may appear as necrotic tis sue. Leaves curl, deform, and may fall of the plant  
(California Department of Food & Agriculture 2016).  On fruit stems and green twigs, lesions (2 – 10 
mm in diameter) may become dark brown to black (Sch oeman and Kallideen 2018). These infections 
may precede those on fruit by several weeks. Lesion s producing spores being present on stems long 
before the fruit (Stevens and Piper 1941). 
Reproduction and transmission  
Under high humidity and warm environmental conditio ns infection is mainly through asexual spores 
(conidia) which grow on specialised stalks called c onidiophores and develop in clusters onto the 
surface of the leaves, stems (including twigs and f ruit stems) and fruit (Schoeman and Kallideen 
2018).  
Conidia are present year-round when moisture (such as rainfall or heavy dew) and humidity is 
suitable (Kallideen 2020)  or the pathogen can overwinter as mycelium (stroma ta) in old, infected 
leaves (Stevens and Piper 1941; Marais 2004; Califo rnia Department of Food & Agriculture 2016) . 
The conidia are carried by wind, rain, insects, and  water (Menge and Ploetz 2003). Spread can also 
occur through contaminated orchard equipment and to ols (Kallideen 2020). The pathogen penetrates 
host tissue either directly (thru uninjured leaves,  stems, or fruit) or through wounds (McMillan 1976;  
California Department of Food & Agriculture 2016).  
Darvas (1982) determined the critical infection per iod for P. purpurea  on avocado fruit. The critical 
infection period is the time or latent phase which must elapse between infection and symptom 
development (Darvas 1982). During his experiment he  enclosed Fuerte fruit, on avocado trees in 
bags. Artificial inoculation of Fuerte fruit with P. purpurea was undertaken and these were then 
reisolated from spots and symptoms analysed. He als o used spore traps to determine daily spore 
numbers in the environment against weather data. Th e findings determined that in South Africa 
(which has a similar climate to New Zealand with a CMI of 0.5-0.9; Phillips et al. 2018), 
Pseudocercospora  purpurea  remains latent for 3 months (Darvas 1982; Menge an d Ploetz 2003). 
Environmental conditions for infection 
Warm, wet, and humid conditions are the environment al conditions most suited to infection. Spore 
release is highest at 18° C and declines as temperat ures increase to 25° C (Darvas 1982). No infection 
occurs below 15° C (Kallideen 2020). 
Significant numbers of spores are produced with the  onset of rainy, warm temperatures. The most 
important environmental parameter is rainfall which  has a significant influence on production of P. 
purpurea conidia. Low temperature however will supress spore  production or release despite 
substantial rainfall (Darvas and Kotzé 1979). When comparing temperature, rainfall and relative 
humidity in South Africa in October, Darvas and Kot zé (1979) found fewer conidia were seen as 
temperatures decreased from 20.8° C to 19.9° C even w ith rainfall increasing from 7.5mm to 31.3mm. 
Relative humidity and leaf wetness are not importan t in conidia release but can influence pathogen 
development (Kallideen 2020). There is a positive c orrelation of symptom development with 
increasing humidity up to at least 84% (Darvas 1982 ).  
In a laboratory setting most of the fresh P. purpurea isolates produced conidia on artificial media 
when kept continuously under near-ultra-violet ligh t (Darvas and Kotze 1987). Sporulation began ca Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 294 10 days after inoculation and a fair amount of coni dia was produced for about another 10 days, after 
which the fungus became sterile. These cultures reg ained the ability to sporulate if transferred to 
sterile, freshly cut, avocado pieces, but again onl y for a limited period (Darvas and Kotze 1987). The  
implications of this for avocado budwood may be tha t under ideal conditions conidia can continue to 
be produced and may resporulate on freshly cut avoc ado plants. 
Spread 
Host tissue is penetrated by the fungus through uni njured leaves, stems or fruit or thorough wounds 
(McMillan 1976; California Department of Food & Agr iculture 2016; Schoeman and Kallideen 2018). 
The fungus then develops small lesions which appear first on the underside o f infected leaves and 
increase abundantly to eventually cover both sides of infected leaves. The infection may progress 
along the stem and cause defoliation of the tree (P erez-Jimenez 2008). New shoot tissues are 
infected wherever this disease occurs (California D epartment of Food & Agriculture 2016) .  The 
disease can infect young stems (McMillan 1976). 
Movement of spore-infected fruit and/or plant mater ial can result in rapid spread of the disease over 
long distances to new areas (Schoeman and Kallideen  2018).  
Spores are produced and spread by nursery stock pla nts, rain and irrigation water, infected leaves, 
fruit, and insects (California Department of Food &  Agriculture 2016).  Contaminated tools, machinery 
and equipment can also spread the fungus to new sit es (Everett and Siebert 2018; Kallideen 2020). 
Spores easily detach and are wind dispersed over lo ng distances (Darvas 1982) . 
Factor s influencing symptom expression (environmental) 
Factors influencing symptom expression include: 
• Availability of conida leading to high risk of inf ection, in addition to favourable weather 
conditions for infection. 
• Lapse between infection and symptom development du e to latent period or interval. 
• Increasing length of exposure time increases sever ity of symptoms. Susceptibility to P. 
purpurea  differs between different cultivars (Kallideen 202 0). Avocado exposed earlier in the 
season have more infection than those later in the season (Schoeman and Kallideen 2018). 
Late maturing cultivars are more susceptible due to  longer time they can be infected (Menge 
and Ploetz 2003).  
• As lesions age the infectious tissue decreases (Ev erett and Siebert 2018; Rodríguez-Polanco 
et al. 2020).   
• The pathogen can be asymptomatic and overwinter as  mycelium in old, infected leaves or 
shoots (Mavuso et al. 2015). 
5.21.4  Likelihood of entry 
Pseudocercospora purpurea is a common pathogen of a vocado with a wide distribution in most 
regions around the world and is considered one of t he most serious pre-harvest diseases in many 
avocado growing countries (Darvas 1977). 
The disease affects Persea  spp., in the family Lauraceae, namely, P. americana  (syn. P. gratissima , 
avocado), along with all cultivars of avocado (Cali fornia Department of Food & Agriculture 2016).  
Symptoms are visible on leaves, fruit, and stems du ring all growth stages (Schoeman and Kallideen 
2018) and is as a result associated with budwood.  In South Africa, the pathogen is latent on Fuerte 
avocados for at least 3 months after penetration (D arvas and Kotzé 1979). Therefore, inspection by 
the NPPO prior to export and on arrival might not d etect non-visible infection. 
Routine disinfection of the imported budwood on arr ival in PEQ with 1% sodium hypochlorite for 2 
minutes would reduce surface spore populations. Env ironmental conditions (assuming warm 
temperature and high humidity are met) within the P EQ facility are likely to cause symptom  
295 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand expression.  Moist conditions such as that provided  by misting could provide optimal conditions given 
that rainfall is considered the most important fact or in symptom expression in the field. 
Although P. purpurea can be latent for 3 months on imported budwood, given the length of time in the 
PEQ facility (minimum of 12 months) the pathogen wi ll eventually be symptomatic and detectable by 
PEQ inspection. 
Given the arguments and evidence above, that is:  
• Wide distribution in many regions of the world whe re it is considered one of the most serious 
pre-harvest diseases in many avocado growing countr ies. 
• Infection is associated with budwood. 
• pathogen is latent for at least 3 months after pen etration. 
• Inspection by NPPO prior to export and on arrival will not detect non-visible infection. 
However, disinfection will reduce surface spore pop ulations on imported budwood on arrival 
in PEQ. Optimisation of environmental conditions (t emperature, humidity, misting) within the 
PEQ facility will maximise symptom expression on bu dwood. 
• Persea nursery stock must be held in an approved Level 3A greenhouse facility and grown for 
12 months providing enough time for any P. purpurea  infection to become symptomatic and 
detected by inspection. 
the likelihood of P. purpurea  entering New Zealand associated with P. americana  budwood is 
considered to be negligible, with low uncertainty. 
5.21.5  Overall level of assessed risk to New Zealand 
Based on the assessment of likelihood above, that:  
• the likelihood of P. purpurea  entering New Zealand associated with Persea americana  
budwood (as described in the commodity description,  and taking into account the proposed 
growing period of active growth with a minimum of t hree distinct phenological growing events 
referred to as ‘shoot flush’ in 3A PEQ) is consider ed to be negligible with very low uncertainty;  
• therefore, continuing the assessment was considere d unnecessary; and 
the overall level of risk to New Zealand from P. purpurea  on imported Persea americana budwood (as 
in the commodity description) is considered to be n egligible, with moderate uncertainty.  
5.21.6  Management considerations 
Pseudocercospora purpurea  can infect leaves, stems, and fruits (Benson 2018) . The pathogen can 
remain dormant (as mycelium (stromata) in old, infe cted leaves or shoots for about three months 
following penetration (Kallideen 2020).  Once optimal environmental conditions (warm (over 1 8 ° C) , 
humid (up to 84%), and wet climate) are available c onidia will be released and initiate infection 
(Stevens and Piper 1941; California Department of F ood & Agriculture 2016; Kallideen 2020). The 
most important environmental parameter is moisture which has a significant influence on production 
of P. purpurea conidia. Upon landing on the surface of a plant host, moistu re is required for conidia to 
germinate and penetrate the host (Darvas 1982). Onc e infected under optimal environmental 
conditions and symptomatic the fungus reproduces ab undantly. Leaves become the primary source of 
continuing disease (Stevens and Piper 1941). 
The latent period appears to be longer than 3 month s in South Africa on Fuerte avocados according 
to Darvas and Kotzé (1979). However, no study menti ons the maximum period of latency. Darvas and 
Kotzé (1979) did however record only a few conidia were seen in late October even with substantial 
rain due to the supressing effects of low temperatu res on spore production. Spore traps recorded 
significant numbers of conidia beginning in Novembe r. Darvas (1982) recorded no conidia in April. 
Given South Africa has a similar climate to New Zea land, the period in PEQ for 12 months will allow 
time to cover any latency period which for this pat hogen is around 3 months. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 296 The fungus is isolated from fresh symptomatic tissu e and inoculated on PDA (potato dextrose agar) 
(Kallideen 2020). The fungus is difficult to isolat e initially, but once isolated it grows readily on 
ordinary nutrient media, producing tufted grey leat hery growth which later becomes brown or blackish-
brown (Marais 2004; Perez-Jimenez 2008). 
As the lesions age the infectious tissue decreases making spores more difficult to isolate and 
eventually no longer produces spores (Rodríguez-Pol anco et al. 2020). It can be difficult to isolate 
from older lesions as other fungi can outcompete P. purpurea  such as Colletotrichum gloesporioides  
which grows faster (Kallideen 2020). Surface disinf ection of plant material is crucial to eliminating 
other fungi (Menge and Ploetz 2003). 
In a laboratory setting, most of the fresh P. purpurea isolates produced conidia on artificial media 
when kept continuously under near-ultra-violet ligh t. Sporulation begins 10 days after inoculation and  
a fair amount of conidia was produced for about ano ther 10 days, after which the fungus became 
sterile. These cultures regained the ability to spo rulate if transferred to sterile, freshly cut, avoc ado 
pieces, but again only for a limited period (Darvas  and Kotze 1987). 
5.21.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? Wha t is the optimum season for 
conducting detection testing?  
Symptoms are visible on leaves, fruit, and stems du ring all growth stages (Rodríguez-Polanco et al. 
2020). New infections produce lesions which become infectious and results in further lesions. As the 
lesions age the infectious tissue decreases and no longer produces spores (Rodríguez-Polanco et al. 
2020). Specifically, the disease appears on leaves as individual spots.  Small lesions initially (1-6m m) 
form, are angular in shape, purple-purplish brown i n colour, and appear as flecks, or spots, near the 
leaf margin. Chlorotic halos are visible on both le af surfaces following the appearance of the lesions .  
In high humidity conditions sporulation causes a gr ey, felty mycelium growth in the centre of the 
lesions. Lesions may coalesce, forming areas of inf ection that may appear as brown coloured necrotic 
tissue and may form irregular patches. Leaves curl,  deform, and may fall off the plant (Darvas 1982; 
California Department of Food & Agriculture 2016). 
Dark brown to black lesion of 2-10mm may appear on stems and fruit pedicels of the plant (Darvas 
1982). Cracks are formed only in older spots and do n’t always develop in lenticels (or the surface of 
stems where gas is exchanged between the atmosphere  and underlying tissue) (fruit stems).  
o What are the known environmental conditions conduci ve to symptom expression?  
Spore release is highest at 18° C (no infection will  occur below 15° C) (Darvas 1982; Everett and 
Siebert 2018). Spore release declines as temperatur es increases to 25° C (Darvas 1982; Everett and 
Siebert 2018). Spore abundance exposes avocados to a greater chance of infection and when this 
occurs early in the critical (wet and warm) period this can lead to significantly more P. purpurea  spots 
(Darvas and Kotzé 1979). Moist conditions are condu cive to symptom expression (Darvas 1982; 
Kallideen 2020). There is a positive correlation of  symptom development with increasing humidity up 
to at least 84% (Darvas 1982). Relative humidity an d leaf wetness are not important in conidia release  
but can influence pathogen development (Kallideen 2 020). Outside the PEQ environment the most 
important environmental parameter is moisture which  has a significant influence on production of P. 
purpurea conidia. Therefore, within the PEQ facility, moistu re will be the most significant factor for 
creating the optimal environment for symptom expres sion. Low temperature (below 18° C) however 
will supress spore production or spore release desp ite substantial moisture (Darvas and Kotzé 1979). 
Significant numbers of spores are produced with the  onset of rainy, warm temperatures.  
o What are the limitations to taking samples for pote ntial testing?   
297 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Detection would have to include symptomatic tissue.  As the pathogen can be latent for at least three 
months after penetration (Darvas and Kotzé 1979), t he best time for detection testing is after three 
months in PEQ. The pathogen is likely to spread to further plant parts when the plants break 
dormancy and produce new shoots and leaves. New sho ot tissue is infected wherever the disease 
occurs (California Department of Food & Agriculture  2016). Samples must be isolated from fresh 
young lesions and the surface disinfected to elimin ate other contaminating fungi that can outgrow P. 
purpurea  (Menge and Ploetz 2003).  
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections? 
Lesions on leaves produce the most conidia and ther efore this plant part constitutes the main source 
of inoculum for primary and secondary infections an d the continuation of the disease from one season 
to another (Benson 2018; Kallideen 2020).   
5.21.8  References 
Benson, I (2018) Evaluating the efficiency thiobendazole 50% 500 SC in the control of Colletotrichum 
gloeispoiroides on harvested avocado.  Degree in bachelor of Science in Agriculture. thes is; University 
of Nairobi, (A22/2198/2015) 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Bruwer, A T; Mhlophe, S D; Kohne, J S; Kremer-Kohne , S; Fernandez, C (2015) 30 years of cultivar 
research at Westfalia technological services.  In A  Proceedings (ed) VIII Congresso mundial de la 
palta . Lima, Peru;  pp. 104-108. 
CABI (2021) Pseudocercospora purpurea . [Distribution map].  (Publication no. 
10.1079/DMPD/20083091293).  
California Department of Food & Agriculture (2016) Pseudocercospora purpurea  (Cooke) Deighton 
1976. In C D o F A (CDFA) (Ed.), Fungal, plant pathogens, ratings . 
Dann, E; Ploetz, R; Coates, L; Pegg, K (2013) Folia r, fruit and soliborne diseases. In B Schaffer; B 
Wolstenholme; A Whiley (eds) The avocado: botany, production and uses. 2nd ed. CABI: London, 
UK. 
Darvas, J (1977) Cercospora spot. In South African Avocado Growers' Association Proceedi ngs of the 
Technical Committee.  (Vol. 1, pp. 3-6). 
Darvas, J (1982) Etiology and control of some fruit diseases of avoc ado (Persea americana Mill) at 
Westfalia Estate.  thesis; University of Pretoria, South Africa., Sou th Africa. Retrieved from 
http://www.avocadosource.com/papers/SouthAfrica_Pap ers/DarvasJozsef1982/THESIS_JOE%20DA 
RVAS_TITLE%20PAGE.pdf   
Darvas, J; Kotze, J (1987) Avocado fruit diseases a nd their control in South Africa. South African 
Avocado Growers' Association Yearbook 10: 117-119. 
Darvas, J; Kotzé, J (1979) Cercospora spot of avoca dos. South African Avocado Growers Association 
Research Report for 1979. 3: 38-39. 
EPPO (2021) Pseudocercospor purpurea  (CERCPU). https://gd.eppo.int/taxon/CERCPU   
Everett, K R; Siebert, B (2018) Exotic plant diseas e threats to the New Zealand avocado industry and 
climatic suitability: a review. New Zealand Plant Protection 71: 25-38. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 298 Kallideen, R (2020) A relook at the epidemiology of Cerospora spot on a vocado in South Africa.  
thesis; KwaZulu-Natal University, Retrieved from 
https://researchspace.ukzn.ac.za/xmlui/handle/10413 /18774   
Marais, L J (2004) Avocado diseases of major import ance worldwide and their management. In S 
Naqui (ed) Diseases of fruits and vegetables.  Kluwer Academic Publishers: Netherlands. 
Mavuso, Z S; Willis, A; van Niekerk, J M (2015) Cha llenges of growing avocados in subtropical South 
Africa.  In A Proceedings (ed) VIII COngreso mundial de la palta . Lima, Peru;  pp. 170-173. 
McMillan, R T J (1976) Disease of avocado. In J W S auls; R L Phillips; L K Jackson (Eds.), First 
International Tropical Fruit Short Course  (pp. 66-70). Gainesville: Fruit Crops Dept., Flori da 
Cooperative Extension Service. Institute of Food an d Agricultural Sciences, University of Florida: 
University of Florida. 
Menge, J A; Ploetz, R C (2003) Diseases of avocado.  In R C Ploetz (ed) Diseases of tropical fruit 
crops.  CABI Publishing: Tropical Research and Education C enter. University of Florida. 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Perez-Jimenez, R M (2008) Significant avocado disea ses caused by fungi and oomycetes. The 
European Journal of Plant Science and Biotechnology  2: 1-24. 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Reina-Noreña, J; Mayorga-Cobos, M J; Caldas-Herrera , S J; Rodríguez-Valenzuela, J; Varón-Devia, 
E H (2015) The spot problem in avocado ( Persea Americana  Mill.) plantations of northern Tolima, 
Colombia. Ciencia y Tecnología Agropecuaria 16(2): 265-278. 
Rodríguez-Polanco, E; Reina-Noreña, J A; Tamayo-Mol ano, P J; Rodríguez-Polanco, L A; Varón-
Devia, E H (2020) Validation of black spot [ Pseudocercospora purpurea  (Cooke) Deighton] 
management strategies in avocado crops in northern Tolima (Colombia). Revista Colombiana de 
Ciencias Hortícolas 14(2): 178-191. 
Schoeman, M H; Kallideen, R (2018) Cercospora spot on avocado-a preliminary report on the relook 
at the epidemiology of the pathogen  (Vol. 41). Agricultural Research Council-Tropical and Subtropical 
Crops. 
Stevens, H E; Piper, R B (1941) Avocado diseases in  Florida. Circular. United States Department of 
Agriculture (582): 46-pp. 
USDA (2021) U.S. National Fungus Collections. In. U .S Department of Agriculture.: Agricultural 
Research Service. 
Willis, A; Mavuso, Z (2007) Evaluation of  alternat ive fungicides for control of Cercospora spot on 
'Fuerte'. In Proceeding VI World Avocado Congress . Viña Del Mar, Chile. 
  
299 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.22  Pseudoidium perseae-americanae  (powdery mildew of avocado) 
Pseudoidium perseae-americanae is a fungus that causes powdery mildew on the leave s, buds and 
herbaceous stems of Persea americana  (avocado) plants.   
5.22.1  Taxonomic description 
Scientific name: Pseudoidium persea-americanae  (Liberato & R.W. Barreto) Liberato & R.W. Barreto 
2012 
Order/Family: Erysiphales, Erysiphaceae  
Other names include : Oidium perseae-americanae  Liberato & R.W. Barreto 2006 
Taxonomic notes:  There have been occasional records of Pseudoidium spp. causing powdery 
mildew on avocado plants in the literature but Pseudoidium perseae-americanae  is the first to be 
described to species level (Liberato and Barreto 20 06). In some records, there is a degree of 
uncertainty about the identity of the causative age nt of powdery mildew on avocado plants because it 
is referred to only by the common name ‘powdery mil dew’ or only described to the genus level, as 
Oidium  species. However, the literature suggests that Pseudoidium perseae-americanae is the most 
prevalent cause of powdery mildew in avocado as the re are very few records of powdery mildew 
being caused by other species, such as Podosphaeria persea-americanae . Podosphaera perseae-
americanae  is distinguishable from Pseudoidium persea-americanae  by morphological 
characteristics, where Podosphaera  produces conidia (asexual spores) in chains (caten ate-type), and 
Pseudoidium  (syn. Oidium ) produces non-catenate conidia (Siahaan et al., 20 16).  
The USDA, Species Fungorum, and much of the recent literature use Pseudoidium persea-
americanae  as the preferred name, and regard Oidium persea-americanae  to be an obsolete name. 
5.22.2  Hazard identification 
Pseudoidium perseae-americanae  is not known to be present in New Zealand: 
• it is not listed in either Biota NZ (2022) or PPIN  (2021), 
• the regulatory status of P. perseae-americanae  has not been assessed (ONZPR 2021). 
Pseudoidium perseae-americanae  has the potential to establish (and spread) in New  Zealand 
because: 
• avocado is the only recorded host plant (Farr and Rossman 2021), and it is grown 
commercially and domestically in northern parts of New Zealand (Plant & Food Research 
2019). 
Pseudoidium perseae-americanae  has the potential to cause harm to New Zealand bec ause: 
• it is a minor disease problem on avocado plants un der prolonged warm and humid conditions 
with low rainfall (Stevens and Piper 1941a; Zentmye r 1953; McMillan 1976). Disease 
promoting conditions may occasionally be met in New  Zealand’s avocado growing regions, 
and frequently met in protected environments such a s nurseries (Chappell 2013c, 2013b; MPI 
2021b). 
Pseudoidium perseae-americanae  is associated with avocado budwood because: 
• avocado is the only known host plant of P. perseae-americanae  (Liberato and Barreto 2006), Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 300 • Pseudoidium perseae-americanae  colonises the epidermis of susceptible host plant tissues 
(leaves, herbaceous stems, buds, shoots and inflore scence) and overwinter on hosts as 
dormant mycelia (Plantwise 2015), 
Given the arguments and evidence above, P. perseae-americanae  meets the criteria to be a hazard 
on avocado budwood (as in the commodity description ) imported to New Zealand. 
5.22.3  Risk assessment 
 Biology and epidemiology of Pseudoidium perseae-am ericanae 
Fungi in the order Erysiphales are commonly referre d to as powdery mildews (Glawe 2008). They 
colonise the epidermis of susceptible host plant ti ssues (leaves, herbaceous stems, buds, shoots and 
inflorescence) (Plantwise 2015) and obtain nutrient s via haustoria (feeding organs) that grow into the  
epidermal cells of the plant organs (Agrios 2005).  
Host range  
Avocado is the only recorded host of  P. perseae-americanae (Farr and Rossman 2021). It is common 
for species that cause powdery mildews to be host s pecific (Liberato and Barreto 2006). 
Distribution  
The recorded distribution of P. perseae-americanae  and climate similarity with New Zealand is 
provided in Table 5-22. 
Table 5-22. The geographic distribution of Pseudoidium perseae-americanae . 
Continent/Region Country (CMI range) (Phillips et al. 2018; Farr and Rossman 2021). CMI* 
Africa  Kenya (0.4-0.8), Togo (0.4-0.5), Uganda (0. 5-0.8), Guinea (0.3-0.5) 0.3-0.8 
Asia  Israel (0.6-0.7) 0.6-0.7 
North, Central and 
South America Barbados, Bermuda, Brazil (0.3-0.9), Costa Rica (0. 3-0.6), Cuba (0.5), Honduras 
(0.3-0.6), Panama (0.3-0.5), Peru (0.4-0.8), United  States of America (0.5-0.8), 
Venezuela (0.4-0.8), West Indies (0.4-0.7). 0.3-0.9 
Oceania  New Caledonia (0.6-0.7) 0.6-0.7 
* Climate Match Index (CMI) with all of New Zealand  (Phillips et al. 2018) 
Symptoms  
Young flushes including leaves, inflorescence and b uds are most susceptible to infection (Plantwise 
2015). Dark green to purplish-brown discolorations develop on the upper surface of leaves along the 
midribs. Leaves may be distorted and curled. These discoloured infection sites produce abundant 
conidia that appear as characteristic white-grey po wder on the underside of the leaves (Zentmyer 
1953). Conidia are produced quickly (3–7 days post infection under disease-promoting conditions) 
and in large amounts. White mycelium can cover juve nile parts (inflorescence and leaves) causing 
damage and even necrosis. Old infection sites appea r as conspicuous chlorotic areas with net-like 
markings (McMillan 1976).  
Optimal conditions for growth and symptom developme nt  
Pseudoidium perseae-americanae  can become severe in humid, damp, shaded areas, es pecially 
nurseries. Rain can prevent spread because it washe s conidia from plant surfaces before they 
germinate (Stevens and Piper 1941a; Zentmyer 1984; Plantwise 2015).  
301 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Reproduction and transmission  
The complete life cycle of P. perseae-americanae may involve an asexual stage as well as a sexual 
stage (Glawe 2008). During asexual reproduction, co nidia (asexual spores) are produced on the host. 
The conidia have a white, powdery appearance, and t he conidia production stage is the state that is 
referred to as ‘powdery mildew’. Conidia are produc ed in large amounts, within a short space of time 
(3–7 days post infection under disease-promoting co nditions) and therefore can cause rapid spread of 
the disease. They are airborne and mostly transmitt ed by wind, but also by human activity on people 
(clothing, hands), on equipment (pruning tools, mec hanical harvesters or hedgers) or on vehicles 
(Agrios 2005; Business Queensland 2019). The conidi a of Pseudoidium (Oidium) spp. do not require 
free water on plant surfaces to initiate infection (Agrios 2005). Powdery mildews can overwinter as 
dormant asexual mycelia in buds of host plants or a s sexual ascospores independent of a host 
(Glawe 2008). The teleomorph (sexual reproductive s tage) of P. perseae-americanae has not been 
observed (Liberato and Barreto 2006). 
5.22.4   Likelihood of entry 
There is potential for P. perseae-americanae to be imported into post-entry quarantine on avocad o 
budwood, in which case it would be highly likely to  produce visible symptoms in PEQ: 
• Pseudoidium perseae-americanae has a tropical/subtropical distribution and is repo rted from 
reported from 17 countries in 5 continents (Table 5 -22), 
• it can be associated with leafless avocado budwood  because it is known to infect buds and 
herbaceous stems of avocado plants (Zentmyer 1953; McMillan 1976; Plantwise 2015),  
• there is a low likelihood that severely infected p lants would be used to produce budwood 
material. However, trees that were only mildly infe cted can appear healthy but harbour 
mycelium in dormant buds (Glawe 2008). Therefore, d uring times of mild disease infection, 
there is the potential for some contaminated materi al to be used for leafless budwood, 
• budwood/leafless cuttings are dipped in 1% sodium hypochlorite for 2 minutes upon entry into 
the quarantine facility, which is likely to kill su rface infections, but may not penetrate into buds 
where dormant mycelium has been shown to overwinter  (Glawe 2008),  
• Pseudoidium perseae-americanae causes disease symptoms under warm and humid 
conditions and especially in nurseries (Zentmyer 19 53; McMillan 1976; Plantwise 2015), 
suggesting that conditions in PEQ are likely to pro mote the expression of symptoms, 
Therefore, the likelihood of infected plants being released from PEQ  is considered to be negligible. 
It is likely that P. perseae-americanae would produce characteristic powdery conidia on inf ected 
plants in PEQ, which may not be contained in level 3A:  
• all plants must be inspected at least twice per we ek during periods of active growth and once 
per week during dormancy (MPI 2021a). Pseudoidium perseae-americanae could produce 
inoculum between inspections because conidia are pr oduced in large amounts, within a short 
space of time (3–7 days post infection under diseas e-promoting conditions) (Glawe 2008),  
• airborne conidia may escape from level 3A faciliti es because the mesh screen over the vents 
is required to have a maximum opening size of 0.04 mm 2 (MPI 2021a), which may be too 
large to contain the conidia of P. perseae-americanae , which are 0.027-0.04 × 0.01-0.02 mm 
(Liberato and Barreto 2006),  
• other measures in place within level 3A glasshouse s (including protective clothing and hand 
washing) (MPI 2021a) would reduce the likelihood of  any spores/conidia leaving the 
glasshouse, to a very low level, 
Given the arguments and evidence above, that is:  
• Pseudoidium perseae-americanae has a reasonably wide geographical distribution but  is 
mostly limited to tropical/subtropical climates, 
• It could be unknowingly imported into PEQ on leafl ess avocado budwood because mycelium 
can overwinter on dormant buds,  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 302 • it is likely that P. perseae-americanae would produce symptoms on infected plants under 
suitable conditions and be detected in PEQ. Therefo re, the likelihood of infected plants being 
released from PEQ  is considered to be negligible, but,  
• airborne conidia may not be contained in level 3A PEQ because they could be produced 
between inspections and are small enough to fit tho ugh the vents. However, the amount of 
conidia likely to escape is small because only a po rtion of spores would escape through the 
vents and plant inspections are likely to detect th e fungus at early stages of sporulation,  
the likelihood of P. perseae-americanae  entering New Zealand associated with avocado budwo od is 
considered to be very low, with low uncertainty.  
5.22.5   Likelihood of exposure 
Since there is a negligible risk of avocado plants infected with P. perseae-americanae  at the time of 
their release from Post Entry Quarantine, this asse ssment is made on the basis that airborne spores  
of P. perseae-americanae  have escaped PEQ and entered New Zealand undetecte d. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. If suitable hosts were  present near the post-entry quarantine facilities,  for 
example, if the facility was located near avocado o rchards, private gardens with avocado trees 
orother native or naturalised plants from the Laura ceae family, the fungus could be exposed to 
suitable host material. However, the amount of inoc ulum likely to escape is considered to be small, 
and the conidia would have to land on a suitable ho st under suitable conditions to germinate and 
cause disease. Due to limited information related t o P. perseae-americanae  the uncertainty 
associated with this assessment is high. 
Given the arguments and evidence above, the likelih ood of exposure of P. perseae-americanae  in 
New Zealand after escaping from Level 3A PEQ is con sidered very low, with low uncertainty. 
5.22.6   Likelihood of establishment 
This assessment is made on the basis that P. perseae-americanae  has been successfully exposed to 
a suitable host plant in the New Zealand environmen t. 
• Pseudoidium perseae-americanae  is mostly distributed in tropical/subtropical regi ons that are 
located in the tropical rain belt, have a rainy and  dry season, and do not share a high level of 
climatic similarity to the whole of New Zealand (Ta ble 5-22) (Phillips et al. 2018).  
• Powdery mildew of avocado is most prevalent during  the dry season because rainfall can 
wash conidia off the leaves before they germinate ( Crane et al. 2019). It can become severe 
in warm, humid and protected areas, especially in n urseries (Stevens and Piper 1941b; 
Zentmyer 1984). 
• Northern parts of the North Island (where most of the commercial avocado is grown (Plant & 
Food Research 2019)) experience high humidity and w arm temperatures during the summer, 
which are likely to be suitable for the establishme nt of P. perseae-americanae. However, 
these regions also receive abundant rainfall within  the range of 1000-2200mm median annual 
total rainfall, which may limit the ability of P. perseae-americanae  to establish and spread 
(Chappell 2013c, 2013a). 
• There is limited information in the literature reg arding optimal temperatures for P. perseae-
americanae,  but it is reported to grow in mild temperatures (<  24° C) (Plantwise 2015). The 
optimal temperature for conidia germination of othe r Oidium  species that cause powdery 
mildew is between 18-25° C (Morrison 1964; Sastra-Hi dayat 1992).  
• The conidia of Pseudoidium (Oidium) spp. do not require free water on plant surfaces to  
initiate infection (Agrios 2005).  
• Avocado is the only reported host of P. perseae-americanae so it’s establishment is highly 
likely to be limited to avocado growing regions due  to host availability and climate, 
• Powdery mildew can overwinter as dormant asexual m ycelia in buds of host plants or as 
sexual ascospores independent of a host (Glawe 2008 ), however, the teleomorph (sexual  
303 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand reproductive stage) of P. perseae-americanae has not been observed (Liberato and Barreto 
2006) suggesting that it is most likely to reproduc e asexually in New Zealand. 
Given the arguments and evidence above, that is: 
• Pseudoidium perseae-americanae  is mostly distributed in tropical/subtropical clim ates, 
indicating that the northern avocado growing region s of New Zealand may have suitable 
conditions for establishment (warm and humid), espe cially during summer,  
• the pathogen could overwinter as dormant asexual m ycelia in buds,   
• Pseudoidium (Oidium)  spp. can spread easily because they produce large amounts of 
airborne conidia within a short period of time (3–7  days) and do not require free water on 
plant surfaces to initiate infection, 
the likelihood of P. perseae-americanae  establishing in New Zealand is considered moderate , with 
moderate uncertainty. 
5.22.7   Impacts in New Zealand 
Airborne conidia of P. perseae-americanae  are produced in large amounts, within a short spac e of 
time (3–7 days post infection under disease-promoti ng conditions) and can cause rapid spread of the 
disease. Conidial dispersal appears to occur mostly  over short distances, but they can be transmitted 
long distances by wind (Glawe 2008) and human activ ity on people (clothing, hands), on equipment 
(pruning tools, mechanical harvesters or hedgers) o r on vehicles (Agrios 2005; Business Queensland 
2019). Rain can prevent spread because it washes co nidia from plant surfaces before they germinate 
(Stevens and Piper 1941b; Zentmyer 1984; Plantwise 2015). 
Avocado is the only reported host of P. perseae-americanae so it’s spread is highly likely to be limited 
to avocado growing regions due to host availability .  
Economic impacts 
In New Zealand, the severity of disease, spread and  consequently the economic impact is highly likely 
to be dependent on host availability and climatic c onditions.  
• Avocado is the only known host of P. perseae-americanae  (Farr and Rossman 2021) and any 
economic impacts are highly likely to be limited to  the avocado industry. 
• Powdery mildew caused by P. perseae-americanae  is typically a minor disease problem that 
does not require control measures.  
• It can become severe in warm, humid and protected areas, such as nurseries (Stevens and 
Piper 1941b; Zentmyer 1984), and impacts may be exa ggerated in these environments. 
• Infections can damage young flushes including leav es, inflorescence and buds (McMillan 
1976; Plantwise 2015), which can weaken the host pl ant, reduce plant growth and fruit yield. 
• If favourable conditions persist and the disease b ecomes severe, fungicide sprays such as 
wettable sulphur can be effective at controlling th e fungus (McMillan 1976). 
• The impact of P. perseae-americanae  on avocado may be mitigated by fungicide sprays us ed 
to control other fungal disease that already occur on avocado plants in New Zealand, such as 
Colletotrichum spp., Botryosphaeria dothidea , Neofusicoccum parvum  and Phomopsis  sp. 
(Everett and Siebert 2018). 
• Pseudoidium perseae-americanae is unlikely to have serious impacts on trade becaus e it has 
not been reported to infect mature fruit and can be  effectively managed by fungicide 
treatments (McMillan 1976). 
Given the arguments and evidence above, that is: 
• Pseudoidium perseae-americanae  is host specific to avocado and is only reported t o cause 
disease in countries with tropical/subtropical clim ates. It is usually a minor disease problem 
but can become severe in prolonged warm, humid and shaded conditions, especially in 
nurseries, Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 304 • Pseudoidium perseae-americanae has not been reported to be associated with fruit a nd can 
be effectively managed by fungicide treatments, sug gesting that it is unlikely to have major 
disease or trade impacts, 
the economic impact of P. perseae-americanae  to New Zealand is considered to be low, with low 
uncertainty. 
Environmental impacts 
Avocado is the only known host of P. perseae-americanae  (Farr and Rossman 2021) and it is 
common for powdery mildews to be host specific (Lib erato and Barreto 2006), indicating that it is 
unlikely that there would be any impacts to native flora in New Zealand. 
Given the arguments and evidence above, the impact on the environment from the establishment of 
P. perseae-americanae  in New Zealand is considered to be negligible, wit h low uncertainty. 
Human health impacts 
Pseudoidium perseae-americanae  is unlikely to cause unwanted impacts on human hea lth. No 
evidence of such impacts has been found. 
Given the evidence above, the health impact of P. perseae-americanae  to New Zealand is considered 
to be negligible with low uncertainty. 
Sociocultural impacts 
Pseudoidium perseae-americanae is reported as a minor disease problem on avocado ( McMillan 
1976), indicating that it is unlikely to cause sign ificant sociocultural impacts in New Zealand. 
Given the arguments and evidence above, the sociocu ltural impact of P. perseae-americanae  to 
New Zealand is considered to be negligible, with lo w uncertainty. 
Overall impact to New Zealand 
The overall impact of P. perseae-americanae  on the New Zealand economy, environment, health an d 
society is considered to be low, with low uncertain ty.  
5.22.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is very low with low uncer tainty, 
• assuming entry, the likelihood of exposure is very  low, with low uncertainty, 
• assuming successful exposure, the likelihood of es tablishment is moderate with moderate 
uncertainty,  
• the impacts on the New Zealand economy, environmen t, health and society are low with low 
uncertainty, 
the overall level of assessed risk to New Zealand f rom P. perseae-americanae  on imported avocado  
budwood (as in the commodity description) is consid ered to be very low, with low uncertainty. 
5.22.9  Management considerations 
Pseudoidium perseae-americanae infects young flushes including leaves, inflorescen ce and buds 
(Plantwise 2015), resulting in dark discolorations,  leaf distortions and the production of characteris tic 
white-grey powder conidia on the surface of infecte d tissue (Zentmyer 1953). Airborne conidia are 
produced quickly and in large amounts (3–7 days pos t infection under disease-promoting conditions), 
allowing the fungus to spread widely and rapidly.  
305 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Powdery mildew symptoms can become severe in warm ( < 24° C), humid, damp, shaded areas, 
especially in nurseries. Rain/water can wash conidi a from plant surfaces before they germinate 
(Stevens and Piper 1941a; Zentmyer 1984; Plantwise 2015). The optimal temperature for conidia 
production of Pseudoidium (Oidium)  spp. is between 18-25° C (Morrison 1964; Sastra-Hid ayat 1992), 
suggesting that it could grow and spread in summer in New Zealand. 
Powdery mildews can overwinter as dormant asexual m ycelia in buds of healthy looking host plants 
(Glawe 2008). In case P. perseae-americanae  is unknowingly imported into PEQ, plants should be  
inspected regularly for symptoms, as airborne conid ia are produced rapidly and in large amounts 
(Zentmyer 1953; McMillan 1976), and may not be cont ained in level 3A PEQ due to their small size 
(Liberato and Barreto 2006; MPI 2021a). 
Protective and eradicant fungicide treatments are e ffective against powdery mildew, although the 
fungus’ development of resistance to fungicides is a growing concern. Rotation of different fungicides  
is recommended to slow the development of resistanc e. Protective fungicides must be applied to 
healthy tissues before infection takes place, and i nclude tebuconazole, cyprodinil/fludioxonil, 
boscalid/pyraclostrobin, fluoxastrobin, wettable su lfur, myclobutanil, azoxystrobin, triadimefon, 
thiophanate-methyl, propiconazole, Reynoutria sacha linensis and potassium bicarbonate. Eradicant 
fungicides are used to treat existing infections, a nd include lime sulfur 28%, neem oil, piperalin, st ylet 
oil and tebuconazole (Koike et al. 2020). 
5.22.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Young flushes including leaves, inflorescence and b uds are most susceptible to infection (Plantwise 
2015). Dark green to purplish-brown discolorations develop on the upper surface of leaves along the 
midribs. Leaves may be distorted and curled. Infect ion sites produce abundant conidia which appear 
as characteristic white-grey powder on the undersid e of the leaves (Zentmyer 1953). Conidia are 
produced quickly and in large amounts (3–7 days pos t infection under disease-promoting conditions). 
White mycelium can cover juvenile parts (infloresce nce and leaves) causing damage and even 
necrosis. Old infection sites appear as conspicuous  chlorotic areas with net-like markings (McMillan 
1976).  
o What are the known environmental conditions conduci ve to symptom expression? 
Powdery mildew symptoms can become severe in warm ( < 24° C), humid, damp, shaded areas, 
especially in nurseries. Rain/water can wash conidi a from plant surfaces before they germinate 
(Stevens and Piper 1941a; Zentmyer 1984; Plantwise 2015). There is limited information in the 
literature regarding the optimal temperature for P. perseae-americanae , but the optimal temperature 
for conidia production of other Pseudoidium (Oidium) spp. is between 18-25° C (Morrison 1964; 
Sastra-Hidayat 1992). 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Powdery mildew overwinters as dormant asexual mycel ia in buds of healthy looking host plants 
(Glawe 2008). In case dormant P. perseae-americanae  mycelia is unknowingly imported into PEQ, 
plants should be inspected regularly for symptoms, as airborne conidia can be produced rapidly and 
in large amounts under disease promoting conditions  (Zentmyer 1953; McMillan 1976), and may not 
be contained in level 3A PEQ due to their small siz e (Liberato and Barreto 2006; MPI 2021a) 
o What is the optimum season for conducting detection  testing? Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 306 Pseudoidium perseae-americanae infections begin in spring when conditions are warm  (< 24° C) and 
humid (Plantwise 2015).  In its natural geographical distribution (tropical/ subtropical climates) (Farr 
and Rossman 2021) it is most prevalent in the dry s eason. This suggests that summer would be the 
optimum season for detection testing in New Zealand .  
5.22.11  References 
Agrios, G N (2005) Plant diseases caused by prokary otes: bacteria and mollicutes. In G N Agrios (ed) 
Plant Pathology. 5 ed. Academic Press: San Diego. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Business Queensland (2019) Citrus powdery mildew. 
https://www.business.qld.gov.au/industries/farms-fi shing-forestry/agriculture/crop-growing/priority-
pest-disease/citrus-powdery-mildew   
Chappell, P R (2013a) The Climate and Weather of Bay of Plenty . NIWA, New Zealand. 
https://niwa.co.nz/static/BOP%20ClimateWEB.pdf  
Chappell, P R (2013b) The climate and weather of Bay of Plenty.  National Institute of Water and 
Atmospheric Research (NIWA),  
Chappell, P R (2013c) The Climate and Weather of Northland . NIWA, New Zealand. 
https://niwa.co.nz/static/Northland%20ClimateWEB.pd f  
Crane, J H; Balerdi, C F; Maguire, I (2019) Avocado growing in the Florida home landscape . UF/IFAS 
Extension, University of Florida, https://edis.ifas.ufl.edu/pdf/MG/MG21300.pdf  
Everett, K R; Siebert, B (2018) Exotic plant diseas e threats to the New Zealand avocado industry and 
climatic suitability: a review. New Zealand Plant Protection 71: 25-38. 
Farr, D F; Rossman, A Y (2021) Fungal databases, U.  S. National Fungus Collections. https://nt.ars-
grin.gov/fungaldatabases/  Accessed Septemeber 27, 2021 
Glawe, D A (2008) The powdery mildews: a review of the world's most familiar (yet poorly known) 
plant pathogens. Annu Rev Phytopathol 46: 27-51. 
Koike, S T; Tjosvold, S A; Mathews, D M (2020) UC I PM Pest Management Guidelines: floriculture 
and ornamental nurseries. https://www2.ipm.ucanr.edu/agriculture/floriculture -and-ornamental-
nurseries/Powdery-mildew/   
Liberato, J; Barreto, R (2006) Oidium perseae-americanae  sp. nov. on avocado. Mycotaxon 98: 189-
192. 
McMillan, R T J (1976) Disease of avocado. In J W S auls; R L Phillips; L K Jackson (Eds.), First 
international tropical fruit short course  (pp. 66-70). Gainesville, University of Florida: U niversity of 
Florida. 
Morrison, R M (1964) Germination of conidia of Erysiphe cichoracearum . Mycologia 56(2): 232-236. 
MPI (2021a) Facility Standard: Post Entry Quarantine for Plants . Ministry for Primary Industries, 
https://www.mpi.govt.nz/dmsdocument/11368-Post-Entr y-Quarantine-forPlants-Facilities-Standard  
MPI (2021b) Import Risk Analysis: Citrus budwood for propagation. In M f P Industries (Ed.),  (Vol. 1). 
New Zealand. 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021  
307 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2019) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2019. pdf  
Plantwise (2015) Powdery mildew on Avocado. 
https://www.plantwise.org/KnowledgeBank/pmdg/201578 00220  Accessed December 2021 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Sastra-Hidayat, A R (1992) Preliminary epidemiologi cal study of powdery mildew ( Oidium 
tingitaninum ) on Citrus sinensis . AGRIS . 
Stevens, H E; Piper, R B (1941a) Avocado Diseases in Florida . U.S. Department of Agriculture. 
Stevens, H E; Piper, R B (1941b) Avocado diseases i n Florida. Circular. United States Department of 
Agriculture (582): 46-pp. 
Zentmyer, G A (1953) Diseases of the Avocado. United States Department of Agriculture. Washington  
D.C. Yearbook of Agriculture.  
Zentmyer, G A (1984) Avocado diseases. Tropical Pest Management 30(4): 388-400. 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 308 5.23  Pyrrhoderma noxium  (brown root rot) 
Pyrrhoderma noxium is a tropical and sub-tropical fungus that causes r oot rot in a wide range of host 
species, frequently resulting in plant death. Avoca do is reported to be a highly susceptible host of t his 
fungus.  
5.23.1  Taxonomic description 
Scientific name: Pyrrhoderma noxium  (Corner) L.W. Zhou & Y. C. Dai  
Order/Family: Hymenochaetales / Hymenochataceae 
Other names include: Fomes noxius, Phellinus noxius 
Taxonomic notes: 
Fomes noxius  is the basionym of this species (Robert et al. 200 5). It was reclassified to Phellinus 
noxius  in 1965 and this is the predominant name found in the literature (Stewart et al. 2020). Recent 
molecular phylogenetic analysis reassigned this fun gus to the genus Pyrrhoderma  under the name P. 
noxium (Zhou et al. 2018). The currently recognised name i s Pyrrhoderma noxium (Robert et al. 
2005), but the phylogeny and taxonomy of this speci es continues to be disputed (Stewart et al. 2020). 
Pyrrhoderma noxium  is a diverse species that likely represent several  distinct genetic groups 
(Garfinkel et al. 2020).  
5.23.2  Hazard identification 
Pyrrhoderma noxium  is not known to be present in New Zealand: 
- The species is listed in the NZOR (2021) and Biot a NZ (2022) as being absent for New 
Zealand. This species is listed as a “regulated” an d “unwanted” organism in ONZPR (2021) 
under the synonym Phillinus noxius .  
Pyrrhoderma noxium  has the potential to establish (and spread) in New  Zealand because: 
- This fungus can be spread though root to root con tact of hosts, or through airborne spores 
infecting fresh wounds of live plants (Dann et al. 2012; Leung et al. 2020).  
- Known hosts of this fungus are prevalent in New Z ealand, including horticultural (e.g. grape 
and avocado) and forestry (e.g. eucalyptus) species .   
- P. noxium  is a tropical or subtropical disease and optimal g rowth occurs at high temperatures. 
Therefore, establishment and spread of this fungus is likely to be limited to warmer regions of 
New Zealand (Everett and Siebert 2018).  
Pyrrhoderma noxium  has the potential to cause harm to New Zealand bec ause: 
- Many economically significant hosts, such as avoc ado, grapevine, and citrus, are grown in 
northern regions of New Zealand where conditions ar e most suitable for establishment.  
- Infections of this fungus frequently cause rapid death of established trees and may cause a 
significant loss of yield for some horticultural sp ecies.  
- Artificial inoculation trials with P. noxium reported 100% loss of avocado seedlings within 3 
months (Dann 2016), and 10% death of trees in Austr alian avocado orchards had an 
estimated cost of AUD$5400 per hectare (Everett and  Siebert 2018).  
Pyrrhoderma noxium  is associated with P. americana budwood because: 
- Avocado has been reported as a host of P. noxium  in Taiwan, Australia, Papua New Guinea 
and the Malay Peninsula (Ann et al. 2002; Dann et a l. 2012; Farr and Rossman 2021).  
- Airborne basiodiospores may be present on the sur face of avocado budwood. 
Given the arguments and evidence above, Pyrrhoderma noxium  meets the criteria to be a hazard on 
P. americana  budwood (as in the commodity description) imported  to New Zealand.  
309 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.23.3  Risk assessment 
Biology and epidemiology of P. noxium 
Host range 
Pyrrhoderma noxium  is reported infecting at least 200 different speci es across 59 plant families (Ann 
et al. 2002). This includes many economically impor t species such as lemon ( Citrus limon ), apricot 
(Prunus armeniaca ), grapevine ( Vitis vinifera ), and avocado ( Persea americana ) (Ann et al. 2002; 
CABI 2021). This fungus appears to be a non-host sp ecific opportunistic pathogen (CABI 2021). 
Infections of avocado have been reported in Taiwan,  Australia, Papua New Guinea and the Malay 
Peninsula (Ann et al. 2002; Dann et al. 2012; Farr and Rossman 2021). 
Distribution 
This pathogen is widespread in tropical and subtrop ical regions around the world (CABI 2021; Farr 
and Rossman 2021) as shown in Table 5-23. 
Table 5-23: The geographical distribution of Pyrrho derma noxium. 
Region Country CMI* 
Africa Angola, Benin, Burkina Faso, Cameroon, Central Afri can Republic, Democratic Republic of 
Congo, Côte d'Ivoire, Gabon, Ghana, Kenya, Nigeria,  Sierra Leone, Tanzania, Togo, Uganda 0.4-0.7 
Asia China, Hong Kong, India, Indonesia, Japan, Mal aysia, Myanmar, Pakistan, Philippines, 
Singapore, Sri Lanka, Thailand, Taiwan, Vietnam 0.4-0.8 
Americas Brazil, Costa Rica, Cuba, Puerto Rico 0.4-0.6 
Oceania American Samoa, Australia, Federated States of Micr onesia, Fiji, Niue, Northern Mariana 
Islands, Papua New Guinea, Samoa, Solomon Islands, Vanuatu 0.4-1.0 
* Climate Match Index (CMI) with all of New Zealand  (Phillips et al. 2018) 
Symptoms 
Infection by P. noxium causes brown root rot in a wide range of hosts, usu ally in woody species 
(Dann et al. 2012; Zhou et al. 2018). Symptoms are typically characterised by a yellow/brown/black 
mycelial mat developing on exposed roots and at the  base of the trunk or stem, often referred to as a 
“stocking” (Ota and Sahashi 2018). Also causes whit e rot of wood, which is spongy, soft, and whiter 
than normal. Conspicuous brown lines are often obse rved permeating through the rotted wood. Early 
stages of the infection can be symptomless, but onc e the disease is established it effectively girdles  
the tree, causing foliar necrosis, defoliation and rapid plant death (Leung et al. 2020). This decline  
typically occurs within a few months of infection, but may take several years in some hosts (Ota and 
Sahashi 2018).  
Symptoms of P. noxium  reported on avocado are severe (Dann et al. 2009; Dann 2016; Everett and 
Siebert 2018). As is typically observed in other ho sts, infections develop a brown mycelial “stocking”  
around the base of the plant (Everett and Siebert 2 018). Underneath the stocking the wood is brown 
with white patches. The infection causes rapid decl ine and death of avocado, often leaving leaves and 
fruit hanging on the tree (Dann et al. 2009). Dann (2016) reported death of avocado seedlings 
occurring within 3 months of inoculation.  
Optimal conditions for growth and symptom developme nt 
The optimum temperature for growth of P. noxium  is 30° C, and it is reported that is does not survi ve 
or spread at low temperatures (Everett and Siebert 2018). The fungus also prefers acidic conditions 
below pH 5.0, and it is reported that it will not g row when pH values are greater than 7.5 (Ann et al.  
1999).  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 310 Reproduction and transmission 
The primary means of spread for this fungus is root -to-root contact (Dann et al. 2012). The fungus 
may remain viable in fragments of infected roots wi thin soil for more than ten years (Chung et al. 
2015; CABI 2021). However, soil without root fragme nts is not a reservoir of disease (Wu et al. 2020).  
The fungus may also be spread through airborne basi diospores, allowing for long-distance dispersal 
(Chung et al. 2015; Leung et al. 2020). Fruiting bo dies producing basidiospores are typically observed  
on dead and fallen trees (Ota and Sahashi 2018). Th ese spores may then enter living hosts through 
wounds (CABI 2021) or survive for 3 to 4.5 months w ithin soil (Chung et al. 2015).  
5.23.4  Likelihood of entry 
Pyrrhoderma noxium  is a disease infecting the roots and trunk of tree s. While the disease does cause 
leaf wilting and defoliation symptoms, mycelia are not known to be present in leaves, branches, or 
shoots (Ann et al. 1999; MPI 2016). Therefore, it i s considered unlikely that the shoots and new 
growth from which avocado budwood cuttings are take n would be contaminated with P. noxium  
mycelia.  
It is suggested that airborne basidiospores may pla y a role in the establishment of P. noxium at new 
sites (Chung et al. 2015; Leung et al. 2020), so ma y  contaminate the surface of avocado budwood. If 
basiodiospores were present on the surface of avoca do budwood, it is expected that the surface 
disinfection procedure (1% sodium hypochlorite dip for 2 minutes) would be effective in making the 
spores inviable.  
Avocado plants are highly susceptible to P. noxium infection. Dann (2016) found that avocado 
seedlings (Reed variety) artificially inoculated wi th a P. noxium  isolate originating from avocado all 
died within 3 months of inoculation. It is not repo rted when the visible symptoms of infection first 
occurred. A second trial found that seedlings of bo th Reed and Hass avocados died within 2 months 
of inoculation. Given the rapid deterioration of av ocado exhibited in these trials, it appears likely that 
symptoms of the disease would be evident during the  period of PEQ if environmental conditions are 
suitable. 
Pyrrhoderma noxium  is a tropical and subtropical disease that require s warm temperatures to 
develop. Therefore, conditions in PEQ may not be su itable for development of the disease. 
Pyrrhoderma noxium  is only thought to persist long-term within wood m aterial and root debris, so if  
fungal mycelia were present on grafted buds it is n ot expected to survive for a significant period at low 
to moderate temperatures (Everett and Siebert 2018) . Basiodiospores may survive up to 4.5 months 
within soil (Chung et al. 2015), but are not expect ed to survive an extensive period without optimal 
conditions.  
The primary means of transmission for this fungus i s root-to-root contact, which is not a risk within a 
Level 3A PEQ facility. Basidiocarps of P. noxium  are uncommon in the field, but may be produced on 
the remnants of fallen or dead trees (Ota and Sahas hi 2018). Basiodiocarps have not been reported 
on avocado (Dann et al. 2012). Therefore, if infect ion of P. noxium were to occur within the PEQ 
facility, it is highly likely that it would be suff iciently contained.  
Given the arguments and evidence above, that is: 
- P. noxium  is not reported to be associated with shoots, stem s or leaves of its hosts so it is 
unlikely that budwood cuttings would contain infect ed tissue,  
- surface sterilisation of avocado budwood is likel y to make any basiodiospores that may be 
present on the surface of the cuttings inviable,  
- symptoms on avocado are severe and develop rapidl y, so are likely to be observed within the 
period of PEQ is environmental conditions are suita ble, 
- if environmental conditions in PEQ are not suitab le for disease development, the fungal 
mycelia or basiodiospores are not expected to remai n viable for a significant period of time, 
and 
- outbreaks of P. noxium  would be effectively contained within Level 3A PEQ ,  
311 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand the likelihood of P. noxium  entering New Zealand associated with P. americana budwood is 
considered to be negligible, with low uncertainty. Therefore, further assessment is considered 
unnecessary at this time; likelihoods of exposure a nd establishment and impacts to New Zealand are 
not further assessed.  
5.23.5  Overall level of associated risk to New Zealand 
Based on the assessment of likelihood above, that: 
• the likelihood of P. noxium  entering New Zealand associated with P. americana  budwood (as 
described in the commodity description, and taking into account the proposed growing period 
of active growth with a minimum of three distinct p henological growing events referred to as 
‘shoot flush’ in 3A PEQ) is considered negligible, with low uncertainty; 
the overall level of risk to New Zealand from P. noxium  on imported P. americana  bedwood is 
considered to be negligible, with low uncertainty.  
5.23.6  Management considerations 
Symptoms of P. noxium  on avocado are reported to be severe (Dann et al. 2009; Dann 2016; Everett 
and Siebert 2018). Infections develop a brown mycel ial “stocking” around the base of the plant 
(Everett and Siebert 2018). Underneath the stocking  the wood is brown with white patches. The 
infection causes rapid decline and death of avocado , often leaving leaves and fruit hanging on the 
tree (Dann et al. 2009). This is consistent with th e symptoms reported on many other host species. 
The disease may be symptomless in the early stages of infection (Leung et al. 2020), but 100% 
dieback within 3 months is reported for avocado see dlings (Dann 2016). Therefore, it appears highly 
likely that infection would be observed within the period of PEQ. 
Pyrrhoderma noxium  is a tropical and sub-tropical disease with a stro ng preference for warm 
temparatures and the optimal temperature for growth  is 30° C (Everett and Siebert 2018; Zhou et al. 
2018). Fungal mycelia can survive extended periods of time in wood tissue and debris (Chung et al. 
2015; CABI 2021), but does not survive for extended  periods in soil without root fragments (Wu et al. 
2020). Long term persistence of the fungus at low t o moderate temperatures is not expected to occur 
in avocado budwood in PEQ. 
This fungus can be readily isolated using cultures from roots or the lower parts of basal stems 
exhibiting rot symptoms and mycelial masses. The fu ngus is not known to be present in shoots or 
leaves, so positive cultures are not expected from these plant parts, even they may be exhibiting 
typical disease symptoms. Pyrrhoderma noxium  can be identified through morphological or molecul ar 
methods (Leung et al. 2020). Molecular methods may use sequencing of the ITS or 28S regions, or 
microsatellites (Chung et al. 2015; Leung et al. 20 20).  
5.23.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
In avocado, P. noxium infection is reported to have severe symptoms (Dann  et al. 2009; Dann 2016; 
Everett and Siebert 2018). As is typically observed  in other hosts, infections cause root rot and the 
development of a brown mycelial “stocking” around t he base of the plant (Everett and Siebert 2018). 
Underneath the stocking the wood is brown with whit e patches. The infection causes rapid decline 
and death of avocado, often leaving leaves and frui t hanging on the tree (Dann et al. 2009). Dann 
(2016) reported death of avocado seedlings occurrin g within 3 months of inoculation.  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 312 o What are the known environmental conditions conduci ve to symptom expression? 
The optimum temperature for growth of P. noxium  is 30° C, and it is reported that is does not survi ve 
or spread at low temperatures (Everett and Siebert 2018). The fungus also prefers acidic soil 
conditions below pH 5.0, and it is reported that it  will not grow when pH values are greater than 7.5 
(Ann et al. 1999).  
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
This fungus can be readily isolated using cultures from roots or lower parts of basal stems exhibiting  
rot symptoms and mycelial masses. The fungus is not  known to be present in shoots or leaves, so 
positive cultures are not expected from these plant  parts, even though they may be exhibiting disease 
symptoms. Asymptomatic infection has not been repor ted in avocado.  
o What is the optimum season for conducting detection  testing? 
Given that high temperature requirements of P. noxium , detection will be most likely during summer. 
5.23.8  References  
Ann, P-J; Chang, T-T; Ko, W-H (2002) Phellinus noxius  brown root rot of fruit and ornamental trees in 
Taiwan. Plant Disease 86(8): 820-826. 
Ann, P-j; Lee, H; Huang, T (1999) Brown root rot of  10 species of fruit trees caused by Phellinus 
noxius  in Taiwan. Plant Disease - PLANT DIS 83: 746-750. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
CABI (2021) Phellinus noxius (brown tea root disease). https://www.cabi.org/isc/datasheet/40154  
Accessed 15 December 2021 
Chung, C-L; Huang, S-Y; Huang, Y-C; Tzean, S-S; Ann , P-J; Tsai, J-N, et al. (2015) The genetic 
structure of Phellinus noxius  and dissemination pattern of brown root rot diseas e in Taiwan. PLOS 
ONE 10(10): e0139445. 
Dann, E (2016) Improving yield and quality in avocado through dise ase management, Phase 2 . 
Sydney, NSW.  
Dann, E; Pegg, G; Shuey, L (2012) Phellinus noxius (Corner) G.H. Cunnungham . Australian Plant 
Pathology Society, Australia.  
Dann, E; Smith, L; Pegg, K; Grose, M; Pegg, G (2009 ) Phellinus noxius: Brown root rot of avocado . 
Queensland Department of Employment, Economic Devel opment and Innovation,  
Everett, K R; Siebert, B (2018) Exotic plant diseas e threats to the New Zealand avocado industry and 
climatic suitability: a review. New Zealand Plant Protection 71: 25-38. 
Farr, D F; Rossman, A Y (2021) Fungal databases, U.  S. National Fungus Collections. https://nt.ars-
grin.gov/fungaldatabases/  Accessed Septemeber 27, 2021 
Garfinkel, A; Cannon, P; Klopfenstein, N; Stewart, J; Kim, M-S (2020) Identification of genetic groups  
within the invasive brown root rot pathogen, Pyrrhoderma noxium  (formerly Phellinus noxius ). In 
Proceedings of the 66th Western International Fores t Disease Work Conference . Estes Park, 
Colorado, USA.  
313 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Leung, K-T; Chen, C-Y; You, B-J; Lee, M-H; Huang, J -W (2020) Brown root rot disease of Phyllanthus 
myrtifolius : The causal agent and two potential biological con trol agents. Plant Disease 104(11): 
3043-3053. 
MPI (2016) Pest Risk Analysis: Phellinus noxius  from all countries. In (Vol. Version 2.0). 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 19 August 2021 
ONZPR (2021) Official New Zealand Pest Register. MP I Public Database. 
https://pierpestregister.mpi.govt.nz/PestsRegister/ ImportCommodity/  Accessed 02 April 2021 
Ota, Y; Sahashi, N (2018) Brown rot caused by Pyrrhoderma noxium in Ogasawara  Islands. Where 
does it come from?  DIVERSITAS in the Western Pacific and Asia, Kyoto University, Otsu, Japan.  
Robert, V; Stegehuis, G; Stalpers, J (2005) The Myc oBank engine and related databases. 
https://www.mycobank.org/  Accessed October 2021 
Stewart, J E; Kim, M S; Ota, Y; Sahashi, N; Hanna, J W; Akiba, M, et al. (2020) Phylogenetic and 
population genetic analyses reveal three distinct l ineages of the invasive brown root-rot pathogen, 
Phellinus noxius , and bioclimatic modeling predicts differences in associated climate niches. 
European Journal of Plant Pathology 156(3): 751-766. 
Wu, Z-C; Chang, Y-Y; Lai, Q-J; Lin, H-A; Tzean, S-S ; Liou, R-F, et al. (2020) Soil is not a reservoir for 
Phellinus noxius . Phytopathology 110(2): 362-369. 
Zhou, L-W; Ji, X-H; Vlasák, J; Dai, Y-C (2018) Taxo nomy and phylogeny of Pyrrhoderma : a 
redefinition, the segregation of Fulvoderma , gen. nov., and identifying four new species. Mycologia 
110(5): 872-889. 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 314 5.24  Raffaelea  spp. (laurel wilt disease) 
The following Raffaelea species will be assessed in this PRA: R. aguacate , R. campbellii , R. 
canadensis  and R. lauricola . 
Raffaelea spp. are typically saprotrophic fungi symbiotically  associated with ambrosia beetles. 
However, Raffaelea lauricola is unique in that it causes the vascular wilt disea se in trees and shrubs 
in the Lauraceae family including Persea americana . Similarly, R. canadensis has also been 
associated with wilt disease. 
5.24.1  Taxonomic description 
Scientific name: Raffaelea aguacate D. R. Simmons, Dreaden & Ploetz (2016) 
Scientific name: Raffaelea campbellii D. R. Simmons, A. Campbell & Ploetz (2016) 
Other names include : Raffaelea campbelliorum D. R. Simmons, A. Campbell & Ploetz (2016) 
Scientific name: Raffaelea canadensis L. R. Batra (1967) 
Other names include : Tuberculariella ambrosiae A. Funk (1965) 
Scientific name: Raffaelea lauricola T. C. Harr., Fraedrich & Aghayeva (2008) 
Order/Family: Ophiostomatales/Ophiostomataceae 
5.24.2  Hazard identification 
Raffaelea spp. ( R. aguacate , R. campbellii , R. canadensis  and R. lauricola ) are not known to be 
present in New Zealand: 
• Raffaelea spp. are not listed in either Biota NZ (2022), NZOR  (2021) or PPIN (2021). 
• Raffaelea lauricola  is a regulated pest for New Zealand (ONZPR 2021). 
• Raffaelea aguacate , R. campbellii , R. canadensis  are not listed in ONZPR (2021). 
Raffaelea spp. have the potential to establish (and spread) i n New Zealand because: 
• Persea americana  is a known host (Eskalen and McDonald 2011; Simmon s et al. 2016) that 
is widely grown in New Zealand, in home gardens and  commercial production, mainly in the 
north of the North Island. Other hosts in the Laura ceae family (e.g. Cinnamomum camphora ) 
are also reported hosts of R. lauricola  (Table 5-25) and are widespread is gardens, parks and 
street verges (NZPCN 2021).   
• Raffaelea spp. cause wilting and tree death in regions such a s the United States (Ploetz et al. 
2017a) that have a climate match index (CMI) ≥ 0.7 indicating a similar climate to the whole of 
New Zealand (Phillips et al. 2018). Specifically, R. lauricola  has the potential to spread 
through vectors that are present in New Zealand ( Xyleborinus saxesenii and Xylosandrus 
crassiusculus ); however, spread would most likely be limited as these beetle species are not 
the primary vector. The primary vector, Xyleborus glabratus , is not present in New Zealand 
(NZOR 2021). 
Raffaelea spp. have the potential to cause harm to New Zealan d because: 
• Raffaelea lauricola and R. canadensis cause vascular wilt disease in avocado trees typica lly 
exhibited by wilting of foliage, sapwood discoloura tion, vascular dysfunction and in severe 
cases, tree death (Ploetz et al. 2012; Ploetz et al . 2017a). Raffaelea spp. have a symbiotic 
relationship with ambrosia beetle vectors; these ve ctors weaken or damage host trees and 
spread the disease to new hosts.,  
315 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • avocados are an important commercial crop in New Z ealand. In the 2019-2020 financial year, 
export sales of fresh avocados earned NZ$112.3 mill ion and domestic sales earned NZ$ 50.6 
million (Plant & Food Research 2020). 
• In Florida alone, the impacts of R. lauricola specifically caused economic impacts between 
$183 million (if control measures were 50% effectiv e) to $356 million (if no controls at all) 
(Olatinwo et al. 2021). 
o In 2017, approximately 3% of avocados grown in com mercial production areas in 
Florida were lost to the disease and farmers had to  incur the cost of tree removal and 
treatments to protect residual trees (Ploetz et al.  2017a; Olatinwo et al. 2021). 
Raffaelea spp. is associated with P. americana  budwood because: 
• Persea americana  is a known host of Raffaelea spp. (Eskalen and McDonald 2011; Ploetz et 
al. 2012; Simmons et al. 2016; Ploetz et al. 2017a) ; 
• Raffaelea spp. have been isolated from branch tissue (Ploetz et al. 2012). 
Given the arguments and evidence above, Raffaelea spp. meet the criteria to be a hazard on P. 
americana  budwood (as in the commodity description) imported  to New Zealand. 
5.24.3  Risk assessment 
Biology and epidemiology of Raffaelea spp. 
Vectors 
Raffaelea species are vectored by ambrosia beetles (Table 5-2 4). The most pathogenic species, R. 
lauricola is vectored by the ambrosia beetle Xyleborus glabratus (Hughes et al. 2017). Raffaelea 
campbellii  and R. canadensis are also vectored by X. glabratus (Table 5-25). Raffaelea aguacate has 
been isolated from  Xyleborus bispinatus (Table 5-25). 
Raffaelea lauricola has been isolated from other beetle species (Table 5-24); however, X. glabratus 
contains 10-1000 times more colony forming units th an other beetles (Ploetz et al. 2017c). Evidence 
suggests that a complex of beetles is involved in d isease dissemination in avocado given that 
susceptible host species within the vicinity of Raffaelea- carrying X. glabratus don’t necessarily 
succumb to infection when colonised by X. glabratus alone (Ploetz et al. 2017a).   
Xyleborus glabratus tends to colonise and reproduce in stressed or dead  trees and tends to have a 
strong preference for trees in the Lauraceae family  (Ploetz et al. 2017a). Stressed trees release a 
metabolite sesquiterpene which attracts the beetles  (Ploetz et al. 2017a). However, there is evidence 
that X. glabratus can also attacks healthy trees (Olatinwo et al. 202 1). Ambrosia beetles carry fungi in 
specialised organs, mycangia (Mayers et al. 2020). Adult female beetles disperse to new trees and 
bore brood galleries into the host xylem (Ploetz et  al. 2017a). Beetles tend to attack stems of larger  
diameter and the probability of beetle attack decre ases with decreasing stem diameter (Olatinwo et al.  
2021). Within the galleries beetles cultivate and f eed on ‘fungal gardens’ along the walls of their 
galleries in tree sapwood (Mayers et al. 2020). 
Table 5-24: List of ambrosia beetles from which Raf faelea lauricola has been isolated from and 
the mean percent of isolations. Data adapted from P loetz et al. (2017c) 
Ambrosia beetle species Percent of individuals 
with Raffaelea lauricola  Status in New Zealand (NZOR 2021) 
Xyleborus glabratus 73 Not listed in NZOR, regulated  
Xyleborus bispinatus 63 Not listed in NZOR or ONZPR 
Xyleborus ferrugineus 57 Not listed in NZOR, regulated  
Xyleborus affinis 13 Not listed in NZOR, regulated  
Xyleborus volvulus 32 Not listed in NZOR or ONZPR 
Ambrosiodmus devexulus 0 Not listed in NZOR or ONZPR Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 316 Ambrosia beetle species Percent of individuals 
with Raffaelea lauricola  Status in New Zealand (NZOR 2021) 
Ambrosiodmus lecontei 2 Not listed in NZOR or ONZPR 
Xyleborinus andrewesi 13 Not listed in NZOR or ONZPR 
Xyleborinus gracilis 50 Not listed in NZOR, not assessed in ONZPR 
Xyleborinus saxesenii 2* Present, non-regulated 
Xylosandrus compactus 0 Not listed in NZOR, regulated  
Xylosandrus crassiusculus 4* Present (Ministry for Primary Industries 2020), regulated  
*Saucedo-Carabez et al. (2018) did not isolate Raffaelea lauricola from X. saxesenii or X. 
crassiusculus 
Symptoms  
At early stages of infection, trees exhibit wilting  of green foliage of branch tips in sections of the  tree 
canopy and wilting of individual branches (Fraedric h et al. 2008). A dark black discolouration is seen  
in the outermost sapwood and occurs as localised st reak in branches and stems in the early stages of 
wilting (Fraedrich et al. 2008). Small beetle entra nce holes (c. 0.75 mm in diameter) can be seen in 
branches and stems with sapwood discolouration; sap wood that is normally cream-white may have 
dark blueish-black streaks. Desiccation and brownin g of leaves soon follows (Fraedrich et al. 2008). 
Eventually, stem and limb dieback occur which can l ead to tree decline and death. Following wilting 
and tree death, trees are repeatedly attacked by X. glabratus  and other ambrosia beetles during 
spring, summer and autumn (Fraedrich et al. 2008). Wilting occurs because the woody xylem 
becomes discoloured and non-functional which causes  foliage to die due to lack of water (Ploetz et al.  
2017a). 
Symptoms tend not to spread further than the hilum (scar on the seed where it was once attached to 
the mother plant) of fruit, but the fungus does col onise pedicels/peduncles (fruit stems) and hila 
(Eskalen and McDonald 2011; Ploetz et al. 2017a). Raffaelea infection does not spread into fruit pulp 
or seed (Ploetz et al. 2012). 
Raffaelea lauricola  is a unique ambrosia fungus in that it systemicall y infects tree xylem and a single 
infection can be fatal (Ploetz et al. 2017a). The f ungus is able to move rapidly in the xylem of trees  
(Fraedrich 2020). Raffaelea canadensis has also been reported to cause wilt on avocado (Es kalen 
and McDonald 2011). In comparison, R. aguacate  is not systemic nor pathogenic on avocado, but is 
closely related to R. lauricola  (Ploetz et al. 2017a; Saucedo-Carabez et al. 2018) . The primary vector 
of R. aguacate  is not known, but it has been isolated from X. bispinatus  infrequently suggesting R. 
aguacate  plays a secondary role in the life cycle of X. bispinatus  (Saucedo-Carabez et al. 2018). 
Raffaelea campbellii has been isolated from X. glabratus  but its pathogenicity on Persea americana is 
not known (Simmons et al. 2016). 
Time to symptom expression 
Inoculated seedlings (through drill hole or slits) in the glasshouse exhibited sapwood discolouration 
and wilted or died within 8 weeks of inoculation (F raedrich et al. 2008). External symptoms can 
develop after 3 weeks inoculation (Dreaden et al. 2 017). In comparison, inoculated trees in the field 
wilted within 12 to 14 weeks after inoculation; sap wood discolouration was observed in all inoculated 
trees in the stems and branches (Fraedrich et al. 2 008). Time to symptom development depends on 
age of the tree, growth conditions (glasshouse vs. field) and tree species (Dreaden et al. 2017). 
Latent infection of R. lauricola , of artificially inoculated avocado, is uncommon a s the fungus is almost 
always isolated on media or detected via PCR from s ymptomatic sapwood (Ploetz et al. 2017b).  
Reproduction and transmission 
First inoculation is by an ambrosia beetle (Ploetz et al. 2017a). Raffaelea are asexual fungi that 
typically produces small conidiophores in sporodoch ia (clusters of conidiophores) within beetle 
galleries (Global Invasive Species Database 2021).  
317 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand The pathogen is able to spread to other trees throu gh root-grafts (Ploetz et al. 2017a). Mechanical 
transmission is possible through infested handsaws on potted plants; however, the pathogen does not 
survive on circular saws commonly used to prune avo cado trees in commercial setting, most likely 
due to the high heat that is generated from these b lades (Ploetz et al. 2017a). Transmission of the 
fungus is also human-mediated through the transport  of wood or wood products (Ploetz et al. 2017a; 
Fraedrich 2020). 
Table 5-25: Host range and geographic distribution of Raffaelea lauricola, R. campbellii, R. 
canadensi and R. aguacate  
Region Country CMI Raffaelea  
species Vector Host species Reference 
North 
America USA 0.5-0.8 Raffaelea 
lauricola Xyleborus 
glabratus Cinnamomum 
camphora Ploetz et al. (2017a) 
Persea americana Ploetz et al. (2012) 
Persea borbonia Harrington et al. (2011) 
Persea palustris Harrington et al. (2011) 
Sassafras albidum Harrington et al. (2011) 
Laurus nobilis Hughes et al. (2014) 
Lindera benzoin Ploetz et al. (2017a) 
Lindera melissifolia Hughes et al. (2017) 
Litsea aestivalis Hughes et al. (2017) 
Persea humilis Ploetz et al. (2017a) 
Persea indica Ploetz et al. (2017a) 
Umbellularia 
californica Ploetz et al. (2017a) 
Licaria triandra Ploetz et al. (2017a) 
Nectandra coriacea Ploetz et al. (2017a) 
Raffaelea 
aguacate Xyleborus 
bispinatus Persea americana Simmons et al. (2016); 
Saucedo-Carabez et 
al. (2018) 
Raffaelea 
campbellii Xyleborus 
glabratus Persea palustris Simmons et al. (2016) 
Persea americana (Simmons et al. 2016) 
Raffaelea 
canadensi Xyleborus 
glabratus Persea americana Eskalen and McDonald 
(2011) 
Asia* Japan 0.6-0.8 Raffaelea 
lauricola Xyleborus 
glabratus  Association 
recorded from 
beetle Harrington et al. (2011) 
Myanmar 0.2-0.7 Raffaelea 
lauricola Xyleborus 
glabratus Persea americana Ploetz et al. (2016) 
Taiwan 0.4-0.8 Raffaelea 
lauricola  Xyleborus 
glabratus  Association 
recorded from 
beetle Harrington et al. (2011) 
* Xyleborus glabratus is also found in India and China but no attempt to isolate Raffaelea lauricola 
has been made (Fraedrich 2020). 
5.24.4  Likelihood of entry 
Raffaelea spp. are found throughout southeast United States ( Fraedrich 2020), Japan and Taiwan 
(Table 5-25). However, epidemics of laurel wilt dis ease caused by R. lauricola  and R. canadensi have 
mainly been reported in the United States (Fraedric h et al. 2008; Eskalen and McDonald 2011; Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 318 Harrington et al. 2011; Hughes et al. 2014; Mayfiel d et al. 2019; Fraedrich 2020) and recently in 
Myanmar (Ploetz et al. 2016). 
Infection of Raffaelea spp. is associated with ambrosia beetle infestation  and with beetle galleries 
(Ploetz et al. 2017a). Specifically, Raffaelea lauricola is the fungal symbiont of the redbay ambrosia 
beetle, Xyleborus glabratus  (Mayfield et al. 2019). Raffaelea lauricola and other Raffaelea spp. are 
also associated with other ambrosia beetles (Table 5-24, Table 5-25). Raffaelea aguacate is reported 
as not being pathogenic or systemic (Ploetz et al. 2017a; Saucedo-Carabez et al. 2018) and 
information regarding the pathogenicity of R. campbellii  is lacking (Simmons et al. 2016). However, 
these species have been isolated from ambrosia beet les (Table 5-25). 
The evidence demonstrates that Raffaelea species assessed here are ambrosia fungi and are 
associated with ambrosia beetle galleries (Olatinwo  et al. 2021). Ambrosia fungi depend on and are 
cultivated by ambrosia beetles (Reverchon et al. 20 21). However, there is some evidence that 
Raffaelea can also be mechanically transmitted through infect ed tools (Ploetz et al. 2017a). 
Irrespective of how Raffaelea is transmitted, symptoms appear within weeks (~3-8 weeks) of infection 
(Fraedrich et al. 2008; Dreaden et al. 2017). There fore, if avocado budwood cuttings have an 
established Raffaelea  infection, it is likely that beetle galleries and symptoms will be detected, and 
infected material removed or destroyed, during prep aration for export, in phytosanitary inspections 
pre-export or on arrival in New Zealand.  
The routine surface disinfection of budwood enterin g PEQ (dipping in 1% sodium hypochlorite for 2 
minutes) will most likely not eliminate infection a s some Raffaelea species are systemic (e.g. R. 
lauricola ) (Ploetz et al. 2017a). 
As part of the commodity description, all imported avocado germplasm will undergo a growing period 
of active growth with a minimum of three distinct p henological growing events referred to as ‘shoot 
flush’ in 3A PEQ. This period in 3A PEQ will impact  on likelihood of entry in the following manner: 
• ambrosia beetle galleries will be visible during i nspection and thus infected budwood would 
be detected and destroyed before they are released from PEQ. 
• Raffaelea  is spread by ambrosia beetles. Budwood will be tre ated with miticides and 
insecticides (see section 2.2). Furthermore, Level 3A PEQ has measures in place to manage 
the risks associated with insects, wastewater, wast e and accidental transfer (see section 2.3), 
therefore ambrosia beetles carrying Raffaelea  are highly unlikely to escape level 3A PEQ to 
infect a suitable host. 
Given the arguments and evidence above, that is:  
• established Raffaelea  infections are highly likely to be detected, and i nfected material 
removed or destroyed, during preparation for export , in phytosanitary inspections pre-export 
or on arrival in New Zealand; 
• residual biosecurity risks from ambrosia entry poi nts or recent infections on the surface of 
avocado budwood are likely to be managed by the gro wing period of active growth with a 
minimum of three distinct phenological growing even ts referred to as ‘shoot flush’ in 3A PEQ; 
the likelihood of Raffaelea  species entering New Zealand associated with P. americana  budwood is 
considered to be negligible, with low uncertainty. 
Therefore, further assessment is considered unneces sary at this time, and likelihoods of exposure 
and establishment, and impacts to New Zealand were not assessed. 
5.24.5  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of Raffaelea species entering New Zealand associated with P. americana  
budwood (as described in the commodity description,  and taking into account the proposed  
319 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand growing period of active growth with a minimum of t hree distinct phenological growing events 
referred to as ‘shoot flush’ in 3A PEQ) is consider ed to be negligible with low uncertainty;  
• therefore, continuing the assessment was considere d unnecessary; and 
the overall level of assessed risk to New Zealand f rom Raffaelea species on imported P. americana 
budwood (as in the commodity description) is consid ered to be negligible, with low uncertainty. 
5.24.6  Management considerations 
At early stages of infection, trees exhibit wilting  of green foliage of branch tips in sections of the  tree 
canopy and wilting of individual branches (Fraedric h et al. 2008). A dark black discolouration is seen  
in the outermost sapwood and occurs as localised st reak in branches and stems in the early stages of 
wilting (Fraedrich et al. 2008). Small beetle entra nce holes (c. 0.75 mm in diameter) can be seen in 
branches and stems with sapwood discolouration; sap wood that is normally cream-white may have 
dark blueish-black streaks. Desiccation and brownin g of leaves soon follows (Fraedrich et al. 2008). 
Eventually, stem and limb dieback occur which can l ead to tree decline and death. Following wilting 
and tree death, trees are repeatedly attacked by X. glabratus  and other ambrosia beetles during 
spring, summer and autumn (Fraedrich et al. 2008). Wilting occurs because the woody xylem 
becomes discoloured and nonfunctional which causes foliage to die due to lack of water (Ploetz et al. 
2017a). 
Warmer temperatures, such as those in spring and su mmer, seem to exacerbate symptom 
development (Fraedrich 2020). Raffaelea lauricola can be detected with species specific primers 
(Dreaden et al. 2014; Wuest et al. 2017). Sequencin g of rDNA has been used for other Raffaelea 
species such as R. canadensis (Eskalen and McDonald 2011).  
5.24.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
At early stages of infection, trees exhibit wilting  of green foliage of branch tips in sections of the  tree 
canopy and wilting of individual branches (Fraedric h et al. 2008). A dark black discolouration is seen  
in the outermost sapwood and occurs as localised st reak in branches and stems in the early stages of 
wilting (Fraedrich et al. 2008). Small beetle entra nce holes (c. 0.75 mm in diameter) can be seen in 
branches and stems with sapwood discolouration; sap wood that is normally cream-white may have 
dark blueish-black streaks. Desiccation and brownin g of leaves soon follows (Fraedrich et al. 2008). 
Eventually, stem and limb dieback occur which can l ead to tree decline and death. Following wilting 
and tree death, trees are repeatedly attacked by Xyleborus glabratus  and other ambrosia beetles 
during spring, summer and autumn (Fraedrich et al. 2008). Wilting occurs because the woody xylem 
becomes discoloured and non-functional which causes  foliage to die due to lack of water (Ploetz et al.  
2017a). 
Symptoms tend not to spread further than the hilum of fruit, but the fungus does colonise 
pedicels/peduncles and hila (Eskalen and McDonald 2 011; Ploetz et al. 2017a). Raffaelea infection 
does not spread into fruit pulp or seed (Ploetz et al. 2012). 
o What are the known environmental conditions conduci ve to symptom expression? 
Temperature and moisture conditions influence the r ate of development of disease and subsequent 
symptoms (Fraedrich 2020). Late in the growing seas on, disease seems to progress relatively slowly. 
For example, trees with partial crown wilt (i.e., o n only a few branches) are observed during winter 
months (Fraedrich 2020). In the spring and summer, when trees are actively transpiring and growing, 
the disease progresses much more rapidly and trees die quickly (Fraedrich 2020). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 320 What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
There is no evidence that R. lauricola or R. canadensis cause asymptomatic infections; both species 
have been reported to cause laurel wilt disease (Es kalen and McDonald 2011). Raffaelea aguacate 
seems to behave as a saprotroph and is not pathogen ic; it also does not occur systemically in the 
plant (Ploetz et al. 2017a; Saucedo-Carabez et al. 2018).  
Raffaelea (specifically R. lauricola ) is a systemic pathogen, thus sampling directly fr om wood tissue 
(after debarking) has been used to extract crude DN A from plant tissues (Hamilton et al. 2020). 
Given all species will be associated with beetle ga lleries (Ploetz et al. 2017a), plant material from 
these areas can be used to be tested for infection.  
o What is the optimum season for conducting detection  testing? 
Rapid disease progression tends to occur in spring and summer, suggesting these seasons would be 
optimal for testing; in comparison, disease progres sion slows in winter (Fraedrich 2020). 
5.24.8  References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Dreaden, T J; Campbell, A S; Gonzalez-Benecke, C A;  Ploetz, R C; Smith, J A (2017) Response of 
swamp bay, Persea palustris  , and redbay, P. borbonia , to Raffaelea spp. isolated from Xyleborus 
glabratus . Forest Pathology 47(1): e12288. 
Dreaden, T J; Davis, J M; Harmon, C L; Ploetz, R C;  Palmateer, A J; Soltis, P S, et al. (2014) 
Development of multilocus PCR assays for Raffaelea lauricola , causal agent of laurel wilt disease. 
Plant Disease 98(3): 379-383. 
Eskalen, A; McDonald, V (2011) First report of Raffaelea canadensis  causing laurel wilt disease 
symptoms on avocado in California. Plant Disease 95(9): 1189-1189. 
Fraedrich, S (2020) Raffaelea lauricola  (laurel wilt). Accessed December 2021 
Fraedrich, S W; Harrington, T C; Rabaglia, R J; Uly shen, M D; Mayfield, A E; Hanula, J L, et al. (2008 ) 
A fungal symbiont of the redbay ambrosia beetle cau ses a lethal wilt in redbay and other Lauraceae in 
the southeastern United States. Plant Disease 92(2): 215-224. 
Global Invasive Species Database (2021) Species profile Raffaelea lauricola . 
http://www.iucngisd.org/gisd/species.php?sc=1549  
Hamilton, J L; Workman, J N; Nairn, C J; Fraedrich,  S W; Villari, C (2020) Rapid detection of 
Raffaelea lauricola directly from host plant and beetle vector tissues using loop-mediated isothermal 
amplification. Plant Disease 104: 3151-3158. 
Harrington, T C; Yun, H Y; Lu, S-S; Goto, H; Aghaye va, D N; Fraedrich, S W (2011) Isolations from 
the redbay ambrosia beetle, Xyleborus glabratus , confirm that the laurel wilt pathogen, Raffaelea 
lauricola , originated in Asia. Mycologia 103(5): 1028-1036. 
Hughes, M A; Black, A; Smith, J A (2014) First repo rt of laurel wilt caused by Raffaelea lauricola  on 
bay laurel ( Laurus nobilis ) in the United States. Plant Disease 98(8): 1159-1159.  
321 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Hughes, M A; Riggins, J J; Koch, F H; Cognato, A I;  Anderson, C; Formby, J P, et al. (2017) No rest 
for the laurels: symbiotic invaders cause unprecede nted damage to southern USA forests. Biological 
Invasions 19(7): 2143-2157. 
Mayers, C G; Harrington, T C; McNew, D L; Roeper, R  A; Biedermann, P H W; Masuya, H, et al. 
(2020) Four mycangium types and four genera of ambr osia fungi suggest a complex history of fungus 
farming in the ambrosia beetle tribe Xyloterini. Mycologia 112(6): 1104-1137. 
Mayfield, A E; Villari, C; Hamilton, J L; Slye, J; Langston, W; Oten, K, et al. (2019) First report of  laurel 
wilt disease caused by Raffaelea lauricola  on sassafras in North Carolina. Plant Disease 103(1): 155-
155. 
Ministry for Primary Industries (2020) Granulate am brosia beetle. 
https://www.mpi.govt.nz/biosecurity/major-pest-and- disease-threats/granulate-ambrosia-beetle/  
Accessed November 2021 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
NZPCN (2021) New Zealand Plant Conservation Network . https://www.nzpcn.org.nz/  Accessed June 
2021 
Olatinwo, R O; Fraedrich, S W; Mayfield III, A E (2 021) Laurel wilt: current and potential impacts and  
possibilities for prevention and management. Forests 12(181): 1-21. 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
Ploetz, R; Kendra, P; Choudhury, R; Rollins, J; Cam pbell, A; Garrett, K, et al. (2017a) Laurel wilt in  
natural and agricultural ecosystems: understanding the drivers and scales of complex pathosystems. 
Forests 8(2): 48. 
Ploetz, R C; Hughes, M A; Kendra, P E; Fraedrich, S  W; Carrillo, D; Stelinski, L L, et al. (2017b) 
Recovery plan for laurel wilt of avocado, caused by  Raffaelea lauricola . Plant Health Progress 18(2): 
51-77. 
Ploetz, R C; Inch, S A; Perez Martinez, J M; White,  T L (2012) Systemic infection of avocado, Persea 
americana , by Raffaelea lauricola , does not progress into fruit pulp or seed. Journal of 
Phytopathology 160(9): 491-495. 
Ploetz, R C; Konkol, J L; Narvaez, T; Duncan, R E; Saucedo, R J; Campbell, A, et al. (2017c) 
Presence and prevalence of Raffaelea lauricola , cause of laurel wilt, in different species of amb rosia 
beetle in Florida, USA. Journal of Economic Entomology : tow292. 
Ploetz, R C; Thant, Y Y; Hughes, M A; Dreaden, T J;  Konkol, J L; Kyaw, A T, et al. (2016) Laurel wilt,  
caused by Raffaelea lauricola , is detected for the first time outside the southe astern United States. 
Plant Disease 100(10): 2166. 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 322 Reverchon, F; Contreras-Ramos, S M; Eskalen, A; Gue rrero-Analco, J A; Quiñones-Aguilar, E E; 
Rios-Velasco, C, et al. (2021) Microbial biocontrol  strategies for ambrosia beetles and their 
associated phytopathogenic fungi. Frontiers in Sustainable Food Systems 5(313). 
Saucedo-Carabez, J R; Ploetz, R C; Konkol, J L; Car rillo, D; Gazis, R (2018) Partnerships between 
ambrosia beetles and fungi: lineage-specific promis cuity among vectors of the laurel wilt pathogen, 
Raffaelea lauricola . Microbial Ecology 76(4): 925-940. 
Simmons, D R; De Beer, Z W; Huang, Y-T; Bateman, C;  Campbell, A S; Dreaden, T J, et al. (2016) 
New Raffaelea  species (Ophiostomatales) from the USA and Taiwan associated with ambrosia 
beetles and plant hosts. IMA Fungus 7(2): 265-273. 
Wuest, C E; Harrington, T C; Fraedrich, S W; Yun, H -Y; Lu, S-S (2017) Genetic variation in native 
populations of the laurel wilt pathogen, Raffaelea lauricola , in Taiwan and Japan and the introduced 
population in the United States. Plant Disease 101(4): 619-628. 
 
