Background
==========

Mosquitoes are vectors for infectious diseases that cause widespread epidemics and human morbidity ([@ref-24]). The pathogens transmitted by mosquitoes are quite diverse and include protozoans, arboviruses, and filarial nematodes ([@ref-47]; [@ref-80]). These pathogens are taken up from one host and transmitted to another during the process of blood feeding. Mosquito-transmitted diseases put hundreds of millions of people at risk and still kill more than half a million people every year despite immense international efforts to combat them ([@ref-89]). Developing countries in tropical and subtropical regions bear the greatest burden with the majority of fatalities being young children ([@ref-109]).

The host-seeking behavior of mosquitoes as well as many other hematophagous arthropods depends heavily on their sense of smell. A battery of specific odorant receptors expressed in odorant receptor neurons within the antennae of mosquitoes enables them to detect a variety of chemical clues that are emitted by the host ([@ref-23]; [@ref-29]). Many of these attractants, for example CO~2~, organic acids, and aldehydes, have been identified and linked to specific receptor proteins ([@ref-16]; [@ref-31]; [@ref-39]; [@ref-49]; [@ref-62]; [@ref-72]; [@ref-90]; [@ref-112]; [@ref-116]; [@ref-122]; [@ref-126]). Olfactory receptor agonists as well as antagonists can impede the mosquito's sense of smell and interrupt host-seeking behavior. Chemicals that elicit such responses are termed mosquito repellents.

Reducing the number of host-vector interactions is an effective way to reduce the spread of vector-borne diseases. Currently, only a small number of active ingredients in a large number of different commercially available formulations are widely used to protect humans from mosquitoes and other blood-sucking arthropods. DEET (N,N-Diethyl-meta-toluamide) is commonly used as an active ingredient in insect repellents ([@ref-55]; [@ref-126]). Unsubstantiated fears of possible side effects of DEET have created a large market for "natural" DEET-free repellents with a variety of active ingredients. Picaridin, IR 3535, and a large assortment of essential oils, such as eucalyptus and lemongrass, are sold as sprays, creams, and integrated in wearable devices for repelling mosquitos ([@ref-127]). For a review of the long history and present use of plant extracts as commercial insecticides please see a recent review by [@ref-92]. A current text search on <http://www.amazon.com> with the search string "insect repellent" resulted in 22,950 hits.

Access to effective repellent products is often limited in developing countries. People with a high risk of vector-borne disease infections often have no or only insufficient means to protect themselves ([@ref-19]). Across cultures, people use a variety of home remedies and traditional practices to repel mosquitos ([@ref-105]). Some of these remedies are likely highly effective, while others ([@ref-2]; [@ref-34]; [@ref-105]) like DEET are expensive and scarce. In addition, some known effective methods, such as the use of mosquito nets, are impractical in particular situations and are therefore not used regularly by community members ([@ref-2]; [@ref-34]; [@ref-105]). Several ethnobotanical research projects have focused on the traditional use of native plants as insect repellents ([@ref-93]; [@ref-119]).

In a recent study, we have determined the efficacy of several commercial products, two fragrances, and a vitamin B patch in repelling mosquitoes ([@ref-99] ). The products were tested using a Y-tube olfactometer setup with *Aedes aegypti* (Linnaeus) and *Aedes albopictus* (Skuse), both major human disease vectors. Repellents with DEET or p-menthane-3,8-diol (PMD) as active ingredients had a prominent repellency effect over longer times and on both species. Some of the DEET-free products containing citronella or geraniol did not have any significant repellency effect. Interestingly, the perfume we tested had a significant repellency effect early after application. These findings were widely reported in the media and we received information from the public about other personal hygiene products that are used as mosquito repellents (see below).

In a follow up study, we performed attraction-inhibition assays using a taxis cage in a wind tunnel setting ([@ref-98]). One person was placed upwind of the taxis cage and the mosquito movement towards or away from the person was recorded. The person was treated with various spray-on repellents or equipped with different 'mosquito repellent devices'. We found that the spray-on repellents containing 98% DEET or 30% PMD had the highest efficacy in repelling mosquitoes compared to repellents with other ingredients. From the five wearable devices that we tested, only the one that releases Metofluthrin significantly reduced the numbers of attracted mosquitoes. A citronella candle had no effect. We concluded that many of the products that we tested that were marketed as repellents do not reduce mosquito attraction to humans.

The current study used an online survey to find unconventional methods for mosquito control and repellent practices that will be tested in future experiments. Here we define an unconventional method as one involving a product that is not commercially available worldwide, or involving products that are not used for their original purpose (i.e., dryer sheets). We also considered behaviors that are not obviously connected to mosquito control (i.e., drinking alcohol or eating bananas) as 'unusual'. Links to the survey were distributed globally in an effort to capture a broad diversity of practices; however, outreach proved to be very complicated. The supplementary material shows the demographics of our study were biased; however, we did attain very useful qualitative input from our respondents.