  
323 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 5.25  Rhizoctonia noxia  (thread blight) 
Rhizoctonia noxia  is a fungal pathogen causing thread blight of coff ee and many other plants 
including avocado. Damage from the disease typicall y occurrs on all parts of the plant except the 
roots. 
5.25.1  Taxonomic description 
Scientific name: Rhizoctonia noxia  (Donk) Oberw., R. Bauer, Garnica, R. Kirschner 201 3  
Order/Family: Cantharalles/Ceratobasidiaceae 
Other names include:  Ceratobasidium noxium  (Donk) P. Roberts 1999, Corticium koleroga  (Cooke) 
Höhn. 1910, Koleroga noxia  Donk 1958, Pellicularia koleroga  Cooke 1876 
Taxonomic notes: The species name Pellicularia koleroga, originally described by Cooke in 1876, 
was revisited von Höhnel in 1910, who assigned the taxon to genus Corticium. This was corroborated 
by Burt (1918). Later, Donk (1954) who disagreed wi th Cooke’s genus Pellicularia assigned a new 
scientific name ( Koleroga noxia ) to the taxon. The reason for these shifts was lik ely due to the 
incorrect description of spores by Cooke (Burt 1918 ; Donk 1954), who probably observed basidia 
(spore bearing cells) and mistook them for basidios pores. Thus, the spore morphology descriptions in 
literature might be conflicting. Nevertheless, it i s assumed that above mentioned names as used in 
the literature refer to the same taxon under the na me Rhizoctonia noxia . However, there is a lack of 
DNA sequencing data available to confirm this (B. W eir, pers. comm.).  
5.25.2  Hazard identification 
Rhizoctonia noxia  is not present in New Zealand: 
• Rhizoctonia noxia  is not listed in NZOR (2021), Biota NZ (2022) or P PIN (2021).   
• The regulatory status of R. noxia  has not been assessed (ONZPR 2021) 
Rhizoctonia noxia  has the potential to establish in New Zealand beca use: 
• There are records of R. noxia in association with avocado, citrus and persimmon p lants. 
These hosts are grown in New Zealand. 
• the climate in New Zealand is unlikely to limit it s development and spread because R. noxia  
has been reported to associate with plant hosts in areas that have a Climate Match Index 
(McMillan 1976) up to 0.7 indicating a similar clim ate to the whole of New Zealand (Phillips et 
al. 2018). 
Rhizoctonia noxia  has the potential to cause harm to New Zealand bec ause: 
• Rhizoctonia noxia  causes thread blight in P. americana  and other important crops such as 
Citrus  spp. 
• Avocados are an important commercial crop in New Z ealand. In the 2019–2020 financial 
year, export sales of fresh avocados earned NZ$112. 3 million and domestic sales earned 
NZ$50.6 million (Plant & Food Research 2020). 
Rhizoctonia noxia  is associated with P. americana  budwood because: 
• Rhizoctonia noxia  has been isolated from the leaves and braches of P. americana  (avocado) 
plants. 
Given the arguments and evidence above, R. noxia  meets  the criteria to be a hazard for 
New Zealand. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 324 5.25.3  Risk assessment 
Biology and epidemiology of Rhizoctonia noxia 
Rhizoctonia noxia  is known to cause thread blight on avocado in Braz il and Honduras, but details 
about the symptoms or the disease are not provided (Muller and Roberts 1961; McGuire and Crandall 
1967; Lourd 1993). Nevertheless, thread blight in c offee and other tree hosts has been reviewed in 
detail by Dechassa (2019). Assuming the synonymy of  Corticium koleroga  with Rhizoctonia noxia   
(Biota NZ 2022), the description of the disease, in cluding symptoms and transmission, is likely to 
apply to P. americana  as a host too, albeit with increased uncertainty. Damage from the disease on 
coffee is described as occurring on all parts of th e plant except the roots. It can occur in shaded an d 
non-shaded coffee plantations at high and low altit udes. The disease appears to be supported by 
periods of high rainfall, mid altitudes and high hu midity as well as shade provided through 
overhanging branches (Dechassa 2019). 
Host range and distribution 
The fungus has a cosmopolitan distribution and dise ase caused by the fungus has been described 
from many economically important crops such as coff ee (Belachew et al. 2015), coconut (Benchimol 
et al. 2001), citrus, persimmon, tea, cacao, mango and many other species ranging from herbaceous 
monocts to woody fruit trees (Dechassa 2019). 
The areas with reported disease on avocado caused b y R. noxia  have a lower climate matching index 
(Phillips et al. 2018) such as Brazil’s amazon (Lou rd 1993) with a CMI <0.5 and 0.5 in Honduras 
(Muller and Roberts 1961). However, the pathogen ha s a global distribution and in some regions 
where it is associated with coffee (e.g. Ethiopia),  the climate matching index reaches 0.7 (Belachew e t 
al. 2015; Phillips et al. 2018). Dechassa et al. (2 020) report that the optimal temperature for growth  of 
the pathogen is 25° C. 
Symptoms 
Rhizoctonia noxia  typically infects plant tissues through stomata or  lenticels but also through wounds. 
The fungus forms long, slender, white or pale mycel ial strands (rhizomorphs) that usually spread 
along veins or ribs of leaves or along branches. Th ese rhizomorphs then infect more leaves and 
branches. Infected leaves turn black initially at t he petiole and the blackening later spreads to the leaf 
blade, predominantly on the underside. Affected lea ves often wilt and sometimes separate at the 
petiole, but usually remain attached to the stem by  fungal rhizomoprhs. Most mycelial formation is on 
the underside of leaves and between the cells of th e leaf parenchyma (inner spongy leaf tissue) with 
minute fruiting bodies emerging at many points givi ng a mottled appearance to the leaf (Dechassa 
2019). The symptoms can be quite severe and inciden ce high, especially if the disease is left 
unmanaged as was the case recently in Ethiopia. In experimental conditions symptoms develop within 
10 days when infecting coffee twigs and leaves eith er by mycelial plugs or basidiospores (Dechassa 
et al. 2020).  
No records were found in the available literature t o suggest that R. noxia  can infect asymptomatically. 
Searches were conducted in Google Scholar  and Goog le with the search terms: “Ceratobasidium 
noxium”, “Corticium koleroga”, “Koleroga noxia”, “R hizoctonia noxia”, “Pellicularia koleroga” each in 
combination with “endophyte” or “asymptomatic” e.g.  [“Pellicularia koleroga” + endophyt*].  
Transmission and lifecycle 
Rhizoctonia noxia (Corticium koleroga ) is an aerial pathogen that is transmitted by free  water and 
splashing over short distances. The fungus can pene trate the host tissues through stomata in leaves, 
lenticels in bark or wounds and spread in the form of rhizomoprhs (mycelial threads) to infect more 
host tissue (Dechassa 2019).   
The spread of the disease is assisted by wind, wate r, insects as well as mechanical means 
(Dechassa 2019). Dispersal over longer distances is  assisted by humans, through the use of infected 
planting material. Over short distances the fungus spreads by growing mycelium, which allows it to 
infect new leaves and branches on the same tree or even between trees (Dechassa 2019).  
325 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Furthermore the fungus can form basidia during rain y weather and this leads to airborne release of 
basidiospores. Expected transmission distances thro ugh airborne basidiospores were not provided 
(Dechassa 2019). The fungus could also be spread th rough insect vectors  in the genera Antestiopsis  
and Usingeria  (Dechassa 2019), but neither of these are  known t o be present in New Zealand 
(NZOR 2021). 
5.25.4  Likelihood of entry: 
Rhizoctonia noxia  is not likely to be imported into post-entry quara ntine (PEQ) on avocado budwood 
due to conspicuous symptoms, unless an emerging inf ection was not visually detected prior to export, 
in which case the fungus would be likely to produce  visible symptoms in PEQ.   
Rhizoctonia noxia  can infect stems through lenticels and wounds. Persea americana  is a known host 
of Rhizoctonia noxia  (Muller and Roberts 1961; McGuire and Crandall 196 7; Lourd 1993), so 
association with leafless avocado budwood is consid ered to be possible.  
Budwood cuttings are dipped in 1% sodium hypochlori te for 2 minutes upon entry into the quarantine 
facility, which would reduce the risk of importing spores and rhizomorphs of R. noxia  into PEQ. 
However, mycelium growing in inner tissues might no t be affected. 
If the fungus is imported into PEQ, then three dist inct phenological growing events referred to as 
‘shoot flush’ is likely to be a sufficient time per iod for the fungus to develop visually detectable 
colonies on the surface infected budwood. No record s of asymptomatic infections were found in the 
literature.   
Basidiospores are small (9–13×3– 5 μm) (Dechassa 2019) and may fit through the mesh scr een over 
the level 3A PEQ vents is required to have a maximu m opening size of 0.04 mm2 (Chapter 2). 
However, it is likely that R. noxia  would be detected by plant inspections before spor es are produced 
because R. noxia  typically produces visible symptoms such as bundle s of mycelial strands growing on 
the surfaces of infected plant tissues, discolourat ion of plant tissues. In addition, production of sp ores 
is supported by rainy weather which and the spores are spread by wind and rain, and such conditions 
are unlikely to occur in PEQ. 
Given the arguments and evidence above, the likelih ood of R. noxia  entering New Zealand associated 
with P. americana  (avocado) budwood is considered to be negligible, with moderate uncertainty. 
5.25.5  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that: 
• the likelihood of R. noxia  entering New Zealand associated with imported P. americana  
(avocado) budwood is considered to be negligible wi th moderate uncertainty. Therefore, 
continuing the assessment is considered unnecessary ; and   
the overall level of risk to New Zealand from R. noxia  on imported P. americana  (avocado) budwood 
is considered to be negligible, with moderate uncer tainty.   
5.25.6  Management considerations 
Rhizoctonia noxia  produces consipcuous symptoms such as leaf wilting , tissue discolouration 
(blackening) mottleded appearance of underside of l eaves upon fruiting, and mycelial strands 
(rhizomorphs) running along leaf ribs, petioles or branches .  
Symptoms caused by R. noxia  occur typically after rain. Although the fungus oc curs in almost all 
continents, it has mostly been reported to associat e with plant hosts in tropical climates (Dechassa 
2019). No records of asymptomatic infections were f ound in the literature. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 326 Information from avocado is rather scarce and most information about the pathogen comes from 
literature on coffee. Furthermore, Lourd (1993) rep orts the disease caused by R. noxia  (in avocado in 
Brazil as not a major problem and when controlled b y cultural practices (e.g. removing crop residues, 
good aeration in the orchards)). 
5.25.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Rhizoctonia noxia  is likely to produce white or pale mycelial strand s (rhizomorphs) that usually spread 
along the veins or ribs of leaves or along branches , infecting leaves and causing discouloration 
(blackening) and rotting of tissues (Dechassa 2019) . 
o What are the known environmental conditions conduci ve to symptom expression? 
Humid conditions, rain and sheltering of plant mate rial from sun are likely to induce symptom 
expression (Dechassa 2019).  
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested? 
Rhizoctonia noxia is likely to infect branches and leaves of avocado through lenticels or stomata 
respectively. The pathogen could also infect the pl ant tissue through fresh wounds so testing of these  
tissues is recommended. 
o What is the optimum season for conducting detection  testing? 
High rainfall and humidity is likely to promote gro wth of the pathogen (Dechassa 2019), increasing the  
chances of detection. 
5.25.8  References  
Belachew, K; Teferi, D; Hagos, L (2015) Coffee thre ad blight ( Corticium koleroga ): a coming threat for 
Ethiopian coffee production. Journal of Plant Pathology & Microbiology 6: 9. 
Benchimol, R L; Poltronieri, L S; Trindade, D R; Al buquerque, F C (2001) White-thread blight: five 
new hosts in the state of Pará, Brasil. Fitopatologia Brasileira 26(4): 778-778. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Burt, E A (1918) Corticium s causing pellicularia disease of the coffee plant,  hypochnose of 
pomaceous fruits, and Rhizoctonia  disease. Annals of the Missouri Botanical Garden 5(2): 119. 
Dechassa, N (2019) Occurrence, distribution, biolog y and management of coffee thread blight 
(Corticium koleroga  (Cke) Hoehnel): a review. J. Environ. Earth Sci 9(2). 
Dechassa, N; Chala, A; Belachew, K; Shikur, E (2020 ) Morphological characterization of Corticium 
koleroga , cause of thread blight on arabica coffee. Pharmaceutical Science and Technology 4(2): 31. 
Donk, M A (1954) Notes on resupinate hymenomycetes - I on Pellicularia Cooke. Reinwardtia 2(3): 
425-434.  
327 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Lourd, M (1993) Os principais patógenos das plantas  cultivadas na Ilha do Careiro. Amazoniana: 
Limnologia et Oecologia Regionalis Systematis Flumi nis Amazonas 12(3/4): 565-576. 
McGuire, J U; Crandall, B S (1967) Survey of insect pests and plant diseases of select ed food crops 
in Mexico, Central America, and Panama  (Vol. no.2). International Agricultural Developmen t Service, 
U.S. Dept. of Agriculture; [Washington] :. 
McMillan, R T J (1976) Disease of avocado. In J W S auls; R L Phillips; L K Jackson (Eds.), First 
International Tropical Fruit Short Course  (pp. 66-70). Gainesville: Fruit Crops Dept., Flori da 
Cooperative Extension Service. Institute of Food an d Agricultural Sciences, University of Florida: 
University of Florida. 
Muller, A; Roberts, D (1961) Plant disease records at Zamorano, Honduras II. August, 1960. 9(1): 49-
54. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 328 5.26  Rhizoctonia theobromae  (vascular-streak dieback) 
Rhizoctonia theobromae  is a leaf-penetrating, xylem-infecting, fungal pat hogen that is the causal 
agent of vascular-streak dieback of cacao. One repo rt was found of it causing vascular-streak dieback 
in avocado plants. 
5.26.1  Taxonomic description  
Scientific name: Rhizoctonia theobromae (P.H.B. Talbot & Keane) Oberw., R. Bauer, Garnica &  R. 
Kirschner  
Order/Family: Cantharalles/Ceratobasidiaceae 
Other names include : Oncobasidium theobromae; Ceratobasidium theobromae;  Thanatephorus 
theobromae 
Common names:  Vascular-streak dieback (VSD) of cocoa 
Taxonomic notes : In a revision of the Rhizoctonia  group, Roberts (1999) moved Oncobasidium 
theobromae  into the genus Thanatephorus , therefore, renaming the fungus Thanatephorus 
theobromae . Although Samuels et al. (2012) agreed that the na me Oncobasidium theobromae was 
not justified, they argued that Oncobasidium theobromae  should instead be moved into the genus, 
Ceratobasidium , with a new name, Ceratobasidium theobromae . This new positioning was challenged 
by Oberwinkler et al. (2013) who argued that Ceratobasidium theobromae  belonged rightfully in 
Thanatephorus  (anamorph Rhizoctonia ). Furthermore, Oberwinkler et al. (2013) suggested  that the 
widely used name Rhizoctonia  should be used in place of Thanatephorus  and therefore suggested 
renaming Oncobasidium theobromae , Rhizoctonia theobromae . 
5.26.2  Hazard identification 
Rhizoctonia theobromae is not known to be present in New Zealand: 
• Rhizoctonia theobromae is not listed in NZOR (2021), Biota NZ (2022) or PP IN (2021). 
• The regulatory status of Rhizoctonia theobromae has not been assessed (ONZPR 2021). 
Rhizoctonia theobromae  is associated with P. americana  budwood because: 
• Rhizoctonia theobromae  has been isolated from P. americana  plants.  
• Rhizoctonia theobromae  is known to infect the vascular tissue inside stem s.  
Rhizoctonia theobromae  has the potential to establish [and spread] in New  Zealand because:  
• Rhizoctonia theobromae is a well-known pathogen of cacao, and one record w as found of it  
associating with avocado plants (Anderson 1989; Sam uels et al. 2012). Avocado is grown 
mainly in the north of the North Island, and avocad o plants are in commercial production in 
Northland and Bay of Plenty. 
• The climate in New Zealand is unlikely to limit it s development and spread because R. 
theobromae has been reported in areas that have a Climate Matc h Index (CMI) ≥ 0.7 (There 
are multiple, reliable records of Akaropeltopsis  sp. causing sooty blotch on avocado in South 
Africa (Theron et al. 1981; Smith et al. 1985; Smit h et al. 1987; Korsten et al. 1997).  
There is little information on the distribution of Akaropeltopsis  sp. elsewhere in the world, and the 
records of its distribution are largely unsubstanti ated or unconfirmed (Theron et al. 1981; Smith et a l. 
1987; Queensland Government 2001), as follows: 
• Sooty blotch on avocado in Australia has been repo rted to be caused by a range of causative 
agents, including Stomiopeltis  sp. (Coates et al. 2001; Willingham 2002; Cooke et  al. 2009), 
Akaropeltopsis  spp./ Stomiopeltis  spp. complex (Queensland Government 2001), and mul tiple 
non-specified fungi (Allen 2004). Given that the ca usative agents of sooty blotch on avocado 
have been confused in the past due to the high leve l of morphological similarity between  
329 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Akaropeltopsis  and Stomiopeltis (Theron et al. 1981; Smith et al. 1987), and that t here were 
no records found describing Akaropeltopsis  sp. on avocado in Australia, there is uncertainty 
regarding the presence of Akaropeltopsis  sp. in Australia.  
• Akaropeltopsis  sp. has been reported to be present and associated  with avocado in 
Colombia, but this is based on international litera ture compilation and not from direct 
observation. According to the USDA (2016), the pres ence of Akaropeltopsis  sp. in Colombia 
is ‘doubtful’. 
o Akaropeltopsis  sp. appears to be similar to A. marchaeriifolii  found on leaves of a 
Machaerium  sp. in Brazil, but these species have not been con firmed to be conspecific 
(Theron et al. 1981; Smith et al. 1987). No other r ecords were found in the literature of 
Akaropeltopsis  sp. causing sooty blotch in Brazil. 
o Table 5-1), indicating a similar climate to the wh ole of New Zealand (Phillips et al. 2018). 
o Rhizoctonia theobromae  needs a living host plant to survive and spreads v ia 
basidiospores. Basidiospores are short-lived (kille d by direct and indirect sunlight), 
dispersed in the air for only short distances (~100 m), and initiate the infection cycle when 
they land on young susceptible leaves (McMahon and Purwantara 2016). 
• Rhizoctonia theobromae  has the potential to cause harm to New Zealand bec ause: 
o Rhizoctonia theobromae damages leaves and vascular tissue, resulting in le af, stem and 
plant death. Although infections of avocado are app arently rare, avocados are an 
important commercial crop in New Zealand. In the 20 18–2019 financial year, export 
sales of fresh avocados earned NZ$110 million and d omestic sales earned NZ$ 56.5 
million (Plant & Food Research 2019). 
Given the arguments and evidence above, R. theobromae  meets the criteria to be a hazard on P. 
americana  budwood (as in the commodity description) imported  to New Zealand. 
5.26.3  Risk assessment 
Biology and epidemiology 
Rhizoctonia theobromae is a basidiomycete (Ceratobasidiales) fungal pathog en that is the causal 
agent of vascular-streak dieback of cacao. Rhizoctonia theobromae  infects the leaves, and spreads 
into the vascular tissue of host plants and needs a  living host plant to survive (McMahon and 
Purwantara 2016). 
Hosts and Distribution 
Rhizoctonia theobromae  causes vascular-streak dieback in cacao (Malvaceae ) plants in Asia and 
parts of Melanesia, but one report was found of it causing similar disease symptoms in avocado 
(Lauraceae) plants in Papua New Guinea (Anderson 19 89; Samuels et al. 2012). Anderson (1989) 
and McMahon and Purwantara (2016) suggested that th e fungus may occur as an innocuous 
endophyte or weak pathogen in unknown native host s pecies in its natural distribution (Southeast 
Asia and parts of Melanesia), where cacao and avoca do are introduced. 
Table 5-26: Distribution of Rhizoctonia theobromae (EPPO 2011). 
Continent Country Status CMI* 
Asia China (Guangdong, Henan) restricted distributi on 0.7 
Asia India restricted distribution 0.2-0.8 
Asia Indonesia widespread 0.4-0.6 
Asia Malaysia  0.4-0.5 
Asia Myanmar  0.2-0.6 
Asia Philippines  0.3-0.6 
Asia Thailand  0.3-0.5 
Oceania Papua New Guinea  0.4-0.7 
* (Phillips et al. 2018)  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 330 Disease symptoms 
The disease symptoms of R. theobromae appear to be similar in avocado and cacao (Anderson  
1989). Initial symptoms in avocado include chloroti c and necrotic spots on leaves. The spores of the 
fungus infect young unhardened leaves but leaf symp toms usually occur 3-5 months after infection, 
by which time the infected leaves will have aged an d hardened, and young healthy looking flushes of 
leaves will have developed on the shoot (Samuels et  al. 2012). The apparent absence of green spots 
on avocado leaves is a notable difference to the gr een spots that present on cacao leaves (Samuels 
et al. 2012; Perrine-Walker et al. 2018).  
As the infection progresses, the vascular tissue be comes blackened and is visible in the leaf scars of  
abscised leaves, or as dark streaks in split stems.  The bark can become rough due to swollen 
lenticels in response to stress. Severe infections result in defoliation, the death of branches and st ems 
and often kill young seedings. White fruiting bodie s develop on leaf scars and stems after several 
days of wet weather (Anderson 1989; Samuels et al. 2012; Perrine-Walker et al. 2018). 
Wet conditions promote symptom development, and the  disease is most common in tropical climates 
and wetter regions where annual rainfall exceeds 2, 500 mm (Guest and Keane 2007). 
Although there is no evidence that R. theobromae  can infect avocado asymptomatically, Anderson 
(1989) and McMahon and Purwantara (2016) suggested that the fungus may occur as an innocuous 
endophyte or weak pathogen in unknown native host s pecies in its natural range, where cacao and 
avocado are introduced. 
Transmission and reproduction 
Rhizoctonia theobromae  is wind dispersed through basidiospores, which are  the only form of 
inoculum. Basidiocarps only develop on fresh leaf s cars during wet weather and release 
basidiospores in relatively low numbers during the night. Basidiospores are airborne but dispersal is 
limited because they lose viability after a few hou rs or after exposure to direct and indirect sunligh t, 
indicating that spores are only capable of spreadin g the disease a short distance. Consequently, very 
few new infections occur beyond <80m from diseased trees (Perrine-Walker et al. 2018). The 
basidiospores land on and penetrate young, unharden ed leaves, and from there the infection spreads 
into the vascular tissue (Samuels et al. 2012). Rhizoctonia theobromae  causes defoliation and cracks 
in leaves and stems several months after the initia l infection, and basidiocarps develop on the fresh 
scars during periods of high rainfall or humidity ( Samuels et al. 2012). 
The fungus is only capable of surviving in associat ion with a living plant host and does not continue to 
sporulate or survive on dead branches (Samuels et a l. 2012). There is strong evidence that R. 
theobromae is not seedborne (Anderson 1989). In cacao, basidio carps do not form on budwood taken 
from infected branches, and grafts prepared from in fected budwood do not take. Therefore, it is highly  
unlikely that infection will spread through graftin g in cacao (Guest and Keane 2007), however, this 
has not been tested in avocado plants. 
5.26.4  Likelihood of entry 
Rhizoctonia theobromae  is well-known to infect cacao plants but one repor t was also found of it 
infecting avocado plants (Anderson 1989).  
New infections may not be detected prior to export as symptoms take several months to appear 
(Samuels et al. 2012). Furthermore, R. theobromae  colonises the vascular tissue of hosts (Samuels 
et al. 2012), indicating that it could be present i nside leafless avocado budwood in the absence of 
visible external symptoms. Surface disinfection (di pping in 1% sodium hypochlorite for 2 minutes upon 
entry into the quarantine facility) is not consider ed to be effective at managing internal infections in 
leafless avocado budwood cuttings. 
In cacao, basidiocarps do not form on budwood taken  from infected branches, and grafts prepared 
from infected budwood do not take. Therefore, it is  highly unlikely that infection is spread through 
grafting in cacao (Guest and Keane 2007). However, this has not been tested in avocado.  
331 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand If R. theobromae  is imported into PEQ, then three distinct phenolog ical growing events referred to as 
‘shoot flush’ is likely to be a sufficient time per iod for the fungus to produce symptoms because 
symptoms have been reported to occur 3-5 months aft er infection (Samuels et al. 2012). The 
recommendation for cacao is to quarantine nursery s tock for six months before distributing to other 
regions to avoid spread of R. theobromae  (McMahon and Purwantara 2016). Although there is n o 
evidence that R. theobromae  can infect avocado asymptomatically, Anderson (198 9) and McMahon 
and Purwantara (2016) suggested that the fungus may  occur as an innocuous endophyte or weak 
pathogen in unknown native host species within its natural range, where cacao and avocado are 
introduced. 
Fruiting bodies develop on leaf scars and cracks in  leaves and stems, which are symptoms of the 
disease (Samuels et al. 2012). The fungus would not  be given the opportunity to sporulate in PEQ 
because it is highly likely that symptoms such as l eaf scars and cracks in leaves and stems would be 
detected during visual inspections, prior to the de velopment of fruiting bodies. Furthermore, the lack  
of overhead watering in PEQ (MPI 2021) will prevent  sporulation because the growth of fruiting bodies 
is dependent on wet foliage (Guest and Keane 2007).  Therefore, it is considered highly unlikely that 
airborne spores would be produced in PEQ. 
Given the arguments and evidence above, that is:  
• Rhizoctonia theobromae  has only been reported to infect cacao plants with  the exception of 
one report found of it infecting avocado plants , 
• new infections may not be detected prior to export  as symptoms take 3-5 months to occur,  
• Rhizoctonia theobromae  could be present inside leafless avocado budwood a nd such 
infections are unlikely to be manged by surface dis infection,  
• cacao budwood harvested from infected branches can not be used for grafting because grafts 
do not take, meaning that infections are highly unl ikely to be spread through grafting in cacao, 
however, this has not been tested in avocado, 
• if R. theobromae  is imported into PEQ then it is likely to produce visible symptoms during the 
period of containment,  
• it is considered highly unlikely that airborne spo res would be produced and escape PEQ via 
air vents, 
the likelihood of R. theobromae  entering New Zealand associated with P. americana  (avocado) 
budwood is considered to be negligible, with low un certainty.   
5.26.5  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of R. theobromae  entering New Zealand associated with P. americana  budwood 
is considered to be negligible with low uncertainty . Therefore, continuing the assessment is 
considered unnecessary; and  
the overall level of risk to New Zealand from R. theobromae  on imported P. americana budwood is 
considered to be negligible, with low uncertainty.  
5.26.6  Management considerations  
Vascular-streak dieback, caused by R. theobromae  is characterised by chlorotic leaf spots, 
defoliation, cracks in leaves and stems showing bla ckened vascular tissue and mortality in young 
seedlings. No evidence or records of asymptomatic R. theobromae infections were found in the 
literature, although Anderson (1989) and McMahon an d Purwantara (2016) suggested that the fungus 
may occur as an innocuous endophyte or weak pathoge n in unknown native host species in its 
natural range. These unknown species may act as an inoculum reservoir. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 332 Symptoms are a key diagnostic indicator for R. theobromae infection because its fastidious nature 
makes it very hard to isolate and maintain in pure culture, and difficult to study (Samuels et al. 201 2; 
Ali et al. 2019). 
Currently, R. theobromae  is identified based on PCR/sequencing of internal transcribed spacer (ITS) 
regions (Samuels et al. 2012; McMahon and Purwantar a 2016). Sampling is likely best performed 
during prolonged warm and wet weather. The best pla nt material to test is the leaf petiole and the 
midrib of mature leaves, or vascular tissue from sy mptomatic plant material (Samuels et al. 2012).  
Wet conditions are important factors for symptom de velopment, reproduction and natural dispersal. 
The disease is most common in tropical climates and  wetter regions where annual rainfall exceeds 
2,500 mm (Guest and Keane 2007). The main commercia l avocado production is centred within 
Northland, Auckland and Bay of Plenty where average  annual rainfall ranges from about 1350 mm in 
Kaitaia to 1180 mm in Tauranga (NIWA 2021). The fun gus requires a living host to survive and does 
not survive on dead plant material. The disease is not transmissible via seed, cuttings or grafting in  
cacao, but this has not been tested in avocado (Gue st and Keane 2007).  
No information was found in the literature on the m anagement of vascular-streak dieback disease in 
avocado plantations but the management methods used  in cacao plantations are likely to apply. 
Monitoring cacao planting materials for symptoms of  vascular-streak disease before distributing is 
recommended to prevent the spread of the disease. T he international movement of cocoa germplasm 
requires a pre-export quarantine period of 6 months  (Perrine-Walker et al. 2018). In cacao, the 
disease can be effectively managed by implementing phytosanitary measures such as nursery 
hygiene, planting in new locations distant from old er diseased plants or covering of plants in nurseri es 
to exclude inoculum. Pruning to remove infected bra nches and to increase aeration and sunlight on 
the foliage will decrease sporulation and new infec tions. Some systemic fungicides have been shown 
to control vascular-streak dieback but are likely t o be uneconomic compared to other management 
methods (Guest and Keane 2007; Perrine-Walker et al . 2018). 
5.26.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
The disease symptoms of R. theobromae appear to be similar in avocado and cacao (Anderson  
1989). Initial symptoms in avocado include chloroti c and necrotic spots on leaves. The spores of the 
fungus infect young unhardened leaves but leaf symp toms usually occur 3-5 months after infection, 
by which time the infected leaves will have aged an d hardened, and young healthy looking flushes of 
leaves will have developed on the shoot (Samuels et  al. 2012). The apparent absence of green spots 
on avocado leaves is a notable difference to the gr een spots that present on cacao leaves (Samuels 
et al. 2012; Perrine-Walker et al. 2018).  
As the infection progresses, the vascular tissue be comes blackened and is visible in the leaf scars of  
abscised leaves, or as dark streaks in split stems.  The bark can become rough due to swollen 
lenticels in response to stress. Severe infections result in defoliation, the death of branches and st ems 
and often kill young seedings. White fruiting bodie s develop on leaf scars and stems after several 
days of wet weather (Anderson 1989; Samuels et al. 2012; Perrine-Walker et al. 2018). 
Although there is no evidence that R. theobromae  can infect cacao or avocado asymptomatically, the 
fungus was assumed to live in unknown native host s pecies in its natural range, in which it perhaps 
occurs as an innocuous endophyte or weak pathogen ( Anderson 1989; McMahon and Purwantara 
2016). 
o What are the known environmental conditions conduci ve to symptom expression?  
333 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Rhizoctonia theobromae  causes disease in tropical climates in Asia and pa rts of Melanesia (Table 
5-26). The rate of symptom development is closely c orrelated with rainfall during a few prior months 
and, the disease is most common in wetter regions w here annual rainfall exceeds 2,500 mm (Guest 
and Keane 2007). The main commercial avocado produc tion is centred within Northland, Auckland 
and Bay of Plenty where average annual rainfall ran ges from about 1350 mm in Kaitaia to 1180 mm in 
Tauranga (NIWA 2021). Periods of high rainfall and humidity are required for the development of 
white fruiting bodies around leaf scars and on stem s (Samuels et al. 2012).   
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
In cacao, vascular tissue may be colonised early on  during infection (Samuels et al. 2012), therefore,  
testing vascular tissue might yield a better chance  of detection than other parts of the plant. The 
emergence of spores appears to happen most frequent ly through fresh leaf scars and cracks in the 
petiole or midrib (McMahon and Purwantara 2016). Th is fastidious49 pathogen is very hard to isolate 
and maintain in pure culture (Samuels et al. 2012; Ali et al. 2019).  
o What is the optimum season for conducting detection  testing?  
Rhizoctonia theobromae  occurs in tropical climates in South East Asia (Ta ble 5-26), suggesting that 
in New Zealand, the fungus is most likely to grow d uring summer, under warm and wet conditions. 
High rainfall and humidity are required for the pro duction of white fruiting bodies around leaf scars and 
on stems (Samuels et al. 2012), but in the absence of overhead irrigation the fungus is unlikely to 
sporulate in PEQ. 
5.26.8  References 
Ali, S S; Asman, A; Shao, J; Firmansyah, A P; Susil o, A W; Rosmana, A, et al. (2019) Draft genome 
sequence of fastidious pathogen Ceratobasidium theobromae , which causes vascular-streak dieback 
in Theobroma cacao . Fungal biology and biotechnology 6(1): 1-10. 
Anderson, R (1989) Avocado, an alternate host for Oncobasidium theobromae . Australasian Plant 
Pathology 18(4): 96. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
EPPO (2011) Rhizoctonia theobromae (ONCOTH): Distribution. 
https://gd.eppo.int/taxon/ONCOTH/distribution   
Guest, D; Keane, P (2007) Vascular-streak dieback: a new encounter disease of cacao in Papua New 
Guinea and southeast Asia Caused by the obligate ba sidiomycete Oncobasidium theobromae . 
Phytopathology® 97(12): 1654-1657. 
McMahon, P; Purwantara, A (2016) Vascular streak di eback ( Ceratobasidium theobromae ): history 
and biology. Cacao Diseases.  Springer. 
MPI (2021) Facility Standard: Post Entry Quarantine for Plants . Ministry for Primary Industries, 
https://www.mpi.govt.nz/dmsdocument/11368-Post-Entr y-Quarantine-forPlants-Facilities-Standard  
NIWA (2021) Climate data and activities. https://niwa.co.nz/education-and-
training/schools/resources/climate  Accessed November 2021 
 
49  A fastidious organism has very complicated nutriti onal and/or environmental requirements and will not  grow without specific 
factors present or in specific conditions.  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 334 NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
Oberwinkler, F; Riess, K; Bauer, R; Kirschner, R; G arnica, S (2013) Taxonomic re-evaluation of the 
Ceratobasidium -Rhizoctonia  complex and Rhizoctonia butinii , a new species attacking spruce. 
Mycological Progress 12(4): 763-776. 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Perrine-Walker, F; McMahon, P; Guest, D (2018) Ceratobasidium theobromae (Talbot & Keane). 
https://www.appsnet.org/Publications/potm/pdf/Sep18 .pdf   
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2019) FreshFacts: New Zealand Horticulture. . The New Zealand Institute for 
Plant and Food Research Ltd; Auckland, New Zealand. ,  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Roberts, P (1999) Rhizoctonia-forming fungi—a taxonomic guide.  
Samuels, G J; Ismaiel, A; Rosmana, A; Junaid, M; Gu est, D; Mcmahon, P, et al. (2012) Vascular 
streak dieback of cacao in Southeast Asia and Melan esia: in planta detection of the pathogen and a 
new taxonomy. Fungal biology 116(1): 11-23. 
Ali, S S; Asman, A; Shao, J; Firmansyah, A P; Susil o, A W; Rosmana, A, et al. (2019) Draft genome 
sequence of fastidious pathogen Ceratobasidium theobromae , which causes vascular-streak dieback 
in Theobroma cacao . Fungal biology and biotechnology 6(1): 1-10. 
Anderson, R (1989) Avocado, an alternate host for Oncobasidium theobromae . Australasian Plant 
Pathology 18(4): 96. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
EPPO (2011) Rhizoctonia theobromae (ONCOTH): Distribution. 
https://gd.eppo.int/taxon/ONCOTH/distribution   
Guest, D; Keane, P (2007) Vascular-streak dieback: a new encounter disease of cacao in Papua New 
Guinea and southeast Asia Caused by the obligate ba sidiomycete Oncobasidium theobromae . 
Phytopathology® 97(12): 1654-1657. 
McMahon, P; Purwantara, A (2016) Vascular streak di eback ( Ceratobasidium theobromae ): history 
and biology. Cacao Diseases.  Springer. 
MPI (2021) Facility Standard: Post Entry Quarantine for Plants . Ministry for Primary Industries, 
https://www.mpi.govt.nz/dmsdocument/11368-Post-Entr y-Quarantine-forPlants-Facilities-Standard  
NIWA (2021) Climate data and activities. https://niwa.co.nz/education-and-
training/schools/resources/climate  Accessed November 2021 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
Oberwinkler, F; Riess, K; Bauer, R; Kirschner, R; G arnica, S (2013) Taxonomic re-evaluation of the 
Ceratobasidium -Rhizoctonia  complex and Rhizoctonia butinii , a new species attacking spruce. 
Mycological Progress 12(4): 763-776.  
335 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Perrine-Walker, F; McMahon, P; Guest, D (2018) Ceratobasidium theobromae (Talbot & Keane). 
https://www.appsnet.org/Publications/potm/pdf/Sep18 .pdf   
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2019) FreshFacts: New Zealand Horticulture. . The New Zealand Institute for 
Plant and Food Research Ltd; Auckland, New Zealand. ,  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Roberts, P (1999) Rhizoctonia-forming fungi—a taxonomic guide.  
Samuels, G J; Ismaiel, A; Rosmana, A; Junaid, M; Gu est, D; Mcmahon, P, et al. (2012) Vascular 
streak dieback of cacao in Southeast Asia and Melan esia: in planta detection of the pathogen and a 
new taxonomy. Fungal biology 116(1): 11-23. 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 336 5.27  Scolecobasidium musae  (sooty blotch and flyspeck (SBFS)) 
Scolecobasidium musae is an epiphytic fungus that has occasionally been r eported to colonise the 
surface of banana and avocado plants. It is conside red to be a part of the sooty blotch and flyspeck 
complex (SBFS) which contains more than 100 species  in 30 genera of Ascomycota and 
Basidiomycota. 
5.27.1  Taxonomic description  
Scientific name: Scolecobasidium musae (G.Y. Sun & Lu Hao) Samerp. & de Hoog Order/Family: 
Venturiales / Sympoventuriaceae 
Other names include : Ochroconis musae G.Y. Sun & Lu Hao and Ochroconis mirabilis Samerp. & 
de Hoog 
Taxonomic notes : The genus Scolecobasidium was historically separated from Ochroconis based on 
morphological differences, but this distinction was  not supported by subsequent molecular 
phylogenetic analyses. Therefore, Scolecobasidium  and  Ochroconis  are currently considered to be 
synonymous (Shen et al. 2020). 
5.27.2  Hazard identification 
Scolecobasidium musae is not known to be present in New Zealand: 
• Scolecobasidium musae is not listed in NZOR (2021), Biota NZ (2022) or PP IN (2021). 
• The regulatory status of S. musae has not been assessed (ONZPR 2021). 
Scolecobasidium musae has the potential to establish (and spread) in New Zealand because: 
• There are two records of S. musae  in association with banana plants, and one record where it 
is associated with an avocado plant. Both of these hosts are grown mainly in the north of the 
North Island, and avocado plants are in commercial production in Northland and Bay of 
Plenty. 
• The climate in New Zealand is unlikely to limit it s development and spread because S. musae 
has been reported in areas that have a Climate Matc h Index (CMI) ≥ 0.9, and reported to 
associate with plant hosts in areas that have a Cli mate Match Index (CMI) ≥ 0.7 (There are 
multiple, reliable records of Akaropeltopsis  sp. causing sooty blotch on avocado in South 
Africa (Theron et al. 1981; Smith et al. 1985; Smit h et al. 1987; Korsten et al. 1997).  
There is little information on the distribution of Akaropeltopsis  sp. elsewhere in the world, and the 
records of its distribution are largely unsubstanti ated or unconfirmed (Theron et al. 1981; Smith et a l. 
1987; Queensland Government 2001), as follows: 
• Sooty blotch on avocado in Australia has been repo rted to be caused by a range of causative 
agents, including Stomiopeltis  sp. (Coates et al. 2001; Willingham 2002; Cooke et  al. 2009), 
Akaropeltopsis  spp./ Stomiopeltis  spp. complex (Queensland Government 2001), and mul tiple 
non-specified fungi (Allen 2004). Given that the ca usative agents of sooty blotch on avocado 
have been confused in the past due to the high leve l of morphological similarity between 
Akaropeltopsis  and Stomiopeltis (Theron et al. 1981; Smith et al. 1987), and that t here were 
no records found describing Akaropeltopsis  sp. on avocado in Australia, there is uncertainty 
regarding the presence of Akaropeltopsis  sp. in Australia.  
• Akaropeltopsis  sp. has been reported to be present and associated  with avocado in 
Colombia, but this is based on international litera ture compilation and not from direct 
observation. According to the USDA (2016), the pres ence of Akaropeltopsis  sp. in Colombia 
is ‘doubtful’. 
• Akaropeltopsis  sp. appears to be similar to A. marchaeriifolii  found on leaves of a 
Machaerium  sp. in Brazil, but these species have not been con firmed to be conspecific  
337 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand (Theron et al. 1981; Smith et al. 1987). No other r ecords were found in the literature of 
Akaropeltopsis  sp. causing sooty blotch in Brazil. 
• Table 5-1) indicating a similar climate to the who le of New Zealand (Phillips et al. 2018). 
Scolecobasidium musae has the potential to cause harm to New Zealand beca use: 
• SBFS results in dark blemishes on the fruit, leave s and stems of host plants, but it does not 
cause any physiological damage to the underlying ti ssue (Hao et al. 2013). However, if 
symptoms occurred on avocado fruit, it could reduce  the marketability and value of avocado 
fruit, 
• avocados are an important commercial crop in New Z ealand. In 2020, export sales of fresh 
avocados earned NZ$100.1 million and domestic sales  earned NZ$50.6 million, while export 
sales of avocado oil earned $NZ9.3 million (Plant &  Food Research 2020). 
Scolecobasidium musae is associated with P. americana  budwood because: 
• it has been isolated from a trichome50 of a P. americana  leaf, 
• no records were found of S. musae on stems of host plants, but SBFS fungi complex (of  
which is S. musae is a part of) is known to occur on stems, 
Given the arguments and evidence above, S. musae  meets the criteria to be a hazard on P. 
americana  budwood (as in the commodity description) imported  to New Zealand. 
5.27.3  Risk assessment 
Biology and epidemiology 
Scolecobasidium musae is an epiphytic fungus that has been occasionally r eported to colonise the 
surface of plants. For this reason, it is considere d to be a part of the sooty blotch and flyspeck 
complex (SBFS), which contains more than 100 specie s in 30 genera of Ascomycota and 
Basidiomycota (Gleason et al. 2019). For this asses sment, where specific information on S. musae  
was not available in the literature, information re garding SBFS complex in general was applied to S. 
musae as it is considered to be a member of the SBFS comp lex.  
Species in the genus  Scolecobasidium  (syn.  Ochroconis ) are oligotrophs51 and opportunistic 
pathogens. Scolecobasidium spp. have been isolated from water, soil, plants, d omestic environments 
(bathrooms, laundries), skin on a human foot, cold blooded animals such as salmon and trout, and 
the cuticle of an ant species (Hao et al. 2013; Sam erpitak et al. 2014).   
Distribution and Host range  
Scolecobasidium musae  appears to be widespread in parts of Asia and Euro pe (Table 5-27). 
However, it has only been reported in association w ith plants under tropical conditions in China and 
Thailand (Table 5-27), and only reported to cause s ymptoms on the leaves (Crous et al. 2021) and 
fruit (Hao et al. 2013) of Musa basjoo . The limited information in the literature suggest s that S. musae  
is either not common, or common but not frequently reported. 
 
50 Trichomes are unicellular or multicellular hair-lik e appendages, that grow from the epidermal cells of  a plant (Wang et al. 
2021). 
51 Oligotrophs are organisms that can live in nutrient  deficient environments. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 338 Table 5-27. The potential geographic distribution o f Scolecobasidium musae .  
Region Country  CMI52  range Host References 
Asia China 0.4 – 0.9 Musa  sp. Hao et al. (2013); Crous et al. (2021) 
Thailand 0.2 – 0.5 Persea americana Crous et al. (2019) 
India 0.2 – 0.9 unknown Institute (2021) 
Africa Egypt 0.4 – 0.6 soil Crous et al. (2021) 
America USA 0.5 – 0.9 unknown Institute (2021) 
Europe Austria 0.7 – 0.9 unknown Institute (2021) 
Denmark 0.8 – 0.9 unknown Institute (2021) 
Germany 0.8 – 0.9 domestic Crous et al. (2021) 
Netherlands 0.9 unknown Institute (2021) 
Sweden 0.6 – 0.9 unknown Institute (2021) 
Symptoms 
The fungi that cause SBFS are epiphytic and colonis e the epicuticular wax layer of stems, twigs, 
leaves, and fruit (Gleason et al. 2019).   
Scolecobasidium musae  is slow growing and does not damage the underlying  tissue (Gleason et al. 
2019; Crous et al. 2021). It produces shiny, black,  sclerotium-like mycelial colonies (Hao et al. 2013 ) 
that appear as a dark speckle on the leaves (Crous et al. 2021) and fruit (Hao et al. 2013) of Musa 
basjoo .  
SBFS causes surface blemishes on hosts plants, howe ver, there are no records in the literature of 
any significant disease problems caused by S. musae . Although S. musae was isolated from leaf 
trichomes of an avocado plant (Crous et al. 2019), no information was found in the literature on the 
symptoms, suggesting that it does not cause signifi cant disease on avocado either. 
Optimal conditions for growth and symptom developme nt 
SBFS occurs in summer in warm and moist conditions (Hao et al. 2013). Scolecobasidium musae has 
only been isolated from plant hosts in tropical cli mates in China and Thailand (Table 5-27). When 
cultured in-vitro, S. musae  formed colonies 30mm in diameter after 20 days at 25 ° C (Hao et al. 
2013). No records of asymptomatic S. musae  infections were found in the literature.  
Reproduction and transmission  
Scolecobasidium musae produces small conidia (6.5–8.5×2.0– 3.0 μm) that are most likely 
transported by wind and rain during the summer (Gle ason et al. 2019). Scolecobasidium spp. are 
known to colonise a wide range of substrates includ ing soil (Hao et al. 2013), indicating their potent ial 
to overwinter and spread on these substrates. 
5.27.4  Likelihood of entry 
There is potential for S. musae to be imported into post-entry quarantine (PEQ) on avocado budwood, 
in which case it would be likely to produce visible  symptoms in PEQ.  
Scolecobasidium musae has been isolated from plants in tropical regions i ncluding Thailand and 
China (Table 5-27).  
 
52  Climate Match Index (CMI) with all of New Zealand (Phillips et al. 2018).  
339 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Scolecobasidium musae has only been recorded on leaves and fruit of host plants, but SBFS (caused 
by a large fungi complex that includes S. musae ) is reported to occur on the leaves, stems and fru it of 
host plants (Gleason et al. 2019), so association w ith leafless avocado budwood is considered to be 
possible. 
Budwood cuttings are dipped in 1% sodium hypochlori te for 2 minutes upon entry into the quarantine 
facility, which is considered to substantially redu ce the risk of importing S. musae into PEQ. 
If the fungus is imported into PEQ, then three dist inct phenological growing events referred to as 
‘shoot flush’ is likely to be a sufficient time per iod for the fungus to develop visually detectable 
colonies on the surface infected budwood. No record s of asymptomatic infections were found in the 
literature.  
Conidia are small (6.5–8.5×2.0– 3.0 μm) and may fit through the mesh screen over the lev el 3A PEQ 
vents is required to have a maximum opening size of  0.04 mm 2 (MPI 2021). However, it is likely that 
S. musae would be detected by plant inspections before spore s are produced because SBFS fungi 
are typically slow growing and not likely to sporul ate rapidly (Gleason et al. 2019). Furthermore, the  
literature suggests that conidia are spread by wind  and rain, and such conditions are unlikely to occu r 
in PEQ. 
Given the arguments and evidence above, that is:  
• Scolecobasidium musae has only been reported in association with plants i n tropical climates 
(Table 5-27).  
• Scolecobasidium musae could be present on the surface of budwood but such  infections are 
highly likely to be manged by 1% sodium hypochlorit e for 2 minutes upon entry into the 
quarantine facility.  
• if S. musae is imported into PEQ then it is likely to produce v isible symptoms during the 
period of containment. 
• Scolecobasidium musae  is unlikely to produce spores between inspections in PEQ. Even 
though S. musae  spores are small enough to fit through the mesh ov er the vents of level 3A 
PEQ, windy and rainy conditions are likely required  for transmission through the air and such 
conditions are unlikely to occur in PEQ. 
the likelihood of S. musae  entering New Zealand associated with P. americana  (avocado) budwood is 
considered to be negligible, with low uncertainty.   
5.27.5  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of S. musae  entering New Zealand associated with P. americana  budwood is 
considered to be negligible with low uncertainty. T herefore, continuing the assessment is 
considered unnecessary; and  
the overall level of risk to New Zealand from S. musae  on imported P. americana budwood is 
considered to be negligible, with low uncertainty.  
5.27.6  Management considerations  
Scolecobasidium musae is an epiphytic fungus that  produces shiny, black, sclerotium-like mycelial 
colonies (Hao et al. 2013). They have been reported  to appear as a conspicuous dark speckle on the 
leaves (Crous et al. 2021) and fruit (Hao et al. 20 13) of Musa basjoo . Although S. musae was isolated 
from leaf trichomes of an avocado plant (Crous et a l. 2019), no information was found in the literatur e 
on the symptoms on avocado, suggesting that it is n ot a major disease of avocado. 
SBFS occurs in summer in warm and moist conditions (Hao et al. 2013). Although Scolecobasidium 
musae is distributed in both temperate to tropical climat es, it has only been reported to associate with Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 340 plant hosts in tropical climates (Table 5-27). No r ecords of asymptomatic S. musae  infections were 
found in the literature. 
Field applications of strobilurin and succinate deh ydrogenase inhibitor fungicides have been shown to 
be very effective against SBFS fungi (Gleason et al . 2019). 
Post-harvest dip solutions, from chlorine bleach to  sodium bicarbonate and various fruit soaps, 
followed by brushing, are effective at removing mos t sooty blotch and flyspeck colonies and 
symptoms (Gleason et al. 2019). 
5.27.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
The fungi that cause sooty blotch and flyspeck (SBF S) are epiphytic53 and colonise the epicuticular 
wax layer 54  of stems, twigs, leaves, and fruit. Their dark-col oured colonies are conspicuous to the 
naked eye and for this reason, fungi in the SBFS co mplex are considered to be highly noticeable 
plant-associated microbes (Gleason et al. 2019). In  particular, S. musae produces shiny, black, 
sclerotium 55 -like mycelial colonies (Hao et al. 2013) that appe ar as a dark speckle on the leaves 
(Crous et al. 2021) and fruit (Hao et al. 2013) of Musa basjoo . Although S. musae was isolated from 
leaf trichomes of an avocado plant (Crous et al. 20 19), no information was found in the literature on 
the symptoms on avocado, suggesting that it is not a major disease in avocado. 
o What are the known environmental conditions conduci ve to symptom expression? 
SBFS occurs in summer in warm and moist conditions.  Scolecobasidium musae is distributed in a 
range of countries, from temperate to tropical clim ates, but it has only been reported in association 
with plants in tropical climates (Table 5-27). When  cultured in-vitro, S. musae  formed colonies 30mm 
in diameter after 20 days at 25° C (Hao et al. 2013) .  
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
SBFS typically occurs on the fruit, leaves and stem s of hosts (Gleason et al. 2019). Only one record 
was found of S. musae on an avocado plant in the literature, where it was  isolated from leaf trichomes 
in 2008 (Crous et al. 2019). No records of asymptom atic S. musae  infections were found. 
o What is the optimum season for conducting detection  testing?  
SBFS is a late-season disease which occurs in moist  and warm growing conditions during the 
summer (Hao et al. 2013). 
5.27.8  References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
 
53  An epiphytic fungus is a fungus that grows on the surface of a living plant.  
54  An epicuticular wax is a coating of wax covering t he outer surface of the plant cuticle in land plant s. 
55  A sclerotium is a hard, dense, compact mass of myc elium that varies in form and has a dark-coloured c overing.  
341 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Crous, P W; Carlier, J; Roussel, V; Groenewald, J Z  (2021) Pseudocercospora  and allied genera 
associated with leaf spots of banana ( Musa  spp.). Fungal systematics and evolution 7: 1–19. 
Crous, P W; Schumacher, R K; Akulov, A; Thangavel, R; Hernández-Restrepo, M; Carnegie, A J, et 
al. (2019) New and interesting fungi. 2. Fungal systematics and evolution 3(1): 57-134. 
Gleason, M L; Zhang, R; J.C;, B; Sun, G (2019) Stea lth pathogens: the sooty blotch and flyspeck 
fungal complex. Annual Review of Phytopathology 57: 135-164. 
Hao, L; Chen, C; Zhang, R; Zhu, M; Sun, G; Gleason,  M L (2013) A new species of Scolecobasidium  
associated with the sooty blotch and flyspeck compl ex on banana from China. Mycol Progress 12: 
489–495. 
Institute, W F B (2021) CBS-KNAW Collections. https://wi.knaw.nl/page/fungal_table   
MPI (2021) Facility Standard: Post Entry Quarantine for Plants . Ministry for Primary Industries, 
https://www.mpi.govt.nz/dmsdocument/11368-Post-Entr y-Quarantine-forPlants-Facilities-Standard  
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX ‘match climates regional’  
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Samerpitak, K; Van der Linde, E; Choi, H J; Gerrits  van den Ende, A H G; Machouart, M; Gueidan, C, 
et al. (2014) Taxonomy of Ochroconis , genus including opportunistic pathogens on humans  and 
animals. Fungal Diversity 65(1): 89-126. 
Shen, M; Zhang, J Q; Zhao, L L; Groenewald, J Z; Cr ous, P W; Zhang, Y (2020) Venturiales. Studies 
in Mycology 96: 185-308. 
Wang, X; Shen, C; Meng, P; Tan, G; Lv, L (2021) Ana lysis and review of trichomes in plants. BMC 
Plant Biology 21(1). 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 342 5.28  Sooty moulds 
Sooty mould is a generic name used to describe a wi de range of fungus species that cover the 
surfaces of above ground plant parts with a black, sooty coating and are generally associated with the  
sugary exudates of sap-sucking insects. Heavy infes tation may inhibit photosynthesis and the 
unsightly mould may degrade the market value of pro duce.  
5.28.1  Taxonomic description 
Table 5-28: Taxonomy of sooty mould species that ma y be associated with avocado budwood. 
Taxonomy determined from Index Fungorum (2022).  
Scientific name Order/Family Other names 
Antennulariella batistae S. 
Hughes Capnodiales/ 
Antennulariellaceae Capnodendron trichomericola, 
Septonema perseae, Antennariella 
perseae, Capnodium capsuliferum 
Calothyrium apiahynum 
(Spegazzini) F. Stevens Microthyriales/ 
Microthyriaceae Calothyriolum apiahynum, 
Calothyriolum aphiaphynum 
Capnodium spp.  Mont. Capnodiales/ Capnodiaceae  
Lembosia perseae Orejuela Asterinales/ Asterinaceae  
Meliola antioquensis 
Orejuela  Meliolales/ Meliolaceae  
Asteridiella perseae (F. 
Stevens) Hansf.  Meliolales/ Meliolaceae Irene perseae , Meliola perseae , 
Irenina perseae , Meliola perseae  f. 
setulifera , Appendiculella perseae  
Periconiella perseae  
McKenzie Mycosphaerellales/ 
Mycosphaerellaceae  
Taxonomic notes:  
The term “sooty moulds” is not clearly defined and refers to a polyphyletic group of fungi. Initially the 
term was used to described fungi in the genus Fumago  (Chomnunti et al. 2014). The classification of 
these fungi varies considerably in the literature. Therefore, it is difficult to determine which speci es 
should be considered as sooty moulds. Sooty moulds are generally considered to be of the orders 
Capnodiales and Chaetothyriales (Chomnunti et al. 2 014; Abdollahzadeh et al. 2020). Hongsanan et 
al. (2015) state that Asterdales and Meliolales are  distinct from sooty moulds as some species may 
penetrate host cells. However, Bernal and Diaz (200 6) consider that Capnodium  spp., Calothyrium 
aphiahynum , Lembosia perseae , Meliola antioquensis  and Asteridiella perseae  found on avocado all 
share the characteristics of sooty moulds. The desc ription of Periconiella perseae  indicates this fungi 
is also superficial (McKenzie 1990) and is consider ed similar to sooty fungi. For the purposes of this  
PRA all the species listed in Table 5-28 are consid ered to be similar enough in biology and 
epidemiology to be assessed as a single group. 
5.28.2  Hazard identification 
The sooty mould species listed in Table 5-28 are no t known to be present in New Zealand: 
o Antennulariella batistae, Calothyrium apiahynum, Le mbosia perseae, Meliola antioquensis  
and Asteridiella perseae are not listed in NZOR (2021), Biota NZ (2022), or ONZPR 
(2021).  
343 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand o Periconiella perseae is recorded as absent from New Zealand in NZOR (202 1) and Biota 
NZ (2022) and  is listed as “regulated” in ONZPR (2021).  
o It is unknown if species of Capnodium that infect avocado are present in New Zealand. 
Capnodium is a large genus of approximately 150 species, only  six of which are reported 
present in New Zealand ( C. annonae , C. australe, C. citri, C. fibrosum, C. walteri and C. 
uniseptatum ) and one species has unknown biostatus ( C. sphaeroideum ).(NZOR 2021; 
Biota NZ 2022). Six species in the genus Capnodium  are listed as “non-regulated” ( C. 
annonae, C. australe, C. citricolum, C. salicinum, C. uniseptatum, and C. walteri ), four 
species are “regulated” ( C. elaeophilum, C. mangiferum, C. citri  and C. tanakae ) and one 
species is “under assessment” ( C. y fumaco ) in ONZPR (2021).  
The sooty mould species listed in Table 5-28 have t he potential to establish (and spread) in New 
Zealand because: 
o These sooty mould species are typically distribute d in tropical and sub-tropical regions 
(Chomnunti et al. 2014), so may find suitable envir onments in some regions of 
New Zealand.  
o Avocado trees are grown commercially and in home g ardens in some parts of 
New Zealand and would provide a host for mould esta blishment.  
The sooty mould species listed in Table 5-28 have t he potential to cause harm to New Zealand 
because: 
o Infections by sooty moulds are predominantly super ficial and rarely damage plant tissues, 
but they can reduce the photosynthetic capabilities  of host plants (Chomnunti et al. 2014). 
o Their presence on fruit may reduce market value of  avocado and other potential hosts 
(Chomnunti et al. 2014). 
The sooty mould species listed in Table 5-28  are associated with P. americana budwood because: 
o They have been reported associated with above grou nd plant parts of avocado so 
propagules may be present on stems and around the b ud on avocado budwood (Tamayo 
and Julián 2007; Unites States Department of Agricu lture 2016).  
Given the arguments and evidence above, the sooty m ould species listed in Table 5-28 meet the 
criteria to be a hazard on P. americana  budwood (as in the commodity description) imported  to 
New Zealand. 
5.28.3  Risk assessment 
Biology and epidemiology of sooty moulds 
Host range and Distribution 
Some sooty moulds reported on avocados appear to ha ve a limited host range, while the host range 
of other species may be much broader. These fungi t ypically develop on the exudates of sap sucking 
insects and it is unclear if association are insect  or plant host specific (Chomnunti et al. 2014). So me 
sooty moulds are not found in association with inse cts and may instead grow on sap released from 
the leaves or stems through structures such as glan dular trichomes (Hughes 1976). However, the 
sooty mould species investigated in this assessment  have not been reported on avocado in the 
absence of insects.  
Table 5-29: Host range of sooty moulds reported in association with avocado.  
Species Known hosts References 
Antennulariella batistae  35 host species are reported in 17 plant families. Hosts 
significant to New Zealand include Persea americana 
and  Citrus sinensis (orange).   Hughes (2000) 
Calothyrium apiahynum  Persea americana, Persea sp., P. palustris Tamayo and Julián (2007) Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 344 Species Known hosts References 
Capnodium spp.  Persea americana 
Capnodium  species are reported on a wide range of 
host plants. Tamayo and Julián (2007); 
Ramírez-Gil and Morales 
(2019) 
Lembosia perseae  Persea americana , Persea sp. Buritica (1999); Tamayo and 
Julián (2007) 
Meliola antioquensis  Persea americana , P. petiolaris Buritica (1999); Tamayo and 
Julián (2007) 
Asteridiella perseae Persea americana Buritica (1999); Tamayo and 
Julián (2007) 
Periconiella perseae  Persea americana McKenzie (1990) 
These sooty mould species are typically distributed  in tropical and sub-tropical regions (Chomnunti et  
al. 2014), so may find suitable environments in som e regions of New Zealand.  
Table 5-30: Distribution of sooty moulds associated  with avocado. 
Species Known distribution References CMI range 
Antennulariella 
batistae  Americas: Bahamas, Belize, Brazil, Cuba, 
Jamaica, Panama, Puerto Rico, USA 
(Florida, Hawaii) 
Asia: Philippines 
Africa: South Africa Hughes (2000) 0.4-0.8 
Calothyrium 
apiahynum  Americas: Brazil, Colombia, USA 
(Florida) Farr and Rossman (2021) 0.4-0.7 
Capnodium spp.  Genus distributed worldwide. Reported 
on P. americana  in Cuba, Venezuela and 
Zimbabwe.  Whiteside (1966); (Urtiaga 1986); 
Ramírez-Gil and Morales (2019); Farr 
and Rossman (2021) 0.5-0.7 
Lembosia 
perseae  Colombia Buritica (1999); Farr and Rossman 
(2021) 0.4-0.8 
Meliola 
antioquensis  Colombia Spaulding (1961); Buritica (1999); 
Farr and Rossman (2021) 0.4-0.8 
Asteridiella 
perseae Americas: Colombia, Dominican 
Republic, Panama, Puerto Rico, USA 
(Florida), Venezuela, Virgin Islands Buritica (1999); Tamayo and Julián 
(2007); Farr and Rossman (2021) 0.3-0.8 
Periconiella 
perseae  Oceania: Australia, Samoa, Vanuatu, 
Palau McKenzie (1990); Farr and Rossman 
(2021); Biota NZ (2022) 0.4-0.9 
Symptoms 
The specific symptoms produced by sooty mould speci es are difficult to ascertain, as they are 
frequently comprised of a mixture of various fungal  species (Hughes 2000; Chomnunti et al. 2014). 
Information regarding the symptoms observed on avoc ado are also limited: 
o Antennulariella batistae predominantly occurs on the leaves of host plants, but specific 
symptoms on avocado are not reported (Hughes 2000).   
o The symptoms of C. apiahynum  and L. perseae on avocado are not specifically reported 
but sooty mould are generally described as causing a thin, black layer on the leaves, 
stems and fruits of avocado (Tamayo and Julián 2007 ). This layer is easily scrapped from 
the plant surface. It may result in stains to the s urface of leaves or fruits.  
o Capnodium sp.  are reported causing sooty mould on P. americana  in Zimbabwe following 
scale infestation (Mwenje et al. 2010). Infection i s characterised by a black layer of mycelia 
on the upper surface of the leaf, or on stems and f ruit (Ramírez-Gil and Morales 2019; 
Ramírez-Gil and Peterson 2019). Outbreaks are typic ally observed on adult avocado trees  
345 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand but may also occur on seedlings (Ramírez-Gil and Mo rales 2019). This genus has also 
been implicated in causing pre-harvest soft rot of avocado fruit (Mwenje et al. 2010).  
o Meliola antioquensis  is reported as causing large black patches on the leaves of P. 
petiolaris  in Colombia (Spaulding 1961). Symptoms on P. americana  have not been 
reported however it has been associated with this h ost (Table 5-30). 
o Asteridiella perseae  is reported to cause a highly visible, dense, velv ety covering on the 
surface of avocado fruit (Unites States Department of Agriculture 2016).  
o McKenzie (1990) described P. perseae  as a superficial black mould growth on the under 
surface of avocado leaves. The leaves showed some r eddish-brown discolouration. The 
conidiophores were observed to be concentrated to t he mid-rib and veins of the leaves. 
Optimal conditions for growth and symptom developme nt 
Sooty moulds are most prevalent in tropical, subtro pical, and warm temperate regions (Chomnunti et 
al. 2014) and growth is favoured by humid condition s and the presence of sap-sucking insects 
(Tamayo and Julián 2007).  
Reproduction and transmission 
Sooty moulds are transmitted through wind, rain or insect dispersal of ascospores, conidia and hyphal 
fragments (Ploetz 2003; Chomnunti et al. 2014). The  spores germinate once in contact with insect 
exudates (Chomnunti et al. 2014).  
5.28.4  Likelihood of entry 
Sooty moulds  usually infect the leaves of hosts but can sometime s colonise the surface of leaf 
petioles and plant stems (Callan and Carris 2004), indicating they may be associated with leafless 
avocado budwood. New infections by sooty moulds may  not be detected prior to export as the 
development of symptoms may be slow and dependent o n environmental conditions (Callan and 
Carris 2004). Therefore, it is possible that propag ules of sooty mould on the surface of avocado 
budwood may be imported into New Zealand and may no t be evident during initial inspection.  
Sooty mould infections are superficial and endophyt ism is not known for any of these species on 
avocado. Dalvi et al. (2002) showed that washing ma ngo fruits with 0.05-0.1% sodium hypochlorite 
was effective at removing sooty moulds (Chomnunti e t al. 2014). Treatment with sodium hypochlorite 
is also generally considered an effective method fo r removal of sooty moulds from avocado fruits 
(Ploetz 2003). Therefore, the risk of importing soo ty mould propagules  into PEQ after dipping 
avocado budwood in 1% sodium hypochlorite for 2 min utes upon entry into the quarantine facility is 
considered to be very low. 
Sooty moulds are strongly associated with the prese nce of sap-sucking insects and proliferate in 
warm, humid conditions (Chomnunti et al. 2014). Whi le quarantine facilities are like to maintain high 
temperatures, insects will not be present, and humi dity may be variable. In the absence of suitable 
growth conditions, propagules are likely to die out  (Prakash and Misra 2001), and would not be viable 
upon release of the plants from PEQ. If environment al conditions within PEQ are suitable, the period 
of PEQ is likely to be sufficient to produce conspi cuous symptoms of sooty moulds on infected 
budwood.  
Ascospores of Capnodium  species may be as small as 10 μm (Ramírez-Gil and Morales 2019) and 
spores of Meliola species are usually no longer than 10 μm (Callan and Carris 2004). This indicates 
that spores of sooty moulds would likely fit throug h the mesh screen of Level 3A PEQ vents, which 
are required to have a maximum opening size of 40 μm (MPI 2021). However, growth of sooty moulds 
is conspicuous and likely to be detected before spo res are produced. Furthermore, windy and wet 
conditions, and potentially insect dispersal, are r equired to transport  spores (Ploetz 2003; Chomnunti 
et al. 2014), and such conditions are unlikely to o ccur in PEQ. 
Given the arguments and evidence above, that is: Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 346 • sooty moulds may be present on the surface of budw ood imported into New Zealand, but 
such infections are highly likely to be manged by 1 % sodium hypochlorite for 2 minutes upon 
entry into the quarantine facility,  
• if sooty moulds  are imported into PEQ, they may not produce visible  symptoms during the 
period of containment but would become inviable, 
• if growth of sooty moulds occurs the symptoms are highly likely to be detected and it is 
unlikely that spores will be produced prior to dete ction, and  
• conditions aiding spore dispersal are unlikely to occur in PEQ, 
the likelihood of the sooty mould species listed in  Table 5-28 entering New Zealand associated with P. 
americana budwood is considered to be negligible, with low un certainty. Therefore, further 
assessment is considered unnecessary at this time; likelihoods of exposure and establishment and 
impacts to New Zealand are not further assessed.  
5.28.5  Overall level of associated risk to New Zealand 
Based on the assessment of likelihood above, that: 
• the likelihood of the sooty mould species listed i n Table 5-28  entering New Zealand 
associated with P. americana  budwood (as described in the commodity description , and 
taking into account the growing period of active gr owth with a minimum of three distinct 
phenological growing events referred to as ‘shoot f lush’ in 3A PEQ) is considered negligible, 
with low uncertainty; 
the overall level of risk to New Zealand from the s ooty mould species listed in Table 5-28 on imported  
P. americana  budwood is considered to be negligible, with low u ncertainty.  
5.28.6  Management considerations 
Information is limited regarding the specific sympt oms of the sooty mould species to deemed them as 
hazard on avocado. Generally, sooty moulds produce a conspicuous dense, black covering on the 
surfaces of above-ground plant parts (Tamayo and Ju lián 2007). The symptoms of the sooty mould 
species being assessed is not expected to differ fr om typical symptoms.  
No reports were found in the literature of sooty mo ulds infecting hosts asymptomatically or 
endophytically. As these fungi are primarily superf icial colonisers, they are only expected to be 
undetectable as propagules and during the earliest stages of infection. These fungi predominantly 
colonise leaves but may also be observed on stems, branches or petioles (Tamayo and Julián 2007). 
Mould growth may be observed on young or mature gro wth, but more growth may occur on the lower 
regions of plants where shading and humidity is gre ater (Tamayo and Julián 2007).  
Any plant surface exhibiting the previously describ ed symptoms can be sampled to identify the 
infection. Identification of sooty moulds is made p rimarily through morphological identification, and 
there are few sequences of sooty moulds available f or molecular identification (Chomnunti et al. 
2014). There are no sequences recorded in GenBank  for any of the species of this assessment, but 
there are sequences of various Capnodium species available (Clark et al. 2016).  
The sooty moulds in this assessment are distributed  in warm and wet climates (Chomnunti et al. 
2014). Mycelial growth is promoted by moisture (dew , rain, high humidity), shade and warm 
temperatures, as well as the presence of sap-suckin g insects (Tamayo and Julián 2007; Chomnunti et 
al. 2014). The conditions conducive to symptom expr ession are the same conditions that promote the 
growth of the fungus, because the main symptom is t he formation of black fungal colonies on the 
surface of the host. The environmental conditions o f a PEQ facility may not be suitable for growth of 
sooty moulds. Humidity may be lower than is necessa ry, and sap-sucking insects are not expected to 
be present. However, if conditions are not conduciv e, it is expected that any propagules that are 
present would become inviable (Prakash and Misra 20 01). Summer is likely the optimum season for 
detection of sooty moulds (Chomnunti et al. 2014). However, given the conspicuous symptoms of 
sooty moulds, growth at any time of year is likely to be detected by visual inspection.   
347 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Spores of sooty mould species are likely small enou gh to fit through the mesh screen of Level 3A 
PEQ vents (Callan and Carris 2004; Ramírez-Gil and Morales 2019), which are required to have a 
maximum opening size of 40 μm (Ramírez-Gil and Morales 2019; MPI 2021). However , growth of 
sooty moulds is conspicuous and likely to be detect ed before spores are produced. Furthermore, 
windy and wet conditions, and potentially insect di spersal, are required to transport  spores (Ploetz 
2003; Chomnunti et al. 2014), and such conditions a re unlikely to occur in PEQ. 
5.28.7  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Information is limited regarding the specific sympt oms of the sooty mould species deemed a hazard 
on avocado. Generally, sooty moulds produce a consp icuous dense, black, mycelial covering on the 
surfaces of above-ground plant parts (Chomnunti et al. 2014; Unites States Department of Agriculture 
2016). The symptoms of the sooty mould species bein g assessed is not expected to differ from typical 
symptoms.  
o What are the known environmental conditions conduci ve to symptom expression? 
The sooty moulds in this assessment are distributed  in warm and wet climates (Chomnunti et al. 
2014). Mycelial growth is promoted by moisture (dew , rain, high humidity), shade and warm 
temperatures, as well as the presence of sap-suckin g insects (Chomnunti et al. 2014). The conditions 
conducive to symptom expression are the same condit ions that promote the growth of the fungus, 
because the main symptom is the formation of black fungal colonies on the surface of the host. 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
No reports were found in the literature of sooty mo ulds infecting hosts asymptomatically. As these 
fungi are superficial colonisers, they are only exp ected to be undetectable as propagules and during 
the earliest stages on infection. These fungi predo minantly colonise leaves but may also be observed 
on stems, branches or petioles (Unites States Depar tment of Agriculture 2016). 
o What is the optimum season for conducting detection  testing? 
Summer is likely the optimum season for detection o f sooty moulds due to warm temperatures and 
high humidity (Chomnunti et al. 2014). However, giv en the conspicuous symptoms of sooty moulds, 
growth at any time of year is likely to be detected  by visual inspection. 
5.28.8  References  
Abdollahzadeh, J; Groenewald, J Z; Coetzee, M P A; Wingfield, M J; Crous, P W (2020) Evolution of 
lifestyles in Capnodiales. Studies in Mycology 95: 381–414. 
Bernal, J; Diaz, C (2006) Tecnología para el Cultivo del Aguacate.  Corporación Colombiana de 
Investigación Agropecuaria, CORPOICA, Centro de Inv estigación La Selva, Rionegro, Antioquia, 
Colombia.  
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 348 Buritica, C (1999) Directorio de patógenos y enfermedades de las plant as de importancia económica 
en Colombia . Instituto Colombiano Agropecuario, Medellin, Colo mbia.  
Callan, B E; Carris, L M (2004) Fungi living on pla nt substrata, including fruits. In G M Mueller; G F  
Bills; M S Foster (eds) Biodiversity of Fungi.  Academic Press: Burlington. 
Chomnunti, P; Hongsanan, S; Aguirre-Hudson, B; Tian , Q; Peršoh, D; Dhami, M K, et al. (2014) The 
sooty moulds. Fungal Diversity 66(1): 1–36. 
Clark, K; Karsch-Mizrachi, I; Lipman, D J; Ostell, J; Sayers, E W (2016) GenBank. Nucleic acids 
research 44(D1): 67–72. 
Dalvi, M B; Godse, S K; Shinde, A K; Patil, B P (20 02) Evaluation of cleaning agents for sooty mould 
(Capnodium species)-affected mango ( Mangifera indica ) fruits. 72: 223–224. 
Farr, D F; Rossman, A Y (2021) Fungal databases, U.  S. National Fungus Collections. https://nt.ars-
grin.gov/fungaldatabases/  Accessed Septemeber 27, 2021 
Hongsanan, S; Tian, Q; Hyde, K; Chomnunti, P (2015)  Two new species of sooty moulds, Capnodium 
coffeicola  and Conidiocarpus plumeriae  in Capnodiaceae. Mycosphere 6: 814–824. 
Hughes, S (2000) Antennulariella batistae  n. sp. and its Capnodendron and Antennariella 
synanamorphs, with notes on Capnodium capsuliferum . Canadian Journal of Botany 78(9): 1215–
1226. 
Hughes, S J (1976) Sooty moulds. Mycologia 68(4): 693-820. 
Index Fungorum (2022) Index Fungorum. http://www.indexfungorum.org/names/Names.asp   
McKenzie, E (1990) New species of Periconiella . Mycotaxon 39: 229–236. 
MPI (2021) Facility Standard: Post Entry Quarantine for Plants . Ministry for Primary Industries, 
https://www.mpi.govt.nz/dmsdocument/11368-Post-Entr y-Quarantine-forPlants-Facilities-Standard  
Mwenje, E; Churu, T; Kudanga, T (2010) Pre-harvest spoilage of avocado ( Persea americana ) fruits 
by Capnodium isolates in Zimbabwe. Journal of Applied Science in Southern Africa 9. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Ploetz, R C (2003) Diseases of tropical fruit crops  (R C Ploetz Ed.). CAB International; United 
Kingdom. 
Prakash, O; Misra, A K (2001) Diseases of mango and  their management. In T S Thind (ed) Diseases 
of Fruits and Vegetables and their Management. 1st ed. Kalyani Publishers. 
Ramírez-Gil, J G; Morales, J G (2019) Polyphasic id entification of preharvest pathologies and 
disorders in avocado cv. Hass. Agronomía Colombiana 37(3): 213-227. 
Ramírez-Gil, J G; Peterson, A T (2019) Current and potential distributions of the most important 
diseases affecting Hass avocado in Antioquia Colomb ia. Journal of Plant Protection Research 59(2). 
Spaulding, P (1961) Foreign diseases of forest trees of the world: an a nnotated list . US Department of 
Agriculture, USA.  
Tamayo, M; Julián, P (2007) Enfermedades del aguaca te. Revista politécnica 3(4): 51–70.  
349 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Unites States Department of Agriculture (2016) Impo rtation of fresh fruit of avocado, Persea 
americana  Miller var. 'Hass', into the continental United St ates from Colombia. In U S D o Agriculture 
(Ed.), (pp. 1-112). USA: Unites States Department o f Agriculture. 
Urtiaga, R (1986) Indice de enfermedades en plantas de Venezuela y Cu ba . 
Whiteside, J O (1966) A revised list of plant disea ses in Rhodesia. Kirkia 5(2): 87–196. 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 350 6. Pest risk assessments: Oomycetes 
6.1  Phytophthora mengei  (Phytophthora trunk canker) 
Phytophthora mengei  is a soil borne water mould (oomycete) that causes  trunk cankers in avocado 
(Persea americana ) plants. It can also infect the structural roots, lower limbs and fruit of the plant/tree.  
6.1.1  Taxonomic description 
Scientific name: Phytophthora mengei G.T. Brown, M.E. Gallegly & C.X. Hong 2009  
Order/Family: Peronosporales/Peronosporaceae.  
Other names include : Phytophthora citricola (prior to 2009, P. mengei  was considered to be a 
subgroup of  P. citricola  that infected avocado). 
Taxonomic notes:  The pathogen was identified first as a Pythiacystis  sp. A year later it was 
redescribed as Phytophthora cactorum  (Lebert and Cohn) J. Schrot. Phytophthora citricola  was 
separated from P. cactorum  by Sawada in 1927. The avocado canker pathogen was  subsequently 
identified as Phytophthora citricola  (Sawada). In 1973,  et al. recognised that the avo cado canker 
pathogen was morphologically distinct from P. citricola  (Hong et al. 2009). 
Hong et al. (2009) recognised the avocado canker pa thogen as a distinct species from P. citricola  
based on morphological and molecular differences an d re-classified it as the novel species 
Phytophthora mengei .  Literature published prior to 2009 that refers t o P. citricola  as a pathogen on 
avocado or other hosts is likely to correspond with  P. mengei , as the literature suggests that P. 
citricola is not a pathogen of avocado. This creates uncertai nty regarding the pathogen’s distribution 
and host associations.  
Phytophthora citricola  was first identified in New Zealand in 1938 in hop s. It has since been found on 
various hosts in New Zealand including avocado. Gen etic analysis conducted by Scion and the Plant 
Health and Environment Laboratory (PHEL) showed tha t some isolates assigned as P. citricola  were 
actually two recently described species within the P. citricola  complex: P. multivora  and P. plurivora  
(Romberg 2010). As there are no records of P. mengei in New Zealand, these records of P. citricola 
on avocado in New Zealand could refer to P. multivora , as it is a known pathogen of avocado (Farr 
and Rossman 2021).  
There are 64 records of Phytophthora on avocado in PPIN (2021), 4 in STARS, 7 in LIMS (M PI 
2021a), and 3 in Biota NZ (2022). The majority of t hese records are P. cinnamomi , followed by P. 
cryptogea  and P. megasperma . The remaining are 3 records of P. citricola and 2 records of 
Phytophthora sp.. Among these 5 records, four records cannot be reassessed due to lack of cultures. 
The remaining record is genetically close to P. drechsleri , which is distinct from the P. citricola  species 
complex. PHEL conducted DNA sequence analysis on pu blished sequences of P. mengei  from 
GenBank with DNA sequences from the PHEL database w hich contains 31k sequences that have 
been generated in the past 13 years. It contains ma ny P. citricola sequences, but analysis shows that 
none of these are P. mengei .  Phytophthora mengei sequences in GenBank are limited (~4) and are 
only from California, Mexico, and Guatemala. PHEL’s  analysis found no evidence to suggest that P. 
mengei is present in New Zealand and suggests that most re cords of P. citricola in New Zealand and 
other countries are unlikely to be P. mengei (W. Ho, pers. comm.). 
6.1.2  Hazard identification 
Phytophthora mengei is not known to be present in New Zealand: 
• Phytophthora mengei is not listed in either Biota NZ (2022) or PPIN (20 21). 
• There is no entry for Phytophthora mengei in ONZPR (2021).  
351 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Phytophthora mengei has the potential to establish (and spread) in New Zealand because: 
• avocado is grown commercially and domestically in northern parts of New Zealand. The climate 
in New Zealand is likely to be suitable for the rep roduction and spread of P. mengei. 
Phytophthora mengei produces abundant chlamydospores, oospores and zoos pores. 
Chlamydospores, oospores can survive in adverse env ironmental conditions for several years 
making it very difficult to eradicate. They are spr ead by watersplash, windblown rain, animals, 
insects, humans, equipment and vehicles (Marais et al. 2002; Marais 2004). 
Phytophthora mengei has the potential to cause harm to New Zealand beca use: 
• it causes trunk canker on avocado trees, resulting  in reduced tree health, reduced productivity 
and eventual tree death. Fungicide applications can  be used to prevent infection and reduce 
disease prevalence, but there is no way of eradicat ing the disease from an orchard (Marais 
2004).  
• Avocados are an important commercial crop in New Z ealand. In the 2019–2020 financial year, 
export sales of fresh avocados earned NZ$110 millio n and domestic sales earned NZ$56.5 
million (Plant & Food Research 2020). 
Phytophthora mengei may be associated with P. americana  budwood because:  
• Persea americana  is a known host of P. mengei  (Eskalen and Faber 2016).   
• Phytophthora mengei infects woody tissue  (Marais 2004). 
Given the arguments and evidence above, P. mengei meets the criteria to be a hazard on P. americana  
budwood (as in the commodity description) imported to New Zealand. 
6.1.3  Risk assessment 
Biology and epidemiology of Phytophthora mengei 
Host range 
Phytophthora mengei is a pathogen of Persea americana (Eskalen and Faber 2016; Farr and 
Rossman 2021). There is one record of Vigna unguiculata  (cowpea) as a host in Australia (Martin et 
al. 2014), but this is the only record of Phytophthora mengei  infecting a host that is not in the  Persea  
genus, as well as the only report of P. mengei in Australia, and should therefore be treated with 
caution.  
Some of the newer clonal rootstocks which are resis tant to Phytophthora root rot (caused by 
Phytophthora cinnamomi ) such as Thomas, are susceptible to P. citricola (now P. mengei ) (El-
Hamalawi and Menge 1994; Marais 2004). Plants propa gated as clones have more Phytophthora  
resistance than plants propagated from seed (Eskale n and Faber 2016).  
Geographical distribution 
Phytophthora mengei  has a limited geographical distribution (Table 5-2 8) 
Table 6-1: The geographical distribution of Phytophthora mengei  (Farr and Rossman 2021). 
Region Country State/Province  (if recorded) CMI56  range 
North America and the 
Caribbean Guatemala  0.3–0.6 
Mexico  0.4–0.8 
USA California 0.5–0.8 
Oceania Australia  0.4–1 
 
56 Climate Match Index (CMI) with all of New Zealand ( Phillips et al. 2018). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 352 Phytophthora mengei is present in Mexico and the United States of Ameri ca (California) (Table 5-28). 
There is some uncertainty associated with the recor ds of in Australia and Guatemala. There is one 
record of P. mengei  in Australia on Vigna unguiculata  (cowpea) (Martin et al. 2014), but this is the 
only record of P. mengei  infecting a non- Persea  host, as well as the only report of P. mengei  in 
Australia and should therefore be treated with caut ion (Table 5-28). Plant Health Australia considers 
P. mengei to be a high priority pest and states that it is no t present in Australia and only present in 
USA and Mexico (Plant Health Australia 2021). Phytophthora mengei  has also been reported in 
Guatemala, which is likely as it is present in Mexi co (Table 5-28).  
Symptoms 
Phytophthora mengei  causes cankers in the structural roots, base of th e trunk and lower limbs of 
older host trees. Cankers grow slowly (over multipl e years) and often go unnoticed until girdling has 
occurred and foliar dieback symptoms appear. Canker s are discoloured and can exude a red 
resinous, water-soluble exudate through cracks in t he bark. This exudate dries to form a white 
crystalline deposit on bark. Cutting into a canker reveals a necrotic brown outer layer of wood instea d 
of the normal white- or cream-coloured tissues and has a fruity odour when exposed to air. The 
cankers have distinct reddish-brown margins from wh ich the fungus can readily be isolated (Marais 
2004).  
Foliar symptoms are similar to those of Phytophthor a root rot (caused by P. cinnamomi ). With 
Phytophthora trunk canker (caused by P. mengei ), leaves retain their normal size and there is a 
gradual loss of leaves causing canopy thinning, whe reas branch dieback (staghorning) is less typical. 
Unlike root rot, canker and collar rot affects the major tree roots, and the smaller feeder roots are 
usually still present. In mild to moderate canker s tages the host tree foliage can appear healthy. Fol iar 
dieback occurs when the canker progresses to a stag e when it starts killing cambium and phloem 
tissues, effectively girdling the trunk (Marais 200 4; Eskalen and Faber 2016). 
The disease may infect low hanging fruit under some  conditions, particularly in prolonged wet 
weather. Infected fruit have a distinct dark circul ar area that usually occurs at the lowest part of t he 
fruit. Internally, the rot extends into the flesh, darkening it in the same pattern as the affected ar ea on 
the surface (Marais 2004). 
Reproduction and spread 
Phytophthora mengei can propagate sexually or asexually, resulting in s everal types of structures that 
are specialised for survival, dispersal, or infecti on.  Sexual reproduction requires both mating types  
and leads to the formation of thick-walled oospores  that can survive for several years in harsh 
environments. In contrast, asexual reproduction inv olves the formation of sporangia and bi-flagellated  
wall-less zoospores (Hwu et al. 2017). The minimum temperature for colony growth is 6–10°  C, the 
optimum about 25°  C, and the maximum 30–33°  C (Hong  et al. 2009). 
The development of lesions and reproductive and dis persive spores is favoured by high soil moisture 
levels, and dispersal is closely related to the mov ement of water. Sporangia develop on lesions and 
release mobile zoospores in moist or wet conditions . Zoospores are the main infective structures 
because they can swim through films of water on tre es or in the soil, and can accumulate in puddles 
and ponds, making them easily dispersed by water sp lash (Martin et al. 2014).  
Wounding is necessary for infection by P. mengei  as spores cannot penetrate the bark or the 
structural barrier of lenticels (Shew and Benson 19 81; Ouimette et al. 1988; El-Hamalawi and Menge 
1994; Martin et al. 2014). Zoospores use chemotaxis  to find wounds, and when they find a suitable 
infection site, they stops swimming, drop their fla gella and develop a cell wall (encyst). Hyphae 
germinate from cysts, invading plant cells to obtai n food. Once the pathogen infects the plant, it 
produces more chlamydospores, oospores, and/or spor angia, thus completing its life cycle (Parke 
2016).  
There are two types of thick-walled resting spores:  vegetative chlamydospores and sexual oospores 
can survive adverse environmental conditions for se veral years and contribute to the pathogen’s 
persistence in soils in the absence of hosts, makin g it very difficult to control (El-Hamalawi and Men ge 
1994; Bunny and Shearer 1995; Bradshaw et al. 2020) .  
353 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand The sugary exudate that is associated with cankers has been shown to be a source of inoculum as it 
contains zoospores, oospores and hyphal fragments. Canker/lesion exudate contaminates the soil 
around the base of the tree. Ants were shown to be attracted to the sugary exudate and could 
possibly  transmit the pathogen. Snails were also i dentified as a possible vector as their faeces were  
shown to contain viable propagules that were not on ly resistant to, but stimulated to germinate by the  
digestive secretion of the snail (El-Hamalawi and M enge 1996). 
One of the primary ways in which the disease is spr ead is through the trade of infected nursery stock.  
Nurseries that do not take precautions to disinfect  water used for irrigation purposes, sterilize pott ing 
media and keep containers off the ground, are respo nsible for disseminating the disease throughout 
the industry (Marais 2004). The pathogen can also b e spread via contaminated pruning tools, harvesting  
equipment and vehicles, on the shoes of pickers cli mbing into the trees, by storms and water movement,  
and by insects and animals (El-Hamalawi and Menge 1 994; El-Hamalawi and Menge 1996; Marais 
2004). 
In avocado orchards, the removal of sucker shoots f rom the crown is common practice. This may be a 
major source of new infection and spread because co ntaminated equipment will injure and inoculate 
host trees with the pathogen (El-Hamalawi and Menge  1994). The use of irrigation systems is another 
source of disease, as cankers and lesions caused by  P. mengei  often occur on the side of trunks wetted 
by irrigation sprinklers. Spore spread and disease development are favoured by wet conditions (Marais 
2004). 
Time to symptom development  
In one greenhouse trial, lesions developed on 5-1 0  month-old avocado plants in under 40 days from 
inoculation of susceptible avocado tissues in suita ble environmental conditions (El-Hamalawi and 
Menge 1994). In another trial, lesions developed on  2-year old avocado plant stems within 4 weeks of 
inoculation (El-Hamalawi and Menge 1996). Foliar di eback symptoms only occur in late stages of 
canker development when the pathogen starts killing  cambium and phloem tissues and disrupting the 
transportation of nutrients (Marais 2004). 
There is no specific information available in the l iterature regarding whether an avocado host can be 
infected by P. mengei  and remain asymptomatic. A range of Phytophthora  species are reported to 
colonise and survive in symptomless or tolerant hos t plants, for example P. rubi  and P. idaei  
(Schlenzig and Chard 2010), P. cryptogea  (Lyubenova et al. 2015), P. erythroseptica  (Peters et al. 
2005), P. cinnamomi  (Jacobs et al. 1997; Crone et al. 2013), P. infestans  (Hussain et al. 2013) P. 
inundata  ((Parkunan et al. 2010), P. ramorum and P. kernoviae  (Denman et al. 2009; Thompson et al. 
2021). Migliorini et al. (2015) tested potted ornam ental plants in the EU using qPCR and detected 
Phytophthora  in 87% of the tested pots and in 70% of the asympt omatic potted plants. Potted plants 
in soil carried several Phytophthora  species without showing any external symptoms. Som e  
Phytophthora  sp. can remain viable within the xylem for a numbe r of years (Brown and Brasier 2007). 
6.1.4  Likelihood of entry 
There is potential for P. mengei to be imported into post-entry quarantine on P. americana nursery stock 
because P. mengei can be present on leafless, rootless budwood cuttin gs and is reported in several 
countries that have a significant avocado industry:   
• It is possible that budwood could be harvested fro m infected trees because cankers often go 
unnoticed for several years, but it is unlikely tha t infected budwood would be harvested 
because infections are usually localised in the tru nk, collar and low hanging branches (Marais 
et al. 2002). If sanitary procedures are not follow ed during budwood harvesting then there 
may be opportunity for budwood to be infected becau se Phytophthora mengei  infects wounds 
and can be transmitted by humans and contaminated e quipment (Marais et al. 2002). 
• Phytophthora mengei causes cankers and lesions on woody avocado stems, therefore it  can 
be associated with leafless, rootless avocado budwo od cuttings. However, such cankers and 
lesions are highly likely to be visually detected o n budwood during preparation for export or on 
arrival in New Zealand. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 354 • Phytophthora mengei is present in  Mexico, the United States of America (California) a nd 
Guatemala. There is one unreliable record of P. mengei  in Australia (Table 5-28). 
If P. mengei is imported on avocado budwood, the residual biosec urity risks may not be managed by 
the proposed growing period of active growth with a  minimum of three distinct phenological growing 
events referred to as ‘shoot flush’ in 3A PEQ becau se: 
• There is no specific evidence for asymptomatic P. mengei infections or longer latent periods 
in avocado plants. El-Hamalawi and Menge (1994) sho wed that lesions on avocado stems 
caused by P. mengei infection developed within 40 days from inoculation , which would be 
enough time to develop, be detected by visual inspe ction and destroyed before they are 
released from PEQ. However, some  Phytophthora  species such as P. cinnamomi  can infect 
hosts asymptomatically (Crone et al. 2013). Phytophthora citricola  has been shown to infect 
the xylem of some hosts, although xylem infections did not extend further than 10cm from the 
source infection (a visible phloem lesion). Some  Phytophthora  sp. can remain viable within 
the xylem for a number of years (Brown and Brasier 2007). If P. mengei is capable if infecting 
the xylem, and if  the budwood is harvested from within close proximit y to a lesion, there is a 
chance that it could be imported in the xylem of bu dwood and not develop external symptoms 
for several years. The fact that Phytophthora  pathogens can be present without visible 
symptoms, provides reason to suggest that P. mengei may not be managed by PEQ in some 
circumstances. 
Given the arguments and evidence above, that is:  
• Phytophthora mengei can infect wounds in woody tissue. It is likely tha t symptoms (lesions) 
will develop and be detected in Level 3A PEQ. Altho ugh there is no evidence of asymptomatic 
P. mengei  infections or longer latent periods in avocado pla nts, other Phytophthora 
pathogens can be asymptomatic or infect the xylem o f hosts. Such infections may not be 
visually detectable, 
the likelihood of P. mengei entering New Zealand associated with P. americana  budwood is 
considered to be low, with moderate uncertainty. 
6.1.5  Likelihood of exposure 
This assessment is made on the basis that P. mengei has entered New Zealand undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for P. mengei .   
If avocado plants are infected with P. mengei at the time of their release from post entry quaran tine 
they will be planted in New Zealand or used to prop agate new plants for planting (see section 2.3 for 
additional information about exposure).  
Given the arguments above, the likelihood of exposu re of P. mengei in New Zealand from P. 
americana  budwood is considered high, with low uncertainty.  
6.1.6  Likelihood of establishment 
This assessment is made on the basis that P. mengei has been successfully exposed to a suitable host 
plant in the New Zealand environment. 
Suitable hosts for P. mengei are widespread in some areas of New Zealand. Commer cial and 
domestic avocado production is concentrated in Nort hland and Bay of Plenty. Of the 3,795 hectares 
that are planted in commercial avocados, 1,647 are in Northland and 1,834 in the Bay of Plenty.  
355 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand There is smaller scale commercial production in Auc kland, Waikato, Gisborne, Hawke’s Bay, 
Taranaki, Manawatu-Wairarapa, Wellington and Tasman /Nelson (Plant & Food Research 2019).  
The required temperature range required for P. mengei colony growth is a minimum of 6-10° C, optimum 
of 25° C and a maximum of 30-33°  C (Hong et al. 2009 ). The mean annual temperature of Northland 
and Bay of Plenty is between 14-16° C. Typical summe r daytime maximum air temperatures range from 
22° C to 26° C in Northland (MPI 2021b). During summe r the Bay of Plenty region experiences average 
daily air temperatures over 20° C (MPI 2021b). This indicates that P. mengei  could grow in New Zealand 
temperatures. 
Northland and Bay of Plenty both receive abundant r ainfall within the range of 1-2.2 metres median 
annual total rainfall (Chappell 2013b, 2013a), whic h would create favourable conditions for disease 
development and spread of  P. mengei . 
It is highly likely that there will be suitable env ironmental conditions for  P. mengei to produce spores 
and infect avocado hosts year-round. Furthermore, P. mengei has been recorded in avocado in 
California, USA (Eskalen and Faber 2016) which has a CMI of ≥0.7, indicating a similar climate to New 
Zealand (Phillips et al. 2018). Marais (2004) repor ted that P. citricola  (now P. mengei ) is more of a 
problem on avocado in the cooler coastal production  areas of California, which is more similar to the 
New Zealand climate than other areas of California.  
Once P. mengei is established in New Zealand, the long-lived resti ng spores of P. mengei could  
continue to provide an ongoing source of inoculum f or several years, making it very difficult to eradi cate 
(El-Hamalawi and Menge 1994; El-Hamalawi and Menge 1996; Marais 2004). 
Host availability is likely to be the main limit on  the extent of spread of P. mengei in New Zealand, given 
that P. americana is the only reliably reported host (see ‘Host range ’ section) . Phytophthora mengei is 
likely to be able to survive and reproduce in any r egion of New Zealand where avocado plants can 
survive. 
Given the arguments and evidence above,  
• avocado is common in many regions of New Zealand a nd is the only known host of P. mengei . 
• the climate, temperature and rainfall in New Zeala nd’s avocado growing regions are 
favourable for P. mengei growth and reproduction. 
• the high levels of rainfall in Northland and Bay o f Plenty would facilitate disease development 
and spread. 
• once P. mengei is established in New Zealand, the long-lived resti ng spores of P. mengei 
could continue to provide an ongoing source of inoc ulum for several years, making it very 
difficult to eradicate; 
the likelihood of P. mengei establishing in New Zealand is considered high with  low uncertainty. 
6.1.7  Impacts in New Zealand 
Phytophthora mengei  causes cankers in the structural roots, base of th e trunk and lower limbs of 
older host trees. Cankers grow slowly (over multipl e years) and often go unnoticed until girdling has 
occurred and foliar dieback symptoms appear. Phytophthora mengei can propagate sexually or 
asexually, resulting in several types of structures  that are specialised for survival, dispersal, or 
infection.  The development of lesions and reproduc tive and dispersive spores is favoured by high soil  
moisture levels, and dispersal is closely related t o the movement of water. Sporangia develop on 
lesions and release mobile zoospores in moist or we t conditions. Zoospores are the main infective 
structures because they can swim through films of w ater on trees or in the soil, and can accumulate in  
puddles and ponds, making them easily dispersed by water splash (Martin et al. 2014). Wounding is 
necessary for infection by P. mengei  as spores cannot penetrate the bark or the structu ral barrier of 
lenticels (Shew and Benson 1981; Ouimette et al. 19 88; El-Hamalawi and Menge 1994; Martin et al. 
2014). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 356 Economic impacts 
Avocado ( P. americana) is the only reliably documented host of P. mengei. However, P. mengei  was 
only differentiated from P. citricola  in 2009, so it is probable that many isolates that  were called P. 
citricola  have not been reidentified as P. mengei.  Given this single host association, the economic 
impacts of P. mengei are considered to be limited to the avocado industr y and communities in avocado 
production areas, with moderate uncertainty. Impact s on the avocado industry are likely to be moderate  
for the following reasons:   
Phytophthora mengei  was reported as the second most limiting pathogen to avocado production in 
California, behind Phytophthora cinnamomi (Marais et al. 2002).  Phytophthora mengei may cause 
similar losses to the avocado industry as Avocado S un Blotch viroid disease (Marais 2004). 
Phytophthora mengei is apparently present in 90% of avocado orchards in  California, but the disease 
only occurs in approximately 5% of these orchards, compared to P. cinnamomi which appears to cause 
disease in 60 to 75% of orchards (Marais 2004). The  difference between the two Phytophthora  species 
in regard to infection rate and subsequent disease in orchards may be due to the fact that P. mengei  
requires wounds to infect the above ground parts of  healthy trees, whereas P. cinnamomi  is primarily a 
root pathogen and can infect roots in the absence o f wounds (Marais 2004).  
Chemical treatments that are used to manage P. cinnamomi and other Phytophthora  pathogens 
already present in New Zealand, are also likely to be effective against P. mengei , so the additional 
costs for chemical treatment of P. mengei may not increase significantly. On the other hand, damage 
caused by P. cinnamomi, animals and tree pruning has been shown to facilita te P. mengei  infection of 
avocado trees (Ouimette et al. 1988). Furthermore, P. mengei  infects the trunk, collar and low 
hanging branches of avocado trees whereas P. cinnamomi  is primarily a root pathogen, suggesting 
that new pest management practices may need to be i mplemented to manage P. mengei  if it were to 
establish. Some of the newer clonal rootstocks whic h are resistant to Phytophthora root rot (caused 
by P. cinnamomi ) such as Thomas, are susceptible to P. citricola (now P. mengei ) (El-Hamalawi and 
Menge 1994; Marais 2004).  
Phytophthora mengei can infect low hanging fruit (within 1 meter from t he ground) in prolonged wet 
conditions, but this is of relatively minor importa nce in California, and is not likely to be a major factor 
in New Zealand.  
The introduction of P. mengei could result in market access restrictions for expo rts of fresh avocados 
to some countries. Australia is currently the main export market for New Zealand avocados, importing 
approximately 80% of export grade fruit. Australia considers P. mengei  to be a high priority (Plant 
Health Australia 2021). The remainder is exported t o Japan, USA and South East Asian markets  
(New Zealand Avocado 2021). 
In the 2018–2019 financial year, 31424 tonnes of av ocados were produced in New Zealand. Export 
sales of fresh avocados in 2018–2019 earned NZ$110 million and domestic sales earned NZ$56.5 
million. In addition, avocado oil earned NZ$10 mill ion (combined domestic and export sales) (Plant & 
Food Research 2019). 
Given the arguments and evidence above, that is: 
• Phytophthora mengei  was reported as the second most limiting pathogen to avocado 
production in California, behind Phytophthora cinnamomi (Marais et al. 2002).  Chemical 
treatments that are used to manage P. cinnamomi and other Phytophthora  pathogens already 
present in New Zealand may also manage P. mengei , which may mitigate some of the impacts 
associated with its establishment in New Zealand,  
• The presence of P. mengei  in New Zealand could result in market access restr ictions for export 
since this pathogen is reported to infect fruit (Ma rais et al. 2002). Export sales of fresh avocados 
in 2018–2019 earned NZ$110m (Plant & Food Research 2019),  
the economic impact of P. mengei  to New Zealand is considered to be moderate, with low uncertainty.  
357 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Environmental impacts 
There are five indigenous New Zealand plant species  in the Lauraceae family (three endemic and two 
non-endemic) (Webb et al. 1988). However, no record s were found of P. mengei infecting any species 
outside of the Persea genus, apart from in Vigna unguiculata  (cowpea) (see ‘Host range’ section) . Since 
the Lauraceae is a widespread family, including oth er important plant species and P. mengei is not 
reported from other genera in the family, the likel ihood that it poses a risk to indigenous New Zealan d 
plant species is considered to be low. 
Given the arguments and evidence above and assuming  that the pathogen is restricted to lauraceous 
hosts, the impact on the environment from the estab lishment of P. mengei in New Zealand is considered 
to be low, with moderate uncertainty. 
Human Health impacts 
No evidence for human  health impacts from P. mengei was found:  
• Searches using the terms ‘Phytophthora mengei’ or ‘Phytophthora citricola’ in Pubmed, Google 
Scholar, CAB abstracts and Google found no mention of adverse effects on humans and 
animals. 
Given the arguments and evidence above, the human h ealth impact of P. mengei to New Zealand is 
considered to be negligible with low uncertainty. 
Sociocultural impacts 
Avocados are widely consumed in New Zealand. In som e parts of the country avocado trees are 
common in domestic gardens. Trunk canker may increa se production costs for growers, but it is unlikely  
to cause scarcity in local markets. 
Given the arguments and evidence above, the social/ cultural  impacts of P. mengei to New Zealand are 
considered to be low, with low uncertainty. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, health and society is considered to be 
moderate, with moderate uncertainty. 
6.1.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above and in table 1, that:  
• the likelihood of entry is low 
• assuming entry, the likelihood of exposure is high  
• assuming successful exposure, the likelihood of es tablishment is high 
• the overall impact on the New Zealand economy, env ironment, health and society is 
considered to be moderate 
the overall level of assessed risk to New Zealand f rom P. mengei  on imported Persea americana 
budwood (as in the commodity description) is consid ered to be moderate, with moderate uncertainty. 
6.1.9  Management considerations 
Phytophthora mengei causes cankers in the structural roots, base of the  trunk and lower limbs of host 
trees (Marais et al. 2002). Cankers grow slowly (ov er multiple years) and often go unnoticed until 
girdling has occurred and foliar dieback symptoms a ppear (Zentmyer et al. 1974). Cankers are 
discoloured and can exude a red resinous, water-sol uble exudate through cracks in the bark. This 
exudate dries to form a white crystalline deposit o n bark. Cutting into a canker reveals a necrotic br own Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 358 outer layer of wood instead of the normal white or cream coloured tissues and has a fruity odour when 
exposed to air. The cankers have distinct reddish-b rown margins from which the fungus can readily be 
isolated (Marais et al. 2002).  
Leaf loss and canopy thinning are typical symptoms of P. mengei  infections. Leaves retain their normal 
size and the smaller feeder roots are usually still  present. In mild to moderate canker stages the hos t 
tree foliage can appear healthy. Foliar dieback occ urs when the canker progresses to a stage when it 
starts killing cambium and phloem tissues, effectiv ely girdling the trunk. Affected trees show a gradu al 
loss of vigour, decline of the top, and death in se vere cases. 
Environmental stress may predispose avocado trees d isease caused by P. mengei . Under field 
conditions, stress of avocado plants could be attri buted to factors such as water deficiency, salinity , 
excess fertilization, low temperatures, or root-rot  disease caused by P. cinnamomi  which affects about 
60-75% of the acreage in southern California alone (Ouimette et al. 1988). The infection rate and cank er 
development is much higher in stressed plants compa red to non-stressed plants (El-Hamalawi and 
Menge 1994).  
Similarly, increased levels of amino acids in the p hloem tissue correlate positively with the rate of 
disease development (El-Hamalawi and Menge 1994). H igh nitrogen levels have been shown to 
correlate with increased lesion size, more lesions and host death in rhododendrons with Phytophthora  
dieback (Hoitink et al. 1986).  
Disease development and spore spread is favoured by  wet conditions. Cankers that are frequently 
exposed to water develop at an increased rate and i ntrude deeper into the phloem than cankers that 
are not frequently exposed (El-Hamalawi and Menge 1 994). Cankers caused by Phytophthora mengei  
often occur on the side of trunks wetted by irrigat ion sprinklers. Furthermore, canker development and  
infection (production of sporangia, zoospores etc) is favoured by wet or moist conditions. The minimum  
temperature for colony growth is 6–10°  C, the optim um about 25°  C, and the maximum 30–33°  C (Hong 
et al. 2009). 
Phytophthora mengei is transmitted via contaminated pruning equipment. There is a chance for 
infection to occur during harvesting of budwood if the harvesting methods are not hygienic. Testing an y 
fresh or historical wounds on the budwood may detec t the presence of the pathogen before symptoms 
develop.  
Confirming the identity of these Phytophthora requi res culturing and/or molecular diagnostic tests. 
Current molecular detection tests for the genus Phytophthora  are specific to several key species rather 
than the entire genus (Pegg et al. 2016). 
It is very difficult to eradicate  Phytophthora  from an orchard once it is established in the soil . However, 
certain phosphonate fungistatics (phosphorous acid and phosphonate compounds) may increase the 
resilience of avocado trees to Phytophthora  infection. They can be applied to the bark, to are as where 
cankers have been removed, injected into the trunk,  or into the soil if the canker extends below groun d 
(Eskalen and Faber 2016). 
6.1.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing events 
referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Phytophthora mengei (formerly recognised as the ‘avocado subgroup’ with in  P. citricola ) causes 
cankers in the structural roots, base of the trunk and lower limbs of older host trees. Cankers grow 
slowly (over multiple years) and often go unnoticed  until girdling has occurred and foliar dieback 
symptoms appear. Cankers are discoloured and can ex ude a red resinous, water-soluble exudate 
through cracks in the bark. This exudate dries to f orm a white crystalline deposit on bark. Cutting in to 
a canker reveals a necrotic brown outer layer of wo od instead of the normal white- or cream-coloured  
359 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand tissues and has a fruity odour when exposed to air.  The cankers have distinct reddish-brown margins 
from which the fungus can readily be isolated (Mara is et al. 2002; Marais 2004).  
Foliar symptoms are similar to those of Phytophthora  root rot (caused by P. cinnamomi ). With 
Phytophthora  trunk canker (caused by P. mengei ), leaves retain their normal size and there is a g radual 
loss of leaves causing canopy thinning, whereas bra nch dieback (staghorning) is less typical. Unlike 
Phytophthora  root rot, Phytophthora  trunk canker affects the major tree roots, and the  smaller feeder 
roots are usually still present. In mild to moderat e canker stages the host tree foliage can appear 
healthy. Foliar dieback occurs when the canker prog resses to a stage when it starts killing cambium 
and phloem tissues, effectively girdling the trunk.  Affected trees show a gradual loss of vigour, decl ine 
of the top and subsequent death.What are the known environmental conditions conducive to symptom 
expression? 
Environmental stress may predispose avocado trees t o disease. Under field conditions, stress of 
avocado plants could be attributed to factors such as water deficiency, salinity, excess fertilization  and 
low temperatures (Ouimette et al. 1988). The infect ion rate and canker development are much higher 
in stressed plants compared to non-stressed plants (El-Hamalawi and Menge 1994).  
Similarly, increased levels of amino acids in the p hloem tissue correlate positively with the rate of 
disease development (El-Hamalawi and Menge 1994). H igh nitrogen levels have been shown to 
correlate with increased lesion size, more lesions and host death in rhododendrons with Phytophthora  
dieback, caused by multiple Phytophthora  species (Hoitink et al. 1986).  
Disease development and spore spread is favoured by  wet soil conditions. Cankers that are frequently 
exposed to water develop at an increased rate and i ntrude deeper into the phloem than cankers that 
are not frequently exposed (El-Hamalawi and Menge 1 994). Cankers caused by Phytophthora mengei  
often occur on the side of trunks wetted by irrigat ion sprinklers. Furthermore, canker development and  
infection (the production of sporangia, zoospores, oospores and chlamydospores) is favoured by wet 
or moist conditions. The minimum temperature for co lony growth is 6–10°  C, the optimum about 25°  C, 
and the maximum 30–33°  C (Hong et al. 2009). 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Phytophthora mengei is a canker pathogen that infects wounds on woody t issue and is known to be 
transmitted by contaminated pruning equipment. Ther e is a chance for infection to occur during 
harvesting of budwood if the harvesting methods are  not hygienic. Testing any fresh or historical 
wounds on the budwood may detect the presence of th e pathogen before symptoms develop.  
o What is the optimum season for conducting detection  testing? 
P. mengei infections last over multiple seasons and years. Ca nker/lesion development and infection is 
favoured by wet/moist conditions. The minimum tempe rature for colony growth is 6–10°  C, the 
optimum about 25°  C, and the maximum 30–33°  C (Hong  et al. 2009).  
6.1.11  References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Bradshaw, R E; Bellgard, S E; Black, A; Burns, B R;  Gerth, M L; McDougal, R L, et al. (2020) 
Phytophthora agathidicida : research progress, cultural perspectives and know ledge gaps in the 
control and management of kauri dieback in New Zeal and. Plant Pathology 69(1): 3-16. 
Brown, A V; Brasier, C M (2007) Colonization of tre e xylem by Phytophthora ramorum , P. kernoviae  
and other Phytophthora  species. Plant Pathology 56(2): 227-241. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 360 Bunny, F; Shearer, B (1995) Biology and ecology of Phytophthora citricola in na tive plant communities 
affected by mining  (0 7309 70108). Minerals and energy research insti tute of Western Australia, 
Western Australia.  
Chappell, P R (2013a) The Climate and Weather of Bay of Plenty . NIWA, New Zealand. 
https://niwa.co.nz/static/BOP%20ClimateWEB.pdf  
Chappell, P R (2013b) The Climate and Weather of Northland . NIWA, New Zealand. 
https://niwa.co.nz/static/Northland%20ClimateWEB.pd f  
Crone, M; McComb, J A; O'Brien, P A; Hardy, G E S J  (2013) Annual and herbaceous perennial 
native Australian plant species are symptomless hos ts of Phytophthora cinnamomi in the Eucalyptus 
marginata  (jarrah) forest of Western Australia. Plant Pathology 62(5): 1057-1062. 
Denman, S; Kirk, S A; Moralejo, E; Webber, J F (200 9) Phytophthora ramorum and Phytophthora 
kernoviae  on naturally infected asymptomatic foliage. EPPO Bulletin 39(1): 105-111. 
El-Hamalawi, Z A; Menge, J A (1994) Avocado trunk c anker disease caused by Phytophthora 
citricola : investigation of factors affecting infection and disease development. Plant Disease 78(3): 
260-264. 
El-Hamalawi, Z A; Menge, J A (1996) The role of sna ils and ants in transmitting the avocado stem 
canker pathogen, Phytophthora citricola . Journal of the American Society for Horticultural S cience 
121(5): 973-977. 
Eskalen, A; Faber, B A (2016) Phytophthora trunk ca nker and crown rot (formerly Citricola canker). 
Accessed October 2021 
Farr, D F; Rossman, A Y (2021) Fungal databases, U.  S. National Fungus Collections. https://nt.ars-
grin.gov/fungaldatabases/  Accessed Septemeber 27, 2021 
Hoitink, H A J; Watson, M E; Faber, W R (1986) Effe ct of nitrogen concentration in juvenile foliage of  
rhododendron on Phytophthora  dieback severity. Plant Disease 70: 292-294. 
Hong, C X; Gallegly, M E; Browne, G T; Bhat, R G; R ichardson, P A; Kong, P (2009) The avocado 
subgroup of Phytophthora citricola constitutes a distinct species, Phytophthora mengei sp. nov. 
Mycologia 101(6): 833-840. 
Hussain, T; Sharma, S; Singh, B P; Jeevalatha, A; S agar, V; Sharma, N N, et al. (2013) Detection of 
latent infection of Phytophthora infestans  in potato seed. Potato Journal 40(2): 142–148. 
Hwu, F-Y; Lai, M-W; Liou, R-F (2017) PpMID1 plays a  role in the asexual development and virulence 
of Phytophthora parasitica . Frontiers in Microbiology 8. 
Jacobs, K; MacDonald, J; Berry, A; Costello, L (199 7) The effect of low oxygen stress on 
Phytophthora cinnamomi infection and disease of cor k oak roots  (PSW-GTR-160). USDA Forest 
Service, USA.  
Lyubenova, A; Kostov, K; Tsvetkov, I; Slavov, S (20 15) Pathogens from the genus Phytophthora  
associated with fruit and forest species in Bulgari a. Nauka za Gorata . 
Marais, L; Menge, J A; Bender, G S; Faber, B (2002)  Avocado stem canker or collar rot . University of 
California, California, USA. 
https://www.avocadosource.com/Journals/AvoResearch/ avoresearch_02_01_2002_Marais_citricola.p 
df    
Marais, L J (2004) Avocado diseases of major import ance worldwide and their management. In S 
Naqui (ed) Diseases of fruits and vegetables.  Kluwer Academic Publishers: Netherlands.  
361 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Martin, F N; Blair, J E; Coffey, M D (2014) A combi ned mitochondrial and nuclear multilocus 
phylogeny of the genus Phytophthora . Fungal Genetics and Biology 66: 19-32. 
Migliorini, D; Ghelardini, L; Tondini, E; Luchi, N;  Santini, A (2015) The potential of symptomless pot ted 
plants for carrying invasive soilborne plant pathog ens. Diversity and Distributions 21(10): 1218-1229. 
MPI (2021a) Complete LIMS 2000-2020.  
MPI (2021b) Import Risk Analysis: Citrus budwood for propagation. In M f P Industries (Ed.),  (Vol. 1). 
New Zealand. 
New Zealand Avocado (2021) The New Zealand avocado industry. https://www.nzavocado.co.nz/the-
new-zealand-avocado-industry/  Accessed May 2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Ouimette, D; Koike, S; Coffey, M D (1988) Pathogeni city of isolates of Phytophthora citricola  from 
different hosts on unripe fruit of avocado. California Avocado Society 1988 Yearbook 72: 249-254. 
Parke, J (2016) Forest Phytophthora s of the world. http://forestphytophthoras.org/phytophthora-basics   
Parkunan, V; Johnson, C S; Bowman, B C; Hong, C X ( 2010) First report of Phytophthora inundata 
associated with a latent infection of tobacco ( Nicotiana tabacum ) in Virginia. Plant Pathology 59(6): 
1164–1164. 
Pegg, K; Forsberg, L; Cooke, T; Coates, L (2016) Phytophthora diseases – problematic in the nursery 
and beyond . Department of Agriculture, Fisheries and Forestry , 
https://www.ngia.com.au/Attachment?Action=Download& Attachment_id=1833  
Peters, R D; Sturz, A V; Carter, M R; Sanderson, J B (2005) Crop rotation can confer resistance to 
potatoes from Phytophthora erythroseptica  attack. Canadian Journal of Plant Science 85: 523-528. 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2019) FreshFacts: New Zealand Horticulture. . The New Zealand Institute for 
Plant and Food Research Ltd; Auckland, New Zealand. ,  
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
Plant Health Australia (2021) Trunk canker. https://www.planthealthaustralia.com.au/pests/trunk -
canker/   
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Romberg, M (2010) Spotlight on new species of Phytophthora : pests and diseases of forestry in New 
Zealand. Biosecurity 97. 
Schlenzig, A; Chard, J (2010) Examination of latent  infection in raspberry canes with Phytophthora 
rubi  and P. idaei  and transmission in micropropagation. EPPO Bulletin 40(2): 213-218. 
Shew, H D; Benson, D M (1981) Fraser Fir Root Rot I nduced by Phytophthora citricola. Plant Disease 
65: 688-689. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 362 Thompson, C H; McCartney, M M; Roubtsova, T V; Kasu ga, T; Ebeler, S E; Davis, C, et al. (2021) 
Analysis of volatile profiles for tracking asymptom atic infections of Phytophthora ramorum  and other 
pathogens in Rhododendron . Phytopathology : 1-46. 
Webb, C J; Sykes, W R; Garnock-Jones, P J (1988) Flora of New Zealand: Naturalised Pteridophytes, 
Gymnosperms, Dicotyledons.  (Vol. Naturalised Pteridophytes, Gymnosperms, Dico tyledons.); Botany 
Division, Department of Scientific and Industrial R esearch. 
Zentmyer, G A; Jefferson, L; Hickman, C J; Chang-Ho , Y (1974) Studies of Phytophthora citricola , 
isolated from Persea americana . Mycologia 66(5): 830-845. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Bradshaw, R E; Bellgard, S E; Black, A; Burns, B R;  Gerth, M L; McDougal, R L, et al. (2020) 
Phytophthora agathidicida : research progress, cultural perspectives and know ledge gaps in the 
control and management of kauri dieback in New Zeal and. Plant Pathology 69(1): 3-16. 
Brown, A V; Brasier, C M (2007) Colonization of tre e xylem by Phytophthora ramorum , P. kernoviae  
and other Phytophthora  species. Plant Pathology 56(2): 227-241. 
Bunny, F; Shearer, B (1995) Biology and ecology of Phytophthora citricola in na tive plant communities 
affected by mining  (0 7309 70108). Minerals and energy research insti tute of Western Australia, 
Western Australia.  
Chappell, P R (2013a) The Climate and Weather of Bay of Plenty . NIWA, New Zealand. 
https://niwa.co.nz/static/BOP%20ClimateWEB.pdf  
Chappell, P R (2013b) The Climate and Weather of Northland . NIWA, New Zealand. 
https://niwa.co.nz/static/Northland%20ClimateWEB.pd f  
Crone, M; McComb, J A; O'Brien, P A; Hardy, G E S J  (2013) Annual and herbaceous perennial 
native Australian plant species are symptomless hos ts of Phytophthora cinnamomi in the Eucalyptus 
marginata  (jarrah) forest of Western Australia. Plant Pathology 62(5): 1057-1062. 
Denman, S; Kirk, S A; Moralejo, E; Webber, J F (200 9) Phytophthora ramorum and Phytophthora 
kernoviae  on naturally infected asymptomatic foliage. EPPO Bulletin 39(1): 105-111. 
El-Hamalawi, Z A; Menge, J A (1994) Avocado trunk c anker disease caused by Phytophthora 
citricola : investigation of factors affecting infection and disease development. Plant Disease 78(3): 
260-264. 
El-Hamalawi, Z A; Menge, J A (1996) The role of sna ils and ants in transmitting the avocado stem 
canker pathogen, Phytophthora citricola . Journal of the American Society for Horticultural S cience 
121(5): 973-977. 
Eskalen, A; Faber, B A (2016) Phytophthora trunk ca nker and crown rot (formerly Citricola canker). 
Accessed October 2021 
Farr, D F; Rossman, A Y (2021) Fungal databases, U.  S. National Fungus Collections. https://nt.ars-
grin.gov/fungaldatabases/  Accessed Septemeber 27, 2021 
Hoitink, H A J; Watson, M E; Faber, W R (1986) Effe ct of nitrogen concentration in juvenile foliage of  
rhododendron on Phytophthora  dieback severity. Plant Disease 70: 292-294. 
Hong, C X; Gallegly, M E; Browne, G T; Bhat, R G; R ichardson, P A; Kong, P (2009) The avocado 
subgroup of Phytophthora citricola constitutes a distinct species, Phytophthora mengei sp. nov. 
Mycologia 101(6): 833-840.  
363 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Hussain, T; Sharma, S; Singh, B P; Jeevalatha, A; S agar, V; Sharma, N N, et al. (2013) Detection of 
latent infection of Phytophthora infestans  in potato seed. Potato Journal 40(2): 142–148. 
Hwu, F-Y; Lai, M-W; Liou, R-F (2017) PpMID1 plays a  role in the asexual development and virulence 
of Phytophthora parasitica . Frontiers in Microbiology 8. 
Jacobs, K; MacDonald, J; Berry, A; Costello, L (199 7) The effect of low oxygen stress on 
Phytophthora cinnamomi infection and disease of cor k oak roots  (PSW-GTR-160). USDA Forest 
Service, USA.  
Lyubenova, A; Kostov, K; Tsvetkov, I; Slavov, S (20 15) Pathogens from the genus Phytophthora  
associated with fruit and forest species in Bulgari a. Nauka za Gorata 51: 79-96. 
Marais, L; Menge, J A; Bender, G S; Faber, B (2002)  Avocado stem canker or collar rot . University of 
California, California, USA. 
https://www.avocadosource.com/Journals/AvoResearch/ avoresearch_02_01_2002_Marais_citricola.p 
df    
Marais, L J (2004) Avocado diseases of major import ance worldwide and their management. In S 
Naqui (ed) Diseases of fruits and vegetables.  Kluwer Academic Publishers: Netherlands. 
Martin, F N; Blair, J E; Coffey, M D (2014) A combi ned mitochondrial and nuclear multilocus 
phylogeny of the genus Phytophthora . Fungal Genetics and Biology 66: 19-32. 
Migliorini, D; Ghelardini, L; Tondini, E; Luchi, N;  Santini, A (2015) The potential of symptomless pot ted 
plants for carrying invasive soilborne plant pathog ens. Diversity and Distributions 21(10): 1218-1229. 
MPI (2021a) Complete LIMS 2000-2020.  
MPI (2021b) Import Risk Analysis: Citrus budwood for propagation. In M f P Industries (Ed.),  (Vol. 1). 
New Zealand. 
New Zealand Avocado (2021) The New Zealand avocado industry. https://www.nzavocado.co.nz/the-
new-zealand-avocado-industry/  Accessed May 2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Ouimette, D; Koike, S; Coffey, M D (1988) Pathogeni city of isolates of Phytophthora citricola  from 
different hosts on unripe fruit of avocado. California Avocado Society 1988 Yearbook 72: 249-254. 
Parke, J (2016) Forest Phytophthora s of the world. http://forestphytophthoras.org/phytophthora-basics   
Parkunan, V; Johnson, C S; Bowman, B C; Hong, C X ( 2010) First report of Phytophthora inundata 
associated with a latent infection of tobacco ( Nicotiana tabacum ) in Virginia. Plant Pathology 59(6): 
1164–1164. 
Pegg, K; Forsberg, L; Cooke, T; Coates, L (2016) Phytophthora diseases – problematic in the nursery 
and beyond . Department of Agriculture, Fisheries and Forestry , 
https://www.ngia.com.au/Attachment?Action=Download& Attachment_id=1833  
Peters, R D; Sturz, A V; Carter, M R; Sanderson, J B (2005) Crop rotation can confer resistance to 
potatoes from Phytophthora erythroseptica  attack. Canadian Journal of Plant Science 85: 523-528. 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 364 Plant & Food Research (2019) FreshFacts: New Zealand Horticulture. . The New Zealand Institute for 
Plant and Food Research Ltd; Auckland, New Zealand. ,  
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
Plant Health Australia (2021) Trunk canker. https://www.planthealthaustralia.com.au/pests/trunk -
canker/   
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Romberg, M (2010) Spotlight on new species of Phytophthora : pests and diseases of forestry in New 
Zealand. Biosecurity 97. 
Schlenzig, A; Chard, J (2010) Examination of latent  infection in raspberry canes with Phytophthora 
rubi  and P. idaei  and transmission in micropropagation. EPPO Bulletin 40(2): 213-218. 
Shew, H D; Benson, D M (1981) Fraser Fir Root Rot I nduced by Phytophthora citricola. Plant Disease 
65: 688-689. 
Thompson, C H; McCartney, M M; Roubtsova, T V; Kasu ga, T; Ebeler, S E; Davis, C, et al. (2021) 
Analysis of volatile profiles for tracking asymptom atic infections of Phytophthora ramorum  and other 
pathogens in Rhododendron . Phytopathology : 1-46. 
Webb, C J; Sykes, W R; Garnock-Jones, P J (1988) Flora of New Zealand: Naturalised Pteridophytes, 
Gymnosperms, Dicotyledons.  (Vol. Naturalised Pteridophytes, Gymnosperms, Dico tyledons.); Botany 
Division, Department of Scientific and Industrial R esearch. 
Zentmyer, G A; Jefferson, L; Hickman, C J; Chang-Ho , Y (1974) Studies of Phytophthora citricola , 
isolated from Persea americana . Mycologia 66(5): 830-845. 
 
  
365 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 6.2  Phytophthora palmivora  (bud rot of palms)   
Phytophthora palmivora  is an oomycete (or water mould) that causes a rang e of rot, canker and dieback 
symptoms on various host tissues. 
6.2.1  Taxonomic description 
Scientific name: Phytophthora palmivora  (E.J. Butler) E.J. Butler (1919)  
Order/Family: Peronosporales/Peronosporaceae 
Other names include: Phytophthora arecae, Phytophthora cactorum var. arecae, Phytophthora 
faberi, Phytophthora hevae, Phytophthora omnivore var.  arecae, Phytophthora palmivora  var.  heveae, 
Phytophthora palmivora var. theobromae, Phytophthor a theobromae , Pythium palmivorum  (CABI 
2018). 
Taxonomic notes: 
Phytophthora palmivora was originally identified as P. omnivora , the causal agent of black pod 
disease of cocoa ( Theobroma cacao) , and as Pythium  palmivorum , the cause of destructive diseases 
in palms. It was renamed P. palmivora  by Butler in 1919 (Cooke et al. 2000; Cline et al.  2008). 
6.2.2  Hazard identification 
Phytophthora palmivora is not known to be present in New Zealand. 
• Phytophthora palmivora is listed as absent from New Zealand in Biota NZ (2 022). There are 
no records for P. palmivora  in PPIN (2021). 
• Phytophthora palmivora is a quarantine pest, regulated and unwanted (ONZPR  2021). 
Phytophthora palmivora  has the potential to establish (and spread) in New  Zealand because: 
• Phytophthora palmivora  has a very wide host range, and known host plants including avocado 
(Farr and Rossman 2021), are widely grown in New Ze aland, both commercially and in 
domestic gardens. 
• Phytophthora palmivora  causes disease in tropical and subtropical countri es with high rainfall. 
Climate matching and climate modelling suggest that  it is likely to have the ability to infect plants 
and spread in northern New Zealand, especially in t he summer months between December 
and March (Figure 6-1). Phytophthora palmivora  may be able to persist in the environment over 
winter months as resistant spores. 
• However, disease expression and spread are very li kely to be limited by climate, particularly in 
the south of New Zealand (Figure 6-1). 
Phytophthora palmivora  has the potential to cause harm to New Zealand bec ause: 
Phytophthora palmivora  infects 130 to 1000 species of crop, ornamental, s hade and hedge plants, 
including tomato, avocado, macadamia, potatoes and orchids (Farr and Rossman 2021). 
• It causes a range of symptoms/diseases on a wide r ange of hosts in humid subtropical and 
tropical areas of the world (Drenth and Sendall 200 4). It has been reported killing kiwifruit plants 
in Turkey (Çiftçi et al. 2015) and is relatively co mmon as the causal agent of black rot of 
economically important orchids in Taiwan (Erwin and  Ribeiro 1996). 
Phytophthora palmivora  is associated with P. americana  budwood. 
• Persea americana  is a known host of P. palmivora .   Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 366 • Phytophthora  species normally attack the root system and stem b ase of the plant, but they are 
able to infect many different tissues (fine roots, bark, stems, leaves, shoots and fruits) on 
different host species (Tkaczyk et al. 2016)  
Given the arguments and evidence above, P. palmivora  meets the criteria to be a hazard for P. 
americana  budwood imported to New Zealand. 
6.2.3  Risk assessment 
Biology and epidemiology of Phytophthora palmivora 
Life cycle 
Phytophthora  are fungus-like eukaryotic microorganisms that all  share similar life cycles (Pegg et al. 
2016). They produce several types of structures ada pted to survival in diverse environments and in 
different seasons. All species can rest for long pe riods (years) in the soil by producing thick-walled  
chlamydospores (asexual) and oospores (sexual) or a s mycelial fragments. In the presence of water 
spores germinate to form sporangia on leaves and ro ots of host plants. In some Phytophthora , 
sporangia can detach and be blown or splashed in wa ter to healthy plants. Sporangia release motile 
zoospores, which can swim through thin films of wat er on leaf surfaces and water-logged soil. 
Zoospores are short lived and susceptible to drying . In water-logged soil, zoospores are attracted to 
plant roots, and form short-lived resting cysts on them. Cysts germinate, forming hyphae, which then 
invade plant cells to infect the plant, producing m ore chlamydospores, oospores, and/or sporangia, thu s 
completing the life cycle (Drenth and Guest 2004). 
Phytophthora palmivora  is heterothallic, and mating types are both found i n many areas of the world 
(Zentmyer 1988). 
Host range 
It is not known for certain how many hosts P. palmivora  can infect but the literature reports from 130 
to 1000 different host species can be affected (Dan iel and Guest 2008; Farr and Rossman 2021), 
including:  Adiantum raddianum (maidenhair fern);  Anacardium occidentale (cashew nut),  Ananas 
comosus (pineapple),  Annona cherimola  (cherimoya) , Antirrhinum majus, Areca catechu (betelnut 
palm) , Areca lutescens, Artocarpus altilis (breadfruit),  Borassus flabellifer  (toddy palm) , Capsicum 
annuum, Cattleya sp.,  Carica papaya (papaya) , Citrus limon, C. aurantiifolia, C. sinensis, C. x 
paradisi (grapefruit), Cocos nucifera  (coconut palm) , Colocasia sp.,  Crotalaria sp.,  Cymbidium sp.,  
Dendrobium sp.,  Dianthus caryophyllus, Dieffenbachia spp.,  Durio zibethinus (durian) , Elaeis 
guineensis (African oil palm),  Ficus carica (fig),  Fuchsia magellanica, Gossypium hirsutum (cotton) , 
Grevillea sp. , Hedera helix (English ivy),  Hevea brasiliensis (rubber) , Hibiscus sp.,  Howea sp.,  
Lavandula sp.,  Lycopersicon esculentum, Macadamia integrifolia, M agnolia grandiflora, Manihot 
esculenta (cassava),  Mangifera indica (mango),  Manilkara zapota (sapodilla),  Myristica fragrans 
(nutmeg),  Oncidium, Paphiopedilum sp.,  Paulowonia, Persea americana (avocado), Petunia violacea, 
Phaseolus sp.,  Philodendron sp.,  Piper nigrum (black pepper),  Rhopalostylis baueri, Solanum 
tuberosum, Syzygium paniculatum, Theobroma cacao (cocoa) , Vanda spp. (Farr and Rossman 
2021). 
Major hosts of P. palmivora  are: betelnut palm, cherimoya, cocoa, coconut palm , durian, papaya, rubber 
and toddy palm (scientific names in bold above) (Fa rr and Rossman 2021). 
Distribution 
Phytophthora palmivora has a very wide geographical distribution (Table 6- 2).  
367 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Table 6-2: The geographic distribution of Phytophthora palmivora.    
Continent/Region   Country/Area (source CPC (2020), unless otherwise noted)  CMI57  range 
Africa  Angola, Cameroon, Central African Republic, Democra tic Republic of the Congo, 
Republic of the Congo, Côte d'Ivoire, Egypt [ Note 1 ], Equatorial Guinea, Gabon, 
Ghana, Liberia, Madagascar, Malawi, Mauritius, Moro cco, Nigeria, Réunion, São 
Tomé and Príncipe, Senegal, Seychelles, Sierra Leon e, Somalia, Tanzania, 
Togo, Uganda, Zimbabwe  0.3-0.8 
Asia  Afghanistan, Brunei, Cambodia, China (Beijing, Fuji an, Guangdong, Hainan, 
Jiangsu, Yunnan, Zhejiang), India, Indonesia, Iran,  Japan (Kyushu, Shikoku), 
Jordan, Korea, Lebanon, Malaysia, Myanmar, Pakistan , Philippines, Singapore, 
Sri Lanka, Taiwan, Thailand, Turkey, Viet Nam  0.2-0.9 
Europe  France, Greece, Italy, Norway, Poland, Spai n (incl. Canary Islands)  0.7-0.9 
North and Central 
America  Belize, Cayman Islands, Costa Rica, Cuba, Dominica,  Dominican Republic, El 
Salvador, Grenada, Guatemala, Haiti, Honduras, Jama ica, Mexico, Nicaragua, 
Panama, Puerto Rico, Saint Kitts and Nevis, Saint L ucia, Saint Vincent and the 
Grenadines, Trinidad and Tobago, United States (Ari zona, California, Florida, 
Hawaii, North Carolina, Tennessee, Virginia)  0.3-0.8 
Oceania  American Samoa, Australia [ Note 2 ], Cook Islands [ Note 3 ], Fiji, French 
Polynesia, New Caledonia, Northern Mariana Islands,  Papua New Guinea, 
Samoa, Solomon Islands [ Note 4 ], Tonga, Vanuatu  0.4-0.7 
South America  Argentina, Bolivia, Brazil (Alagoas, Bahia, Espírit o Santo, Maranhão, Pará, 
Paraná, São Paulo), Colombia, Ecuador, Guyana, Peru , Suriname, Venezuela  0.3-0.9 
Note 1 . Regarded as a regulated non-quarantine pest by Eg ypt (EPPO 2020). 
Note 2.  Phytophthora palmivora  is present in Australia, including Western Austral ia (Barber et al. 2013) 
where it was previously considered to be absent and  was treated as a quarantine pest (Biosecurity 
Australia 2005). 
Note 3.  Reported from the Cook Islands (Dingley et al. 198 1). 
Note 4.  Reported from Solomon Islands (Newhook and Jackson  1977). 
Symptoms  
Phytophthora palmivora is partially adapted to infect aerial portions of m any of its hosts, in contrast to 
species such as P. cinnamomi , which is primarily a root and soil inhabiting pat hogen. This allows it to 
infect and cause symptoms on various tissues on the  same host (Erwin et al. 1995).  
Phytophthora palmivora  has been reported to cause a range of symptoms in P. americana  including 
seedling blight, leaf infections and dieback of you ng stems (Zentmyer 1976), crown and root rot 
(Kurbetli et al. 2020) and cankers (Drenth and Gues t 2004).  
Leaf lesions are reddish-brown-black, enlarge rapid ly along the larger veins and frequently cause 
contortion of the leaves. Dark, sunken, elongated l esions develop on young stems, and terminal buds 
are often killed. Conidia can develop in necrotic l esions on the leaf (Zentmyer 1976).  
Symptoms disease occurs occasionally in the summer months, in periods of heavy rainfall and high 
humidity (Zentmyer 1976). 
Asymptomatic infections 
A range of Phytophthora  species are reported to colonise and survive in sy mptomless or tolerant host 
plants, including P. rubi  and P. idaei  (Schlenzig and Chard 2010), P. cryptogea (Lyubenova et al. 
2015), P. erythroseptica  (Peters et al. 2005), P. cinnamomi  (NCSU 2016), P. infestans  (Hussain et al. 
2013),  P. inundata  (Parkunan et al. 2010), P. ramorum  and P. kernoviae  (Denman et al. 2009). 
Migliorini et al. (2015) tested potted ornamental p lants in the EU using qPCR, and detected 
 
57 Climate Match Index (CMI) with all of New Zealand ( Phillips et al. 2018). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 368 Phytophthora  in 87% of the tested pots and in 70% of the asympt omatic potted plants. Potted plants 
in soil carried several Phytophthora  species without showing any external symptoms. 
There is no information about the asymptomatic infe ction of avocado plants but P. palmivora  was 
occasionally recovered from the roots of asymptomat ic windmill palm ( Trachycarpus fortunei ) 
(Cacciola 2011), so asymptomatic infections are ass umed to be possible.  
Reproduction and transmission 
Phytophthora  species spread by the movement of infected soil, i rrigation/rainwater and plant 
fragments, and by human activities involving the mo vement of these commodities and infected plants. 
Insects such as ants, beetles and flies are conside red the main vectors of Black Pod disease of 
cocoa, caused by P. palmivora  (Agrios 2008).  
Low population levels of P. palmivora  can persist in the soil. In citrus orchards, falle n fruit attracts P. 
palmivora  from the soil, and sporulation is profuse under mo ist conditions. Sporangia are caducous 58  
and can be dispersed at least 0.5m by rain splash ( Martin et al. 2012). Fruits approaching maturity ar e 
infected by the sporangia and zoospores this way.  
Although fresh wounds and stomata are considered ke y infection courts, P. palmivora  is capable of 
direct penetration of leaf and fruit tissues (Drent h and Guest 2004). Secondary infections are then 
caused by sporangia spread through the tree by spla shing water, windblown rain and, less commonly, 
invertebrates, such as snails and ants (Taylor and Griffin 1981; Graham and Menge 2000). According 
to Timmer et al. (2000), rain drops would be suffic ient to propel small sporangium-filled droplets int o the 
air where they could be carried some distance by wi nd, but sporangia are not dispersed by wind current s 
alone (as are sporangia of some Phytophthora  species, e.g.  P. infestans ). Most infected fruit soon 
abscise but harvested fruit may not show symptoms u ntil after they have been held in storage for a few  
days (Graham and Menge 2000).  
Soil populations are maintained by repeated infecti ons of the fibrous roots of host plants and P. 
palmivora  can persist in unfavourable conditions for some ti me as chlamydospores (Graham and 
Menge 2000).  
Phytophthora palmivora’s  ability to infect aerial portions of many of its h osts may theoretically allow 
spores to spread more easily via wind and windborne  rain in contrast to  Phytophthora  species that are 
limited to the roots of hosts, such as P. cinnamomi. This allows it to infect and cause symptoms on 
various tissues on the same host, meaning that inoc ulum and susceptible host tissue are continuously 
available, and disease potential is always present (Erwin et al. 1995; Drenth and Guest 2004). 
Climate 
Phytophthora palmivora  is a warm-climate species, historically restricted  in distribution to tropical or 
subtropical regions. However, extrapolations from o ther hosts in other parts of the world and recent 
climate match assessments conducted by MPI (Appendi x 6.2.12) suggest that this species is likely to 
establish in northern New Zealand, including avocad o growing regions. Phytophthora palmivora  has 
been reported on avocado in Florida, China, Hondura s, Philippines, Thailand and Turkey (Farr and 
Rossman 2021). Spore spread is heavily reliant on w ater, and disease outbreaks often co-occur with 
rainy periods or waterlogged areas (Drenth and Gues t 2004). 
Optimal growth temperature 
Phytophthora palmivora  is a warm-climate species. Reported temperature op tima for sporulation, 
infection and disease development and mycelial grow th range from 24 to 30° C as follows: 
• the optimum for mycelial growth was reported as 30 ° C by (Timmer et al. 2000), with little 
or no growth at 15 or 33° C (Zitko et al. 1991), 
• Timmer et al. (2000) found the optimum temperature s for infection and disease 
development on citrus fruit were 27 to 30° C, and th at wetness of varying duration 
 
58 They become dislodged readily and separated from th e sporangiophore and therefore are readily disperse d.   
369 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand depending on the pathosystem was required for infec tion to take place. Brown rot caused 
by P. palmivora  on citrus fruit did not develop at 22° C or below, 
• the optimum temperature for sporulation in culture  and on the fruit surface was 24° C, with 
sporangium production decreasing rapidly at higher or lower temperatures (Timmer et al. 
2000). This optimum is considerably lower than the optimum for growth in vitro  of 30° C, or 
for infection and disease development of 27 to 30° C  (Zitko et al. 1991; Timmer et al. 
2000).  
6.2.4  Likelihood of entry 
There is potential for P. palmivora  to be imported into post-entry quarantine on P. americana nursery 
stock because: 
Phytophthora palmivora  is known to infect and cause symptoms on various t issues (Zentmyer 1976), 
including stems, therefore, it  could be associated with leafless, rootless P. americana  budwood cuttings.  
Phytophthora palmivora  has a wide global distribution (Table 6-2), though  it may not be reported from 
P. americana  or as causing disease on P. americana  in those countries:  
• Phytophthora palmivora  is present in Australia, Brazil, China, the Cook I slands, Egypt, Fiji, 
Japan, Korea, Mexico, New Caledonia, Samoa, Solomon  Islands, Spain, Peru, the United 
States, Vanuatu, Viet Nam and other countries liste d in Table 6-2.  
If P. palmivora is imported on avocado budwood, the residual biosec urity risks may not be managed by 
the proposed growing period of active growth with a  minimum of three distinct phenological growing 
events referred to as ‘shoot flush’ in 3A PEQ becau se: 
• There is no specific evidence for asymptomatic P. palmivora infections or longer latent periods 
in P. americana , however, P. palmivora  was occasionally recovered from the roots of 
asymptomatic windmill palm ( Trachycarpus fortunei ) (Cacciola 2011), so asymptomatic 
infections are assumed to be possible.  
• A range of Phytophthora  species are are reported to colonise and survive i n symptomless or 
tolerant host plants (Denman et al. 2009; Parkunan et al. 2010; Schlenzig and Chard 2010; 
Hussain et al. 2013; Lyubenova et al. 2015; NCSU 20 16).  
• Timmer et al. (2000) and Zitko et al. (1991) showe d that mycelium grew above 15° C, but 
disease only developed above 22° C, highlighting a t emperature range where infection could 
occur with suppressed disease symptoms. If symptoms  are produced then they are highly likely 
to be visually detected on budwood during preparati on for export, in phytosanitary inspections 
prior to export or on arrival in New Zealand. 
• Phytophthora palmivora  has been identified at the New Zealand border appr oximately 14 times, 
all either on nursery stock ( Dracaena, Epipremnum ) or on unknown pathways (MPI 2021). It 
has also been detected post border in 2018, in asso ciation with ornamental plants imported 
from Malaysia. The affected plants Epipremnum , Philodendron  and Ficus ) were destroyed in 
post-entry quarantine (MPI internal report).  
Given the arguments and evidence above, that is:  
• Phytophthora palmivora has a wide geographical range that overlaps with P. americana.  
• Phytophthora palmivora can infect stems, indicating that it could be assoc iated with budwood.  
• Infections could be asymptomatic or not visually d etectable if suitable environmental conditions 
are not met in PEQ. 
the likelihood of P. palmivora  entering New Zealand associated with P. americana  budwood is 
considered to be low, with moderate uncertainty. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 370 6.2.5  Likelihood of exposure 
The commodity (imported avocado budwood, as describ ed, see section 2.1) is intended to generate 
plants for planting in New Zealand. Avocado plants derived from avocado budwood will be planted and 
nurtured to survive in optimal or near optimal cond itions in controlled or natural environments in New  
Zealand. Avocado ( P. americana ) is a suitable host for P. palmivora .   
If avocado plants are infected with  P. palmivora  at the time of their release from Post Entry Quaran tine 
they will be planted in New Zealand or used to prop agate new plants for planting (see section 2.3 for 
additional information about exposure).  
Given the arguments above, the likelihood of exposu re of P. palmivora  in New Zealand from P. 
americana  budwood  is considered high, with low uncertainty. 
6.2.6  Likelihood of establishment 
Assuming it has entered undetected and been success fully exposed to a suitable host plant, 
P. palmivora  may establish in New Zealand because:  
• The optimum temperature for sporangium production by P. palmivora  (in vitro ) is 24° C, and wet 
conditions are necessary for 18 to 72 hours (Timmer  et al. 2000). Under these conditions, which 
may not be commonly met in New Zealand, sporulation  is profuse.  
• Sporangia can germinate and infect host tissues di rectly, or they can release large numbers of 
zoospores. Sporangia are spread by windblown rain t hrough the air and are carried with water 
movement in soil. Phytophthora palmivora  sporangia are caducous  and can be dispersed at 
least 0.5 m by rain splash (Martin et al. 2012). Zo ospores are released in water and are 
dispersed by irrigation or surface water. Zoospores  are able to swim for several hours and can 
directly infect plant tissues (Lamour et al. 2003; Babadoost 2004) however a large amount of 
surface moisture is required for their movement (Ro berts and Kucharek 2018). 
• Phytophthora species grow and reproduce on both li ving and dead tissue in soil. Because they 
require water for spore production and infection, r oot and trunk rots are most frequent in sites 
with poor drainage and frequent waterlogging. Fruit  infection can be initiated during wet 
conditions when spores are splashed from the soil o nto fruit that are touching, or near, the 
ground. According to Timmer et al. (2000), raindrop s would be sufficient to propel small 
sporangium-filled droplets into the air where they could be carried some distance by wind, but 
sporangia of P. palmivora  are not dispersed by wind currents alone (unlike s porangia of some 
Phytophthora  species, e.g. P. infestans ). If wet weather persists, secondary infections ar e 
caused by spores produced on those fruit being spla shed or blown onto fruit higher on the tree 
and, less commonly, invertebrates such as snails an d ants (Taylor and Griffin 1981; Graham 
and Menge 2000; Mooney 2001). 
• Other Phytophthora  species have been transmitted from experimentally infected detached fruit 
on the soil surface to growing plants. Phytophthora ramorum  was transmitted from infected 
Pyracantha  fruit to the roots of Viburnum plants (Tooley et al. 2016). Tooley et al. (2016) 
commented that “Regulators will have to consider fr uit transmission [of  P. ramorum ] as a 
possibility allowing for spread of the disease”.  
• The spread of P. palmivora  is unlikely to be limited by host availability. Th e pathogen has been 
reported from numerous species of crop, ornamental,  shade and hedge plants, including many 
that are common in the New Zealand environment, e.g . Capsicum annuum (peppers) , Citrus 
species,  Colocasia species (taro),  Dianthus species,  Ficus carica (fig),   Fuchsia species , 
Grevillea species,  Hedera helix (English ivy),  Hibiscus species,   Lycopersicon esculentum 
(tomato) , Persea americana (avocado),  Phaseolus species (green and dried beans),  
Philodendron species,  Solanum tuberosum (potato)  and  Syzygium species (Farr and Rossman 
2021). 
Phytophthora palmivora is a warm-climate species that is most prevalent in  tropical and subtropical 
regions. New Zealand’s temperate climate is not opt imal for this species, however: 
• Major impacts were reported on kiwifruit in Elazı ğ Province, Turkey (38° 29 /uni02B9/uni0030/uni0031/uni02BA/uni0020/uni004E/uni003B/uni0020/uni0033/uni0038/uni00B0 34 /uni02B9/uni0034/uni0034/uni02BA/uni0020/uni0045/uni003B/uni0020 
(Çiftçi et al. 2015). Most of this region has a 0.7  climate match index (CMI) with all of New  
371 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Zealand (Phillips et al. 2018), indicating that at least some parts of New Zealand are climatically 
suitable for establishment and disease expression.   
• Climate match assessments conducted by MPI (Figure  6-1) indicate that this species is likely 
to be capable of infecting susceptible hosts and sp reading in northern New Zealand, especially 
in the summer months of December to March. Phytophthora palmivora  can also persist in the 
environment as dormant forms such as oospores 59  and chlamydospores, which are resistant 
to unfavourable conditions. Chlamydospores may form  when soil moisture is limiting, conditions 
are cool or where the host roots are not actively g rowing and producing susceptible tissues for 
infection. Chlamydospores of some Phytophthora  species can remain in the soil for several 
years (Kunta et al. 2020) and can serve as an inocu lum source until the environmental 
conditions are optimal. However, it is uncertain ho w long chlamydospores of P. palmivora  can 
survive and how long they would survive under condi tions in New Zealand.   
• Therefore, it is likely that P. palmivora  would be able to infect plants and be able to spre ad in 
northern New Zealand, especially in the summer mont hs of December to March. Disease 
expression and spread are very likely to be limited  by climate, even in northern New Zealand, 
and the pathogen is unlikely to establish in southe rn regions. 
 
Figure 6-1: The potential distribution of P. palmivora  in New Zealand, as predicted by CLIMEX 
modelling 1.  
1The Eco-climate index shows the potential long-term  establishment of the species and ranges from 
low (white) through increasing suitability (green t hrough to red). The index for P. palmivora  is around 
40 (out of 100) in suitable areas in New Zealand. T his index for tropical areas is above 90. This 
indicates that although New Zealand is less suitabl e compared to tropical and subtropical areas, the 
environment may still facilitate establishment.  
Given the arguments and evidence above, that is: 
• Warm (24° C) and prolonged wet conditions (18 to 72  hours) are optimal for sporangium 
production. Sporangia and zoospores are spread by w indblown rain through the air and are 
carried with water movement in soil, 
 
59  Oospores are formed when two different mating type s are present.  
Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 372 • Phytophthora species require water for spore produ ction and infection, root and trunk rots are 
most frequent in sites with poor drainage and frequ ent waterlogging,  
the likelihood of P. palmivora  establishing in New Zealand is considered high wit h low uncertainty. 
6.2.7  Impacts in New Zealand 
Phytophthora palmivora  would be able to infect plants and be able to spre ad in northern New 
Zealand, especially in the summer months of Decembe r to March. Disease expression and spread 
are very likely to be limited by climate, even in n orthern New Zealand, and the pathogen is unlikely t o 
establish in southern regions. 
The spread of P. palmivora  is unlikely to be limited by host availability bec ause the pathogen has been 
reported from over 130 species of plant, some of wh ich are common in the New Zealand environment. 
Economic impacts 
Phytophthora palmivora  has an extremely wide host range and can cause sev ere losses to many 
tropical crops, for example, cocoa, durian, rubber,  coconut, pineapple and oil palm. It has been 
reported attacking commercial crops overseas that a re economically important in New Zealand, such 
as kiwifruit, citrus, apple, avocado and cut flower s (Farr and Rossman 2021). Losses resulting from  P. 
palmivora  are difficult to quantify because the pathogen cau ses a range of diseases and often occurs 
alongside other Phytophthora species. Furthermore, severity of disease is heavil y influenced by 
climate conditions. Severe losses can occur after p rolonged rains and high temperatures in late 
summer and early autumn (Graham and Menge 2000; Tim mer et al. 2000) 
• Phytophthora palmivora  was reported to cause brown rot epidemics on citru s in Florida and 
California (CMI 0.5-0.8), that resulted in typical yield losses of up to 30% in some cases 
(Graham et al. 1998; Graham and Menge 2000). In Sou theast Asia (CMI 0.3-0.6), P. 
palmivora  is one of the most common species causing Phytopht hora disease in citrus (Drenth 
and Sendall 2004). 
• Phytophthora palmivora  has been isolated from the roots and crowns of inf ected Actinidia 
chinensis var.  deliciosa  (cv. Hayward) plants in Turkey (CMI 0.7-0.9), caus ing crown and root 
rot symptoms on approximately 10% of plants in an e xperimental orchard (Çiftçi et al. 2015). 
Within two years, all the kiwifruit vines in the ex perimental orchard had died. Çiftçi et al. 
(2015) considered this to be a new host record and concluded that P. palmivora  had the 
potential to be a major limiting factor in kiwifrui t production, however, the host range and 
cultivar susceptibility within Actinidia  is unknown. Furthermore, it is not known whether 
kiwifruit in New Zealand would be impacted since th is appears to be the only report of 
infection of kiwifruit by P. palmivora .  
• In Taiwan (CMI 0.4-0.8), P. palmivora  is known to cause severe black rot in economically  
important orchids, including Cattleya, Cymbidium, Dendrobium, Oncidium and  Phalaenopsis  
(Tsai et al. 2006). Many of these species are grown  in New Zealand.  
• Severe economic impacts of this pathogen are larg ely limited to tropical fruit crops in warm 
regions. In New Zealand, the severity of symptoms, spread and consequently the impact is 
likely to be limited by the climate (figure 1). Imp acts in protected environments such as 
nurseries and glasshouses are likely to be more sev ere than in unprotected environments; for 
example, heavy losses in nurseries (up to 20% seedl ing mortality) are reported due to 
seedling blight caused by Phytophthora  species including P. palmivora  (Daniel and Guest 
2008; Savita et al. 2012).   
• An Australian risk assessment (Biosecurity Austra lia 2005) concluded that programmes to 
minimise the impact of P. palmivora  on host plants are not likely to be more costly th an 
existing management programs for other Phytophthora  species; however this may depend on 
the crop and the country. For example, Zitko and Ti mmer (1994) report that P. palmivora  is a 
more aggressive and competitive pathogen of citrus roots, stems and fruit tissues than P. 
nicotianae . Therefore, even if P. nicotianae  (for example) is being managed, the 
establishment of P. palmivora  may result in extra costs and damage.  
The establishment of P. palmivora  is unlikely to cause serious trade impacts.   
373 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • Phytophthora palmivora  is widely distributed globally. However, some trad ing partners may 
impose trade restrictions in the event of an incurs ion, e.g.:  
o EPPO reports that several countries regard P. palmivora  as a quarantine pest (Morocco, 
Bahrain and Chile), and Egypt regards it as a regul ated non-quarantine pest. 
o In 2014, China closed the Californian fresh citrus  fruit market (worth approximately 
US$140 million), based on detections of two other Phytophthora species ( P. syringae  
and P. hibernalis , claimed to be absent from China) on Californian f ruit. The Chinese 
market is open again to Californian growers, but st rict export protocols have been 
implemented to manage the pathogens (Hao et al. 201 8).  
Given the arguments and evidence above, that is: 
• Phytophthora palmivora  has an extremely wide host range and can cause sev ere losses to 
many crops, but this usually limited to tropical cr ops and regions. Thus, impacts in protected 
environments such as nurseries and glasshouses are likely to be more severe than in 
unprotected environments in New Zealand, 
• Hosts that are economically important to New Zeala nd include citrus, kiwifruit and cut flowers, 
• Given the global distribution of P. palmivora,  its establishment in New Zealand is unlikely to 
cause serious trade impacts, 
the economic impact of P. palmivora  to New Zealand is considered to be moderate with m oderate 
uncertainty. 
Environmental impacts 
The establishment of P. palmivora may cause environmental impacts, but these are like ly to be limited 
by climatic unsuitability:  
 Phytophthora palmivora  has been recorded on several species represented b y genera in the 
native flora including Hibiscus, Solanum, Pittosporum and Syzygium  species (Farr and 
Rossman 2021). 
 It is most likely to establish in warmer, more hum id regions of New Zealand. Although there are 
no native orchid species in the genera known to be affected by P. palmivora , Northland is the 
centre of diversity of native orchids in New Zealan d, and this overlaps with the most likely area 
of establishment.  
 Phytophthora agathidicida  has been found in northern parts of New Zealand at tacking kauri 
(Agathis australis ), an iconic New Zealand tree species (Beever et al . 2007). Its biostatus 
(whether native or introduced) is not fully resolve d, but it is reported to kill trees of all ages in 
natural forest remnants, amenity stands and silvicu ltural plantations (Bellgard et al. 2016). This 
indicates the potential for Phytophthora  species to negatively impact on the natural 
environment and on socio-cultural values.  
Given the evidence above, the impacts on the New Ze aland environment from the establishment of P. 
palmivora  in New Zealand is considered to be moderate with m oderate uncertainty. 
Health impacts 
Phytophthora palmivora  is unlikely to cause unwanted impacts on human hea lth. No evidence of such 
impacts has been found. 
Given the evidence above, the health impact of P. palmivora  to New Zealand is considered to be 
negligible with low uncertainty. 
Social/cultural impacts  
Phytophthora palmivora is unlikely to cause significant social/cultural im pacts.  Amenity plants grown in 
sheltered conditions, such as tropical plant collec tions in botanic gardens, could be affected by this  
species. Host plants are common in domestic gardens  but its impact and spread is likely to be limited 
by climate.  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 374 Given the evidence above, the social/cultural  impacts of P. palmivora  to New Zealand is considered to 
be low with moderate uncertainty. 
6.2.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is low with moderate uncer tainty, 
• assuming entry, the likelihood of exposure is high  with low uncertainty, 
• assuming successful exposure, the likelihood of es tablishment is high with low uncertainty,  
• the impacts on the New Zealand economy, environmen t, health and society are moderate with 
moderate uncertainty, 
the overall level of assessed risk to New Zealand f rom P. palmivora  on imported P. americana  budwood 
is considered to be moderate, with moderate uncerta inty. 
6.2.9  Management considerations 
Phytophthora palmivora  is known to cause multiple diseases on the same ho st. On avocado, it causes 
seedling blight (Zentmyer 1976), root rot (Kurbetli  et al. 2020), cankers (Tsao et al. 1994), leaf inf ections 
and dieback of young stems  (Zentmyer 1976). One or  more of these symptoms could be expressed on 
infected budwood if suitable conditions are met in PEQ. 
Phytophthora palmivora  is a high temperature organism. Reported optima fo r sporulation, infection, 
disease development and mycelial growth range from 24 to 30° C (Zitko et al. 1991; Timmer et al. 2000).  
Phytophthora palmivora  was recovered from the roots of asymptomatic windm ill palm ( Trachycarpus 
fortunei ) (Cacciola 2011) and is spread naturally through s oil and water. Phytophthora  species normally 
attack the root system and stem base of the plant, causing root rot (Parke 2016). Migliorini et al. (2 015) 
tested potted ornamental plants in the EU using qPC R and detected Phytophthora  in 87% of the tested 
pots and in 70% of the asymptomatic potted plants. Potted plants in soil carried several Phytophthora  
species without showing any external symptoms. Ther efore, testing the roots and potting mix may 
provide the best opportunity to detect the pathogen  in the case of asymptomatic infections. 
The disease occurs occasionally in the summer month s, in periods of heavy rainfall and high humidity 
(Zentmyer 1976). Therefore, testing in the summer m ay provide the best opportunity for detecting 
presence of the pathogen.  
Confirming the identity of these Phytophthora requi res culturing and/or molecular diagnostic tests. 
Current molecular detection tests for the genus Phytophthora  are specific to several key species rather 
than the entire genus (Pegg et al. 2016). 
It is very difficult to eradicate  Phytophthora  from an orchard once it is established in the soil . However, 
certain phosphonate fungistatics (phosphorous acid and phosphonate compounds) may increase the 
resilience of avocado trees to Phytophthora  infection. They can be applied to the bark, to are as where 
cankers have been removed, injected into the trunk,  or into the soil if the canker extends below groun d 
(Eskalen and Faber 2016). 
6.2.10  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing events 
referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit?  
375 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Phytophthora palmivora  is known to cause multiple diseases on the same ho st. On avocado, it causes 
seedling blight, leaf infections and dieback of you ng stems (Zentmyer 1976), crown and root rot (Kurbe tli 
et al. 2020) and cankers (Drenth and Guest 2004). 
Leaf lesions are reddish-brown-black, enlarge rapid ly along the larger veins and frequently cause 
contortion of the leaves. Dark, sunken, elongated l esions develop on young stems, and terminal buds 
are often killed. Conidia can develop in necrotic l esions on the leaf (Zentmyer 1976). One or more of 
these symptoms could be expressed on infected budwo od if suitable conditions are met in PEQ. 
o What are the known environmental conditions conduci ve to symptom expression? 
The optimal growing condition for Phytophthora palmivora  is between 24-30° C. This range is optimal 
for sporulation, mycelial growth, infection and dis ease development:  
• the optimum for mycelial growth was reported as 30 ° C by Timmer et al. (2000), with little or no 
growth at 15 or 33° C (Zitko et al. 1991),  
• Timmer et al. (2000) found the optimum temperature s for infection and disease development 
on citrus fruit were 27 to 30° C, and that wetness o f varying duration depending on the 
pathosystem was required for infection to take plac e. Brown rot caused by P. palmivora  on 
citrus fruit did not develop at 22° C or below, 
• the optimum temperature for sporulation in culture  and on the fruit surface was 24° C, with 
sporangium production decreasing rapidly at higher or lower temperatures (Timmer et al. 2000). 
This optimum for sporulation is considerably lower than the optimum for growth in vitro of 30° C, 
or for infection and disease development of 27 to 3 0° C (Zitko et al. 1991; Timmer et al. 2000). 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Phytophthora palmivora  was recovered from the roots of asymptomatic windm ill palm ( Trachycarpus 
fortunei ) (Cacciola 2011) and is spread naturally through s oil and water. Phytophthora  species normally 
attack the root system and stem base of the plant, causing root rot (Parke 2016). Migliorini et al. (2 015) 
tested potted ornamental plants in the European Uni on (EU) using qPCR and detected Phytophthora  
in 87% of the tested pots and in 70% of the asympto matic potted plants. Potted plants in soil carried 
several Phytophthora  species without showing any external symptoms. The refore, testing the roots, 
potting mix or water may provide the best opportuni ty to detect the pathogen in the case of 
asymptomatic infections. 
o What is the optimum season for conducting detection  testing? 
Phytophthora palmivora  is a warm climate organism. The associated disease s occur in the summer 
months, in periods of heavy rainfall and high humid ity (Zentmyer 1976). Therefore, testing in the 
summer may provide the best opportunity for detecti ng presence of the pathogen.  
6.2.11  References  
Agrios, G N (2008) Transmission of plant diseases b y insects. In J L Capinera (ed) Encyclopedia of 
Entomology.  Springer: Dordrecht. 
Babadoost, M (2004) Phytophthora  blight:  a serious threat to cucurbit industries. In APSnet Features . 
Online. 
Barber, P; Paap, T; Burgess, T; Dunstan, W; Hardy, G (2013) A diverse range of Phytophthora  
species are associated with dying urban trees. Urban Forestry & Urban Greening 12(4): 569-575. 
Beever, J E; Coffey, M D; Ramsfield, T D; Dick, M A ; Horner, I J (2007) Kauri ( Agathis australis ) under 
threat from Phytophthora ? In Fourth Meeting of IUFRO Working Party S07.02.09  (Vol. General 
Technical report PSW-GTR-221). Monterey, California : U.S. Department of Agriculture, Forest 
Service Pacific Southwest Research Station. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 376 Bellgard, S; Pennycook, S; Weir, B; Ho, W; Waipara,  N W (2016) Phytophthora agathidicida . In Forest 
Phytophthoras  (Vol. 6): Oregon State University. 
Biosecurity Australia (2005) Final report for the extension of existing policy f or sweet oranges from 
Italy . Canberra, Australia. 
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379 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 6.2.12  Appendix: Climate suitability of Phytophthora palmivora  
Phytophthora palmivora  is primarily known to be a warm-climate species re ported from Malaysia, 
Hawaii, Brazil, Spain, Taiwan, Italy, Australia, Eu rope, Argentina, among other countries, causing cro wn 
rot, cankers and fruit rot in more than 200 host sp ecies where most of the tropical crops are impacted . 
Establishment of this species in the NZ climate nee ds to be assessed. 
Advice 
• Both models, CLIMEX and MaxEnt, predicted that Nor th Island, especially the Northland area 
in New Zealand is generally suitable for the establ ishment of P. palmivora (Figure 6-1 and 
Figure 6-2). The weekly growth index was the highes t from Dec to March (0.7) (Figure 6-3). 
This is due to suitable temperature (NZ summer) whi ch allows the species to grow and 
establish. For the rest of the year, temperature se ems to be the main limiting factor (Figure 6-3). 
Figure 6-2: The potential distribution of P. palmiv ora in NZ predicted by MaxEnt model 
• The Eco-climate index which shows the potential lo ng-term establishment of the species is 
around 40 (out of 100) in suitable area in NZ. This  index for tropical areas is above 90. This 
indicates although NZ is less suitable compared to tropical and subtropical area but the 
environment still may facilitate the pathogen estab lishment.  
• This advice only considers the climate and current  distribution of this pathogen. No other factors 
that may further facilitate or prohibit the species  establishment have been considered. 
• It should be noted that some worldwide reports are  from greenhouses when the indoor 
environment is controlled, and the pathogen cannot grow in outdoor (such as Norway).  
 
Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 380 Table 6-3: Parameter values used in developing CLIM EX model for P. palmivora . 
Index  Parameters Values  Unit  
DV 0 Lower temperature threshold 10 0C 
DV 1 lower optimum temperature 24 0C 
DV 2 upper optimum temperature 27 0C 
DV 3 Upper temperature threshold 35 0C 
SM 0 Lower soil moisture threshold 0.35 - 
SM 1 Lower optimum soil moisture 0.7 - 
SM 2 upper optimum soil moisture 1.5 - 
SM 3 Upper soil moisture threshold 2.5 - 
TTCS Cold stress temperature threshold 8 0C 
THCS Cold stress temperature rate - Week -1 
DTCS Cold stress degree-day threshold - 0C 
DHCS Cold stress degree-day rate 0.008 Week -1 
TTHS Heat Stress Temperature threshold 35 0C 
THHS Heat Stress Temperature rate 0.0002 Week -1 
SDMS Dry Stress Threshold 0.25 Week -1 
HDS Dry Stress Rate -0.01 Week -1 
DTCS Cold-Dry Stress threshold (1-100) 1 - 
MTCD 
PCD Cold-Dry Moisture threshold (0-5) 
Cold-Dry Stress rate 2.5 
 
0.01 - 
 
Week -1 
 
Figure 6-3: CLIMEX model output showing weekly grow th index of P. palmivora  in Northland, 
New Zealand 
Current global distribution of the P. palmivora  which includes 132 points were gleaned from a lite rature 
review (Figure 6-4). These presence data and long-t erm climate data were used to develop CLIMEX 
and MaxEnt models. For the CLIMEX model, the initia l parameters were collected from literature (Table 
6-3). An iterative adjustment of each parameter was  done to reach a satisfactory agreement between 
the potential and the current know distribution of P. palmivora  in these areas. 
The current model predictions were made in a limite d time period based on the available resource and 
the current distribution of the pathogen.   
 
381 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Figure 6-4: Current global distribution 
 
 
Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 382 7. Pest risk assessments: Viroids 
7.1   Avocado sunblotch viroid  (ASBVd) 
Avocado sunblotch viroid  is distributed in most avocado-producing areas glo bally and causes 
significant reductions in yield and fruit quality. All avocado cultivars have been reported as suscept ible 
and infected asymptomatic trees play an important r ole in the epidemiology and spread of this 
disease. 
7.1.1  Taxonomic description 
Scientific name: Avocado sunblotch viroid  
Order/Family: Avsunviroidae (Di Serio et al. 2018; ICTV 2021)  
Other names include : Avocado sun blotch viroid, sun blotch of avocado,  sunblotch, mancha de sol 
de los aguacate, viroide de la manche amarilla del aguacate, Sunblotch virus of avocado, Avocado 
sunblotch virus, kitmey shemesh, avokado sonvlek, A SBVd, avocado sun blotch (CABI 2021) 
Taxonomic notes: Avocado sunblotch viroid  is the single species in the genus Avsunviroid and  the 
type member of the family Avsunviroidae. Sequence v ariation and high mutation rates are 
characteristic for viroids, and sequence variants o f Avocado sunblotch viroid  have been observed 
within a single tree, between trees with different symptoms, and from a single tree sampled over a 
period of years (Kuhn et al. 2017). Three types of sequence variants of Avocado sunblotch viroid  
have been described: B (from trees with bleached le aves), V (from trees with variegated leaves), and 
SC (from symptomless carrier trees) (Kuhn et al. 20 17). Tissues with localized bleached symptoms 
usually contain higher titers of the variant B than  non-symptomatic portions of the same leaf whereas 
a variegated leaf pattern is accompanied by the var iant V (Markarian et al. 2004). The most 
commonly isolated variant is the asymptomatic varia nt SC (Markarian et al. 2004). 
7.1.2  Hazard identification 
Avocado sunblotch viroid  is not known to be present in New Zealand. It had been listed as present in 
New Zealand (Pearson et al. 2006); however, followi ng a surveillance survey carried out in 2009, it 
has been officially declared absent from New Zealan d (Veerakone et al. 2015; PPIN 2021). Avocado 
sunblotch viroid  is a regulated pest for New Zealand and has unwant ed status (ONZPR 2021).  
Avocado sunblotch viroid  has the potential to establish (and spread) in New  Zealand because: 
• its natural host ( P. americana ) is available for its establishment (NZPCN 2021), and 
• suitable climate is available for its establishmen t (Phillips et al. 2018). 
Avocado sunblotch viroid  has the potential to cause harm to New Zealand bec ause: 
• Avocado sunblotch viroid  causes symptoms on  P. americana , such as variegation on leaves, 
depressions and distortions on fruit, cracked bark,  discoloured streaks on shoots, dwarfed, 
fruitless, and stunted trees and a diminished canop y (Kuhn et al. 2017; Saucedo Carabez et 
al. 2019), and 
• even asymptomatic P. americana  trees can have large yield reductions (Kuhn et al.  2017). 
Avocado sunblotch viroid  is associated with P. americana  budwood because: 
• Persea americana  is a known host of Avocado sunblotch viroid  (Saucedo Carabez et al. 
2019), and 
• Avocado sunblotch viroid  infection is systemic (Markarian et al. 2004; Ding  and Itaya 2007), it 
is graft-transmissible and diseased propagative mat erial, such as budwood is a major route 
responsible for its spread (Saucedo Carabez et al. 2019).  
383 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Given the arguments and evidence above, Avocado sunblotch viroid  meets the criteria to be a hazard 
on P. americana  budwood (as per the commodity description) importe d into New Zealand. 
7.1.3  Risk assessment 
Biology and epidemiology of Avocado sunblotch viroi d 
Host range 
The only natural host of Avocado sunblotch viroid  is P. americana . However, other members in the 
Lauraceae family have been inoculated experimentall y, such as Cinnamomum camphora (present in 
New Zealand (NZPCN 2021)), Cinnamomum zeylanicum , Ocotea bullata  and Persea schiedeana  
(Kuhn et al. 2017).  
Symptoms 
Avocado sunblotch viroid  causes a variety of symptoms depending on avocado cultivar, 
environmental conditions, and the variants of the v iroid that predominate in the host (Saucedo 
Carabez et al. 2019). The most recognizable symptom  on fruits is sunken crevices of white, yellow, 
purple or reddish colour (Saucedo Carabez et al. 20 19). The sunken areas on severely affected fruits 
sometimes become necrotic. Yellow or lighter-colour ed streaks may occur on the younger branches 
and shoots of the tree and are usually most promine nt in the new flush growth (Kuhn et al. 2017). 
Some leaves of infected trees develop distorted and  variegated areas from the central vein that may 
progress and deform the entire leaf blade, however,  leaves can remain asymptomatic (Kuhn et al. 
2017). Bark symptoms are more common on mature tree s, where rectangular checking or cracking 
(“crocodile bark” or “alligator skin”) may be obser ved. Diseased trees may also be dwarfed with a 
diminished canopy, can be fruitless or remain stunt ed (Saucedo Carabez et al. 2019). The distribution 
of symptoms is usually irregular. Infected trees ma y develop only one or multiple symptoms or remain 
asymptomatic for their whole life (Saucedo Carabez et al. 2019). Diseased trees can become 
asymptomatic, and vice versa, symptoms can re-emerg e following stress conditions such as hard 
pruning (Kuhn et al. 2017). 
Transmission 
Avocado sunblotch viroid  is transmitted in seed and pollen, by grafting and  by mechanical means 
(Kuhn et al. 2017). Transmission rates of 86%–100% occur in seed from asymptomatic carrier trees, 
however, transmission rates are much lower (0%–5.5% ) in seed from symptomatic trees (Kuhn et al. 
2017). Plants with seed-borne infection are often a symptomatic and infection may not become 
apparent until grafted with a scion of a susceptibl e plant. Pollen transmission of Avocado sunblotch 
viroid  was demonstrated with a low transmission rate of 1 .8–3.1% (Saucedo-Carabez et al. 2014). 
The principal route of spread of Avocado sunblotch viroid  is grafting (Saucedo Carabez et al. 2019). 
The unintentional infection of grafted trees using contaminated tools and working surfaces, and the 
use of infected seedlings and budwood in avocado nu rseries is likely to have spread Avocado 
sunblotch viroid  widely throughout the avocado industries globally (Pegg et al. 2002; Kuhn et al. 
2017). Natural spread through root grafts have also  been reported as a mechanism of spread in the 
field (Ploetz 2003). Currently, Avocado sunblotch viroid has no known vector (Morey-León et al. 
2018). 
Time to symptom development and factors influencing  symptom expression 
The timeline of symptom development following infec tion by the Avocado sunblotch viroid  is not well 
understood because the disease mechanism generating  the symptoms of sunblotch disease in 
avocado is yet unknown (Kuhn et al. 2017). Furtherm ore, not all viroid-infected plants develop 
symptoms (Saucedo Carabez et al. 2019). Thus, diagn osis based on symptoms is not reliable and 
molecular diagnostic techniques are necessary to de tect asymptomatic plants (Saucedo Carabez et 
al. 2019). 
Factors influencing symptom expression is highly va riable. Avocado sunblotch symptoms in 
“Collinson” indicator seedlings have been reported to develop significantly faster in hot (30/28° C, 
day/night) than in a cool (20/18° C, day/night) glas shouse after grafting (Da Graca and Van Vuuren Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 384 1981). Some plants develop symptoms after 2 months (Da Graca and Van Vuuren 1981), other 
remain symptomless (Kuhn et al. 2017). Traditionall y, symptom development was observed over a 
period of at least 2 years using indexing (Kuhn et al. 2017). 
7.1.4  Likelihood of entry 
This assessment is made on the basis that Avocado sunblotch viroid  is present in the countries where 
avocado budwood is being imported from. Avocado sunblotch viroid  has been reported from all major 
avocado growing areas in the world, including Europ e, Asia, Africa, Australia, and North, Central and 
South America (Saucedo Carabez et al. 2019; CABI 20 21).  
Avocado sunblotch viroid  infection is systemic (Markarian et al. 2004; Ding  and Itaya 2007), it is graft-
transmissible and diseased propagative material, su ch as budwood is a major route responsible for its 
spread (Saucedo Carabez et al. 2019). Surface steri lisation would not affect the viroid. Therefore, 
Avocado sunblotch viroid  can be associated with P. americana  budwood. 
Symptom expression and time to symptom development is highly variable. Symptom expression has 
been observed within 2 months to 2 years, however, asymptomatic variants of Avocado sunblotch 
viroid are also common (Da Graca and Van Vuuren 1981; Kuhn  et al. 2017). In case of symptom 
expression during PEQ, the most likely observed sym ptoms would be yellow or lighter-coloured 
streaks on young branches and shoots usually exhibi ted in the new flush growth and occasionally 
white, yellow, or grey–green variegation of leaves.  Some infected avocado plants remain 
asymptomatic for their entire life (Schnell et al. 2001; Saucedo Carabez et al. 2019). Therefore, 
Avocado sunblotch viroid  can pass undetected during PEQ without molecular t esting.  
Given the arguments and evidence above, that is:  
• Avocado sunblotch viroid  symptom expression and time to symptom development  is highly 
variable (Saucedo Carabez et al. 2019), and  
• Avocado sunblotch viroid  can replicate in avocado budwood without causing s ymptoms for 
the entire PEQ period (Schnell et al. 2001; Kuhn et  al. 2017) 
the likelihood of Avocado sunblotch viroid  entering New Zealand associated with P. americana  
budwood is considered to be high with low uncertain ty. 
7.1.5  Likelihood of exposure 
This assessment is made on the basis that Avocado sunblotch viroid  has entered New Zealand 
undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for Avocado 
sunblotch viroid (Saucedo Carabez et al. 2019; NZPCN 2021). 
If P. americana  plants are infected with Avocado sunblotch viroid  at the time of their release from 
PEQ they will be planted in New Zealand or used to propagate new plants for planting (see section 
2.3 for additional information about exposure).  
Given the arguments and evidence above, Avocado sunblotch viroid  meets the criteria to be a hazard 
for New Zealand. 
7.1.6  Likelihood of establishment 
This assessment is made on the basis that Avocado sunblotch viroid  has been successfully exposed 
to a suitable host plant in the New Zealand environ ment.  
385 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand The natural host range of Avocado sunblotch viroid  is reported to be restricted to P. americana . This 
host in the form of cultivated avocados is availabl e for its establishment in the North Island (see 
section 2.3). If the host range includes other memb ers of the family Lauraceae then the number of 
potential host species available for the establishm ent of these pathovars is greatly increased – there  
are five native and four introduced species (in add ition to P. americana ) from the Lauraceae family 
found in New Zealand (NZPCN 2021). Out of these pre sent in New Zealand, only Cinnamomum 
camphora  is confirmed as an experimental host of Avocado sunblotch viroid  (Kuhn et al. 2017).  
Avocado sunblotch viroid  is reported from all major avocado growing areas i n the world (Kuhn et al. 
2017; Saucedo Carabez et al. 2019). Some avocado gr owing regions, such as California, the coastal 
areas in Israel, South Africa, East Australia, have  a similar climate to the whole of New Zealand, as 
well as to the Auckland and Northland regions, as i ndicated by a climate match index of ≥0.7 (Phillips 
et al. 2018). Therefore, climate suitable for the e stablishment of Avocado sunblotch viroid  is readily 
available. In addition, climate suitability is supp orted by the fact that Avocado sunblotch viroid  was 
reported from New Zealand (Pearson et al. 2006) pri or to its eradication (Veerakone et al. 2015).  
Given the arguments and evidence above, that is: 
• hosts (in the form of cultivated avocados) are ava ilable for the establishment of Avocado 
sunblotch viroid  (NZPCN 2021), and 
• suitable climate is available for the establishmen t of Avocado sunblotch viroid  (Phillips et al. 
2018), and 
• the wetter conditions of New Zealand compared to t he major avocado growing areas are 
likely to favour establishment of Avocado sunblotch viroid , and 
• Avocado sunblotch viroid  had been reported from New Zealand (Pearson et al.  2006), prior to 
its eradication (Veerakone et al. 2015) 
the likelihood of Avocado sunblotch viroid  establishing in New Zealand is considered high, wi th low 
uncertainty. 
7.1.7  Impacts in New Zealand 
The spread of Avocado sunblotch viroid infection is slow and more likely due to the reintr oduction of 
infected asymptomatic materials than to natural pro cesses. An average annual growth rate of 2.3% to 
4.7% of disease incidence has been reported (Pegg e t al. 2002). Thus, the greatest impact on 
New Zealand’s avocado industry is assumed to occur years after first introduction. 
Economic impacts 
The economic impacts of Avocado sunblotch viroid  are likely limited to the avocado industry because  
P. americana  is the only known natural host. The most relevant economic impact to New Zealand of 
sunblotch disease would likely be the effect on avo cado yield (Kuhn et al. 2017). Likewise, the fruit 
quality and the tree growth are affected (Kuhn et a l. 2017). All avocado cultivars have been reported 
as susceptible to this disease. For example, yield losses of 14% in symptomatic “Fuerte” trees and 
80% in asymptomatic “Edranol” have been reported (K uhn et al. 2017). High yield losses of 95% were 
observed in both asymptomatic “Caliente” and “Reed”  trees (Kuhn et al. 2017). Yield loss in 
asymptomatic “Hass” trees is in the range of 15–30% , while symptomatic “Hass” trees have yield 
losses of 50–80% (Saucedo-Carabez et al. 2014; Kuhn  et al. 2017). In addition, about 50% of the fruit 
produced by a symptomatic “Hass” trees may be scarr ed and therefore downgraded in quality 
(Saucedo-Carabez et al., 2014).  
The costs of managing Avocado sunblotch viroid  is high because infected trees need to be removed 
as well as all trees within 15 m and there is no cu re for the disease (Kuhn et al. 2017). If there was  an 
outbreak of Avocado sunblotch viroid  in one of the major avocado-producing regions in N ew Zealand, 
all trees would need to be tested including asympto matic avocado trees. Disinfestation of pruning 
tools and harvesting and grafting material is cruci al to prevent the undetected spread of Avocado 
sunblotch viroid . Eradication could be possible by testing and wide -scale removal of infected avocado 
trees in the area, causing significant economic los ses for a large portion of the industry. If new tre es 
were planted it would take approximately 3 years fo r them to produce their first commercial crop and 
up to 10 years for them to become as productive as older trees which were removed (Tupu.nz 2021). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 386 The indirect impact of an outbreak of Avocado sunblotch viroid on trade is considered negligible for 
New Zealand because the viroid  is reported from all major trading partners and avo cado growing 
areas around the world, including Australia which i s New Zealand’s biggest export market for avocado 
(Saucedo Carabez et al. 2019; CABI 2021). Furthermo re, trade restrictions seem unlikely as 
asymptomatic fruits can still be exported since the y are for human consumption rather than for 
propagation (Kuhn et al. 2017).  
Given the arguments and evidence above, that is: 
• avocados are the only natural hosts of Avocado sunblotch viroid commercially produced 
in New Zealand, and 
• infection of avocado trees with Avocado sunblotch viroid could cause large yield losses 
and significant downgrading in quality of the fruit , and  
• control of an outbreak could involve wide scale de struction of avocado trees (e.g., 
removal of all infected trees), and 
• there are likely to be negligible trade restrictio ns, and 
• a slow spread of disease incidence 
the economic impact of Avocado sunblotch viroid  to New Zealand is considered to be moderate, with 
low uncertainty. 
Environmental impacts 
The natural host range of Avocado sunblotch viroid  is restricted to P. americana  (Saucedo Carabez et 
al. 2019). There are no reports of natural infectio n of other plant species (google scholar search ter ms 
["wild plants" AND "Avocado sunblotch viroid"] and ["reservoir plants" AND "Avocado sunblotch 
viroid"] and ["Avocado sunblotch viroid" AND "natur al environments"]). 
Given the arguments and evidence above, the impact on the environment from the establishment of 
Avocado sunblotch viroid  in New Zealand is considered to be negligible, wit h low uncertainty. 
Human health impacts 
There are no known human health impacts associated with Avocado sunblotch viroid  (google scholar 
search terms ["human health" AND "Avocado sunblotch  viroid"] and ["toxin" AND "Avocado sunblotch 
viroid"]). 
Given the arguments and evidence above, the human h ealth impact of Avocado sunblotch viroid  to 
New Zealand is considered to be negligible, with lo w uncertainty. 
Sociocultural impacts 
A response to an outbreak of Avocado sunblotch viroid  may involve the removal of infected or 
exposed avocado trees growing on residential proper ties. This is likely to cause distress to affected 
residents, however, this impact is likely to be loc alised and short-lived. Moreover, a response would 
rather target commercial growers and nurseries as t he main grafters. 
Given the arguments and evidence above, the sociocu ltural impact of Avocado sunblotch viroid  to 
New Zealand is considered to be negligible, with hi gh uncertainty. 
Overall impact to New Zealand 
The overall impact of Avocado sunblotch viroid  on the New Zealand economy, environment, human 
health and society is considered to be moderate, wi th low uncertainty. 
7.1.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:   
387 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • the likelihood of entry is high 
• assuming entry, the likelihood of exposure is high  
• assuming successful exposure, the likelihood of es tablishment is high 
• the overall impact on the New Zealand economy, env ironment, human health and society 
is considered to be moderate 
the overall level of assessed risk to New Zealand f rom Avocado sunblotch viroid  on imported P. 
americana budwood (as in the commodity description) is consid ered to be moderate, with low 
uncertainty. 
7.1.9  Management considerations 
In case of symptom expression during PEQ, the most likely observed symptoms would be yellow or 
lighter-coloured streaks on young branches and shoo ts usually exhibited in the new flush growth and 
occasionally white, yellow, or grey–green variegati on of leaves (Kuhn et al. 2017; Saucedo Carabez 
et al. 2019). However, some infected avocado plants  remain asymptomatic for their entire life and 
asymptomatic variants are commonly isolated (Schnel l et al. 2001; Saucedo Carabez et al. 2019). 
Therefore, Avocado sunblotch viroid  can pass undetected during PEQ without molecular t esting. 
Usually the pathogen is detected using RT-qPCR, no matter where on the tree the leaf samples are 
taken and in what month of the year the tree is sam pled (Geering 2011). 
7.1.10   Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Symptom expression of Avocado sunblotch viroid  is highly variable because changes in single 
nucleotides in the viroid genome can result in alte red symptoms in avocado trees (Schnell et al. 
2001). In case of symptom expression during PEQ, th e most likely observed symptoms would be 
yellow or lighter-coloured streaks on young branche s and shoots usually exhibited in the new flush 
growth and occasionally white, yellow, or grey–gree n variegation of leaves (Kuhn et al. 2017; 
Saucedo Carabez et al. 2019). However, some infecte d avocado plants remain asymptomatic for their 
entire life and asymptomatic variants are commonly isolated (Schnell et al. 2001; Saucedo Carabez et 
al. 2019). Therefore, Avocado sunblotch viroid  can pass undetected during PEQ without molecular 
testing. 
o What are the known environmental conditions conduci ve to symptom expression? 
The factors influencing symptom expression after in fection with Avocado sunblotch viroid  are not well 
understood. Using indexing, symptom expression was reported to increase during higher 
temperatures, stress and heavy pruning. Traditional ly, symptom development was observed over a 
period of at least 2 years using indexing and a ran ge of indicator seedlings (Kuhn et al. 2017). 
However, the possibility of remaining asymptomatic even during periods of stress and high 
temperatures cannot be ruled out (Schnell et al. 20 01; Saucedo Carabez et al. 2019). 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections? 
Flower buds are preferable over leaves for diagnosi s, as the viroid titer is suspected to be higher an d 
carbohydrate contamination of the RNA extract less of a problem (Kuhn et al. 2017). The preferred 
method sensitive enough for detecting Avocado sunblotch viroid  in leaves and young leaf flushes is 
real-time reverse transcription PCR (RT-qPCR) (More y-León et al. 2018). 
o What is the optimum season for conducting detection  testing? Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 388 The concentration of Avocado sunblotch viroid  can fluctuate during the season. However, usually the 
pathogen is detected using RT-qPCR, no matter where  on the tree the leaf samples are taken and in 
what month of the year the tree is sampled (Geering  2011). 
7.1.11   References 
CABI (2021) Avocado sunblotch viroid (avocado sun b lotch). https://www.cabi.org/cpc/datasheet/8083  
Accessed October 2021 
Da Graca, J V; Van Vuuren, S P (1981) Use of high t emperature to increase the rate of avocado 
sunblotch symptom development in indicator seedling s. Plant Disease 65(1): 46-47. 
Di Serio, F; Li, S-F; Matoušek, J; Owens, R A; Pall ás, V; Randles, J W, et al. (2018) ICTV Virus 
Taxonomy Profile: Avsunviroidae. Journal of General Virology 99(5): 611-612. 
Ding, B; Itaya, A (2007) Viroid: a useful model for  studying the basic principles of infection and RNA  
biology. Molecular plant-microbe interactions 20(1): 7-20. 
Geering, A D (2011) Investigation of the distribution and incidence of Avocado sunblotch viroid in 
Australia . Horticulture Australia. 
ICTV (2021) International Committee on Taxonomy of Viruses. https://ictv.global/taxonomy/  Accessed 
June 2021 
Kuhn, D N; Geering, A D; Dixon, J (2017) Avocado su nblotch viroid. Viroids and satellites.  Elsevier. 
Markarian, N; Li, H W; Ding, S W; Semancik, J S (20 04) RNA silencing as related to viroid induced 
symptom expression. Archives of Virology 149(2): 397-406. 
Morey-León, G; Ortega-Ramirez, E; Julca-Chunga, C; Santos-Chanta, C; Graterol-Caldera, L; Mialhe, 
E (2018) The detection of avocado sunblotch viroid  in avocado using a real-time reverse transcriptase  
polymerase chain reaction. BioTechnologia 99(2): 99-107. 
NZPCN (2021) New Zealand Plant Conservation Network . https://www.nzpcn.org.nz/  Accessed June 
2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Pearson, M N; Clover, G R G; Guy, P L; Fletcher, J D; Beever, R E (2006) A review of the plant virus, 
viroid and mollicute records for New Zealand. Australasian Plant Pathology 35(2): 217. 
Pegg, K; Coates, L; Korsten, L; Harding, R (2002) F oliar, fruit and soilborne diseases. In ‘The 
avocado–botany, production and uses’.(Eds AW Whiley , B Schaffer, BN Wolstenholme) pp. 299–338. 
In: CABI Publishing: Oxon. 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX match climates regional 
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Ploetz, R C (2003) Diseases of tropical fruit crops  (R C Ploetz Ed.). CAB International; United 
Kingdom. 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Saucedo-Carabez, J; Téliz-Ortiz, D; Ochoa-Ascencio,  S; Ochoa-Martínez, D; Vallejo-Pérez, M; 
Beltrán-Peña, H (2014) Effect of Avocado sunblotch viroid (ASBVd) on avocado yield in Michoacan, 
Mexico. European Journal of Plant Pathology 138(4): 799-805.  
389 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Saucedo Carabez, J R; Téliz Ortiz, D; Vallejo Pérez , M R; Beltrán Peña, H (2019) The avocado 
sunblotch viroid : an invisible foe of avocado. Viruses 11(6): 491. 
Schnell, R J; Kuhn, D N; Olano, C T; Quintanilla, W  E (2001) Sequence diversity among avocado 
sunblotch viroids isolated from single avocado tree s. Phytoparasitica 29(5): 451-460. 
Tupu.nz (2021) Land use fact sheet - Avocados . https://www.tupu.nz/en/fact-sheets/avocados  
Veerakone, S; Tang, J; Ward, L; Liefting, L; Perez- Egusquiza, Z; Lebas, B, et al. (2015) A review of 
the plant virus, viroid, liberibacter and phytoplas ma records for New Zealand. Australasian Plant 
Pathology 44: 463-514. 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 390 7.2  Potato spindle tuber viroid 
Potato spindle tuber viroid (PSTVd) is a plant pathogen which consists of a sma ll, unencapsidated (no 
coat protein), circular, single-stranded RNA molecu le 356-361 nucleotides in length. It causes disease  
primarily in solanaceous plants, including potato, tomato and capsicum. However, the reported natural 
host range is large and includes avocado.  
7.2.1  Taxonomic description 
Scientific name: Potato spindle tuber viroid  
Order/Family: Lefavirales / Pospiviroidae  (ICTV 2021)  
Other names include : PSTVd, Potato gothic virus, Potato spindle tuber pospiviroid, Potato spindle 
tuber virus (PSTV, prior to 1971), Tomato bunchy to p viroid (EPPO 2020). 
Taxonomic notes: Potato spindle tuber viroid was initially isolated from diseased potato plants and 
was the first viroid to be identified (Diener, 1971  in Diener 2003). It is the type species of both th e 
genus Pospiviroid and family Pospiviroidae (Di Serio et al. 2021). St rains used to be classified as 
mild, intermediate or severe based on symptoms obse rved in sensitive tomato cultivars but these 
designations do not necessarily reflect the severit y of symptoms seen in natural hosts under field 
conditions (Owens 2007). Potato spindle tuber viroid  is known for a constant change in sequence 
variation throughout infection (so-called quasispec ies, Adkar-Purushothama et al. 2020). Because of 
its high mutation rate, PSTVd is highly adaptable ( i.e. new hosts, environment) and highly variable (i n 
terms of symptoms and transmission). An arbitrary l evel of less than 90% sequence identity and 
distinct biological properties are the main criteri a for separating viroid species within a genus (Adk ar-
Purushothama et al. 2020). 
7.2.2  Hazard identification 
Potato spindle tuber viroid  is not known to be present in New Zealand: 
• Potato spindle tuber viroid  has occurred transiently in New Zealand, mainly in  commercial 
glasshouse tomatoes and capsicums (Lebas et al. 200 5). The viroid has been eradicated and 
is considered to not be established in NZ (Veerakon e et al. 2015; PPIN 2021), and  
• it is a regulated pest and an unwanted organism (O NZPR 2021). 
Potato spindle tuber viroid  has the potential to establish (and spread) in New  Zealand because: 
• Hosts in the form of commercial crops (e.g. potato es, avocadoes and tomatoes), common 
weeds (e.g. black nightshade, cape gooseberry, and wavy-leaved fleabane) and common 
ornamentals (e.g. dahlias, petunias and angel’s tru mpets) are available for its establishment 
(EPPO 2021; NZOR 2021; NZPCN 2021), and 
• Potato spindle tuber viroid  has been recorded from all continents, from the tr opics as far north 
as Russia (EPPO 2021). Thus, suitable climate is av ailable for the establishment of the viroid 
(Phillips et al. 2018) and temperatures are high en ough to support its transmission and 
spread (Verhoeven et al. 2010a; NIWA 2021).  
Potato spindle tuber viroid  has the potential to cause harm to New Zealand bec ause: 
• Potato spindle tuber viroid  can cause direct impacts on the potato, tomato and  capsicum 
industry through large yield losses, and 
• Potato spindle tuber viroid  can cause indirect impacts through export or trade  restrictions 
imposed by other countries, and 
• control of an outbreak would involve wide scale te sting of growing areas and destruction of 
infected plants and trees. 
Potato spindle tuber viroid  can be associated with Persea americana  budwood because:  
391 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • Persea americana  is a known host of PSTVd (Querci et al. 1995; Barr era and Rojas 2007; 
Nieto-Taype et al. 2014); 
• Potato spindle tuber viroid  infection is systemic and graft-transmissible (Zhu  et al. 2001; Di 
Serio et al. 2020). 
Given the arguments and evidence above, Potato spindle tuber viroid  meets the criteria to be a 
hazard on Persea americana  budwood (as in the commodity description) imported  to New Zealand. 
7.2.3  Risk assessment 
Biology and epidemiology of Potato spindle tuber vi roid 
Host range 
Potatoes and other tuber-bearing Solanum  species are considered to be the main hosts of Potato 
spindle tuber viroid (EPPO 2021). In addition, PSTVd has been found natu rally infecting a range of 
solanaceous crop species such as tomato ( S. lycopersicum ) (Puchta et al. 1990; Lebas et al. 2005) 
and capsicum ( Capsicum annuum ) (Lebas et al. 2005), eggplant ( S. melongena ), pepino ( S. 
muricatum ), as well as solanaceous ornamentals like potato v ine ( S. jasminoides ) (Di Serio 2007; 
Verhoeven et al. 2010b) and angel's trumpets ( Brugmansia spp.) (Verhoeven et al. 2010b). Various 
solanaceous and non-solanaceous plants have also be en identified as reservoirs of PSTVd (Mackie 
et al. 2016). EPPO (2021) lists 34 known hosts (fro m six families) and a further 32 experimental hosts  
(from 9 families). 
Potato spindle tuber viroid was first reported from avocado in 1995 after it  was detected in 72% of 
symptomatic and 21% of asymptomatic avocado trees s urveyed in Peru (Querci et al. 1995). Although 
eradication of PSTVd in avocado breeding stock in P eru has been attempted (Barrera and Rojas 
2007) it is still considered an avocado pest in tha t country (Nieto-Taype et al. 2014). Potato spindle 
tuber viroid has been reported from the following avocado variet ies: 
• Hass (Barrera and Rojas 2007) 
• Naval (Barrera and Rojas 2007) 
• Bacon (Barrera and Rojas 2007) 
• Fuerte (Querci et al. 1995) 
• Super Fuerte (Querci et al. 1995) 
• Topa Topa (Querci et al. 1995) 
• Zutano (Querci et al. 1995) 
• Duke (Querci et al. 1995) 
• Campong (Querci et al. 1995) 
• P-11 (Querci et al. 1995) 
• Mexicano (Querci et al. 1995). 
• Collinred (Querci et al. 1995; Barrera and Rojas 2 007) 
• Villacampa (Querci et al. 1995; Barrera and Rojas 2007). 
Mild, intermediate and severe strains of PSTVd have  all been reported from avocados (Querci et al. 
1995). 
Symptoms 
Potato spindle tuber viroid infection in avocados is associated with a range of  symptoms including: 
• A vertical branching pattern with weak, slender br anches (Querci et al. 1995; Barrera and 
Rojas 2007), 
• slender horizontal branching (Querci et al. 1995),  
• leaf size reduction, chlorosis and defoliation (Qu erci et al. 1995), 
• lack of fruit setting (Barrera and Rojas 2007) and  a decrease in fruit size and number (Querci 
et al. 1995), 
• bunchiness or proliferation of inflorescences (Que rci et al. 1995; Barrera and Rojas 2007), 
• stunting (Barrera and Rojas 2007),  
• decline in the organoleptic properties of the frui t (Nieto-Taype et al. 2014), and Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 392 • death of branches, desiccation and tree death (Que rci et al. 1995). 
It is difficult to definitively ascribe all of thes e symptoms to infection with PSTVd because some 
symptomatic trees were also infected with Avocado sunblotch viroid (ASBVd) (Querci et al. 1995; 
Barrera and Rojas 2007) . One report ascribes leaf yellowing and fruit groov ing to ASBVd infection, 
vertical branching and prolific inflorescences to P STVd, and stunting and lack of fruit set to infecti on 
by both viroids (Barrera and Rojas 2007). However, the data and analysis underpinning this 
conclusion are not presented in Barrera and Rojas ( 2007). In addition, symptoms were not associated 
with infection by either viroid in 25% of trees sur veyed in Peru (Querci et al. 1995). As it is the ca se 
for ASBVd, PSTVd likely causes a variety of symptom s depending on avocado cultivar, environmental 
conditions, and the variants of the viroid that pre dominate in the host but can also remain 
asymptomatic (Hadidi et al. 2017; Saucedo Carabez e t al. 2019; Adkar-Purushothama et al. 2020). 
Life cycle and transmission 
Viroids replicate autonomously and usually infect t heir hosts systemically (Di Serio et al. 2020). Potato 
spindle tuber viroid is imported into cell nuclei prior to replication, exported out of the nucleus after 
replication, and then travels from cell to cell via  plasmodesmata (Ding et al. 1997). In tomatoes 
(Palukaitis 1987; Zhu et al. 2001) and the experime ntal host Nicotiana benthamiana (Zhu et al. 2001) 
PSTVd has been shown to move systemically in phloem . It is generally assumed that this is the case 
for all viroids (Di Serio et al. 2020) and it is li kely that PSTVd moves in the phloem of all host pla nts, 
including avocado.  
Potato spindle tuber viroid is efficiently transmitted by vegetative propagatio n and this mode of 
transmission is a major cause of spread of PSTVd in  potatoes and vegetatively-propagated 
ornamentals (EPPO 2021). Mechanical transmission ha s also been demonstrated experimentally in a 
range of species including from potatoes to potatoe s, and from solanaceous ornamentals (angel's 
trumpets and potato vine) to potatoes and tomatoes.  Potato spindle tuber viroid has been successfully 
transmitted by applying infected sap to abraded, br uised or cut plant parts, cutting plants with 
contaminated tools, or rubbing leaves with contamin ated fingertips (Bonde and Merriam 1951; 
Verhoeven et al. 2010a).  
High rates of field transmission have been shown in  potatoes due to tractor tyres being contaminated 
by driving over infected plants (Merriam and Bonde 1954 in Verhoeven 2020) and by using 
contaminated cultivating and hilling equipment (Man zer and Merriam 1961 in Verhoeven 2020). The 
transmission rate is dependent on which species and  varieties are used as the inoculum source and 
which are inoculated (Bonde and Merriam 1951; Verho even et al. 2010a). The temperature at which 
inoculation takes place also affects transmission r ates, with the highest rates occurring at 20–
25° C(Verhoeven et al. 2010a). At 15° C, transmission  failed in potato and was rare in tomatoes 
(Verhoeven et al. 2010a).  
The rod-like secondary structure of PSTVd makes it resistant to nuclease degradation (Owens 2007). 
The viroid’s stability means that it can remain inf ective in extracted tomato sap on common surfaces 
such as cotton, wood, rubber tire, leather, metal, plastic, and string for up to 24 hours, although it  
remains infective on human skin for only 30 minutes  (Mackie et al. 2015). In addition, PSTVd remains 
infectious in water at 20 ± 4° C for up to seven wee ks (Mehle et al. 2013).  
Many pospiviroids, including PSTVd, are predominate ly located in the nuclei of infected cells and are 
seed-transmitted (CABI 2021). Potato spindle tuber viroid was detected in true potato seeds that had 
been stored for 21 years (Singh et al. 1991). Conta minated seed is an important source of spread of 
PSTVd but efficiency of transmission of PSTVd can b e highly variable. The rate of seed-transmission 
of pospiviroids is dependent on the viroid strain, host plant species, cultivar and distribution of vi roids 
in seed parts (Matsushita et al. 2018). The rate of  PSTVd seed-transmission was found to be 0–90.2 % 
in tomato, 0.3 % in Capsicum annuum  var. grossum , 0.5 % in C. annuum  var. angulosum , 1.2 % in 
Glebionis coronaria , and 81 % in Petunia  × hybrida  (Matsushita et al. 2018). No seed-transmission was  
observed for C. annuum  cv. Yolo Wonder (Verhoeven et al. 2020).  
Pollen is another potential source of infection. Tr ansmission of PSTVd from infected plants to pollen 
has been demonstrated experimentally in potatoes. P ollination of potato plants with infected pollen  
393 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand results in infection of apical leaves, inflorescenc es, sepals on fruit, fruit skin, fruit pulp, tubers , and 
true seed (Singh et al. 1992).  
Transmission of PSTVd by the aphid Myzus persicae  has been demonstrated in potatoes and cape 
gooseberry ( Physalis  floridana ) (Syller et al. 1997). However,  transmission likely only occurs if plants 
are co-infected with Potato leafroll virus  (Querci et al. 1997; Singh and Kurz 1997; Syller e t al. 1997). 
Potato leafroll virus and  M. persicae  are both reported from New Zealand (Veerakone et a l. 2015; 
NZOR 2021). Grasshoppers, beetles (Han činský et al. 2020) and oomycetes (Afanasenko et al.  2021) 
are also suspected to transmit PSTVd to host plants .  
It is likely that all of the described transmission  modes of PSTVd apply to avocado.   
Factors influencing symptom expression and rate of asymptomatic infection 
Potato spindle tuber viroid symptom expression is highly variable and influence d by the viroid strain, 
environmental conditions and host species and culti var (Mackie et al. 2019).  
In potato warm and dry climatic conditions usually increase symptoms of PSTVd (Schmitz and Steger 
2007) and are more obvious at 25 ˚C than at 15 ˚C ( Goss and Peltier 1925). Similarly, in tomato 
plants more obvious symptoms may develop at high te mperatures (24-39˚C) at higher light intensity, 
but tomatoes infected with the mild strain of PSTVd  may never develop symptoms despite high viroid 
concentrations (Harris and Browning 1980; Grasmick and Slack 1985). In peppers, symptoms in 
response to PSTVd infection are usually mild and de pend on variety (Lebas et al. 2005). Infections of 
solanaceous ornamentals and weeds are usually mild or symptomless (Matsushita and Tsuda 2015; 
Mackie et al. 2016).  
Whether the relationship between temperature, light  intensity and strain type holds true for symptom 
expression in avocados is not known. However, asymp tomatic infection of avocados by PSTVd is 
common (Hadidi et al. 2017). A survey in Peru showe d that approximately 21% of asymptomatic trees 
were infected with PSTVd and at some sites 93-100% of all asymptomatic trees sampled were 
PSTVd positive (Querci et al. 1995). It was hypothe sised that PSTVd infections in avocado are often 
latent unless the tree is co-infected with ASBVd (Q uerci et al. 1995). However, vertical branching and  
prolific inflorescences symptoms were also ascribed  to single infection with PSTVd (Querci et al. 
1995; Barrera and Rojas 2007). 
7.2.4  Likelihood of entry 
This assessment is made on the basis that Potato spindle tuber viroid  is present in the countries 
where avocado budwood is being imported from.  Potato spindle tuber viroid infects its hosts 
systemically (Zhu et al. 2001; Di Serio et al. 2020 ). Therefore, it may be associated with avocado 
budwood. Rates of up to 100% asymptomatic infection  of avocado trees have been reported (Querci 
et al. 1995). Because infection can be asymptomatic  it is possible that budwood may be harvested 
from infected trees, and infection would not be evi dent in quarantine inspections (in exporting countr y 
and in NZ).  
Given the arguments and evidence above, that is:  
• Potato spindle tuber viroid infects its hosts systemically (Zhu et al. 2001; Di  Serio et al. 2020) 
and can therefore be associated with avocado budwoo d, and 
• it is likely to display no symptoms during the PEQ  period (Querci et al. 1995) 
the likelihood of PSTVd entering New Zealand associ ated with Persea americana  budwood is 
considered to be high, with low uncertainty. 
7.2.5  Likelihood of exposure 
This assessment is made on the basis that Potato spindle tuber viroid  has entered New Zealand 
undetected. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 394 When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand.   
If avocado plants are infected with PSTVd at the ti me of their release from Post Entry Quarantine they  
will be planted in New Zealand or used to propagate  new plants for planting (see section 2.3 for 
additional information about exposure).  
Given the arguments and evidence above, the likelih ood of exposure of PSTVd in New Zealand from 
Persea americana  budwood is considered high, with low uncertainty. 
7.2.6  Likelihood of establishment 
This assessment is made on the basis that Potato spindle tuber viroid has been successfully exposed 
to a suitable host plant in the New Zealand environ ment. Potato spindle tuber viroid has a very broad 
host range (EPPO 2021) and many of its hosts are ei ther grown commercially in New Zealand (i.e. 
potatoes, avocadoes, eggplant and tomatoes), are co mmon ornamentals (e.g. Dahlia spp., Petunia  
spp. and Brugmansia spp.), or are common weeds (e.g. black nightshade, Solanum nigrum ; cape 
gooseberry, Physalis peruviana ; and wavy-leaved fleabane, Erigeron bonariensis ) (NZOR 2021; 
NZPCN 2021). Therefore, hosts for the establishment  of PSTVd are readily available. 
Climate is likely to influence the distribution of PSTVd mainly through influencing the distribution o f its 
hosts. Under laboratory conditions, temperature can  influence the transmission rate of PSTVd with a 
higher rate at 20-25° C than 15° C (Verhoeven et al. 2010a). In the main avocado growing regions of 
New Zealand daily maximum temperatures at or above 20° C are common in the summer months, and 
above 15° C for the majority of the year (NIWA 2021) . Therefore, temperatures to support 
transmission and establishment of PSTVd are readily  available. 
Potato spindle tuber viroid  has occurred transiently in New Zealand in the pas t. It had been detected 
on a few occasions in New Zealand in tomato, tobacc o and capsicum glasshouse plants and in Cape 
gooseberry, but was eradicated each time (Lebas et al. 2005; Ward et al. 2010). Successful 
eradication of the viroid was likely aided by the f act that it was detected early and in an environmen t 
that was relatively easy to control (i.e., inside a  glasshouse and seeds). Due to the many reported 
reservoir plants, eradication seems unlikely in cas e undetected spread occurs in an outdoor 
environment. 
Given the arguments and evidence above, that is: 
• Hosts and reservoir plants for the establishment o f PSTVd are readily available (NZOR 2021; 
NZPCN 2021), and 
• climate suitable for the establishment of PSTVd is  readily available (Phillips et al. 2018; NIWA 
2021) 
the likelihood of PSTVd establishing in New Zealand  is considered high, with low uncertainty. 
7.2.7  Impacts in New Zealand 
There is no effective chemical control known for PS TVd. The most effective means of control is using 
certified viroid-free planting material, planting r esistant cultivars and maintaining sanitary cultura l 
practices. Control of an outbreak is generally achi eved by removal and destruction of infected plants,  
sanitation of the production location, temporarily banning cultivation of host plants, and thorough 
cleaning and disinfection of tools, machinery and o ther equipment (Verhoeven 2020). 
If PSTVd were introduced to an avocado producing re gion of New Zealand, it may remain undetected 
for a prolonged period given the high rates of asym ptomatic infection reported (Querci et al. 1995). 
This allows time for the viroid to spread to other crops and reservoir plants. Successful mechanical 
transmission from solanaceous ornamentals ( Brugmansia  spp. and S. jasminoides ) to tomatoes has  
395 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand been demonstrated (Verhoeven et al. 2010a). In addi tion, phylogenetic analyses have indicated that 
volunteer crop plants, weeds and native plants are likely to be the source of recurring outbreaks of 
PSTVd in field-grown tomatoes, capsicums and chilli es in a remote agricultural area in Australia 
(Mackie et al. 2016). Intercropping of potatoes wit h avocadoes in Peru is suspected to be the source 
of PSTVd in avocados (Querci et al. 1995). Therefor e, spread of PSTVd from avocados to other 
species in the field is plausible. 
Economic impacts 
Hosts of PSTVd, such as avocados, potatoes, tomatoe s and capsicums are high value crops for New 
Zealand. They had a combined domestic value of $163 .5 million and an export value of $259 million 
in 2020 (Plant & Food Research 2020).  
Direct impacts would likely occur on the tomato, po tato and capsicum industry (Lebas et al. 2005; 
Mackie et al. 2019). Yield losses vary with host cu ltivar, PSTVd variant and season, and are 
particularly strong under warm conditions (Harris a nd Browning 1980). The general pattern is of a 
progressive decrease in yield as infection increase s. In eastern Canada, field trials of potatoes (wit h 
100% infection rates) have shown that even the mild  strain can cause up to 24% yield reductions 
whereas the severe strain has been reported to caus e reductions of up to 64-90%% (Singh et al. 
1971; Mackie et al. 2016; Mackie et al. 2019). With  infection rates of 3.8% in the field, and an 
observed ratio of 11:1 of the mild to severe strain s, yield loss in the field was calculated to be 
approximately 1% (Singh et al. 1971). Higher infect ion rates (6.5%) among field-sampled commercial 
seed potatoes have been reported in China (Qiu et a l. 2016), although yield losses were not reported 
during this survey. A previous survey in northern C hina reported yield losses of 20-30% (Cui et al. 
1992), but information about infection rates and th e strains involved is unavailable. Depending on 
cultivar and strain, in a small-scale pot experimen t, PSTVd was reported to decrease the yield of 
tomato fruit by up to 47% (Mackie et al. 2019). Fre shFacts (2019) estimated New Zealand’s tomato 
exports at around 15 million NZD, capsicum exports at around 20 million NZD and potato exports at 
around 130 million NZD. Generally, the magnitude of  the PSTVd-induced yield losses overseas has 
been found considerable, regardless of cultivar or crop: 50 to 90% for potato tubers and 52 to 89% for  
tomato fruit (Mackie et al. 2019). 
It is likely establishment of PSTVd would have addi tional implications for New Zealand’s horticultural  
industry through export or trade restrictions impos ed by other countries. Given the presence of 
PSTVd in the EU, Australia and China (EPPO 2021), t he biggest potential loss of market access 
would likely be to the USA and South Asia.  
The costs from eradication attempts or a response t o an outbreak of PSTVd are considered high 
because they would include widespread testing and t he destruction of infected plants (including 
avocado trees), sanitation of the production locati on, temporarily banning cultivation of host plants,  
and thorough cleaning and disinfection of tools, ma chinery and other equipment (Verhoeven 2020). 
Moreover, host crops of PSTVd should not be grown i n the infested fields for 3 years (Verhoeven 
2020). 
Given the arguments and evidence above, that is: 
• direct impacts would likely occur on the tomato, p otato and capsicum industry in 
New Zealand through yield losses, and  
• indirect impacts would occur from export or trade restrictions imposed by other countries, 
and  
• control of an outbreak would involve wide scale te sting of growing areas and destruction 
of infected plants and trees 
the economic impact of Potato spindle tuber viroid to New Zealand is considered to be moderate, with 
low uncertainty. 
Environmental impacts 
The natural host range of PSTVd is large and increa sing (Matsushita and Tsuda 2015). In Australia 
PSTVd was detected infecting native plants and weed s after floodings (Mackie et al. 2016). Native Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 396 New Zealand plant species from the nightshade famil y, such as Poroporo ( Solanum aviculare var. 
aviculare , Solanum aviculare  var. latifolium , Solanum laciniatum ) (NZPCN 2021) could be prone to 
PSTVd infection. Although no evidence of Poroporo a s a host of PSTVd could be found, this 
relationship seems plausible as PSTVd naturally inf ect solanaceous plants (Han činský et al. 2020). 
However, PSTVd infections in wild reservoir plants are usually asymptomatic and few are mildly 
symptomatic (Mackie et al. 2016), so PSTVd would li kely have minimal impact on New Zealand native 
species. Overseas impacts from PSTVd infection are,  so far, only known for potato, tomato and 
capsicum (Matsushita and Tsuda 2015; Verhoeven 2020 ) and no evidence could be found that 
PSTVd severely impacts natural ecosystems. 
Given the arguments and evidence above, the impact on the environment from the establishment of 
Potato spindle tuber viroid  in New Zealand is considered to be negligible, wit h moderate uncertainty. 
Human health impacts 
There are no known human health impacts associated with Potato spindle tuber viroid  (google scholar 
search terms ["human health" AND "Potato spindle tu ber viroid"] and ["toxin" AND "Potato spindle 
tuber viroid"]). 
Given the arguments and evidence above, the human h ealth impact of Potato spindle tuber viroid  to 
New Zealand is considered to be negligible, with lo w uncertainty. 
Sociocultural impacts 
A response to an outbreak of Potato spindle tuber viroid  may involve the removal of infected or 
exposed avocado trees, tomato and capsicum plants, ornamental and reservoir hosts growing on 
residential properties. This is likely to cause dis tress to affected residents, however, this impact i s 
likely to be localised.  
Given the arguments and evidence above, the sociocu ltural impact of Potato spindle tuber viroid  to 
New Zealand is considered to be very low, with low uncertainty. 
Overall impact to New Zealand 
The overall impact of Potato spindle tuber viroid  on the New Zealand economy, environment, human 
health and society is considered to be moderate, wi th low uncertainty. 
7.2.8  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is high 
• assuming entry, the likelihood of exposure is high  
• assuming successful exposure, the likelihood of es tablishment is high 
• the overall impact on the New Zealand economy, env ironment, human health and society 
is considered to be moderate 
the overall level of assessed risk to New Zealand f rom Potato spindle tuber viroid  on imported P. 
americana budwood (as in the commodity description) is consid ered to be moderate, with low 
uncertainty. 
7.2.9  Management considerations 
Potato spindle tuber viroid  was detected in asymptomatic avocado trees surveye d in Peru (Querci et 
al. 1995). Therefore, PSTVd can be asymptomatic in avocado budwood and pass undetected during 
PEQ without molecular testing. The preferred method s sensitive enough for detecting PSTVd are 
real-time reverse transcription PCR (RT-qPCR) or re al-time RT-PCR (Botermans et al. 2020). 
Detailed management options to reduce the risk of e ntry, spread and consequences of PSTVd were 
identified and evaluated by EFSA (2011).   
397 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Potato spindle tuber viroid  was detected in 72% of symptomatic and 21% of asym ptomatic avocado 
trees surveyed in Peru (Querci et al. 1995). Theref ore, PSTVd can be asymptomatic and can pass 
undetected during PEQ without molecular testing. In  case of symptom expression, PSTVd likely 
causes a variety of symptoms depending on avocado c ultivar, environmental conditions, and the 
variants of the viroid that predominate in the host  (Saucedo Carabez et al. 2019; Adkar-
Purushothama et al. 2020). Vertical branching and p rolific inflorescences in avocado were attributed 
to PSTVd infection, and stunting and lack of fruit set to co-infection with Avocado sunblotch viroid 
(ASBVd) (Barrera and Rojas 2007). 
As it is the case for many viroids, PSTVd likely ca uses a variety of symptoms depending on avocado 
cultivar, environmental conditions, and the variant s of the viroid that predominate in the host 
(Saucedo Carabez et al. 2019; Adkar-Purushothama et  al. 2020). In hosts such as potato and tomato, 
high temperatures (>24˚C) and high light intensity were reported to favour symptom expression of 
PSTVd (Harris and Browning 1980; Grasmick and Slack  1985). However, it is unknown if this 
relationship holds true for symptom expression in a vocado. Likely symptom expression also depends 
on the avocado variety and the viroid strain. Moreo ver, asymptomatic infection of avocados by PSTVd 
is common. A survey in Peru showed that approximate ly 21% of asymptomatic trees were infected 
with PSTVd and at some sites 93–100% of all asympto matic avocado trees sampled were PSTVd 
positive (Querci et al. 1995). 
The preferred methods sensitive enough for detectin g PSTVd is real-time reverse transcription PCR 
(RT-qPCR) or real-time RT-PCR (Botermans et al. 202 0). Usually flowers, leaves and young leaf 
flushes are used for viroid testing in avocado (Mor ey-León et al. 2018). Methods have been optimised 
for testing for both ASBVd and PSTVd in avocado (Ni eto-Taype et al. 2014; Mathews et al. 2022). In 
young trees usually one leaf from each branch that traces back to the trunk should be collected 
(Mathews et al. 2022). 
The concentration of viroids can fluctuate during t he season and within an infected plant. However, 
usually systemic infection of a viroid is detected using a sensitive method such as RT-qPCR no 
matter where on the tree the leaf samples are taken  and in what month of the year the tree is sampled 
(Geering 2011). 
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spindle tuber viroid in cape gooseberry ( Physalis peruviana ) in New Zealand. Plant Disease 94(4): 
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 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 402 Appendix 1.  Summary of taxa excluded at PRA 
The following organisms were excluded at the PRA st age. Fifteen species (including two diseases of 
unknown aetiology) were selected for PRA but upon i nvestigation were excluded and required further 
rationale that was not suitable for a table (i.e. e xcluded hazard table in Appendix 2). Diplodia 
pseudoseriata was completed as a full PRA but while this IRA was being prepared Diplodia 
pseudoseriata  became known to be present in New Zealand and was thus, included in this appendix. 
App 1.1  Avocado Black Streak Disease 
Taxonomic notes 
Disease of unknown etiology 
NZ status  
• not known to be present in New Zealand (NZOR, acce ssed 20/12/2021). 
• regulated (ONZPR, accessed 20/12/2021) 
Summary of reason for exclusion 
Avocado Black Streak Disease can be excluded from t he Avocado Germplasm Import Risk Analysis 
(IRA) because: 
• To date there is no evidence that this disease is caused by biotic stress.  
• There is no evidence of graft transmission or by v ectors 
• Current literature suggests that this disease is a  result of abiotic stress and that symptoms can 
be overturned by good irrigation and fertilization schemes 
Supporting information  
Avocado black streak (ABS) was first reported in 19 34 (Carrillo and Eskalen 2017) . This disease has 
been predominantly reported in avocado producing re gions in California with isolated reports from 
Florida in the 1990s and outside the United States,  in the Canary Islands and in Israel in the 1980s 
(Marais 2004; Carrillo and Eskalen 2017). However, in the case of Florida and in the Canary Islands, i t 
is known that budwood from symptomatic trees were b rought from California (Marais 2004; Carrillo 
and Eskalen 2017). 
Trunk and branch cankers are the most obvious sympt oms and are used as the “indicator” symptom of 
ABS (Ohr and Murphy 1987) . However, using cankers as an indicator symptom has been a subject of 
debate. The canker has being described as visible w hen there is accumulation of dry sugar exudate 
(Marais 2004).  When the canker first appears, the resulting lesion under the outer bark is reddish 
brown and is usually limited to the phloem but can extend past the vascular cambium into the xylem 
tissue (Carrillo and Eskalen 2017). Cankers often f irst appear on the lower trunk and underside of 
lower branches and then later appear higher in the tree (Eskalen and Faber 2016).  Initially, the cank er 
formation was attributed to a potential viral etiol ogy, but survey results from Carrillo and Eskalen 
(2017) suggest that canker formation is likely due to a complex of fungi. One of the hypotheses is tha t 
environmental stress triggers symptom development o f ABS and this leads to the formation of small 
open wounds which serve as entry points for seconda ry, opportunistic fungi (Carrillo and Eskalen 
2017). Given the information above, it is uncertain  if cankers should be considered as the indicator 
symptom for this disease. 
Other symptoms reported are chlorosis, early bloom,  branch dieback, leaf blotching, zinc deficiency, 
wilting of foliage and rapid death of new growth (C arrillo and Eskalen 2017). This disease usually 
results in tree death, but if the tree recovers fru it production is impacted (Ohr and Murphy 1987). 
Affected trees under normal progression of the dise ase can gradually decline and eventually die, 
however there are reports of rapid tree collapse. T he symptoms associated with ABS are varied and 
can be attributed to other causes such as abiotic s tress and local farm management practices (Ohr 
and Murphy 1987).  
403 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Studies performed by Ohr et al. (1976) indicate tha t this disease occurs mainly in Guatemalan 
avocado varieties, including the market dominant “H ass” variety.  The disease is known to affect trees  
of all ages, since symptoms have been observed on t rees ranging from 1 year to over 35 years old 
(Eskalen and Faber 2016).  The results of a survey undertaken by Ohr and Murphy (1987) during 
three consecutive years in two selected orchards in  the Ventura and San Diego County, California 
revealed a 13.2% and 20.1% increase respectively, i n the number of diseased trees (Table 7-1).  
Table 7-1 Results of a survey performed during thre e consecutive years (1975 -1977) in two 
orchards, one in Ventura Country containing 1,731 ( 10-year-old) Hass trees on mixed 
rootstocks and the other in San Diego County contai ning 374 (22-year-old) trees on Topa-Topa 
rootstocks (Ohr and Murphy 1987).  
Year Location Percentage (%) 
infected trees Number of trees 
infected 
1975 
Ventura County 6.7 116 
1976 15.1 261 
1977 19.9 344 
1975 
San Diego County  17.1 64 
1976 30.2 113 
1977 37.2 139 
The causal agent/s of avocado black streak is/are u nknown. Possible causes that have been 
investigated include: 
Fungi: symptomatic and asymptomatic mature branch s amples were obtained from three to five trees 
within each orchard. The most consistently isolated  organisms included Lasiodiplodia  spp., 
Neofusicoccum luteum , Diplodia mutila , and Phaeoacremonium  spp. However, pathogenicity tests 
revealed that the lesions and necrosis observed on the mature avocado branches were not consistent 
with symptoms of ABS (Carrillo and Eskalen 2017).  One of the hypotheses is that the isolated 
organisms are secondary fungi that causes damage up on introduction into the host from open wounds 
formed during ABS disease development (Carrillo and  Eskalen 2017).  
Bacteria: antibiotic treated trees still produced s ymptoms of ABS therefore, infection by bacteria was  
ruled out (Ohr and Murphy 1987). 
Virus and viroids: not detected with electron micro scope and no double stranded ribonucleic acid 
(dsRNA) were detected using polyacrylamide gels. Th ree separate dsRNA were detected that might 
indicate a combination of three viruses, but the pr esence of the dsRNA patterns is not consistent 
amongst avocado varieties. Field surveys revealed t hat most avocado varieties have at least one of 
the patterns and that some have all three (Ohr and Murphy 1987).  Further studies to determine 
dsRNA-ABS correlation were performed by Ohr (unpubl ished work), but because of the few samples 
that they were able to analyse (343 trees) it was n ot possible to support a correlation between dsRNA 
and ABS. 
Graft transmission of dsRNA patterns:  Jordan et al . (1983) reported two of the three dsRNA patterns 
are able to be transmitted from the rootstock to th e scion in avocado.  The transmission of a conditio n 
called “pitting” suggested that some agent could be  transmitted from scion to rootstock. However, 
Marais (2004) considers that graft transmission of dsRNA patterns could not be proven in the Jordan 
et al. (1983) study because it was not designed to test this due to the difficulties associated with 
analysing rootstock material. Observations of sprea d in the field in the past twenty years have not ye t 
been substantiated by graft transmission (Marais 20 04). 
Nematodes: Xiphinema americanum  nematodes were collected from ABS and healthy tree s, but no 
correlation was found with ABS (Ohr et al. 1976). 
Nutrient deficiency or toxicity: no consistent resu lts (Ohr et al. 1976). 
Currently this disease is considered of minor econo mic importance (Carrillo and Eskalen 2017) but 
there is still uncertainty regarding the cause of A BS.  In recent years, authors have hypothesized tha t Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 404 it is possible that this disease is related to mois ture stress. After periods of abiotic stress (espec ially 
conditions of high salinity and insufficient water) , trees died faster, but with improved agricultural  
management practices (e.g., irrigation and fertiliz ation schemes),  trees recovered and symptoms 
disappeared (Eskalen and Faber 2016; Carrillo and E skalen 2017). 
Efforts to use molecular techniques to trace fungi,  bacteria, viruses, and mycoplasma organisms in 
infected samples and to investigate if there is any  correlation with ABS are underway (Carrillo and 
Eskalen 2017).  
Given the evidence above, it is concluded that: 
• This disease is likely to be a result of abiotic s tress since recent literature report that with 
improved agricultural management practices (irrigat ion and fertilization schemes) the trees 
recovered, and symptoms disappear. 
• Symptoms observed on avocado branches (i.e., canke rs) are likely to be a result of 
opportunistic fungi that entered into the host from  open cracks caused by abiotic stress. 
These opportunistic fungi are being assessed in sep arate pest risk assessments in the 
current avocado budwood IRA. Therefore, it is consi dered that the current measures are likely 
to mitigate the entry of these fungi into New Zeala nd. 
There is no evidence that supports that this diseas e is a result of biotic stress. 
Due to the unresolved causal agent of ABS, the high  uncertainty about its transmission and the recent 
observations that the symptoms of this disease can be overturned by good irrigation and fertilization 
practices, it is not justified to consider ABS, at this point, as a hazard requiring further assessmen t in 
the avocado budwood IRA.  The Emerging Risk System was checked on December 20 th , 2021 and no 
alert has been registered under the Causative Agent  Name: ‘Avocado Black Streak Disease’ or 
‘Blackstreak’.  A monitoring system its being set u p for active monitoring of this disease and if furt her 
information is available this disease could be reas sessed. 
Literature search 
Searches of Google Scholar and Google were conducte d using the search terms “Avocado Black 
Streak Disease” and “Black Streak in Avocado”. Six pages with a total of 60 results were screened for 
relevant information and the search stopped after t hat because unrelated or repeated information 
started to appear. 
References 
Carrillo, J; Eskalen, A (2017) Avocado black streak  disease revisited: an unsolved mystery. In 
California Avotech  (Vol. 7, pp. 36 — 38). California, USA: California  Avocado Commission. 
Eskalen, A; Faber, B A (2016) Avocado black streak.  
https://www2.ipm.ucanr.edu/agriculture/avocado/Avoc ado-black-streak/  Accessed October 2021 
Jordan, R; Dodds, J; Ohr, H (1983) Evidence of viru s like agents in avocado. Avocado Phytopathology 
73: 1130 — 1135. 
Marais, L J (2004) Avocado diseases of major import ance worldwide and their management. In S 
Naqui (ed) Diseases of fruits and vegetables.  Kluwer Academic Publishers: Netherlands. 
Ohr, H; Murphy, M (1987) Blackstreak disease of avo cado in California. South African Avocado 
Growers' Association Yearbook 10: 123 — 126. 
Ohr, H D; Platt, R G; Zentmyer, G (1976) Black stre ak disease of avocados. California Avocado 
Society  Yearbook 60: 177 — 179.  
405 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand App 1.2  Botryobasidium perseae  
Scientific name: Botryobasidium perseae (R.F. Castañeda) G. Langer (2021)  
Order/Family: Cantharellales/Botryobasidiaceae 
Other names include : Haplotrichum perseae R. F. Castañeda 1996 
NZ status 
• Not listed in Biota NZ (2022), PPIN (2021) or ONZP R (2021). 
Reason for exclusion 
Botryobasidium perseae (syn.  Haplotrichum perseae ) can be deemed not to be a hazard and 
excluded from the Avocado Germplasm Import Risk Ana lysis (IRA) because: 
• Castañeda (1996) reported the fungus on dead branc hes of a living avocado tree in Cuba, 
which is the only record of it associating with Persea americana  (avocado),  
• there is insufficient evidence that the fungus is associated with living Persea americana  tissue, 
and insufficient information available on the fungu s to carry out a PRA, 
• other species in the Botryobasidiaceae family are wood-rotting saprotrophs and none are of 
economic importance (Cannon and Kirk 2007). 
Literature Search  
Searches of Google Scholar, CAB abstracts, CPC, USD A fungal database and Google were 
conducted using the search terms ‘ Haplotrichum perseae ’ and ‘ Botryobasidium perseae ’. 
References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Cannon, P F; Kirk, P M (2007) Fungal families of the world . CABI; Wallingford, Oxford. 
Castañeda, R (1996) New species of Haplotrichum and Solicorynespora  from Cuba. 59: 449-452. 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 406 App 1.3  Ceratocystis fimbriata (Ceratocystis blight)  
Scientific name : Ceratocystis fimbriata Ellis & Halsted (1890) 
Taxonomic position : Microascales/Ceratocystidaceae 
Synonyms :  Ceratostomella fimbriata (Ellis & Halst.) J. A. Eilliot (1923), Endoconidiophora fimbriata 
(Ellis & Halst.) R. W. Davidson (1935), Rostrella coffeae  Zimm. (1900), Sphaeronaema fimbriatum 
(Ellis & Halst.) Sacc. (1892), Ophiostoma fimbriatum  (Ellis & Halst.) Nannf. (1934) 
Taxonomic notes:  Ceratocystis has been placed into four geographical clades, the Latin American 
clade (LAC), the North American clade (NAC), the Af rican clade (AFC) and the Asian-Australian clade 
(AAC) (Holland et al. 2019). Ceratocystis fimbriata is in the LAC (Holland et al. 2019) and causes 
black rot of sweet potato and wilt or cankers on co ffee, Eucalyptus spp., rubber trees and mango 
(Holland et al. 2019).  
NZ status  
• Recorded in New Zealand; however, it seems the str ain infecting kumara (Ipomoea batatas)  is 
the only strain present (Biota NZ 2022). 
• Ceratocystis fimbriata (Ipomoea strain) is non-regulated (ONZPR 2021) 
• Ceratocystis fimbriata (strains not in New Zealand) is regulated (ONZPR 20 21) 
Summary of reason for exclusion 
Ceratocystis fimbriata can be deemed not to be a hazard and excluded from the Avocado Germplasm 
Import Risk Analysis (IRA) because: 
• there is no evidence that Persea americana is a host of C. fimbriata , 
• one record in Portuguese literature states symptom s on dead and dying avocado trees in 
Brazil showed symptoms similar to those observed by  C. fimbriata  (Mariano and Menezes 
1989). 
o this study (Mariano and Menezes 1989) isolated a f ungus which had characteristic 
macroconidia and endoconidia, but the identity of t he fungus was not confirmed (by 
either morphological or sequence confirmation) (Mar iano and Menezes 1989). 
o since this study there have been no further record s of this host-pathogen association. 
o this study is the only one underpinning the inclus ion of avocado as host of C. fimbriata 
in USDA. 
• a further literature search produced no records of  C. fimbriata causing disease in P. 
americana  
o a single record from Portuguese literature states the possibility of P. americana  being 
resistant to C. fimbriata , but this has also not been confirmed (Fernández e t al. 1987). 
o No further studies have been conducted showing thi s resistance. 
Supporting information  
Searches of Google Scholar, CAB abstracts, CPC, USD A fungal database and Google were 
conducted using the search terms ‘ Ceratocystis fimbriata ’ (and synonyms) and ‘ Persea americana ’ 
(and ‘avocado’). The record from USDA refers to Mar iano and Menezes (1989) and neither CABI 
(2021) or EPPO (2021) list Persea americana as a host of C. fimbriata . In addition, searching the 
same search terms in Web of Science produced no res ults. 
References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
CABI (2021) Ceratocystis fimbriata  (Ceratocystis blight). https://www.cabi.org/cpc/datasheet/12143  
Accessed December 2021  
407 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand EPPO (2021) Ceratocystis fimbriata . https://gd.eppo.int/taxon/CERAFI  Accessed December 2021 
Fernández, A; Prieto, D; Amaro, C (1987) Susceptibi lidad de especies cultivables a Ceratocystis 
fimbriata. Ciencia y Tecnica en la Agricultura. Proteccion de Plantas . 
Holland, L A; Lawrence, D P; Nouri, M T; Travadon, R; Harrington, T C; Trouillas, F P (2019) 
Taxonomic revision and multi-locus phylogeny of the  North American clade of Ceratocystis . Fungal 
systematics and evolution 3(1): 135-156. 
Mariano, R L R; Menezes, M (1989) Ocorrencia da sec a do abacateiro ( Persea americana Mill.) e da 
bisbagueira ( Spathodea campanulata Beauv.) causada por Ceratocystis fimbriata  E. & H. 
Fitopatologia Brasileira 14: 160. 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 408 App 1.4  Diaporthe pascoei 
Scientific name: Diaporthe pascoei R.G. Shivas, Jacq. Edwards & Y.P. Tan (2013)  
Order/Family: Diaporthales/Diaporthaceae 
Synonyms: None 
Known distribution: Australia and Malaysia  
NZ status (Lim et al. 2019) 
• Not reported to be present in New Zealand (not lis ted in Biota NZ (2022), accessed 1/11/2021, 
or PPIN, accessed 21/12/2021)  
• Not listed in ONZPR (2021) (accessed 1/11/2021)  
Summary reason for exclusion 
Diaporthe pascoei can be deemed not to be a hazard and excluded from the avocado Germplasm 
Import Risk Analysis (IRA) because: 
• There is insufficient information available on the  fungus to carry out a PRA, and insufficient 
evidence that the fungus is associated with fruits with stem-end rot disease in Persea 
americana . 
• There is only a single report of this species in a ssociation with Perseae americana  fruit  
• Pathogenicity test was not done to confirm if the pathogen caused disease symptoms 
observed on avocado fruit. 
Supporting Information 
Tan et al. recently described D. pascoei and other five new species of Diaporthe , on the basis of 
morphological characteristics and molecular analyse s (Tan et al. 2013). Diaporthe pascoei was 
isolated from decayed patches on P. americana (avocado) fruit with stem-end rot disease symptoms 
on one occasion in Australia (Tan et al. 2013). Pat hogenicity tests was not carried out to confirmed i f 
D. pascoei was responsible for causing disease symptoms on avo cado fruit because it did not grow on 
culture media (Tan et al. 2013). As such, there is no clear information linking this fungus to the 
symptoms noted, which could be due to other pathoge ns present at the same time.  
Diaporthe pascoei was recently associated with mangos. It was isolate d along with other pathogens 
known to cause stem-end rot disease ( Diaporthe  spp.). Pathogenicity test confirmed D. pascoei to 
cause disease symptoms (stem-end rot) in mango in M alaysia (Lim et al. 2019).  
Searches using the search term ‘ Diaporthe pascoei on avocado’ from Google, Google scholar, CABI 
and the USDA fungal database found no additional re cords (other than the single reference above) of 
D. pascoei association with avocado. 
References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Lim, L; Mohd, M H; Zakaria, L (2019) Identification  and pathogenicity of Diaporthe species associated 
with stem-end rot of mango ( Mangifera indica  L.). European Journal of Plant Pathology 155(2): 687-
696. 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Tan, Y; Edwards, J; Grice, K; Shivas, R (2013) Mole cular phylogenetic analysis reveals six new 
species of Diaporthe from Australia. Fungal diversity 61(1): 251-260.  
409 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand App 1.5  Duke 6 stem pitting 
Taxonomic notes: disease of unknown aetiology 
NZ status  
• not known to be present in New Zealand (not listed  in NZOR (2021)or PPIN (2021), accessed 
6/01/2022) 
• not listed in ONZPR (2021) (accessed 6/01/2022) 
Summary of reason for exclusion 
Duke 6 stem pitting  can be excluded from the Avocado Germplasm Import R isk Analysis (IRA) 
because: 
• the disease is restricted to the variety Duke 6 wh ich is no longer planted commercially 
anywhere in the world, 
• it was identified in South Africa and since then i t has not been reported elsewhere, 
• no other variety has been reported to have similar  symptoms, 
• the most recent literature catalogues this disease  as a minor problem which rarely impacts 
plant health and does not reduce yield, 
• it appears to be triggered by a source of extreme drought stress, 
• there is no indication in the literature of ongoin g research to determine the source of the 
observed symptoms 
Supporting information 
Duke 6 stem pitting was first reported in the 1980s  when the avocado cultivar ‘Duke 6’ was planted on 
a commercial scale at Westfalia Estate in South Afr ica (Roe et al. 1995). The Californian cultivar Duk e 
6 was known to be a root rot tolerant rootstock and  therefore was amongst the cultivars imported to 
South Africa for evaluation under South African con ditions. After 2 to 3 years the trees began dying 
due to an unidentified disease associated with the formation of depressions or indentations in the ste m 
(stem pitting) (Kremer-Köhne and Köhne 2007). 
The first symptom observed was wilting of the leave s which subsequently abscised, leaving the tree 
almost bare of leaves. This resulted in severe sunb urn of bark, twigs and branches.  In addition, a ve ry 
clear pitting, confined to the rootstock, could be observed in the wood when the bark was stripped 
across the grafting point and protuberances were ob served on the bark removed (Moll et al. 1987).  
In one orchard in South Africa containing 4,000 avo cado trees, of which 2,000 trees where Hass 
scions grafted on clonal Duke 6 and 2,000 trees whe re Hass scions grafted on Guatemalan seedling 
(cv Edranol), the trees that were grafted on Duke 6  started defoliating and declined rapidly after thr ee 
years of vigorous growth. Later on, this disease sp read to further 1,200 trees grafted on Edranol 
rootstock (Moll et al. 1987). This raised questions  about the ability of this disease to spread rapidl y. In 
addition, it was observed that when Duke 6 was budd ed to other rooststocks (i.e. Duke 7 and G6) a 
distinct leaf symptom developed within six months a nd the plants were relatively stunted. The 
observations above prompted a series of research, t o determine the source of the observed symptoms 
(Moll et al. 1987).  
Fungi: Fifteen root and soil samples were taken fro m diseased avocado trees and fungi isolated on 
P10 VP and PDA agar were incubated at 25° C in a dark in cubator for 10 days. One of the samples 
tested positive for Phytophthora cinnamomi  whereas Fusarium  was isolated from several samples. 
There were no fungi consistently associated with th e diseased samples (Moll et al. 1987). No 
conclusive results to date regarding this disease b eing ascribed to fungi. 
Bacteria: Fifteen root and soil samples were taken from diseased avocado trees and isolates were 
made into nutrient agar and incubated at 22 ° C and compared under a light microscope after being 
Gram stained. Numerous bacteria were isolated but t here was no bacteria consistently associated with 
the diseased samples (Moll et al. 1987). No conclus ive results to date regarding this disease have 
being ascribed to bacteria. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 410 Nematodes: Five root (10 g per sample) and five soi l samples (250 g per sample) were extracted from 
diseased and healthy trees as well as samples from an adjacent field that had not been disturbed by 
agricultural practices. No nematode was found distr ibuted consistently throughout the samples and 
when nematodes were encountered, the numbers were l ow (Moll et al. 1987). 
Insect vectors: No arthropod was found with suffici ent consistency to support the hypothesis of spread  
of the disease by an insect vector (Moll et al. 198 7). 
Nutrition: Samples of wood were obtained from prima ry roots, the trunk above and below the grafting 
point and primary branches from diseased and health y trees.  Zinc levels were higher in diseased 
trees as opposed to nitrogen, phosphates, potassium , and magnesium levels, which were higher in 
healthy trees. Levels of all the other nutrient ele ments (copper manganese, iron and boron) were the 
same in healthy and diseased trees (Moll et al. 198 7).  According to Moll et al. (1987), no nutrient w as 
either sufficiently deficient or excessive to cause  the symptoms observed  
Viruses: Leaf samples from diseased trees from diff erent rootstocks were analysed using the Bar-
Joseph et al. (1983) extraction technique and poly- acrylamide gel electrophoresis.  Avocado samples 
known to be infected with sunblotch viroid and Nicotiana glauca  infected with cucumber mosaic virus 
were used as positive controls. The cultivar Duke 6  failed to yield any viruses (Moll et al. 1987). 
Despite the fact that no foreign RNA could be detec ted in the cultivar Duke 6, Moll et al. (1987) 
suggested that the stem-pitting symptoms, the diffe rential host symptom expression, and the observed 
transmissibility in the field all indicated a viral  pathogen.  According to da Graca and Trench (1985) , 
not detecting dsRNA in Duke 6 does not eliminate th e possibility that the causal virus agent might be 
present. It could be that the levels are too low to  detect, or the sample material might need to be 
increased above the levels already tested, or perha ps the causal agent is a DNA virus. 
The observations in South Africa prompted research in Israel on similar disease problems in local 
avocado plants. After screening several top grafted  trees with different varieties, they concluded tha t 
these phenomena were not caused by a particular dis ease (Bar-Joseph et al. 1987). 
It has been suggested that Duke 6 stem pitting symp tom is similar to the avocado black streak disease 
(another disease of unknown aetiology) and that it could be possibly that the disease reported in 
California, is the same as the one reported in Sout h Africa. However this has been rebuked by 
researchers in California by saying that the pittin g symptom is not observed throughout all the trees 
showing black streak cankers and that Duke 6 is not  a variety of common use as there are more 
resistant cultivars developed since the first relea se of Duke 6 in the 1980s (Moll et al. 1987).  
Currently, this disease is catalogued as a minor pr oblem which rarely impacts plant health and does 
not reduce yield (Dann et al. 2013).  It appears th at this disease is exacerbated by severe stress 
conditions, like prolonged drought periods (i.e. se vere drought in 1984 in South Africa) (Moll et al. 
1987). 
The cultivar Duke 6 is no longer commercially plant ed in South Africa or other countries. As soon as 
the unidentified disease was detected in the 1980’s , all the Duke 6 plant material (including mother 
plants) were destroyed in an attempt to eradicate t he disease and therefore this rootstock no longer 
exists in South African orchards (Kremer-Köhne and Köhne 2007).  
Due to the unresolved causal agent of Duke 6 Stem P itting, the high uncertainty about its 
transmission, its restricted distribution and that no recent information regarding new avocado varieti es 
showing similar symptoms, it is not justified to co nsider this ‘disease’ as a hazard. The Emerging Ris k 
System was checked on January 6, 2022 and no alert has been registered under the Causative Agent 
Name: ‘Duke 6 stem pitting”. A monitoring system ha s been set up for active monitoring of this disease  
and if further information is available this diseas e could be reassessed. 
Literature search 
Searches of Google Scholar and Google were conducte d using the search terms “Duke 6 Stem 
pitting” and “Duke 6 Stem pitting” AND “avocado”. T hree pages with a total of 30 results were 
screened for relevant information and the search st opped after that because unrelated (e.g., ‘Duke 
university’ or ‘Cherry Stem Pitting’) or repeated i nformation started to appear.  
411 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand References 
Bar-Joseph, M; Giband, M; Yesodi, V (1987) Viruses,  viroids and diseases of unknown etiology 
observed in avocado groves in Israel. In First World Avocado Congress  (Vol. 10, pp. 226-128). South 
Africa. 
Bar-Joseph, M; Rosner, A; Moscovitz, M; Hull, R (19 83) A simple procedure for the extraction of 
double-stranded RNA from virus-infected plants. Journal of Virological Methods 6(1): 1-8. 
da Graca, J; Trench, T (1985) Evidence of dsRNA in South African avocados. In South African 
Avocados Growers' Association  (Vol. 8, pp. 72-74). 
Dann, E; Ploetz, R; Coates, L; Pegg, K (2013) Folia r, fruit and soliborne diseases. In B Schaffer; B 
Wolstenholme; A Whiley (eds) The avocado: botany, production and uses. 2nd ed. CABI: London, UK. 
Kremer-Köhne, S; Köhne, J (2007) 25 years of avocad o rootstock development in South Africa. In 
Proceedings VI World Avocado Congress . Viña del Mar, Chile. 
Moll, J N; Grech, N M; van Vuuren, S P (1987) A let hal, transmissible stem-pitting of avocados 
associated with Duke 6 rootstocks. In South African Avocado Growers' Association Yearbook  (Vol. 10, 
pp. 122-127). South Africa. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Roe, D; Kremer-Köhne, S; Köhne, J (1995) Local and imported avocado rootstocks in South Africa. In 
World Avocado Congress III  (pp. 132-139). Israel. 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 412 App 1.6  Guignardia foeniculacea 
Scientific name:  Guignardia foeniculacea  (Mont.) Arx & E. Müll. (1954) 
Taxonomic position (order/family):  Botryosphaeriales /Phyllostictacea 
Synonyms:  Sphaeria foeniculacea  Mont. (1849), Diaporthe foeniculacea  (Mont.) Niessl. (1879) 
NZ status 
• Absent from New Zealand (Biota NZ 2022) (accessed Sept 2021). 
• Not listed in ONZPR (2021) (accessed Sept 2021). 
Summary of reason for exclusion 
Guignardia foeniculacea  (syn.  Diaporthe foeniculacea ) can be deemed not to be a hazard and 
excluded from the Avocado Germplasm Import Risk Ana lysis (IRA) because: 
• the pathogen reported by Guarnaccia et al. (2016) on avocado in Italy is most likely Diaporthe 
foeniculina (already present in New Zealand) and, 
• there is insufficient evidence that Guignardia foeniculacea  is associated with avocado 
Supporting information 
Guarnaccia et al. (2016) reported  Diaporthe foeniculacea  as a mildly virulent pathogen on avocado 
branches in Italy. Guarnaccia et al. (2016) refer t o Diaporthe foeniculacea and D. foeniculina as 
synonyms but this synonymy is not supported by Mana aki Whenua Landcare Research (P. Johnston, 
pers. comm.) or by the Biota New Zealand database ( accessed Sept 2021) (Biota NZ 2022), or based 
on information in a study by Udayanga et al. (2014) . Furthermore, taxonomic trees based on 
molecular sequence alignments show that the CBS iso late (CBS-111553) referred to by Guarnaccia et 
al. (2016) as D. foeniculacea  actually corresponds with D. foeniculina in the CBS-KNAW culture 
collection and is closely related to an isolate fro m blackcurrants ( Ribes ) in New Zealand (Udayanga et 
al. 2014). This indicates that the pathogen reporte d by Guarnaccia et al. (2016) on avocado in Italy i s 
Diaporthe foeniculina , which is already present in New Zealand (Biota NZ  2022). This is the only study 
that has reported Diaporthe foeniculacea  (syn.  Guignardia foeniculacea ) as a pathogen of avocado. 
Literature Search  
Google and Google Scholar were used to search for i nformation on Guignardia foeniculacea  and its 
synonyms ( Sphaeria foeniculacea, Diaporthe foeniculacea ). Diaporthe foeniculina and its synonyms 
(Phoma foeniculina,  Phomopsis theicola  and Diaporthe neotheicola ) were also searched for in Google 
and Google Scholar . The USDA fungal database (Farr and Rossman 2021) a nd CBS-KNAW culture 
collection database were also used to search for sp ecies and isolates.  
References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Farr, D F; Rossman, A Y (2021) Fungal databases, U.  S. National Fungus Collections. https://nt.ars-
grin.gov/fungaldatabases/  Accessed Septemeber 27, 2021 
Guarnaccia, V; Vitale, A; Cirvilleri, G; Aiello, D;  Susca, A; Epifani, F, et al. (2016) Characterisati on and 
pathogenicity of fungal species associated with bra nch cankers and stem-end rot of avocado in Italy. 
European Journal of Plant Pathology 146(4): 963-976. 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021  
413 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Udayanga, D; Castlebury, L A; Rossman, A Y; Hyde, K  D (2014) Species limits in Diaporthe : 
molecular re-assessment of D. citri , D. cytosporella , D. foeniculina  and D. rudis . Persoonia 32: 83-101. 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 414 App 1.7  Lasiodiplodia  mahajangana 
Scientific name: Lasiodiplodia  mahajangana  Begoude, Jol. Roux & Slippers  
Order/Family: Botryosphaeriales/Botryosphaeriaceae 
Synonyms: None 
Known distribution: Australia, Madagascar, South Africa, USA and Venezu ela 
NZ status 
• Not reported to be present in NZ (not listed in Bi ota NZ (2022), accessed 2/11/2021, or PPIN 
(2021), accessed 21/12/2021)  
• Not Listed in ONZPR (2021) (accessed 2/11/2021)  
Summary reason for exclusion 
Lasiodiplodia  mahajangana can be deemed not to be a hazard and excluded from the avocado 
Germplasm Import Risk Analysis (IRA) because: 
• A pathogen was isolated on rotten avocado fruit sh owing stem-end rot disease symptoms. 
The isolated pathogen showed some sequence similari ty with Lasiodiplodia  mahajangana  
• It has not been associated with avocado budwood.  
Supporting Information 
A pathogen was isolated on avocado fruits with stem -end disease symptoms in South Africa (Majola 
2020). Majola (2020) inferred from molecular analys is that the isolated avocado stem-end rot 
pathogen was a member of the genus Lasiodiplodia , possibly L mahajangana , but concluded that the 
identity of the species requires further investigat ion and confirmation. 
So far, this inconclusive evidence is the only repo rt that associates L.  mahajangana with avocado.  
Lasiodiplodia  mahajangana has been associated with about 20 different host pl ants from five 
countries. In a study in the Kimberley region of We stern Australia, it was the dominant species 
sampled among native trees in an isolated habitat ( Sakalidis et al. 2011).  However, the only report 
that associates L. mahajangana  with avocado is inconclusive and requires confirma tion is strong 
enough as a reason to exclude this species as a haz ard. 
Searches using the search term ‘ Lasiodiplodia  mahajangana  on avocado’ from Google, Google 
scholar, CABI and the USDA fungal database found no  additional record (other than the references 
above) of L.  mahajangana association with avocado.  
References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Majola, T F (2020) The potential of combined rapid hot water treatment  and yeast biocontrol for 
suppressing postharvest avocado anthracnose and ste m-end rot diseases.  thesis; University of 
Kwazulu-Natal, South Africa.  
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021  
415 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Sakalidis, M L; Ray, J D; Lanoiselet, V; Hardy, G E  S; Burgess, T I (2011) Pathogenic 
Botryosphaeriaceae associated with Mangifera indica  in the Kimberley region of Western Australia. 
European Journal of Plant Pathology 130(3): 379-391. 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 416 App 1.8  Microthia  havanensis  
Scientific name : Microthia havanensis  (Bruner) Gryzenh. & M.J.Wingf.  
Taxonomic position (order/family) : Diaporthales/Cryphonectriaceae 
Taxonomic notes: This species was initially described by Bruner (191 6) as Endothia havanensis  
Bruner, and later named  Cryphonectria havanensis  (Bruner) M.E. Barr.  The results from phylogenetic  
analyses and morphological comparisons performed by  Gryzenhout et al. (2006), demonstrated that 
C. havanensis  do not reside under Cryphonectria  but under the genus Microthia . This fungus and 
Amphilogia gyrosa  have been considered as synonyms when the latter f ungus was still known as 
Cryphonectria gyrosa  (Hodges 1980), but Gryzenhout et al. (2006) has de monstrated that these 
species should be considered as distinct species.  The name C. havanensis  has also been used for 
collections of a fungus from Eucalyptus globulus  in Japan (Kobayashi 1970). However, DNA sequence 
comparisons performed by Myburg et al. (2004) showe d that C. havanensis  in Japan is the same as 
Cryphonectria nitschkei  (G.H. Otth) M.E. Barr. It is unclear if C. havanensis  collected from Cuba is 
synonym to C. nitschkei because Myburg et al. (2004) did not consider this comparison in their study.  
NZ status  
• The species is not known to be present in New Zeal and (not listed in Biota NZ (2022), 
accessed 8/12/2021, or PPIN (2021), accessed 17/12/ 2021)  
• The species is regulated under the name Cryphonectria havanensis  (ONZPR 2021) (accessed 
8/12/2021) 
 
Summary of reason for exclusion 
Microthia havanensis  can be excluded from the Avocado Germplasm Import Risk Analysis (IRA) 
because: 
• There is insufficient evidence that Microthia havanensis  is associated with the commodity (i.e., 
healthy looking budwood/leafless cuttings of Persea americana ). 
Supporting information  
The initial description of Microthia havanensis , performed by Bruner (1916) under the name Endothia 
havanensis,  was performed by sourcing the fungus from Eucalyptus  twigs. The author mentioned that 
the habitat of this fungus is dead bark of Eucalyptus  followed by a list of hosts of which Persea 
gratissima  (syn. Persea americana ) is included.  There is no indication from this st udy that M. 
havanensis  is associated with the commodity. 
Furthermore, Gryzenhout et al. (2006) mentioned tha t this fungus was found on dead branches of 
mango ( Mangifera indica ) and avocado ( Persea gratissima ) that were lying on the ground in the 
vicinity of Eucalyptus trees and refers to Bruner ( 1916), who first described this fungus. 
The author (Roux et al. 2020) mentioned that this f ungus is known as a saprobe mainly in Eucalyptus  
but also in other hosts like avocado and also refer s to Bruner (1916). 
Literature search  
Searches of Google Scholar and Google were conducte d using the search terms ‟Microthia 
havanensis”, ‟Cryphonectria havanensis” and ‟Endothia havanensis” combined with the search terms  
‟avocado”, “aguacate” and ‟Persea americana”. In addition, searches were perfo rmed in Index 
Fungorum, USDA Fungal databases to determine host a nd commodity association and GBIF 
database to obtain the taxonomy of the fungus. 
References 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022  
417 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Bruner, S (1916) A New Species of Endothia. Mycologia 8(5): 239-242. 
Gryzenhout, M; Myburg, H; Hodges, C; Wingfield, B; Wingfield, M (2006) Microthia , Holocryphia  and 
Ursicollum , three new genera on Eucalyptus  and Coccoloba  for fungi previously known as 
Cryphonectria . Studies in Mycology 55: 35-52. 
Hodges, C (1980) The taxonomy of Diaporthe cubensis . Mycologia 72(3): 542-548. 
Kobayashi, T (1970) Taxonomic studies of Japanese D iaporthaceae with special reference to their life 
histories. Bulletin of the Government Forest Experiment Statio n 226: 132-147. 
Myburg, H; Gryzenhout, M; Wingfield, B; Milgroom, M ; Shigeru, K; Wingfield , M (2004) DNA 
sequence data and morphology define Cryphonectria  species in Europe, China and Japan. Canadian 
Journal of Botany 82(12): 1730-1743. 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Roux, J; Kamgan Nkuekam, G; Marincowitz, S; van der  Merwe, N; Uchida, J; Wingfield, M, et al. 
(2020) Cryphonectriaceae associated with rust-infec ted Syzygium jambos  in Hawaii. MycoKeys 76: 
49-79. 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 418 App 1.9  Physalospora  abdita  and Physalospora perseae  
Scientific name:  Physalospora abdita  (Berk. & M.A.Curtis) N.E.Stevens 
Taxonomic position (order/family):  Amphisphaeriales (Xylariales)/Hyponectriaceae   
Taxonomic notes:  The exact taxonomic position is uncertain. Current ly, it is placed under synonymy 
with  Physalospora fusca , Barriopsis fusca , and Botryosphaeria fusca (Biota NZ 2022) based on Weiss 
(1950). Physalospora fusca was incorrectly recorded from New Zealand based on specimens later 
identified as Sphaeropsis citrigena  (Biota NZ 2022). 
NZ status 
• Uncertain due to taxonomy (Biota NZ 2022). 
• Uncertain regulatory status due to taxonomy (ONZPR  2021). 
Summary of reason for exclusion 
Physalospora abdita  can be deemed not to be a hazard and excluded from  the Avocado Germplasm 
Import Risk Analysis (IRA) because: 
• the pathogen reported as Physalospora  abdita  on avocado was described morphologically 
and there is no sequence data available to clarify its taxonomic position, 
• many Physalospora species that were described morphologically have si nce been moved into 
different genera using molecular methods, such as i n Botryosphaeria, Lasiodiplodia, Diplodia, 
Mycospaerella, Guignardia, Barriopsis, Phyllosticta , Stigmatula, Colletotrichum, Polystigma, 
Vestergrenia, Pseudomassaria  and Phyllachora  (Biota NZ 2022), 
• symptoms of dieback and canker on avocado are more  likely attributed to other fungal genera, 
such as Botryosphaeria, Lasiodiplodia, Diplodia, Mycospaere lla, Phyllachora  and  
Colletotrichum  (Valencia et al. 2019; Biota NZ 2022), 
• a literature search found no reports of Physalospora  species associated with avocado since 
the use of molecular identification methods (1980s) . 
Scientific name: Physalospora perseae  Doidge 1923 
Order/Family: Amphisphaeriales (Xylariales)/Hyponectriaceae 
Taxonomic notes: Physalospora perseae  was described in 1922 as an avocado pathogen but t he 
name has barely been used since (Doidge 1922) and h as only been found in some poorly referenced 
lists of plant diseases. In the 1920s and 30s it wa s considered to be the pathogen on avocado causing 
black spot, leaf spot, die-back or wither tip and c anker on avocado (Carpenter 1931) and described as 
the higher stage of “the avocado Gloeosporium  or Colletotrichum ”. It was intercepted in the United 
States from South Africa in the 1930s (USDA 2016). In 1934 the species was redescribed, considered 
to be a typical Melanops , and renamed to Melanops perseae  (Doidge) Petr. 1934. Since then no 
Melanops  or Physalospora species have been reported from avocado (Jiang et a l. 2018). 
Physalospora perseae or  Melanops perseae  have never been used in a New Zealand context (Bio ta 
NZ 2022). There is no genetic data available to res olve the exact taxonomic position of the species.  
NZ status:  
• Uncertain due to taxonomy (Biota NZ 2022). 
• Uncertain regulatory status due to taxonomy (ONZPR  2021). 
Summary of reason for exclusion 
Physalospora perseae  can be deemed not to be a hazard and excluded from  the Avocado Germplasm 
Import Risk Analysis (IRA) because: 
• the pathogen reported as Physalospora  perseae  on avocado was described morphologically 
and there is no sequence data available to clarify its taxonomic position,  
419 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand • many Physalospora species that were described morphologically have si nce been moved into 
different genera using molecular methods, such as i n Botryosphaeria, Lasiodiplodia, Diplodia, 
Mycospaerella, Guignardia, Barriopsis, Phyllosticta , Stigmatula, Colletotrichum, Polystigma, 
Vestergrenia, Pseudomassaria  and Phyllachora  (Biota NZ 2022), 
• nowadays symptoms of dieback and canker on avocado  are more likely attributed to other 
fungal genera, such as Botryosphaeria, Lasiodiplodia, Diplodia, Mycospaere lla, Phyllachora  
and  Colletotrichum  (Valencia et al. 2019; Biota NZ 2022), 
• a literature search found no reports of Physalospora  species associated with avocado since 
the use of molecular identification methods (1980s) . 
Supporting information 
There is very little information associated with Physalospora abdita  and Physalospora perseae . Both 
species had been reported as pathogens on avocado p rior to molecular identification methods. There 
is no sequencing data available to clarify their ta xonomic position.  
When the two species were initially described as pa thogens on avocado (Doidge 1922; Weiss 1950) 
they were referred to as Physalospora because their symptoms and morphology resembled the se of  
Physalospora cydoniae  on the limbs and twigs of apple trees. Many Physalospora species that were 
described morphologically have since been moved int o different genera using molecular methods, 
such as in Botryosphaeria, Lasiodiplodia, Diplodia, Mycospaere lla, Guignardia, Barriopsis, 
Phyllosticta, Stigmatula, Colletotrichum, Polystigm a, Vestergrenia, Pseudomassaria  and Phyllachora  
(NZFungi2 2021).   
Literature Search 
Searches of Google Scholar, CAB abstracts, CPC, ICM P, USDA fungal database, CBS-KNAW culture 
collection database and Google were conducted using  the search terms ‘Physalospora abdita’,  
‘Sphaeria abdita ‘, ‘ Physalospora perseae ’ and ‘ Melanops perseae’  60. The last Physalospora  species 
record on avocado was likely an interception of Physalospora perseae  from South Africa in 1935 
(USDA 2016), although a pathogen resembling Physalospora perseae was described from Morocco in 
the 1960s and synonymised with Macrophoma allospora  (Rieuf and Yeasca 1970). No other specimen 
records or cultures have been found.  
Symptom development 
In the original publication by Doidge (1922) the pl ants which were inoculated with Physalospora 
perseae  spores soon showed signs of infection. The tissues  around the incision became discoloured 
and sunken; in some cases the affected area slowly increased in size for a few weeks until it was 
about 1 cm. After six months typical conidia were p roduced. Based on the original publication by 
Doidge (1922) it seems likely that Physalospora perseae  would be detected in PEQ due to symptom 
development within weeks.  
References and relevant literature 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Carpenter, C W (1931) Diseases of the avocado. California Avocado Association 1931 Yearbook 16: 
102-106. 
Doidge, E M (1922) A Fungus of economic importance on the avocado ( Persea americana ). Bothalia 
1(3): 179-186. 
Jiang, N; Phillips, A; Zhang, Z; Tian, C (2018) Mor phological and molecular identification of two nove l 
species of Melanops in China. Mycosphere 9(6): 1187-1196. 
NZFungi2 (2021) New Zealand Fungi and Bacteria (NZF UNGI). 
https://nzfungi2.landcareresearch.co.nz/  Accessed September 2021 
 
60 Literature in the Spanish, French and Portuguese  languages was only checked if it was found in sear ches on the species 
names. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 420 ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Rieuf, P; Yeasca, G (1970) Champignons sur avocatie r au maroc. Al Awamia (34): 47-90. 
USDA (2016) Importation of Fresh Fruit of Avocado, Persea americana  Miller var. ‘Hass’, into the 
Continental United States from Colombia. https://www.regulations.gov/document/APHIS-2016-002 2-
0025   
Valencia, A L; Gil, P M; Latorre, B A; Rosales, I M  (2019) Characterization and pathogenicity of 
Botryosphaeriaceae species obtained from avocado tr ees with branch canker and dieback and from 
avocado fruit with stem end rot in Chile. Plant Disease 103(5): 996-1005. 
Weiss, F A (1950) Index of plant diseases in the United States . Division of Mycology and Disease 
Survey; Plant Industry Station, Beltsville. 
  
421 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand App 1.10  Plagiostoma  perseae  
Scientific name:  Plagiostoma perseae Hyde (1995) 
Taxonomic position (order/family):  Diaporthales / Gnomoniaceae 
Synonyms:   nil 
NZ status:  Not known to be present in New Zealand:  not liste d in (NZOR 2021; Biota NZ 2022), or 
PPIN (2021). Organism is not listed in ONZPR (2021) . 
Summary of reason for exclusion 
Plagiostoma perseae can be excluded as a hazard on avocado budwood (as per the commodity 
description) because: 
• This  fungus was described from a single isolate from liv ing leaves of avocado ( Persea 
americana ) in Papua New Guinea (Hyde 1995). The isolate was collected in 1992 and the 
aetiology of the disease was not tested. Therefore,  it cannot be verified that the fungus 
detected on the avocado leaves was the cause of dis ease symptoms.  
• There were no further reports found of this fungus  being detected on avocado or any other 
host species. Therefore, there is insufficient evid ence that this fungus is pathogenic or has an 
association with the commodity.  
Supporting information: 
This fungus was described in association with leaf spots on the upper and lower surfaces of living 
avocado leaves in Papua New Guinea (Hyde 1995). Irr egular lesions were up to 7mm in diameter, 
brown and necrotic, with blackened centres were rep orted. Ascomata occurred mostly on the lower 
surface of the leaf. Hyde (1995) does not report if  the fungus was observed on multiple leaves of the 
avocado plant, or if multiple plants appeared to be  infected. No testing of pathogenicity or aetiology  
was reported. 
A literature search in Google and Google Scholar us ing the search term “ Plagiostoma perseae ” did not 
yield any other occurrences of this fungus on avoca do or any other host.  
The genus Plagiostoma  are microscopic fungi that are often found on the leaves, stems, twigs and 
branches of a variety of host plants (Mejía et al. 2011). They are most prevalent in temperate regions  
of the northern hemisphere. Some Plagiostoma  species are reported to cause plant disease and ma y 
infect hosts asymptomatically. They are particularl y noted as a cause of cankers on willows ( Salix 
spp. ) and poplars ( Populus spp. ). The genus may also be an important endophyte. A literature search 
in Google and Google Scholar using the search terms  “ Plagiostoma ” AND “avocado” OR “ Persea 
americana ” and “ Plagiostoma ” AND “Lauraceae” found no association of fungi wit hin this genus with 
avocados or any plant species in the Lauraceae fami ly.  
References: 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Hyde, K D (1995) Two new interesting Ascomycetes fr om Irian Jaya and Papua New Guinea. 
Mycotaxon 55: 275-282. 
Mejía, L C; Castlebury, L A; Rossman, A Y; Sogonov,  M V; White, J F, Jr. (2011) A systematic 
account of the genus Plagiostoma (Gnomoniaceae, Diaporthales) based on morphology, h ost-
associations, and a four-gene phylogeny. Studies in Mycology 68: 211-235. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 422 ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
  
423 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand App 1.11  Pseudomonas  syringae  pathovar (causing avocado bacterial 
blast) 
Scientific name : Pseudomonas syringae van Hall, 1902 
Taxonomic position (order/family) : Pseudomonadales / Pseudomonadaceae 
Taxonomic notes: Other names include: Phytomonas vignae; Pseudomonas holci; Pseudomonas 
japonica; Pseudomonas medicaginis; Pseudomonas stri afaciens var. japonica; Pseudomonas 
syringae pv. japonica; Pseudomonas vignae (EPPO 2020)(accessed 23/1/2022). The  ‘P. syringae 
complex ’ encompasses up to 10 Pseudomonas  species (Arnold and Preston 2019), about 400 strai ns 
with known genome (Dillon et al. 2017), and over 60  pathogenic variants (pathovars) with different 
host ranges (Bull et al. 2010; Arnold and Preston 2 019). A pathovar (pv.) is defined as a bacterial 
strain or set of strains with the same or similar c haracteristics that is differentiated from other st rains of 
the same species or subspecies on the basis of dist inctive pathogenicity to one or more plant hosts 
(Xin et al. 2018). Pseudomonas syringae pv. syringae  is a pathovar originally isolated from lilac (genu s 
Syringa ) but which has subsequently been shown to share ho sts in common from many 
dicotyledonous and monocotyledonous hosts. Bradbury  (1986) attributed all hosts of P. syringae  to P. 
syringae  pv. syringae  and in so doing almost certainly included hosts of  unidentified but related 
pathovars (Bradbury 1986). There are more than 100 strains of P. syringae pv. syringae (Scortichini et 
al. 2003). 
NZ status :  
• Pseudomonas syringae  is known to be present in New Zealand, with 61 ide ntified strains 
(potential synonyms) recorded (NZOR 2021) (accessed  24/1/2022) 
• Pseudomonas syringae pv. syringae  is non-regulated (ONZPR 2021) (accessed 24/1/2022, ) 
• Pseudomonas syringae, and all pv’s , is not assessed, it is non-regulated for strains p resent in 
New Zealand and pv. nerii, and it is regulated for strains not present in New Zealand and pv. 
papulans (ONZPR 2021) (accessed 24/1/2022) 
Summary of reason for exclusion: 
The P. syringae  pathovar causing avocado bacterial blast can be ex cluded from the Avocado 
Germplasm Import Risk Analysis (IRA) because: 
• Evidence was found that a P. syringae pathovar causing bacterial blast is already present  in 
New Zealand. 
o There is no available evidence suggesting the exis tence of multiple P. syringae  pv’s causing 
avocado bacterial blast. 
o The current evidence does not justify concerns abo ut potential exotic P. syringae avocado 
pv’s causing avocado blast and impacts other than n egligible in New Zealand. 
Supporting information : 
Pseudomoas syringae  is ubiquitous, and particularly abundant in habita ts associated with water 
(Morris et al. 2013). It is found in rain, rivers, alpine streams, lakes, wild plants, as well as in e pilithic 
biofilms (Morris et al. 2008), and has an important  role in processes leading to rain and snowfall 
(Morris et al. 2013). As a plant pathogen, P. syringae  can infect a wide range of species (Bull et al. 
2010). There are both non-pathogenic and pathogenic  strains of P. syringae (Xin et al. 2018). 
Collectively, the pathogenic strains (pathovars) of  P. syringae  infect almost all economically important 
crop species, which makes P. syringae  one of the most common plant pathogens (Xin et al.  2018). 
Yet, each pathovar infects a characteristic group o f host plants (Xin et al. 2018).  
There are two avocado diseases associated with Pseudomonas syringae  found in the literature: 
avocado blast, affecting the fruit (Lunar and Fucik ovsky 1987), and avocado bacterial canker, affectin g 
the plant (trunk and branches) (Korsten and Kotzé 1 987; Marais 2004). Both avocado blast and 
canker were attributed to bacterial complexes inclu ding P. syringae  pv. syringae and other bacteria  
(Korsten and Kotzé 1987; Lunar and Fucikovsky 1987;  Korsten and Towsen 1997; Marais 2004),  and  
P. syringae  pv. syringae  was listed as a potential exotic pest threats to t he New Zealand avocado 
industry (New Zealand Avocado 2021). When first des cribed in California, avocado fruit blast was 
attributed to Bacterium citriputeale (Smith 1926). The correct name for the blast organi sm was later Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 424 identified as P. syringae  (Schroth 1981). After its description in Californi a (Smith 1926), avocado fruit 
blast symptoms were later described in Israel (Volc ani 1946), and in Mexico (Lunar and Fucikovsky 
1987). 
Lunar and Fucikovsky (1987) reported that the avoca do blast was characterized by appearance of 
dark brown irregular areas which merged and covered  a significant part of the maturing avocado fruit. 
Affected areas took on a variety of forms. In some cases, lesions were raised above the surface of the  
fruit and were frequently located in the central or  distal part. In other cases, lesions were not rais ed 
and were frequently depressed. In later stages, les ions cracked, exposing the mesocarp tissue. As 
these dark lesions enlarged, the mesocarp tissue so ftened and became sunken. Infected avocado 
fruits were randomly distributed throughout the cro wn of 10-year-old trees. In advanced stages of 
infection, the avocado fruit produced a brown exuda te from the lenticels. Dried exudate had a whitish 
appearance and dissolved rapidly with rain (Lunar a nd Fucikovsky 1987). The bacteria associated with 
diseased fruits were predominantly Pseudomonas syringae pv. syringae ; however, Erwinia herbicola  
(Pantoea agglomerans ) was also present and could have been accountable for a portion of the 
damage (Lunar and Fucikovsky 1987). 
There is evidence that a P. syringae pathovar causing bacterial blast is already present  in New 
Zealand. The International Collection of Microorgan isms from Plants (ICMP) includes isolates of P. 
syringae pv. syringae  associated to avocado diseases in New Zealand. One  culture (ICMP 458) was 
isolated in Auckland (Mt Albert) from avocado “blas t” in 1955. The other culture (ICMP 7405) was 
isolated in the Bay of Plenty (Te Puke) from avocad o canker, a “twig lesion”, in 1981. A third reporte d 
record (Bevan Weir pers. comm) refers to an isolate  of P. syringae  associated to avocado canker and 
not pathogenic to lilac.  These records suggest that three P. syringae pv’s associated to avocado are 
already present in New Zealand, with one P. syringae pv. isolated from avocado with blast symptoms, 
and possibly two P. syringae pv’s isolated from avocado with canker symptoms.  
There is no available evidence suggesting the exist ence of multiple P. syringae  pv’s causing avocado 
bacterial blast. There are no sequence data availab le to clarify the taxonomic position of the P. 
syringae pv’s associated to the avocado disease symptoms rep orted overseas and the P. syringae 
pv’s already present in New Zealand (Kerry Everett,  Bevan Weir pers. comm). Given the uncertainty, 
potential testing options were suggested by both Pl ant And Food Research (Kerry Everett pers. 
comm) and Maanaki Whenua - Landcare Research (Bevan  Weir pers. comm). There could be 
concerns about the existence of exotic P. syringae  pv’s causing avocado bacterial blast and other 
impacts. These concerns could stem from the huge di versity of the ‘P. syringae complex ’ and its 
changing taxonomy (Dillon et al. 2017), and from th e severe impacts of Pseudomonas syringae pv. 
actinidiae (Psa) on the kiwifruit industry (Vanneste 2017). 
The current evidence does not justify concerns abou t potential exotic P. syringae avocado pv’s 
causing avocado blast and impacts other than neglig ible in New Zealand. In fact, in almost a century 
since its description, the disease “avocado blast” was reported sporadically and on a local orchards 
(Smith 1926; Volcani 1946; Lunar and Fucikovsky 198 7), and no original articles referring to avocado 
blast could be found after Lunar and Fucikovsky’s w ork published in 1987 (Dann et al. 2013). Avocado 
blast is not listed in a recent review of the avoca do diseases, listing avocado canker (Marais 2004). 
When avocado blast was first described, it was note d that the disease had limited distribution and lit tle 
significance (Smith 1926). Also the avocado canker attributed to P. syringae pv. syringae was 
described as having little significance (Korsten an d Kotzé 1987). Although avocado canker was 
observed in all major avocado-growing areas of Sout h Africa, it had no economic importance to the 
industry because of the small percentage of trees i nfected (Korsten and Kotzé 1984). Neither avocado 
blast nor avocado canker are listed among the avoca do diseases by EPPO (EPPO, accessed 
24/1/2022).  
Literature search : 
Searches of Google Scholar and Google were conducte d using the search terms ‟ Pseudomonas ”, ‟ 
Pseudomonas syringae ”, combined with the search terms ‟avocado blast” ‟avocado”, “aguacate”, 
“Persea ” and ‟Persea americana ”. In addition, searches were performed in the PPIN  and ICPM 
databases. 
References 
Arnold, D L; Preston, G M (2019) Pseudomonas syring ae: Enterprising epiphyte and stealthy parasite. 
Microbiology 165(3): 251-253.  
425 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Bradbury, J F (1986) Guide to plant pathogenic bacteria . CAB international. 
Bull, C T; De Boer, S; Denny, T; Firrao, G; Saux, M  F-L; Saddler, G, et al. (2010) Comprehensive list 
of names of plant pathogenic bacteria, 1980-2007. Journal of Plant Pathology : 551-592. 
Dann, E; Ploetz, R; Coates, L; Pegg, K (2013) Folia r, fruit and soilborne diseases. The avocado: 
botany, production and uses : 380. 
Dillon, M; Thakur, S; Almeida, R; Guttman, D (2017)  Recombination of ecologically and evolutionarily 
significant loci maintains genetic cohesion in the Pseudomonas syringae species complex. 
EPPO (2020) EPPO global database. https://gd.eppo.int  Accessed 29/10/2020 
Korsten, L; Kotzé, J (1984) Bacterial canker of avo cado. South African Avocado Growers' Association 
Yearbook 7: 73-74. 
Korsten, L; Kotzé, J (1987) Bark canker of avocado,  a new disease presumably caused by 
Pseudomonas syringae  in South Africa. In (Vol. 71, pp. 850-850): AMER P HYTOPATHOLOGICAL 
SOC 3340 PILOT KNOB ROAD, ST PAUL, MN 55121. 
Korsten, L; Towsen, E (1997) Update on bacterial ca nker of avocado. South African Avocado 
Growers' Association Yearbook (South Africa) . 
Lunar, I; Fucikovsky, L (1987) Avocado Bacterial Bl ast in Mexico. Plant Pathogenic Bacteria.  Springer. 
Marais, L (2004) Avocado diseases of major importan ce worldwide and their management. Diseases 
of Fruits and Vegetables: Volume II.  Springer. 
Morris, C E; Monteil, C L; Berge, O (2013) The life  history of Pseudomonas syringae : linking 
agriculture to earth system processes. Annual Review of Phytopathology 51: 85-104. 
Morris, C E; Sands, D C; Vinatzer, B A; Glaux, C; G uilbaud, C; Buffiere, A, et al. (2008) The life his tory 
of the plant pathogen Pseudomonas syringae is linke d to the water cycle. The ISME journal 2(3): 321-
334. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Schroth, M H, DC; Starr, MP (1981) Phytopathogenic members of the genus Pseudomonas . The 
Prokaryotes. Springer, Verlag, Berlin Heidelberg, New York, 1102  pp. ed. 
cortichini, M; Marchesi, U; Dettori, M; Rossi, M (2 003) Genetic diversity, presence of the syrB gene, 
host preference and virulence of Pseudomonas syringae  pv. syringae  strains from woody and 
herbaceous host plants. Plant Pathology 52(3): 277-286. 
Smith, C (1926) Blast of avocados—a bacterial disea se. Calif. Citrograph 11: 163. 
Vanneste, J L (2017) The scientific, economic, and social impacts of the New Zealand outbreak of 
bacterial canker of kiwifruit ( Pseudomonas syringae  pv. actinidiae ). Annual Review of Phytopathology 
55: 377-399. 
Volcani, Z (1946) Bacterial rot of avocado fruit. I n (Vol. 5 (2), pp. 169-180). Palestine Jour. Bot. S er. R. 
Xin, X-F; Kvitko, B; He, S Y (2018) Pseudomonas syringae : what it takes to be a pathogen. Nature 
Reviews Microbiology 16(5): 316-328. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 426 App 1.12  Rhizoctonia  solani 
Scientific name:  Rhizoctonia solani J. G. Kühn 1858 
Taxonomic position (order/family):  Cantharellales/Ceratobasidiaceae   
Synonyms: Corticium sasakii (Shirai) H. Matsumoto 1934, Corticium solani (Prill. & Delecr.) Bourdot 
& Galzin 1911, Corticium vagum var. solani  Burt 1903, Hypochnus cucumeris A. B. Frank 1883, 
Hypochnus filamentosus  Pat. 1891, Hypochnus sasakii  Shirai 1906, Hypochnus solani  Prill. & Delacr. 
1891, Pellicularia filamentosa (Pat.) D. P. Rogers 1943, Thanatephorus cucumeris  (A. B. Frank) Donk 
1956, Thanatephorus sasakii (Shirai) C. C. Tu & Kimbr. 1978 
Taxonomic notes:  Rhizoctonia solani  is a large species complex composed of genetically  distinct 
groups with diverse life histories (Cubeta and Vilg alys 1997). These groups are known as anastomosis 
groups (AGs) and differ in their ability to cause d isease on crops (Cubeta & Vilgalys 1997, Windels et  
al. 1994). There are at least 14 AGs within the R. solani  complex (Cubeta and Vilgalys 1997; Zheng et 
al. 2019). AGs have been further subdivided into su bgroups that differ in their biochemical, genetic o r 
pathogenic characteristics (Cubeta and Vilgalys 199 7). 
Thanatephorus cucumeris  is the teleomorph of Rhizoctonia solani  (Adams and Butler 1978; Strauss et 
al. 2000). 
NZ status:  
• Recorded as present in New Zealand (Biota NZ 2022) . 
o It is unknown which AG the Persea americana isolate belongs to. 
o AG-3PT, AG-2-1 and AG-6 are known to be present in  New Zealand (Das 2013; Biota 
NZ 2022) 
• Strains of Thanatephorus cucumeris  that are recorded as present in New Zealand are no n-
regulated (ONZPR 2021). 
• Strains of Thanatephorus cucumeris that are recorded as absent from New Zealand are 
regulated and unwanted (ONZPR 2021). 
Summary of reason for exclusion 
Rhizoctonia solani  can be deemed not to be a hazard and excluded from  the Avocado Germplasm 
Import Risk Analysis (IRA) because: 
• Rhizoctonia solani  is primarily a soilborne pathogen that has only be en reported to infect 
roots, seeds and young seedlings of Persea americana , and 
• a literature search found no reports to suggest th at R. solani can be associated with the 
commodity, Persea americana budwood. 
Supporting information 
Rhizoctonia solani has an extremely large host range across multiple p lant families with symptoms 
specific to the host (i.e. symptoms are not the sam e across species) (Chase 1991; PPIN 2021) and 
has been isolated from 46 species in New Zealand (P PIN 2021). Symptoms can include stem and root 
rot and leaf blight but this depends on the AG (Cha se 1991). Specifically, AG2-1 and AG4 are 
associated with stem and root rot diseases in dicot s (e.g. Brassicaceae species), while AG8 causes 
root rot in monocots (Williamson-Benavides and Dhin gra 2021). In general, the first four AGs (AG-1, -
2, -3, and -4) cause important diseases in plants w orldwide, whereas the remaining AGs (AG-5, -6, -7, 
-8, -9, -10, -11, -12) are less destructive and gen erally have a restricted geographic distribution 
(Williamson-Benavides and Dhingra 2021). 
Rhizoctonia solani was first reported being pathogenic on Persea americana in 1960 (Mircetich and 
Zentmyer 1960). Rhizoctonia solani causes root and seed rot in P. americana (González ‐Sánchez et 
al. 2010; Horst 2013). Specifically, the fungus inv ades seedlings through cotyledons (leaves at first 
emergence) and can cause rot of young roots and sho ots (Mircetich and Zentmyer 1960; Zentmyer  
427 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand 1961). In some cases the embryo will be killed and germination does not occur (Mircetich and 
Zentmyer 1960; Zentmyer 1961). 
If infection occurs after primary root formation, t he pathogen will attack the youngest part of the ro ot 
causing brown lesions and will spread until the roo t system has been destroyed (Mircetich and 
Zentmyer 1960; Zentmyer 1961; Snyman and Darvas 198 3). It may occassionally infect small roots on 
adult trees, but these roots usually regenerate  (M ircetich and Zentmyer 1960; Zentmyer 1961). The 
disease primarly occurs in seed flats in nurseries or in seed beds in the field (Mircetich and Zentmye r 
1960; Zentmyer 1961).  
Literature Search 
Searches of Google Scholar, CAB abstracts, CPC, ICM P, USDA fungal database, CBS-KNAW culture 
collection database and Google were conducted using  the search terms [‘ Rhizoctonia solani ’ OR 
‘Thanateporus cucumeris ’ AND ‘ Persea americana ’ OR ‘avocado’]. Results associated with P. 
americana  refer to symptoms described above. There have been  no significant outbreaks of this 
pathogen in P. americana  since the 1960s and 1970s. Current literature focu ses on biological control 
by bacteria (e.g. González ‐Sánchez et al. 2010). 
References 
Adams, G C; Butler, E (1978) Serological relationships among anastomosis groups of Rhizoctonia 
solani.  thesis; U. of Calif., Davis, California, USA.  
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Chase, A R (1991) Characterization of Rhizoctonia species isolated from ornamentals in Florida. Plant 
Disease 75(3): 234-238. 
Cubeta, M; Vilgalys, R (1997) Population biology of  the Rhizoctonia solani complex. Phytopathology 
87(4): 480-484. 
Das, S (2013) Rhizoctonia solani on potato in New Zealand: Pathog en characterisation and 
identification of double-stranded RNA viruses that may affect their virulence.  thesis; Lincoln University, 
Lincoln, New Zealand.  
González ‐Sánchez, M Á; Pérez ‐Jiménez, R M; Pliego, C; Ramos, C; De Vicente, A; C azorla, F M 
(2010) Biocontrol bacteria selected by a direct pla nt protection strategy against avocado white root r ot 
show antagonism as a prevalent trait. Journal of Applied Microbiology 109(1): 65-78. 
Horst, R K (2013) Field manual of diseases on trees and shurbs . Springer; New York. 
Mircetich, S M; Zentmyer, G A (1960) Rhizoctonia se ed and root rot of avocado. 44: 119-120. 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Snyman, C; Darvas, J (1983) Pathogenicity of avocad o root isolates to Edranol seedlings and Duke 7 
rooted cuttings. Afr. Avocado Grws. Assc. Yrbk 6. 
Strauss, E E; Lakshman, D K; Tavantzis, S M (2000) Molecular characterization of the genome of a 
partitivirus from the basidiomycete Rhizoctonia sol ani. Microbiology 81(2): 549-555. 
Williamson-Benavides, B A; Dhingra, A (2021) Unders tanding root rot disease in agricultural crops. 
Horticulturae 7(2): 33. 
Zentmyer, G A (1961) Avocado diseases in the Americ as. CEIBA 9(2): 61-79. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 428 Zheng, L; Shu, C; Zhang, M; Yang, M; Zhou, E (2019)  Molecular characterization of a novel 
endornavirus conferring hypovirulence in rice sheat h blight fungus Rhizoctonia solani AG-1 IA Strain 
GD-2. Viruses 11(2): 178. 
  
429 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand App 1.13  Thielaviopsis  sp. 
Scientific name:  Thielaviopsis sp.  Went 
Taxonomic position:  Microascales/ Ceratocystidaceae  
Synonyms:   n/a 
NZ status:  At least one species in this genus, T. ethacetica , is present in New Zealand (NZOR 2021). 
Of the species in this genus listed in ONZPR (2021) , T. quercina  (syn. Bretziella fagacaerum ) and T. 
punctulata (syn. Ceratocystis radicicola ) are listed as regulated, T. thielavioides  (syn. Chalara 
thielavioides ) and T. basicola  are listed as non-regulated, and T. paradoxa  is listed as not assessed.  
Summary of reason for exclusion 
Thielaviopsis sp.  can be deemed not to be a hazard and excluded from the Avocado Germplasm 
Import Risk Analysis (IRA) because: 
• There is insufficient evidence that avocado is a h ost of any species in the genus Thielaviopsis .  
Supporting information 
Thielaviopsis sp . reported as “bark rot” of avocado by Alvarez (1976 ) is the only record of association 
with avocado. This association is based on morpholo gical identification from herbarium specimens, so 
the identity of this fungal isolate cannot be verif ied. The association of Thielaviopsis sp. with Persea 
americana stated in the USDA Fungal Database refers to the sa me source by Alvarez (1976). Based 
on the lacking information provided by this source,  and that no other instances of an association with  
avocado being found in the literature, this genus s hould not be considered a hazard on avocado 
budwood. Some species in this genus are economicall y significant pathogens known to cause root or 
post-harvest rot (i.e., T. paradoxa and T. basicola ), but have not been reported on any part of the 
avocado plant (Hewajulige and Wijesundera 2014; Zep eda-Giraud et al. 2020; Williamson-Benavides 
and Dhingra 2021).  
Literature search 
Searches of Google Scholar and Google were conducte d using the search terms “ Thielaviopsis ” AND 
“avocado” OR “ Persea americana”. Searches in CPC, EPPO and USDA fungal database used  the 
search terms “Thielaviopsis ”.  
References 
Alvarez, M (1976) Primer catalogo de enfermedades d e plantas Mexicanas. Fitofilo 71: 1-169. 
Hewajulige, I G N; Wijesundera, R L C (2014) Chapte r 9 - Thielaviopsis paradoxa , Thielaviopsis 
basicola  (black rot, black root rot). In S Bautista-Baños ( ed) Postharvest Decay.  Academic Press: San 
Diego. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 19 August 2021 
ONZPR (2021) Official New Zealand Pest Register. MP I Public Database. 
https://pierpestregister.mpi.govt.nz/PestsRegister/ ImportCommodity/  Accessed 02 April 2021 
Williamson-Benavides, B A; Dhingra, A (2021) Unders tanding root rot disease in agricultural crops. 
Horticulturae 7(2): 33. 
Zepeda-Giraud, L F; Olicón-Hernández, D R; Pardo, J  P; Villanueva, M G A; Guerra-Sánchez, G 
(2020) Biological control of Thielaviopsis paradoxa  and Colletotrichum gloeosporioides  by the 
extracellular enzymes of Wickerhamomyces anomalus . Agriculture 10(8): 325. 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 430 App 1.14  Verticillium  alboatrum  (Verticillium wilt) 
Scientific name : Verticillium alboatrum  (Verticillium albo-atrum ) Reinke and Berthold (1879). 
Taxonomic position (e.g., order/family) : Glomerellales/Plectosphaerellaceae. 
Taxonomic notes:  This organism was split into three different speci es ( V. alboatrum , V. alfalfae  and 
V. nonalfalfae ) in a recent taxonomic revision of Verticillium  (Inderbitzin et al. 2011). Following this 
taxonomic revision some pathogenic isolates previou sly identified as V. alboatrum  were confirmed to 
be V. nonalfalfae (Kasson et al. 2014; Mellow et al. 2019). All three  Verticillium  species are known to 
occur in New Zealand (NZOR 2021). 
Synonyms:  Verticillium albo-atrum  var. caespitosum Wollenweber (1929), Verticillium albo-atrum  var. 
tuberosum Rudolphi. 
NZ status : Recorded in New Zealand (NZOR 2021) and non-regul ated except for some unspecified 
severe strains (ONZPR 2021). 
Summary of reason for exclusion:  
Verticillium alboatrum  can be excluded from the Avocado Germplasm Import Risk Analysis (IRA) 
because: 
• V. alboatrum is known to occur in New Zealand (NZOR 2021). 
• The severe regulated strains of V. alboatrum  are most likely limited to hops ( Humulus lupulus ), 
hence are not associated with the commodity.  
• There are no records of avocado-associated V. alboatrum  strains which may pose a risk if not 
present in New Zealand. 
• Recent studies of Verticillium wilt disease in avo cado associated the disease with V. dahliae 
rather than with V. alboatrum.  
Supporting information: 
A few commodities are known to be associated with d ifferent strains of V. alboatrum  and some of 
these strains are regulated in New Zealand (ONZPR 2 021). The regulated strains are likely related to 
a group of V. alboatrum strains  from England and Slovenia which have been observed to be severely 
pathogenic on hops (Radišek et al. 2003; Radišek et  al. 2006; Cregeen et al. 2015); these strains are 
not known to be present in New Zealand. In addition , no evidence was found in the literature to 
suggest that the hops-associated strains are pathog enic on avocado or other host plants. While 
commodities like hops are known to be associated wi th some strains of V. alboatrum , no evidence 
was found to indicate that there are strains specif ically associated with avocado. In contrast, previo us 
reports indicate that V. alboatrum  from avocado equally infects other hosts e.g. toma to, pepper and 
eggplant (Zentmyer 1949; McMillan 1976; Zentmyer 19 84; Luna and Fucikovsky 1987).  
Before 1980, there was no clear distinction between  V. dahliae  and V. alboatrum  (Fitzell et al. 1980) 
thus some reports of Verticium wilt disease in avoc ado may have erroneously been attributed to V. 
alboatrum . Recent studies of Verticillium wilt disease of av ocado are associated with V. dahliae rather 
than V. alboatrum  (Dann et al. 2010; Markakis et al. 2014; Haberman et al. 2020; Ramírez-Gil and 
Morales-Osorio 2020, 2021) suggesting that V. alboatrum  is not a significant pathogen of avocado and 
V. dahliae  may have been misidentified as V. alboatrum  in the past. 
Literature Search 
Google and Google Scholar were used to search for i nformation on Verticillium alboatrum  and its 
synonyms ( Verticillium albo-atrum  var. caespitosum and Verticillium albo-atrum  var. tuberosum ). 
Search terms include “Verticillium wilt disease”, “ Avocado”, “ Persea americana ”, “ Verticillium  
431 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand alboatrum ”, “ Verticillium alboatrum  strains”. Additionally, USDA fungal database was a lso searched for 
the species and isolates. 
References 
Cregeen, S; Radisek, S; Mandelc, S; Turk, B; Stajne r, N; Jakse, J, et al. (2015) Different gene 
expressions of resistant and susceptible hop cultiv ars in response to infection with a highly aggressi ve 
strain of Verticillium albo-atrum . Plant molecular biology reporter 33(3): 689-704. 
Dann, E K; Smith, L A; Pegg, K G (2010) Soilborne d iseases impacting avocado production in 
Australia. Proceedings of the 6th Australasian Soilborne Disea ses Dymposium : 40. 
Fitzell, R; Fahy, P; Evans, G (1980) Serological st udies on some Australian isolates of Verticillium spp. 
Australian Journal of Biological Sciences 33(1): 115-124. 
Haberman, A; Lazare, S; Hazanovsky, M; Lebiush, S; Zipori, I; Busatn, A, et al. (2020) Management of 
verticillium wilt of avocado using tolerant rootsto cks. Plants 9(4): 531. 
Inderbitzin, P; Bostock, R M; Davis, R M; Usami, T;  Platt, H W; Subbarao, K V (2011) Phylogenetics 
and taxonomy of the fungal vascular wilt pathogen Verticillium , with the descriptions of five new 
species. PLOS ONE 6(12): e28341. 
Kasson, M; Short, D; O'Neal, E; Subbarao, K; Davis,  D (2014) Comparative pathogenicity, biocontrol 
efficacy, and multilocus sequence typing of Verticillium nonalfalfae  from the invasive Ailanthus 
altissima and other hosts. Phytopathology 104(3): 282-292. 
Luna, I; Fucikovsky, L (1987) Soil-borne avocado di seases of economic importance in Mexico. South 
African Avocado Growers' Association Yearbook 10. 
Markakis, E; Kavroulakis, N; Koubouris, G (2014) Fi rst report of verticillium wilt caused by Verticillium 
dahliae on avocado trees in Greece. Plant Disease 98(11): 1584-1584. 
McMillan, R T J (1976) Disease of avocado. In J W S auls; R L Phillips; L K Jackson (Eds.), First 
International Tropical Fruit Short Course  (pp. 66-70). Gainesville: Fruit Crops Dept., Flori da 
Cooperative Extension Service. Institute of Food an d Agricultural Sciences, University of Florida: 
University of Florida. 
Mellow, K D; Tyson, J L; Manning, M A; Wright, P J (2019) Preliminary pathogenicity screening of 
Verticillium  spp. on kiwifruit in New Zealand. New Zealand Plant Protection 72: 89-94. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Radišek, S; Jakše, J; Javornik, B (2006) Genetic va riability and virulence among Verticillium albo-
atrum  isolates from hop. European Journal of Plant Pathology 116(4): 301-314. 
Radišek, S; Jakše, J; Simon čič, A; Javornik, B (2003) Characterization of Verticillium albo-atrum  field 
isolates using pathogenicity data and AFLP analysis . Plant Disease 87(6): 633-638. 
Ramírez-Gil, J G; Morales-Osorio, J G (2020) Develo pment and validation of severity scales of 
avocado wilt complex caused by Phytophthora cinnamomi , Verticillium dahliae  and hypoxia-anoxia 
disorder and their physiological responses in avoca do plants. Agronomía Colombiana 38(1): 85-100. 
Ramírez-Gil, J G; Morales-Osorio, J G (2021) Propos al for integrated management of verticillium wilt 
disease in avocado cultivar Hass crops. Agronomy 11(10): 1932. 
Zentmyer, G A (1949) Verticillium wilt of avocado. Phytopathology 39: 677-682. 
Zentmyer, G A (1984) Avocado diseases. Tropical Pest Management 30(4): 388-400. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 432 App 1.15  Diplodia pseudoseriata 
Diplodia pseudoseriata  is a fungus with a wide host and environmental ran ge. It can cause disease on 
many important host plants but can also have an end ophytic lifestyle. In avocado, D. pseudoseriata 
causes branch canker and dieback.  
App 1.15.1  Summary of PRA conclusions 
Given the arguments and evidence presented: 
• Diplodia pseudoseriata  meets the criteria to be a hazard on imported Persea americana  
budwood imported to New Zealand because it: 
o is not known to be present in New Zealand, 
o has the potential to establish in New Zealand and cause unwanted harm, and 
o has the potential to enter New Zealand on Persea americana  budwood (as described 
in the commodity description). 
• Diplodia pseudoseriata  poses an overall moderate risk on P. americana  budwood imported to 
New Zealand because it: 
o has a high likelihood of entering New Zealand on P. americana  budwood (with 
moderate uncertainty) because: 
 Diplodia pseudoseriata  can be associated with avocado budwood without 
causing visible symptoms 
 disease symptoms may not develop throughout the en tire Post Entry 
Quarantine (PEQ) period 
o has a high likelihood of transferring from P. americana  budwood to a suitable host in 
New Zealand (with low uncertainty) because: 
 imported avocado budwood is intended to generate p lants for planting in New 
Zealand and avocado plants (which are a suitable ho st for these pathogens) 
derived from avocado budwood will be planted and nu rtured to survive in 
optimal or near optimal conditions in controlled or  natural environments, and  
 if the commodity is infected with this pathogen at  the time of their release 
from PEQ and they are used as propagative material then the pathogen can 
be transferred to a suitable host on multiple occas ions.  
o has a high likelihood of establishing in New Zeala nd (with low uncertainty) because: 
 hosts (in the form of cultivated avocados and othe r cultivated crops) are 
available for the establishment of D. pseudoseriata  
 suitable climate is available for the establishmen t of D. pseudoseriata  
o may cause moderate overall impact on New Zealand ( with moderate uncertainty) 
because: 
 Diplodia pseudoseriata  can affect a broad range of host plants that are o f 
economic importance in Aotearoa New Zealand 
 direct impacts of D. pseudoseriata  are difficult to assess as the pathogen 
usually infects plants alongside other pathogens 
The following table contains a summary of risk asse ssment against the criteria: 
Criteria Rating Uncertainty  
The likelihood of entry on the commodity, given the  commodity description High Moderate 
The likelihood of transferring from the imported co mmodity onto a suitable host High Low 
The likelihood of establishing in the New Zealand e nvironment High Low 
Impact on the New Zealand economy, environment, hum an health and society Moderate Moderate 
Overall level of assessed risk to New Zealand Moderate Moderate  
433 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand App 1.15.2  Taxonomic description 
Scientific name: Diplodia pseudoseriata C.A. Pérez et al. (2010) 
Order/Family: Botryosphaeriales/Botryosphaeriaceae  
Other names include : Diplodia alatafructa  Mehl & Slippers, Diplodia insularis  Linaldeddu, A. Alves & 
A.J.L. Phillips, Diplodia pseudoplatani  Wijayaw., A.J.L. Phillips, D.J. Bhat & K.D. Hyde 
Taxonomic notes: Names above were synonymised with the current name by Zhang et al. (2021). 
App 1.15.3  Hazard identification 
Diplodia pseudoseriata  is not known to be present in New Zealand as it is  not listed in NZOR (2021) 
or PPIN (2021). The regulatory status of D. pseudoseriata  has not been assessed (ONZPR 2021). 
Biota NZ (2022) lists the D. pseudoseriata complex as present in New Zealand but it is not kno wn 
which species within this complex is present. 
Diplodia pseudoseriata  has the potential to establish (and spread) in New  Zealand because: 
• Diplodia pseudoseriata  has a wide host range and known host plants includ ing P. americana  
(avocado) (Valencia et al. 2019) are widely grown i n New Zealand, both in home gardens and 
commercial production. 
Diplodia pseudoseriata  has the potential to cause harm to New Zealand bec ause: 
• Diplodia pseudoseriata causes branch canker and dieback in avocado (Valenc ia et al. 2019) 
and other host plants such as Acacia spp., Citrus  spp. and Eucalyptus  sp. (Table 7-2). 
• Avocado fruit are an important commercial crop in New Zealand. In the 2019–2020 financial 
year, export sales of fresh avocados earned NZ$112. 3 million and domestic sales earned 
NZ$50.6 million (Plant & Food Research 2020). 
Diplodia pseudoseriata  is associated with P. americana  budwood because: 
• Persea americana  is a known host of D. pseudoseriata  (Valencia et al. 2019); 
• Diplodia pseudoseriata  occurs in association with stems endophytically or  pathogenically 
causing branch canker (Valencia et al. 2019). 
Given the arguments and evidence above, D. pseudoseriata  meets the criteria to be a hazard on P. 
americana  budwood (as in the commodity description) imported  to New Zealand. 
App 1.15.4  Risk assessment 
Biology and epidemiology of Diplodia pseudoseriata 
Host range and distribution 
Diplodia pseudoseriata  was first described in Uruguay on myrtaceous hosts  species native to 
Uruguay (Pérez et al. 2010). It was later isolated from several hosts in 7 families (Table 7-2).  
Table 7-2: Host range and distribution of Diplodia pseudoseriata  
Host Host family Country CMI Reference 
Acacia karroo Fabaceae South Africa 0.7–0.8 Jami et al. (2014) 
Acca sellowiana Myrtaceae Uruguay 0.8 Pérez et al. (2010) 
Blepharocalyx salicifolius Myrtaceae Uruguay 0.8 Pérez et al. (2010) Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 434 Host Host family Country CMI Reference 
Citrus limon Rutaceae Spain 0.7–0.9 Bezerra et al. (2021) 
Citrus reticulata Rutaceae Spain 0.7–0.9 Bezerra et al. (2021) 
Citrus sinensis Rutaceae Portugal 0.8–0.9 Bezerra et al. (2021) 
Eriobotrya japonica Rosaceae Spain 0.8 González-Domínguez et 
al. (2017) 
Eugenia involucrata Myrtaceae Uruguay 0.8 Pérez et al. (2010) 
Eugenia uniflora Myrtaceae Uruguay 0.8 Pérez et al. (2010) 
Fraxinus angustifolia Oleaceae Italy 0.8–0.9 Bezerra et al. (2021) 
Hexachlamis edulis Myrtaceae Uruguay 0.8 Pérez et al. (2010) 
Myrceugenia euosma  Myrtaceae Uruguay 0.8 Pérez et al. (2010) 
Myrcianthes cisplatensis Myrtaceae Uruguay 0.8 Pérez et al. (2010) 
Myrciaria tenella Myrtaceae Uruguay 0.8 Pérez et al. (2010) 
Persea americana Lauraceae Chile 0.8 Valencia et al. (2019) 
Pistacia lenticus Anacardiaceae  Italy 0.8 Linaldeddu et al. (2016) 
Pterocarpus angolensis Fabaceae South Africa 0.8 Mehl et al. (2011) 
Retama raetam Fabaceae Tunisia 0.7–0.8 Hlaiem et al. (2019)  
Acacia sp.  Fabaceae Australia 0.7 Tan et al. (2019) 
Eucalyptus globulus Myrtaceae Portugal 0.8–0.9 Batista et al. (2020) 
Life cycle 
Available literature on D. pseudoseriata  does not specifically focus on life cycle or trans mission mode. 
However, D. pseudoseriata  is usually isolated alongside other fungi from the  Botryosphaeriaceae 
family and therefore it also likely shares similar life cycle and transmission modes with other fungi in 
the Botryosphaeriaceae family (Pérez et al. 2010; L inaldeddu et al. 2016; Valencia et al. 2019; Batist a 
et al. 2020; Bezerra et al. 2021).  
Healthy plants are usually infected through wounds or natural openings such as stomata (Slippers 
and Wingfield 2007). Some species of fungi in the B otryosphaeriaceae family can be seed borne or 
infect seeds, but most infections of woody hosts ar e through horizontal transmission via spores 
(Slippers and Wingfield 2007). Diplodia pseudoseriata  produces conidia (asexual spores) in spherical 
fruiting bodies (pycnidia) and the sexual form (tel eomorph) of the fungus has not yet been observed 
(Zhang et al. 2021). Similar to other Botryosphaeri aceae fungi, the spores are likely transmitted 
naturally a short distance by water splashes or rai n, but could be transmitted longer distances by 
anthropogenic means such as grafting or tools (Slip pers and Wingfield 2007). 
Optimal growth conditions 
Optimal temperature for mycelial growth of D. pseudoseriata  isolates under laboratory conditions was 
25° C with a range of 5–30° C (Valencia et al. 2019).   
Symptoms and asymptomatic infections 
Diplodia pseudoseriata  can cause branch canker and dieback, necrosis of s tems but can also infect 
host plants without developing any symptoms.  
Under field conditions D. pseudoseriata  was associated with branch canker, dieback and ass ociated 
wilting of leaves and inflorescence and impeded fru it growth in avocado (Valencia et al. 2019). Brown 
exudate and necrosis developed in the vascular syst em 3 weeks after artificial inoculation of 1-year- 
435 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand old avocado plants (Valencia et al. 2019). In Chile , where the disease was first described on avocado,  
the disease symptoms were likely triggered by a sev ere drought that affected avocado production 
(Valencia et al. 2019). 
Diplodia pseudoseriata  was also isolated from healthy tissues of several hosts in the Myrtaceae family 
when it was first described (Pérez et al. 2010), in dicating its ability to cause asymptomatic infectio n.  
App 1.15.5  Likelihood of entry 
This assessment is made on the basis that D. pseudoseriata  is present in the countries where 
avocado budwood is being imported from.  Diplodia pseudoseriata  has been reported from several 
countries (Table 7-2) but the only record of associ ation with Persea americana  is from Chile (Valencia 
et al. 2019). 
Diplodia pseudoseriata  can cause branch canker in avocado, but has also b een isolated from healthy 
(asymptomatic) tissues of several hosts plants (Pér ez et al. 2010). It is likely that the pathogen cou ld 
be associated with avocado budwood without causing visible symptoms.  
The routine surface disinfection of budwood enterin g PEQ, (dipping in 1% sodium hypochlorite for 2 
minutes), will not reduce the risk of entry since m ost studies with D. pseudoseriata  isolated the 
pathogen from surface sterilised tissues (Pérez et al. 2010). 
Similar to other species in the Botryosphaeriaceae family, D. pseudoseriata  infection is more likely to 
become symptomatic when the host plant is stressed (Slippers and Wingfield 2007). In Chile, where 
the disease was first described on avocado, the ris e in disease incidence coincided with a severe 
drought that affected avocado production (Valencia et al. 2019). However, the appropriate 
environmental conditions for symptom development ma y be absent throughout the entire PEQ period 
and the infection could remain undetected. 
Given the arguments and evidence above, that is:  
• Diplodia pseudoseriata  can be associated with avocado budwood without cau sing visible 
symptoms 
• disease symptoms may not develop throughout the en tire PEQ period 
the likelihood of D. pseudoseriata  entering New Zealand associated with P. americana  budwood is 
considered to be high , with moderate  uncertainty. 
App 1.15.6  Likelihood of exposure 
This assessment is made on the basis that D. pseudoseriata  has entered New Zealand undetected. 
When a pest or pathogen arrives in a new area, it u sually needs to find or encounter a growing host 
plant in order to establish. The commodity (importe d avocado budwood, as described, see section 
2.1) is intended to generate plants for planting in  New Zealand. Avocado plants derived from avocado 
budwood will be planted and nurtured to survive in optimal or near optimal conditions in controlled or  
natural environments in New Zealand. Avocado ( P. americana ) is a suitable host for D. 
pseudoseriata .   
If avocado plants are infected with D. pseudoseriata  at the time of their release from PEQ they will be  
planted in New Zealand or used to propagate new pla nts for planting (see section 2.3 for additional 
information about exposure).  
Given the arguments and evidence above, the likelih ood of exposure of D. pseudoseriata  in 
New Zealand from P. americana  budwood is considered high, with low uncertainty. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 436 App 1.15.7  Likelihood of establishment 
This assessment is made on the basis that D. pseudoseriata  has been successfully exposed to a 
suitable host plant in the New Zealand environment.  
Diplodia pseudoseriata  has a broad host range (Table 7-2) and many of its  hosts are either grown 
commercially in New Zealand (e.g., Acacia spp., Citrus  spp., Eucalyptus  sp.) or as backyard plants in 
many home gardens. Therefore, hosts for the establi shment of D. pseudoseriata  are readily available.  
Diplodia pseudoseriata  is also found across a broad geographic range from  countries (Table 7-2) that 
have a similar climate to the whole of New Zealand,  as well as to the Auckland and Northland regions, 
as indicated by a climate match index of ≥0.7 (Phillips et al. 2018). 
Given the arguments and evidence above, that is: 
• hosts (in the form of cultivated avocados and othe r cultivated crops) are available for the 
establishment of D. pseudoseriata  
• suitable climate is available for the establishmen t of D. pseudoseriata  (Phillips et al. 2018) 
the likelihood of D. pseudoseriata  establishing in New Zealand is considered high, wi th low 
uncertainty. 
App 1.15.8  Impacts in New Zealand 
Diplodia pseudoseriata can be asociated with a wide  range of plants including avocado and other 
economically important hosts such as citruses, Eucalyptus  and Acacia  (Table 7-2). The fungus can 
cause branch canker and dieback, but can also infec t the plants without developing any symptoms. 
Diplodia pseudoseriata likely spreads naturally by water splashes or rain over short distances, but 
could be transmitted over longer distances by anthr opogenic means such as grafting or tools 
(Slippers and Wingfield 2007). As such, symptomless  cuttings of avocado plants infected with 
Diplodia pseudoseriata  can be transmitted and spread through grafting esp ecially in commercial 
avocado plant nurseries. 
Economic impacts 
Given the broad host range of the D. pseudoseriata , it is likely that avocados would not be the only 
commercially produced hosts affected by this pathog en (Table 7-2). Eucalyptus  and Acacia  species 
are known hosts of D. pseudoseriata   and are grown on more than 1.2% area of commercia l forests in 
Aotearoa New Zealand (Forest Owners Association 202 0). Lemons, oranges and mandarins are 
known hosts of D. pseudoseriata  with a combined value of $55.8 million on the dome stic market and 
$9 million in exports (Plant & Food Research 2020).   
Outbreaks of Diplodia pseudoseriata  could cause stem canker and yield losses of avocad o (Valencia 
et al. 2019). However, assessments of direct impact s of D. pseudoseriata  are unavailable as the 
pathogen usually infects host plants alongside othe r fungi from the family Botryosphaeriaceae (Pérez 
et al. 2010; Linaldeddu et al. 2016; Valencia et al . 2019; Batista et al. 2020; Bezerra et al. 2021).  
Given the arguments and evidence above, that is: 
• the broad host range D. pseudoseriata  includes many plants that are of economic 
importance in Aotearoa New Zealand (Table 7-2) 
• Diplodia pseudoseriata  may cause disease  
• direct impacts of D. pseudoseriata  are difficult to assess as the pathogen usually in fects 
plants alongside other pathogens 
the economic impact of D. pseudoseriata  to New Zealand is considered to be moderate, with 
moderate uncertainty.  
437 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Environmental impacts 
Diplodia pseudoseriata  is not known to infect plants native to Aotearoa N ew Zealand, but given its 
broad host range, it is likely some native plants, especially in the Myrtaceae family might be 
susceptible to the pathogen (Table 7-2). Furthermor e, fungi from the Botryosphaeriaceae family 
including several species of Diplodia  have already established in Aotearoa, New Zealand (Biota NZ 
2022) with low impacts on the environment to date, suggesting other members of this genus may do 
the same.  
Given the arguments and evidence above, the impact on the environment from the establishment of 
D. pseudoseriata  in New Zealand is considered to be low, with high uncertainty. 
Human health impacts 
There are no known human health impacts associated with  D. pseudoseriata.  
Given the arguments and evidence above, the human h ealth impact of D. pseudoseriata  to 
New Zealand is considered to be negligible, with lo w uncertainty. 
Sociocultural impacts 
Plant disease associated with D. pseudoseriata  could negatively affect fruit trees (e.g., citrus and 
avocado) growing on residential properties, as well  as amenity plants (e.g., Acacia  spp. and 
Eucalyptus  spp.).  The extent of these impacts, however, is u nknown.  
Given the arguments and evidence above, the sociocu ltural impact of D. pseudoseriata  to 
New Zealand is considered to be moderate, with mode rate uncertainty. 
Overall impact to New Zealand 
The overall impact on the New Zealand economy, envi ronment, human health and society is 
considered to be moderate, with moderate uncertaint y. 
App 1.15.9  Overall level of assessed risk to New Zealand 
Based on the assessments of likelihood and conseque nce above, that:  
• the likelihood of entry is high 
• assuming entry, the likelihood of exposure is high  
• assuming successful exposure, the likelihood of es tablishment is high  
• the overall impact on the New Zealand economy, env ironment, human health and society 
is considered to be moderate 
the overall level of assessed risk to New Zealand f rom D. pseudoseriata  on imported P. americana 
budwood (as in the commodity description) is consid ered to be moderate, with moderate uncertainty. 
App 1.15.10  Management considerations 
Diplodia pseudoseriata  can cause branch canker and dieback, necroses of s tems but can also infect 
host plants without developing any symptoms.  Simil ar to other species in the Botryosphaeriaceae 
family, D. pseudoseriata  infection is more likely to become symptomatic whe n the host plant is 
stressed (Slippers and Wingfield 2007). In Chile, w here the disease was first described on avocado, 
the rise in disease incidence coincided with a seve re drought that affected avocado production 
(Valencia et al. 2019).  Diplodia pseudoseriata  was isolated from branches and inner woody tissues  of 
avocado, therefore testing stem or woody tissues wo uld increase the chances of detecting the pest. 
Phylogenettic analysis of Internal transcribed spac er region (ITS1-5.8S-ITS2) and the translation 
elongation factor 1- α (TEF1- α) should be specific enough to identify D. pseudoseriata  in PCR testing 
(Valencia et al. 2019). Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 438 App 1.15.11  Answers to Risk Management Questions 
What factors influence the likelihood of the pest o r disease being detected during the growing 
period (a period of active growth with a minimum of  three distinct phenological growing 
events referred to as ‘shoot flush’) in 3A PEQ? 
o What symptoms will the pest or disease exhibit? 
Diplodia pseudoseriata  can cause branch canker and dieback, necrosis of s tems but can also infect 
host plants without developing any symptoms.  
o What are the known environmental conditions conduci ve to symptom expression? 
Similar to other species in the Botryosphaeriaceae family, D. pseudoseriata  infection is more likely to 
become symptomatic when the host plant is stressed (Slippers and Wingfield 2007). In Chile, where 
the disease was first described on avocado, the ris e in disease incidence coincided with a severe 
drought that affected avocado production (Valencia et al. 2019). 
What are the limitations to taking samples for pote ntial testing? 
o What plant part should be tested in order to maximi se the chances of detection of the pest 
in PEQ in the case of asymptomatic infections?  
Diplodia pseudoseriata  was isolated from branches and inner woody tissues  of avocado, therefore 
testing stem or woody tissues would increase the ch ances of detecting the pest. 
o What is the optimum season for conducting detection  testing? 
Similar to other species in the Botryosphaeriaceae family, D. pseudoseriata  infection is more likely to 
become symptomatic when the host plant is stressed.  
App 1.15.12  References 
Batista, E; Lopes, A; Alves, A (2020) Botryosphaeri aceae species on forest trees in Portugal: 
diversity, distribution and pathogenicity. European Journal of Plant Pathology 158(3): 693-720. 
Bezerra, J D P; Crous, P W; Aiello, D; Gullino, M L ; Polizzi, G; Guarnaccia, V (2021) Genetic diversit y 
and pathogenicity of Botryosphaeriaceae species ass ociated with symptomatic Citrus  plants in 
Europe. Plants 10(3): 492. 
Biota NZ (2022) Biota of New Zealand: names and cla ssification of bacteria, fungi, land invertebrates 
and plants. https://biotanz.landcareresearch.co.nz/  Accessed February 2022 
Forest Owners Association (2020) Facts and figures 2019/20 New Zealand plantation fo rest industry . 
https://nzfoa.org.nz/images/Facts_and_Figures_2018- 2019_Web.pdf  
González-Domínguez, E; Alves, A; León, M; Armengol,  J (2017) Characterization of 
Botryosphaeriaceae species associated with diseased  loquat ( Eriobotrya japonica ) in Spain. Plant 
Pathology 66(1): 77-89. 
Hlaiem, S; Boutiti, M Z; Jamaa, M L B (2019) Diplod ia species associated with dieback of Retama 
raetam  in Tunisia. New Disease Reports 40(1): 21-21. 
Jami, F; Slippers, B; Wingfield, M J; Gryzenhout, M  (2014) Botryosphaeriaceae species overlap on 
four unrelated, native South African hosts. Fungal biology 118(2): 168-179.  
439 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Linaldeddu, B; Maddau, L; Franceschini, A; Alves, A ; Phillips, A (2016) Botryosphaeriaceae species 
associated with lentisk dieback in Italy and descri ption of Diplodia insularis  sp. nov. Mycosphere 7(7): 
962-977. 
Mehl, J W; Slippers, B; Roux, J; Wingfield, M J (20 11) Botryosphaeriaceae associated with 
Pterocarpus angolensis  (kiaat) in South Africa. Mycologia 103(3): 534-553. 
NZOR (2021) The New Zealand Organisms Register. http://nzor.org.nz  Accessed 03/03/2021 
ONZPR (2021) Official New Zealand Pest Register. MP I public database. 
https://pierpestregister.mpi.govt.nz/  Accessed 17 March 2021 
Pérez, C A; Wingfield, M J; Slippers, B; Altier, N A; Blanchette, R A (2010) Endophytic and canker-
associated Botryosphaeriaceae occurring on non-nati ve Eucalyptus and native Myrtaceae trees in 
Uruguay. Fungal Diversity 41(1): 53-69. 
Phillips, C B; Kean, J M; Vink, C J; Berry, J A (20 18) Utility of the CLIMEX ‘match climates regional’  
algorithm for pest risk analysis: an evaluation wit h non-native ants in New Zealand. Biological 
Invasions 20(3): 777-791. 
Plant & Food Research (2020) Fresh Facts: New Zealand Horticulture . Auckland, New Zealand. 
https://www.freshfacts.co.nz/files/freshfacts-2020. pdf  
PPIN (2021) Plant Pest Information Network, Version  5.03.01. Ministry for Primary Industries Internal 
Database. Accessed June 2021 
Slippers, B; Wingfield, M J (2007) Botryosphaeriace ae as endophytes and latent pathogens of woody 
plants: diversity, ecology and impact. Fungal biology reviews 21(2-3): 90-106. 
Tan, Y P; Shivas, R G; Marney, T S; Edwards, J; Dea rnaley, J; Jami, F, et al. (2019) Australian 
cultures of Botryosphaeriaceae held in Queensland a nd Victoria plant pathology herbaria revisited. 
Australasian Plant Pathology 48(1): 25-34. 
Valencia, A L; Gil, P M; Latorre, B A; Rosales, I M  (2019) Characterization and pathogenicity of 
Botryosphaeriaceae species obtained from avocado tr ees with branch canker and dieback and from 
avocado fruit with stem end rot in Chile. Plant Disease 103(5): 996-1005. 
Zhang, W; Groenewald, J Z; Lombard, L; Schumacher, R K; Phillips, A J L; Crous, P W (2021) 
Evaluating species in Botryosphaeriales. Persoonia - Molecular Phylogeny and Evolution of Fu ngi . 
 
 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 440 Appendix 2.  Summary of taxa excluded at hazard 
identification 
Groups and species identified at the hazard idendif ication stage as not requiring further assessment 
and not requiring measures over and above basic mea sures, and the rationale for exclusion (a total of 
382 organisms). DUA are diseases of unknown aetiolo gy. No subspecific taxa highlights that there 
are no subspecific taxa that increase the risk to N ew Zealand (e.g. either no subspecific taxa or 
subspecific taxa is present in New Zealand). 
Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Cephaleuros virescens Algae Present No subspecific 
taxa  
Agrobacterium 
radiobacter rhizogenic 
strain  Bacteria Present No subspecific 
taxa  
Agrobacterium 
radiobacter  tumorigenic 
strain  Bacteria Present No subspecific 
taxa  
Bacillus licheniformis Bacteria Present No subspecific 
taxa  
Bacillus subtilis Bacteria Present No subspecific 
taxa  
Erwinia aroideae Bacteria Present Synonymy Pectobacterium 
aroidearum 
Erwinia atroseptica Bacteria Present Synonymy Pectobacterium 
atrosepticum 
Pantoea agglomerans Bacteria Present No subspecific 
taxa  
Pectobacterium 
aroidearum Bacteria Present No subspecific 
taxa  
Pectobacterium 
carotovorum Bacteria Present No subspecific 
taxa  
Pectobacterium 
carotovorum 
carotovorum Bacteria Present No subspecific 
taxa  
Pseudomonas 
citriputealis Bacteria Present Synonymy Pseudomonas 
syringae pv.  
syringae 
Pseudomonas syringae 
bacterial canker-causing 
strains  Bacteria Present No subspecific 
taxa  
Rhizobium rhizogenes Bacteria Present No subspecific 
taxa  
Peduncle ringing DUA Present Not applicable  
Acremonium Fungus Present 
(genus) Insufficient 
information for host 
association Literature search 
Acrodontium 
crateriforme Fungus Present No subspecific 
taxa Korsten et al. (1988) 
Acrosporium Fungus Absent Not associated 
with the host Cline and Farr 
(2006) 
Acrostalagmus 
luteoalbus Fungus Present No subspecific 
taxa  
Akanthomyces lecanii Fungus Present No subspecific 
taxa    
441 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Albonectria rigidiuscula Fungus Present No subspecific 
taxa  
Alternaria alternata Fungus Present No subspecific 
taxa  
Alternaria citri Fungus Present No subspecific 
taxa  
Alternaria mouchaccae Fungus Uncertain Insufficient 
information for host 
association Literature search 
Alternaria tenuissima Fungus Present Synonymy Alternaria alternata 
Armillaria limonea Fungus Present No subspecific 
taxa  
Armillaria lutea Fungus Absent Not associated 
with commodity Kurbetli et al. (2020) 
Armillaria mellea Fungus Absent Not associated 
with commodity Luna and Fucikovsky 
(1987) 
Armillaria novae-
zelandiae Fungus Present No subspecific 
taxa  
Arthrinium 
phaeospermum Fungus Present No subspecific 
taxa  
Ascochyta citri Fungus Absent Not associated 
with the host Literature search 
Aspergillus candidus Fungus Present No subspecific 
taxa  
Aspergillus niger Fungus Present No subspecific 
taxa  
Asteromella gratissima Fungus Absent Insufficient 
information for 
commodity 
association Petrak and Ciferri 
(1930) 
Athelia rolfsii Fungus Present No subspecific 
taxa  
Aureobasidium 
pullulans Fungus Present No subspecific 
taxa  
Barriopsis fusca Fungus Absent Insufficient 
evidence for host 
association  
Bipolaris sorokiniana Fungus Present No subspecific 
taxa  
Botryodiplodia Fungus Present 
(genus) Synonymy Species associated 
with Persea is a 
synonym of 
Lasiodiplodia 
theobromae ; Darvas 
and Kotze (1987) 
Botryosphaeria australis Fungus Present No subspecific 
taxa  
Botryosphaeria dothidea Fungus Present No subspecific 
taxa  
Botryosphaeria 
quercuum Fungus Absent Not associated 
with the host Literature search 
Botryosphaeria 
stevensii Fungus Present No subspecific 
taxa  
Botryotinia fuckeliana Fungus Present No subspecific 
taxa  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 442 Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Botrytis cinerea Fungus Present No subspecific 
taxa  
Cadophora luteo-
olivacea Fungus Present No subspecific 
taxa  
Calonectria 
cylindrospora Fungus Present No subspecific 
taxa  
Calonectria ilicicola Fungus Absent Not associated 
with commodity Dann et al. (2012) 
Calonectria insularis Fungus Absent Insufficient 
information for 
commodity 
association Schoch et al. (1999) 
Calonectria kyotensis Fungus Present No subspecific 
taxa  
Calonectria morganii Fungus Present No subspecific 
taxa  
Calonectria 
pauciramosa Fungus Present No subspecific 
taxa  
Calonectria scoparia Fungus Present No subspecific 
taxa  
Capnodium citri Fungus Present No subspecific 
taxa  
Cephalothecium  sp. Fungus Present No subspecific 
taxa  
Ceratocystis fimbriata Fungus Present No subspecific 
taxa  
Cercospora Fungus Present 
(genus) Synonymy Pseudocercospora 
Ceriporia purpurea Fungus Absent Not associated 
with the host Gilbertson et al. 
(2002) 
Chaetomium spirale Fungus Present No subspecific 
taxa  
Chrysoporthe cubensis Fungus Absent Not associated 
with commodity Seixas et al. (2004) 
Cladosporium citri Fungus Absent Misidentification Stevens and Piper 
(1941) 
Cladosporium 
cladosporioides Fungus Present No subspecific 
taxa  
Cladosporium herbarum Fungus Present No subspecific 
taxa  
Clasterosporium 
roupalae Fungus Absent Not associated 
with the host Literature search 
Clonostachys rosea Fungus Present No subspecific 
taxa  
Cochliobolus 
intermedius Fungus Present No subspecific 
taxa  
Cochliobolus setariae Fungus Present No subspecific 
taxa  
Colletotrichum acutatum Fungus Present No subspecific 
taxa  
Colletotrichum alienum Fungus Present No subspecific 
taxa  
Colletotrichum aotearoa Fungus Present No subspecific 
taxa  
Colletotrichum 
boninense Fungus Present No subspecific 
taxa   
443 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Colletotrichum cigarro Fungus Present No subspecific 
taxa  
Colletotrichum 
crassipes Fungus Present No subspecific 
taxa  
Colletotrichum 
dematium Fungus Present No subspecific 
taxa  
Colletotrichum fioriniae Fungus Present No subspecific 
taxa  
Colletotrichum fructicola Fungus Border 
intercept Not associated 
with commodity Sharma et al. (2017); 
Hofer et al. (2021) 
Colletotrichum 
gigasporum Fungus Present No subspecific 
taxa  
Colletotrichum 
gloeosporioides Fungus Present No subspecific 
taxa  
Colletotrichum godetiae Fungus Present No subspecific 
taxa  
Colletotrichum kahawae Fungus Present No subspecific 
taxa  
Colletotrichum karsti Fungus Present No subspecific 
taxa  
Colletotrichum 
nupharicola Fungus Absent Misidentification Johnson et al. 
(1997); Khodadadi et 
al. (2020) 
Colletotrichum perseae Fungus Present No subspecific 
taxa  
Colletotrichum 
siamense Fungus Present No subspecific 
taxa  
Colletotrichum 
simmondsii Fungus Present No subspecific 
taxa  
Colletotrichum 
theobromicola Fungus Present No subspecific 
taxa  
Coprinus Fungus Present 
(genus) Not associated 
with the host Baker (1938) 
Corallomycetella repens Fungus Present No subspecific 
taxa  
Coriolopsis occidentalis Fungus Absent Not associated 
with the host Literature search 
Cornuvesica falcata Fungus Present No subspecific 
taxa  
Corynespora cassiicola Fungus Present No subspecific 
taxa  
Cryptococcus gattii Fungus Present No subspecific 
taxa  
Cryptococcus 
neoformans Fungus Present No subspecific 
taxa  
Curvularia lunata Fungus Present No subspecific 
taxa  
Curvularia senegalensis Fungus Absent Not associated 
with commodity Korsten et al. (1988) 
Cylindrocarpon 
didymum Fungus Present No subspecific 
taxa  
Cylindrocladiella parva Fungus Present No subspecific 
taxa  
Cylindrocladiella 
pseudoinfestans Fungus Absent Not associated 
with commodity Parkinson et al. 
(2017b) Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 444 Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Cylindrocladiella 
stellenboschensis Fungus Present No subspecific 
taxa  
Cylindrocladium Fungus Absent Not associated 
with commodity Raabe et al. (1981) 
Cytospora actinidiae Fungus Absent Not associated 
with the host Literature search 
Dactylonectria 
anthuriicola Fungus Absent Not associated 
with commodity Parkinson et al. 
(2017b) 
Dactylonectria 
macrodidyma Fungus Present No subspecific 
taxa  
Dactylonectria 
novozelandica Fungus Present No subspecific 
taxa  
Dactylonectria 
pauciseptata Fungus Present No subspecific 
taxa  
Desarmillaria tabescens Fungus Absent Not associated 
with commodity Horst (2013) 
Dialonectria episphaeria Fungus Present No subspecific 
taxa  
Diaporthe ampelina Fungus Present No subspecific 
taxa  
Diaporthe 
australafricana Fungus Present No subspecific 
taxa  
Diaporthe citri Fungus Present No subspecific 
taxa  
Diaporthe foeniculacea Fungus Absent Synonymy Guignardia 
foeniculacea 
Diaporthe rudis Fungus Present No subspecific 
taxa  
Didymostilbe cubensis Fungus Absent Not associated 
with commodity Arnold and Ruiz 
(1984) 
Diplodia mutila Fungus Present No subspecific 
taxa  
Diplodia perseana Fungus Absent Insufficient 
information for host 
association Kobayashi (2007) 
Diplodia pseudoseriata Fungus Present No subspecific 
taxa  
Diplodia seriata Fungus Present No subspecific 
taxa  
Dipodascus geotrichum Fungus Present No subspecific 
taxa  
Dothichiza Fungus Present 
(genus) Insufficient 
information for host 
association Alvarez (1976) 
Dothiorella iberica Fungus Present No subspecific 
taxa  
Elsinoe pyri Fungus Present No subspecific 
taxa  
Epicoccum nigrum Fungus Present No strains specific 
to host Fávaro et al. (2011) 
Erysiphe betae Fungus Present No subspecific 
taxa  
Erythricium 
salmonicolor Fungus Present No subspecific 
taxa  
Exserohilum rostratum Fungus Present No subspecific 
taxa   
445 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Fomitella supina Fungus Absent Not associated 
with commodity The Global Fungal 
Red List Initiative 
(2021) 
Fracchiaea heterogenea Fungus Absent Not associated 
with commodity Raymundo et al. 
(2017) 
Fusarium acuminatum Fungus Present Not applicable  
Fusarium avenaceum Fungus Present Not applicable  
Fusarium compactum Fungus Recorded 
in error Not associated 
with the host Frisullo et al. (1994) 
Fusarium crookwellense Fungus Present Synonymy Fusarium cerealis 
Fusarium equiseti Fungus Present Not associated 
with commodity Biota NZ (2022) 
Fusarium expansum Fungus Absent Not associated 
with commodity Baker (1938) 
Fusarium fujikuroi Fungus Present No subspecific 
taxa  
Fusarium gibbosum Fungus Present Synonymy Fusarium equiseti 
Fusarium graminearum Fungus Present No subspecific 
taxa  
Fusarium incarnatum Fungus Present No subspecific 
taxa  
Fusarium lateritium Fungus Present No subspecific 
taxa  
Fusarium oxysporum Fungus Present No subspecific 
taxa  
Fusarium pallidoroseum Fungus Present Synonymy Fusarium incarnatum 
Fusarium roseum Fungus Present No subspecific 
taxa  
Fusarium scirpi Fungus Absent Insufficient 
information for host 
association Korsten et al. (1988) 
Fusicoccum aesculi Fungus Present Synonymy Botryosphaeria 
dothidea 
Ganoderma lucidum Fungus Absent Not associated 
with commodity Loyd et al. (2018) 
Ganoderma zonatum Fungus Absent Not associated 
with commodity CABI (2021) 
Ganoderma zonatum 
sulcatum Fungus Not 
applicable Misidentification No record of this 
name 
Gibberella Fungus Present 
(genus) Synonymy Fusarium 
Gliocladiopsis curvata Fungus Present No subspecific 
taxa  
Gliocladiopsis 
sumatrensis Fungus Absent Not associated 
with commodity Lombard and Crous 
(2012) 
Gliocladiopsis tenuis Fungus Present No subspecific 
taxa  
Gliocladiopsis whileyi Fungus Absent Not associated 
with commodity Parkinson et al. 
(2017a) 
Gloeosporium Fungus Present 
(genus) Taxonomy Some species are 
considered 
Colletotrichum which 
are assessed  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 446 Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Glomerella Fungus Present 
(genus) Taxonomy Some species are 
considered 
Colletotrichum which 
are assessed  
Gnomonia Fungus Present 
(genus) Not associated 
with the host EPPO (2020) 
Gracilistilbella clavulata Fungus Present No subspecific 
taxa  
Helminthosporium Fungus Present 
(genus) Taxonomy Genus has been split 
into multiple genera 
Hendersonia Fungus Present 
(genus) Taxonomy Genus has been split 
into multiple genera 
Hexagonia rigida Fungus Absent Not associated 
with commodity Lee et al. (2012) 
Humicola Fungus Present 
(genus) Not associated 
with the host Rashmi et al. (2019) 
Ilyonectria destructans Fungus Present No subspecific 
taxa  
Ilyonectria liriodendri Fungus Present No subspecific 
taxa  
Laetiporus sulphureus Fungus Absent Not associated 
with commodity Horst (2013) 
Lasiodiplodia 
theobromae Fungus Present No subspecific 
taxa  
Lentinus stuppeus Fungus Absent Insufficient 
information for host 
association Literature search 
Leptosphaeria 
gratissitnae Fungus Absent Insufficient 
information for 
commodity 
association Rieuf and Yeasca 
(1970) 
Leptosphaerulina trifolii Fungus Present No subspecific 
taxa  
Macrophoma perseae Fungus Absent Insufficient 
information for 
commodity 
association Index Fungorum 
(2022) 
Macrophomina 
phaseolina Fungus Present No subspecific 
taxa  
Macrosporium Fungus Present 
(genus) Synonymy Alternaria 
Marasmiellus scandens Fungus Absent Insufficient 
information for host 
association Peregrine and 
Ahmad (1982) 
Marssonina Fungus Present 
(genus) Taxonomy Genus has been split 
into multiple genera 
Microporus affinis Fungus Absent Insufficient 
information for 
commodity 
association Gilbertson et al. 
(2002) 
Monilia Fungus Present 
(genus) Taxonomy Genus has been split 
into multiple genera 
Monochaetia Fungus Present 
(genus) Taxonomy Genus has been split 
into multiple genera 
Mucor Fungus Present 
(genus) Taxonomy Genus has been split 
into multiple genera  
447 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Mycoacia kurilensis Fungus Absent Not associated 
with the host Index Fungorum 
(2022) 
Mycosphaerella 
tassiana Fungus Present Synonymy Cladosporium 
herbarum 
Nectria cinnabarina Fungus Present No subspecific 
taxa  
Nectria pseudotrichia Fungus Present No subspecific 
taxa  
Nectricladiella infestans Fungus Present No subspecific 
taxa  
Neocosmospora 
ramosa Fungus Absent Not associated 
with commodity Sandoval-Denis and 
Crous (2018) 
Neocosmospora solani Fungus Present No subspecific 
taxa  
Neofusicoccum australe Fungus Present No subspecific 
taxa  
Neofusicoccum 
cryptoaustrale Fungus Present No subspecific 
taxa  
Neofusicoccum luteum Fungus Present No subspecific 
taxa  
Neofusicoccum 
mangiferae Fungus Present No subspecific 
taxa  
Neofusicoccum 
mediterraneum Fungus Absent Not associated 
with the host CABI (2021) 
Neofusicoccum parvum Fungus Present No subspecific 
taxa  
Neofusicoccum ribis Fungus Present No subspecific 
taxa  
Neofusicoccum 
stellenboschiana  Fungus Present No subspecific 
taxa  
Neofusicoccum 
vitifusiforme Fungus Absent Not associated 
with the host Phillips et al. (2013) 
Neofusioccum luteum Fungus Not 
applicable Misidentification No record in 
Mycobank (Robert et 
al. 2005) or Index 
Fungorum (2022) 
Neonectria ditissima Fungus Present No subspecific 
taxa  
Neopestalotiopsis 
clavispora Fungus Present No subspecific 
taxa  
Neoscytalidium 
dimidiatum Fungus Present No subspecific 
taxa  
Nigrospora oryzae Fungus Present No subspecific 
taxa  
Nothoramichloridium 
perseae Fungus Absent Insufficient 
information for 
commodity 
association Crous et al. (2019) 
Ovularia Fungus Present 
(genus) Taxonomy Genus has been split 
into multiple genera 
Oxychaete cervinogilva Fungus Absent Insufficient 
information for host 
association Literature search 
Oxyporus 
latemarginatus Fungus Absent Not associated 
with commodity Ploetz (2003) Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 448 Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Parencoelia 
myriostylidis Fungus Absent Insufficient 
information for host 
association Literature search 
Penicillium 
chrysogenum Fungus Present No subspecific 
taxa  
Penicillium digitatum Fungus Present No subspecific 
taxa  
Penicillium expansum Fungus Present No subspecific 
taxa  
Penicillium italicum Fungus Present No subspecific 
taxa  
Penicillium 
simplicissimum Fungus Present No subspecific 
taxa  
Periconia byssoides Fungus Present No subspecific 
taxa  
Periconia cambrensis Fungus Present No subspecific 
taxa  
Pestalotia eriobotryae-
japonicae Fungus Absent Insufficient 
information for host 
association Literature search 
Pestalotiopsis adusta Fungus Present No subspecific 
taxa  
Pestalotiopsis alo ës Fungus Absent Insufficient 
information for host 
association Literature search 
Pestalotiopsis 
disseminata Fungus Present No subspecific 
taxa  
Pestalotiopsis gracilis Fungus Absent Not associated 
with the host Granados-Montero 
et al. (2018) 
Pestalotiopsis guepinii Fungus Present No subspecific 
taxa  
Pestalotiopsis 
leprogena Fungus Absent Insufficient 
information for host 
association Literature search 
Pestalotiopsis 
mangiferae Fungus Absent Not associated 
with the host Kamhawy et al. 
(2011) 
Pestalotiopsis phoenicis Fungus Absent Insufficient 
information for host 
association Literature search 
Pestalotiopsis versicolor Fungus Present No subspecific 
taxa  
Peyronellaea obtusa Fungus Absent Insufficient 
information for host 
association Literature search 
Phanerochaete australis Fungus Present No subspecific 
taxa  
Phellinus gilvus Fungus Present No subspecific 
taxa  
Phellinus grenadensis Fungus Absent Insufficient 
information for host 
association Literature search 
Phlebia acanthocystis Fungus Present No subspecific 
taxa  
Phoma persicae Fungus Present No subspecific 
taxa   
449 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Phomopsis achilleae Fungus Absent Insufficient 
information for host 
association Literature search 
Phomopsis phaseoli Fungus Present No subspecific 
taxa  
Phyllosticta capitalensis Fungus Present No subspecific 
taxa  
Phyllosticta citricarpa Fungus Recorded 
in error Insufficient 
information for host 
association Meyer et al. (2001) 
Phyllosticta micropuncta Fungus Absent Synonymy Phyllosticta perseae 
Phymatotrichopsis 
omnivora Fungus Absent Not associated 
with commodity Bragard et al. (2019) 
Phymatotrichum Fungus Absent Synonymy Phymatotrichopsis 
Pionnotes capillacea Fungus Absent Insufficient 
information for host 
association Teodoro (1937) 
Pithomyces graminicola Fungus Absent Not associated 
with commodity Thomas et al. (1994) 
Podoconis anacardii Fungus Absent Not associated 
with commodity Shaw (1984) 
Podosphaera tridactyla Fungus Present No subspecific 
taxa  
Polyporus sanguineus Fungus Present No subspecific 
taxa  
Pseudopestalotiopsis 
theae Fungus Absent Insufficient 
information for host 
association Liu (1977) 
Pseudopithomyces 
chartarum Fungus Present No subspecific 
taxa  
Pseudopithomyces 
maydicus Fungus Uncertain Not associated 
with commodity Baker (1938) 
Puccinia scimitriformis Fungus Absent Insufficient 
information for host 
association Literature search 
Purpureocillium 
lilacinum Fungus Present No subspecific 
taxa  
Pyrrhoderma 
lamaoense Fungus Absent Not associated 
with commodity Khan et al. (2020) 
Rhizomorpha 
subcorticalis Fungus Absent Synonymy Armillaria mellea 
(anamorph of)  
Rhizopus arrhizus Fungus Present No subspecific 
taxa  
Rhizopus stolonifer Fungus Present No subspecific 
taxa  
Rigidoporus microporus Fungus Uncertain Not associated 
with commodity Shaw (1984) 
Rigidoporus ulmarius Fungus Absent Not associated 
with commodity Ploetz (2003) 
Rosellinia bunodes Fungus Absent Insufficient 
information for 
commodity 
association Lavaire and Morazán 
(2013); Ploetz et al. 
(1994) 
Rosellinia necatrix Fungus Present No subspecific 
taxa  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 450 Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Rosellinia pepo Fungus Uncertain Insufficient 
information for 
commodity 
association Lavaire and Morazán 
(2013); Ploetz et al. 
(1994) 
Rugonectria rugulosa Fungus Absent Insufficient 
information for 
commodity 
association Samuels and 
Brayford (1994) 
Sarocladium strictum Fungus Present No subspecific 
taxa  
Schizophyllum 
commune Fungus Present No subspecific 
taxa  
Sclerostagonospora Fungus Present 
(genus) Insufficient 
information for host 
association Korsten et al. (1988) 
Sclerotinia sclerotiorum Fungus Present Not applicable  
Septoria Fungus Absent Synonymy Mycosphaerella  
Sesquicillium Fungus Present 
(genus) Synonymy Clonostachys 
Sphaceloma purea Fungus Not 
applicable Taxonomy Invalid name 
Sphaerostilbe 
cinnabarina Fungus Present Synonymy Nectria pseudotrichia 
Stemphylium Fungus Present 
(genus) Synonymy  
Stilbella Fungus Present 
(genus) Synonymy  
Stomiopeltis citri Fungus Absent Misidentification Smith et al. (1985)  
Strigula smaragdula Fungus Present No subspecific 
taxa  
Trametes coccinea Fungus Present No subspecific 
taxa  
Trametes elegens Fungus Absent Insufficient 
information for host 
association Teodoro (1937) 
Trametes hirsuta Fungus Present No subspecific 
taxa  
Trametes nivosa Fungus Present No subspecific 
taxa  
Trametes versicolor Fungus Present No subspecific 
taxa  
Trichocladium Fungus Present 
(genus) Synonymy Chaetomium 
Trichoderma harzianum Fungus Present No subspecific 
taxa  
Trichoderma koningii Fungus Present No subspecific 
taxa  
Trichoderma viride Fungus Present No subspecific 
taxa  
Trichomerium ornatum Fungus Absent Not associated 
with commodity Chomnunti et al. 
(2012) 
Trichothecium roseum Fungus Present No subspecific 
taxa  
Tubercularia lateritia Fungus Present Synonymy Nectria pseudotrichia  
451 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Venturia carpophila Fungus Present No subspecific 
taxa  
Verticillium dahliae Fungus Present No subspecific 
taxa  
Xenasma 
tulasnelloideum Fungus Present No subspecific 
taxa  
Xenosporium berkeleyi Fungus Present No subspecific 
taxa  
Zygosporium Fungus Present 
(genus) Insufficient 
information for host 
association Literature search 
Aphelenchoides 
bicaudatus Nematode Present No subspecific 
taxa  
Aphelenchus avenae Nematode Absent Not associated 
with commodity Walker (1984) 
Aphelencoides sp.  Nematode Uncertain Insufficient 
information for 
commodity 
association Williams (1980) 
Boleodorus Nematode Absent Not associated 
with commodity Munawar et al. 
(2021) 
Criconema demani Nematode Absent Not associated 
with commodity Siddiqi (2000b) 
Criconema mutabile Nematode Present No subspecific 
taxa  
Criconemoides Nematode Absent Not associated 
with commodity Siddiqi (2000b) 
Discocriconemella 
perseae Nematode Absent Not associated 
with commodity Siddiqi (2000b) 
Ditylenchus sp.  Nematode Uncertain Insufficient 
information for 
commodity 
association Siddiqi (2000a) 
Geocenamus brevidens Nematode Absent Not associated 
with commodity Siddiqi (2000d) 
Helicotylenchus 
cavenessi Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Helicotylenchus 
dihystera Nematode Present No subspecific 
taxa  
Helicotylenchus 
erythrinae Nematode Present No subspecific 
taxa  
Helicotylenchus indicus Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Helicotylenchus 
microcephalus Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Helicotylenchus 
mucronatus Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Helicotylenchus 
multicinctus Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Helicotylenchus 
pseudorobustus Nematode Present No subspecific 
taxa  
Hemicriconemoides 
cocophillus Nematode Absent Not associated 
with commodity Siddiqi (2000b) 
Hemicriconemoides 
mangiferae Nematode Absent Not associated 
with commodity Siddiqi (2000b) Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 452 Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Hemicriconemoides 
strictathecatus Nematode Absent Not associated 
with commodity Siddiqi (2000b) 
Hemicycliophora 
penetrans Nematode Absent Not associated 
with commodity Chitambar and 
Subbotin (2014) 
Heterodera zeae Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Longidorus africanus Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Longidorus 
laevicapitatus Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Meloidogyne enterolobii Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Meloidogyne javanica Nematode Present No subspecific 
taxa  
Mesocriconema 
denoudeni Nematode Absent Not associated 
with commodity Siddiqi (2000b) 
Mesocriconema 
sosamossi Nematode Absent Not associated 
with commodity Siddiqi (2000b) 
Nanidorus minor Nematode Present No subspecific 
taxa  
Paratrichodorus 
porosus Nematode Present No subspecific 
taxa  
Paratylenchus hamatus Nematode Absent Not associated 
with commodity Ghaderi (2019) 
Pratylenchus 
brachyurus Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Pratylenchus coffeae Nematode Present No subspecific 
taxa  
Pratylenchus goodeyi Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Pratylenchus neglectus Nematode Present No subspecific 
taxa  
Pratylenchus penetrans Nematode Present No subspecific 
taxa  
Pratylenchus thornei Nematode Present No subspecific 
taxa  
Pratylenchus vulnus Nematode Present No subspecific 
taxa  
Radopholus similis Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Rotylenchulus 
reniformis Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Rotylenchus breviglans Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Rotylenchus colbrani Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Rotylenchus uniformis Nematode Present No subspecific 
taxa  
Scutellonema 
brachyurus Nematode Present No subspecific 
taxa  
Scutellonema 
clathricaudatum Nematode Absent Not associated 
with commodity Siddiqi (2000c) 
Trichodorus Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Tylenchorhynchus 
clarus Nematode Absent Not associated 
with commodity Siddiqi (2000d)  
453 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Tylenchorhynchus 
claytoni Nematode Absent Not associated 
with commodity Siddiqi (2000d) 
Tylenchulus 
semipenetrans Nematode Present No subspecific 
taxa  
Xiphinema americanum Nematode Present No subspecific 
taxa  
Xiphinema brasiliense Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema brevicollum Nematode Present No subspecific 
taxa  
Xiphinema bricolensis Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema californicum Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema diffusum Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema 
diversicauadatum Nematode Present No subspecific 
taxa  
Xiphinema elongatum Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema 
ensiculiferum Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema inaequale Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema insigne Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema intermedium Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema pachtaicum Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema rivesi Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema tarjanense Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema turcicum Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Xiphinema vuittenezi Nematode Absent Not associated 
with commodity Decraemer and 
Geraert (2006) 
Globisporangium 
debaryanum Oomycete Uncertain Not associated 
with commodity Radwan and Hassan 
(2018) 
Globisporangium 
irregulare Oomycete Present No subspecific 
taxa  
Globisporangium 
rostratum Oomycete Present No subspecific 
taxa  
Globisporangium 
splendens Oomycete Present No subspecific 
taxa  
Globisporangium 
ultimum Oomycete Present No subspecific 
taxa  
Phytophthora 
boehmeriae Oomycete Present No subspecific 
taxa  
Phytophthora cactorum Oomycete Present No subspecific 
taxa  
Phytophthora cambivora Oomycete Present No subspecific 
taxa  Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 454 Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Phytophthora capsici Oomycete Absent Insufficient 
information for host 
association Literature search 
Phytophthora 
cinnamomi Oomycete Present No subspecific 
taxa  
Phytophthora citricola Oomycete Present No subspecific 
taxa  
Phytophthora 
citrophthora Oomycete Present No subspecific 
taxa  
Phytophthora cryptogea Oomycete Present No subspecific 
taxa  
Phytophthora kernoviae Oomycete Present No subspecific 
taxa  
Phytophthora 
megakarya Oomycete Absent Not associated 
with commodity Bailey et al. (2016) 
Phytophthora 
megasperma Oomycete Present No subspecific 
taxa  
Phytophthora multivora Oomycete Present No subspecific 
taxa  
Phytophthora nicotianae Oomycete Present No subspecific 
taxa  
Phytophthora 
niederhauseri Oomycete Present No subspecific 
taxa  
Phytophthora ramorum Oomycete Absent Insufficient 
information for host 
association Literature search 
Phytopythium vexans Oomycete Present No subspecific 
taxa  
Pythium afertile Oomycete Present No subspecific 
taxa  
Pythium coloratum Oomycete Present No subspecific 
taxa  
Pythium 
cucurbitacearum Oomycete Not 
applicable Taxonomy Invalid name (Robert 
et al. 2005; Index 
Fungorum 2022) 
Pythium deliense Oomycete Absent Not associated 
with commodity CABI (2021) 
Pythium oligandrum Oomycete Present No subspecific 
taxa  
Pythium torulosum Oomycete Present No subspecific 
taxa  
Trachysphaera 
fructigena Oomycete Absent Insufficient 
information for 
commodity 
association Dade (1940) 
Tomato apical stunt 
viroid Viroid Absent Insufficient 
information for host 
association Literature search 
Avocado 3 
alphacryptovirus Virus Not 
applicable Not applicable Not a legitimate 
pathogen 
Cucumber leaf spot 
virus Virus Absent Not associated 
with the host CABI (2021) 
Cucumber mosaic virus Virus Present No subspecific 
taxa  
Papaya mosaic virus Virus Absent Not associated 
with the host CABI (2021)  
455 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Scientific name Organism Presence 
in New 
Zealand  Rationale for 
exclusion Reference 
Persea americana 
alphaendornavirus 1 Virus Present No subspecific 
taxa  
Persea americana 
chrysovirus Virus Present No subspecific 
taxa  
Tobacco mosaic virus Virus Present No subspecific 
taxa  
References for Appendix 2 
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Liu, P S W (1977) A supplement to a host list of pl ant diseases in Sabah, Malaysia. Phytopathological 
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457 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Lombard, L; Crous, P W (2012) Phylogeny and taxonom y of the genus Gliocladiopsis . Persoonia - 
Molecular Phylogeny and Evolution of Fungi 28(1): 25-33. 
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Smith, E; Kotzé, J; Wehner, F (1985) Sooty blotch o f avocado caused by Akaropeltopsis  sp. 
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Thomas, T V; Eicker, A; Robbertse, P J (1994) Possi ble role of fungi in negatively affecting fruit-set  in 
avocados. South African Journal of Botany 60(5): 251-256. 
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459 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Appendix 3.  Hosts of Grovesinia moricola  
Family Species Common name Reference 
Adoxaceae Viburnum recognitum Arrowwood Trolinger et al. (1978) 
Adoxaceae Viburnum  sp. Viburnum Trolinger et al. (1978) 
Amaranthaceae Chenopodium ambrosioides Mexican tea Trolinger et al. (1978) 
Anacardiaceae Toxicodendron pubescens Poison oak Trolinger et al. (1978) 
Annonaceae Annona muricata Soursop Bezerra et al. (2008) 
Annonaceae Asimina triloba Pawpaw Trolinger et al. (1978) 
Asteraceae Bidens frondosa begger-ticks Trolinger et al. (1978) 
Asteraceae Eupatorium coelestinum Mistflower Trolinger et al. (1978) 
Asteraceae Eupatorium rugosum white snakeroot Trolinger et al. (1978) 
Asteraceae Solidago canadensis goldenrod Trolinger et al. (1978) 
Balsaminaceae Impatiens pallida pale touch-me-not Trolinger et al. (1978) 
Batulaceae Alnus incana Grey alder Trolinger et al. (1978) 
Bignoniaceae Campsis radicans trumpet vine Trolinger et al. (1978) 
Bignoniaceae Catalpa speciosa Catalpa Trolinger et al. (1978) 
Campanulaceae Lobelia inflata Indian tobacco Trolinger et al. (1978) 
Campanulaceae Lobelia siphilitica Blue cardinal flower Trolinger et al. (1978) 
Cannabaceae Celtis laevigata  or Celtis 
occidentalis  Hackberry Trolinger et al. (1978) 
Cannabaceae Humulus japonicus Japanese hop Cho et al. (2013) 
Commelinaceae Commelina diffusa Dayflower Trolinger et al. (1978) 
Convolvulaceae Ipomoea hederacea Morning glory Trolinger et al. (1978) 
Convolvulaceae Ipomoea lacunosa Morning glory Trolinger et al. (1978) 
Convolvulaceae Ipomoea quamoclit Cypress vine Trolinger et al. (1978) 
Cornaceae Cornus amomum red-willow Trolinger et al. (1978) 
Cornaceae Cornus florida Flowering dogwood Trolinger et al. (1978) 
Ericaceae Oxydendron arboreum Sourwood Blake et al. (2015) 
Ericaceae Vaccinium  sp. Blueberry Trolinger et al. (1978) 
Euphorbiaceae Aleurites fordii tung Trolinger et al. (1978) 
Fabaceae Arachis hypogaea Peanut Niedbalski et al. (1979), Vyas et al. (1982)  
Fabaceae Arachis hypogaea peanut Trolinger et al. (1978) 
Fabaceae Desmodium canescens Tick clover Trolinger et al. (1978) 
Fabaceae Glycine max Soybean Cho et al. (2012) 
Fabaceae Lespedeza cyrtobotrya Leafy bush-clover Park et al. (2019) 
Fabaceae Millettia pinnata Indian beech Chang (1995) 
Fabaceae Phaseolus lunatus Fordhook lima bean Niedbalski et al. (1979) 
Fabaceae Phaseolus lunatus lima bean Trolinger et al. (1978) 
Fabaceae Phaseolus lunatus var. 
Harvester snap bean Trolinger et al. (1978) 
Fabaceae Vigna angularis Adzuki bean Cho et al. (2017) 
Fabaceae Vigna vexillata  var. 
tsusimensis  Wild cowpea Lee & Kim (2007) 
Hydrangeaceae Hydrangea petiolaris Hydrangea Trolinger et al. (1978) Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 460 Family Species Common name Reference 
Juglandaceae Carya illinoiensis Pecan Niedbalski et al. (1979) 
Juglandaceae Carya illinoiensis pecan Trolinger et al. (1978) 
Juglandaceae Juglans cinerea Butternut Trolinger et al. (1978) 
Juglandaceae Juglans nigra Black walnut Niedbalski et al. (1979) 
Juglandaceae Juglans nigra Black walnut Trolinger et al. (1978) 
Lamiaceae Perilla frutescens perilla Trolinger et al. (1978) 
Lauraceae Cinnamomum kanehirae camphor tree Fu & Lin (2012) 
Lauraceae Lindera benzoin Spicebush Trolinger et al. (1978) 
Lauraceae Persea americana Avocado Bezerra et al. (2008) 
Lauraceae Persea americana Avocado Trolinger et al. (1978) 
Lauraceae Sassafras albidum Sassafras Trolinger et al. (1978) 
Lythraceae Cuphea viscosissima Blue waxweed Trolinger et al. (1978) 
Lythraceae Lagerstroemia indica Crape myrtle Blake et al. (2015) 
Magnoliaceae Liriodendron tulipifera tulip-poplar Trolinger et al. (1978) 
Magnoliaceae Magnolia fraseri Mountain magnolia Trolinger et al. (1978) 
Magnoliaceae Magnolia tripetala umbrella magnolia Trolinger et al. (1978) 
Malvaceae Abelmoschus esculentus Okra Trolinger et al. (1978) 
Malvaceae Gossypium hirsutum cotton Trolinger et al. (1978) 
Malvaceae Hibiscus cannabinus kenaf Trolinger et al. (1978), Colyer et al. (1992)  
Malvaceae Sida spinosa Prickly mallow Trolinger et al. (1978) 
Malvaceae Tilia americana American basswood Trolinger et al. (1978) 
Meliaceae Melia azedarach Chinaberry tree Chang (1995) 
Menispermaceae Cocculus orbiculatus red-berried moonseed Trolinger et al. (1978), Lee &  Kim (2002) 
Menispermaceae Menispermum canadense Moonseed Trolinger et al. (1978) 
Moraceae Artocarpus altilis Breadfruit Hu et al. (2002) 
Moraceae Broussonetia papyrifera Paper mulberry Chang (1995) 
Moraceae Ficus pumila Creeping fig Wang et al. (2020) 
Myrtaceae Eucalyptus benthamii Camden white gum Aubrey et al. (2017) 
Oleaceae Fraxinus americana White ash Trolinger et al. (1978) 
Passifloraceae Passiflora incarnata passion-flower Trolinger et al. (1978) 
Phytolaccaceae Phytolacca americana Pokeweed Trolinger et al. (1978) 
Plantanaceae Plantanus acerifolia London planetree Trolinger et al. (1978) 
Plantanaceae Platanus occidentalis Sycamore   Trolinger et al. (1978) 
Polygonaceae Polygonum pensylvanicum Pinkweed Trolinger et al. (1978) 
Polygonaceae Polygonum scandens Climbing false 
buckwheat Trolinger et al. (1978) 
Polygonaceae Rumex crispus Yellow dock Trolinger et al. (1978) 
Rhamnaceae Zizyphus mauritiana Indian jujube Su & Leu (1983) 
Rosaceae Amelanchier arborea Serviceberry Grand & Vernia (2004) 
Rosaceae Malus domestica Apple Trolinger et al. (1978) 
Rosaceae Malus sylvestris Crab apple Grand & Vernia (2004) 
Rosaceae Prunus persica  var. nectarina  Nectarine Trolinger et al. (1978) 
Rosaceae Prunus subhirtella Japanese flowering 
cherry Trolinger et al. (1978)  
461 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Family Species Common name Reference 
Rubiaceae Paederia foetida Chinese fevervine Trolinger et al. (1978) 
Sapindaceae Acer negundo Boxelder Niedbalski et al. (1979) 
Sapindaceae Acer nigrum Black maple Trolinger et al. (1978) 
Sapindaceae Acer plantanoides Norway maple Trolinger et al. (1978) 
Sapindaceae Acer pseudoplatanus Sycamore maple Niedbalski et al. (1979) 
Sapindaceae Acer rubrum Red maple Trolinger et al. (1978) 
Sapindaceae Acer saccharum Sugar maple Trolinger et al. (1978) 
Simaroubaceae Ailanthus altissima Tree-of-heaven Trolinger et al. (1978) 
Smilacaceae Smilax herbacea Carrion flower Grand & Vernia (2004) 
Solanaceae Solanum lycopersicum Tomato Trolinger et al. (1978) 
Solanaceae Solanum lycopersicum Tomato Dillard et al. (1995) 
Solanaceae Solanum tuberosum Potato Trolinger et al. (1978) 
Styracaceae Halesia diptera Siverbell Holcomb (1994) 
Ulmacae Ulmus parvifolia Chinese elm Trolinger et al. (1978) 
Vitaceae Parthenocissus quinquefolia Virginia creeper Trolinger et al. (1978) 
Vitaceae Parthenocissus  sp. Virgin ivy Trolinger et al. (1978) 
Vitaceae Parthenocissus tricuspidata Boston ivy Shin et al. (2019) 
Vitaceae Vitis aestivalis Summer grape Trolinger et al. (1978) 
Vitaceae Vitis labrusca Fox grape Trolinger et al. (1978) 
Vitaceae Vitis palmata Catbird-grape Trolinger et al. (1978) 
Vitaceae Vitis rotundifolia Muscadine grape Brennerman at al. (1993) 
Vitaceae Vitis  sp. Grape Takahashi & Tanba (1980) 
Vitaceae Vitis vinifera Grape Trolinger et al. (1978), NA RO  (2013) , 
Jayawardena et al. (2018)  
References for Appendix 3 
Aubrey, D P; Fraedrich, S W; Harrington, T C; Olati nwo, R (2017) Cristulariella moricola associated 
with foliar blight of Camden white gum ( Eucalyptus benthamii ), a bioenergy crop. Biomass and 
Bioenergy 105: 464-469. 
Bezerra, J; Luz, E; Gramacho, K; De Figueirêdo, V; Bezerra, K J P P (2008) Occurrence of 
Grovesinia pyramidalis  on soursop and avocado in Brazil. 57(2). 
Blake, J; Williamson, M; Ellington, K (2015) Index of plant diseases in South Carolina  (3rd ed.). 
Brenneman, T B; Hadden, J F; Ruter, J M (1993) Firs t report of Cristulariella moricola  causing zonate 
leaf spot on muscadine grape. Plant Disease 77(7). 
Chang, T T 1995. Zonate leaf spot on three woody pl ants in Taiwan. Bulletin of Taiwan Forestry 
Research Institute 10: 235–240. 
Dillard, H; Cobb, A; Garman, W; Brewer, R (1995) Fi rst report of zonate leaf spot on tomato, caused 
by Cristulariella moricola , in New York. Plant Disease 79(3): 319. 
Fu, C H; Lin, F Y (2012) First report of zonate lea f spot of Cinnamomum kanehirae  caused by 
Hinomyces moricola  in Taiwan. Plant Disease 96(8): 1226. 
Grand, L E; Vernia, C S (2004) Fungi on Plants in N orth Carolina. 
https://projects.ncsu.edu/cals/course/pp318/North_C arolina_index.html  Accessed 08/12/2021 Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 462 Holcomb, G (1994) First report of zonate leaf spot on silverbell tree caused by Cristulariella moricola . 
Plant Disease 78(12). 
Hu, B; Hsiao, W; Fu, C (2002) First report of zonat e leaf spot of Artocarpus altilis  caused by 
Cristulariella moricola  in Taiwan. Plant Disease 86(10): 1179-1179. 
Jayawardena, R S; Purahong, W; Zhang, W; Wubet, T; Li, X; Liu, M, et al. (2018) Biodiversity of fungi 
on Vitis vinifera  L. revealed by traditional and high-resolution cul ture-independent approaches. Fungal 
Diversity 90(1): 1-84. 
NARO (2013) National Agriculture and Food Research Organization Genebank. 
https://www.gene.affrc.go.jp/databases-micro_pl_dis eases_en.php . Accessed 12/12/2021 
Niedbalski, M; Crane, J L; Neely, D (1979) Illinois  fungi 10. Development, morphology, and taxonomy 
of Cristulariella pyramidalis . Mycologia 71(4): 722–730. 
Shin, H-D; Choi, Y J; Hong, S H; Lee, Y-h (2019) Grovesinia moricola  occurring on Parthenocissus 
tricuspidata . The Korean Journal of Mycology 47: 271-274. 
Su, H; Leu, S (1983) Zonate leaf spot of Indian juj ube caused by Cristulariella moricola . Plant Disease 
67(8): 915-916. 
Trolinger, J; Elliott, E; Young, R (1978) Host rang e of Cristulariella pyramidalis . Plant Disease 
Reporter 62(8): 710. 
Wang, C-T; Hsieh, C-M; Lin, L-D; Yeh, Y-W; Kirschne r, R (2020) New records of two fungal 
pathogens associated with premature leaf fall of tw o varieties of Ficus pumila  in Taiwan. Fungal 
Science 35: 9–16. 
  
463 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Appendix 4.  Glossary and Abbreviations 
 
Term or abbreviation Definiton 
CMI  Climate (or composite) match index, a value that in dicates the 
similarities between a location overseas and New Ze aland (Phillips et 
al. 2018). 
commercial production Definition for the purposes of risk assessment: a p rocess/system 
where activities, such as in-field monitoring, in-f ield pest control 
activities, harvesting, cleaning, sorting and gradi ng have been 
undertaken to produce a commodity that is free of d efects such as 
broken skin, rot and damage. Depending on the syste ms in place, 
these activities can be undertaken at any stage fro m the point of 
planting to the point of export. 
commodity description  The commodity description defines the form of the c ommodity that is 
covered by the IRA, e.g. the commodity species and the countries 
under consideration. The commodity description may also include 
commercial production and/or grading requirements o r other 
commodity quality specifications. 
conditional non-host Fruit or vegetable at a specified maturity and spec ified physical 
condition that cannot support the complete developm ent of a particular 
pest species. 
CPC  Crop Protection Compendium . A CABI database that provides 
information about crop pests. 
disease A disorder of structure or function in a plant, esp ecially one that affects 
a specific location and is not simply a direct resu lt of physical injury. 
endemic  An animal, plant, pest, or disease that is native t o and is not naturally 
found outside a defined geographical area. 
establishment Perpetuation, for the foreseeable future, of an org anism or disease 
within an area after entry. 
ERS Emerging Risk System, an MPI workflow system that a llows MPI to 
receive, process and store information about new bi osecurity risks and 
to manage those risks in a timely fashion. 
exposure The process of the hazard organism moving from the commodity it 
arrived on to another host (also called “transfer”) . 
exotic This word has different meanings in different field s, but in this 
document, it is defined as an animal, plant, pest o r disease that is not 
indigenous to New Zealand. 
hazard A hazard is a pest (including arthropods and pathog ens) or disease 
that is not present in the PRA area, e.g. New Zeala nd (or is present 
but still represents a biosecurity risk, e.g. is ca pable of vectoring 
pathogens not present in the PRA area), has the abi lity to establish 
and cause harm in the PRA area and is associated wi th the entry 
pathway (commodity/country of origin) under conside ration. 
indigenous Native; organism originating or occurring naturally  in a specified area. 
inspection Official visual examination of plants, plant produc ts or other regulated 
articles to determine if pests are present and/or t o determine 
compliance with phytosanitary regulations (FAO 2012 ). 
introduced Not indigenous, not native to the area in which it now occurs, having 
been brought into this area directly or indirectly by human activity. Biosecurity New Zealand  Persea americana plants for planting IRA, June 2022 • 464 Term or abbreviation Definiton 
IPPC International Plant Protection Convention, a 1951 m ultilateral treaty 
overseen by the Food and Agriculture Organization t hat aims to 
secure coordinated, effective action to prevent and  to control the 
introduction and spread of pests of plants and plan t products. 
ISPM International Standards for Phytosanitary Measures,  international 
standards adopted by the Conference of the Food and  Agriculture 
Organization, the Interim Commission on phytosanita ry measures or 
the Commission on phytosanitary measures, establish ed under the 
IPPC. 
IHS Import Health Standard (See “Import Health Standard ” for a definition.) 
Import Health Standard An import health standard (IHS) is a document issue d under section 
24A of the Biosecurity Act 1993. It states the requ irements that must 
be met before risk goods can be imported into New Z ealand. 
IRA Import Risk Analysis, an administrative process thr ough which 
quarantine policy is developed or reviewed, incorpo rating risk 
assessment, risk management and risk communication.  
MPI Ministry for Primary Industries, New Zealand 
non-host Fruit or vegetable that will not support the comple te development of a 
particular pest species regardless of the stage of maturity and physical 
characteristics. 
NPPO National Plant Protection Organisation, official se rvice established by 
a government to discharge the functions specified b y the IPPC. 
NZOR New Zealand Organisms Register, an actively maintai ned compilation 
of all organism names relevant to New Zealand: indi genous, endemic 
or exotic species or species not present in New Zea land but of 
national interest. 
ONZPR  Official New Zealand Pest Register. MPI database th at records 
organisms that may be associated with plants or pla nt products that 
are imported into New Zealand. Plant and plant prod uct importers can 
use ONZPR to find out the quarantine status of a sp ecies – regulated 
or non-regulated. 
pest Any species, strain or biotype of plant, animal, or  pathogenic agent 
injurious to plants or plant products. 
pest-free area An area in which a specific pest does not occur as demonstrated by 
scientific evidence and in which, where appropriate , this condition is 
being officially maintained. 
pest-free place of 
production A place of production in which a specific pest does  not occur as 
demonstrated by scientific evidence and in which, w here appropriate, 
this condition is being officially maintained for a  defined period. 
PFA Pest-free area (See “Pest-free area” for a definiti on.) 
PFPP Pest-free place of production (See “Pest-free place  of production” for a 
definition.) 
PPIN Plant Pest Information Network database (MPI), a re cord of organisms 
collected in New Zealand and identified by MPI’s Pl ant Health and 
Environment Laboratory. 
PRA Pest Risk Assessment or Pest Risk Analysis 
QuanCargo New Zealand border transaction database, detailing commercial 
consignments and interceptions of pests made by qua rantine 
inspection (MPI).  
465 • Persea americana plants for planting IRA, June 2022 Biosecurity New Zealand Term or abbreviation Definiton 
quarantine pest A pest of potential economic importance to the area  endangered 
thereby, e.g. New Zealand, and not yet present ther e, or present but 
not widely distributed and being officially control led. 
systems approach The integration of different pest risk management m easures, at least 
two of which act independently, and which cumulativ ely achieve the 
appropriate level of phytosanitary protection. Meas ures can be 
undertaken at any stage from the point of planting to the point of 
export. 
vector An organism or object that transfers a pest, parasi te, pathogen or 
disease from one area or host to another. 
 