Methods
=======

Online survey
-------------

We developed a nine question online survey (see [Supplemental Information 1](#supp-1){ref-type="supplementary-material"}). Demographic variables included gender, age, education levels and residence. Survey questions assessed people's awareness of mosquitoes, general knowledge about mosquito-borne diseases and mosquito repellents and what mosquito control strategies people most frequently use. Two survey questions were specifically designed to gather unconventional mosquito repellent methods and strategies. The survey was available in English, Spanish, and Portuguese and was distributed in countries in which residents were likely to speak one of the above three languages. Convenience and snowball sampling were used.

Data collection
---------------

The data was collected anonymously through the online portal Survey Monkey (Palo Alto, CA, USA). Participants were recruited through various electronic means including postings on Facebook or other social media, and email list serves. The survey was shared on Facebook groups most of which were academics-led with 'entomology' or 'health' in the title, with the assumption that these groups are interested in this topic resulting in more participation and shares. The survey was also provided to various universities through personal contacts of the authors. The authors also forwarded the survey to their personal email contact lists. Those who agreed to participate had the option to enter a drawing for one of 10 gift cards valued between \$50 and \$100.

Data analysis
-------------

The data was exported into excel from Survey Monkey and categorized by manual inspection. For questions for which answers were provided, the Excel sort function was used to group and count identical answers. Answers to the open questions were analyzed by the authors and placed into different categories that we defined. Geographic region was determined by the continental location of the respondents' current residence. Open-ended responses to the survey question regarding unconventional practices were categorized by type of mosquito control or repellent method.

Ethics statement
----------------

The study was approved by the NMSU Institutional Review Board (IRB \# 15378, approved July 10th 2017). Consent was obtained by participants' selecting to continue on to the survey after reading a description of the study, including risks and benefits.

Results
=======

Demographics
------------

We received a total of 5,209 responses to our survey (for raw data, please see [Supplemental Information 2](#supp-2){ref-type="supplementary-material"}). [Figure 1](#fig-1){ref-type="fig"} shows the demographics of the survey participants, where 67.71% of participants identified as female, 31.7% as male, and 0.59% as other; the majority of respondents were 18 to 37 years , followed by ages 38 to 57 years with ages over 58 years being the lowest (*N* = 789); and almost 50% held a graduate degree. Listed in [Supplemental Information 3](#supp-3){ref-type="supplementary-material"} are the regions and countries in which the respondents stated they were currently residing at the time of the survey. Over 76% were from North America, with 70% of the total participants listing the United States. Europe had the next highest number of responses, totaling to a little over 7% of total respondents followed by Australia (6.3%), Asia (4%), Africa (3.8%) and South America (3.3%).

![Demographics of study participants.\
(A) Gender of participants. (B) Age of participants in years. (C) Educational level of study participants.](peerj-06-5151-g001){#fig-1}

Mosquito repellent methods
--------------------------

We chose 13 mosquito repellent/control methods and asked respondents to select all methods they had ever used. Answer choices can be seen in [Fig. 2](#fig-2){ref-type="fig"}. Out of the 5,209 total respondents, 4,773 responded to the multiple choice question. The most common repellent method chosen by the respondents was spray-on mosquito repellent with DEET, closely followed by citronella candles and 'natural' spray-on repellents ([Fig. 2](#fig-2){ref-type="fig"}). In the open ended question picaridin was mentioned by 59 participants and IR3535 only once.

![Commonly used mosquito repellent methods.\
The number of each response from one of the multiple choice questions.](peerj-06-5151-g002){#fig-2}

10.7717/peerj.5151/table-1

###### Table showing mosquito repellent methods & strategies.

Shown are mosquito repellent methods that were collected through the open ended survey question, along with the way of administration or preparation and the region(s) they were listed from. The methods/strategies are listed according to the numbers of references (from high to low).

![](peerj-06-5151-g003)

  Responses                                                                                                                                              Administration/preparation                   Region                                                                   Ref. No.
  ------------------------------------------------------------------------------------------------------------------------------------------------------ -------------------------------------------- ------------------------------------------------------------------------ -----------------------
  Telephone app (sound)                                                                                                                                  Application                                  Sweden                                                                   
  Cut down on sugar                                                                                                                                      Avoidance, Ingestion                         USA, Denmark                                                             
  No meat consumption                                                                                                                                    Avoidance                                    UK                                                                       
  Bananas                                                                                                                                                Avoidance, Ingestion, Topical, Unspecified   USA, Canada, New Zealand, Pakistan                                       [@ref-43]
  Scented perfume/lotions/detergents                                                                                                                     Avoidance, Topical                           USA, Canada, Australia, Brazil, Switzerland, Ireland, China, Sri Lanka   [@ref-41]
  Animal dung (cow, elephant)                                                                                                                            Burning                                      N. America, Australia, India                                             [@ref-73]
  *Artemesia vulgaris* (L.) (Asian mugwort)                                                                                                              Burning, Planting                            USA                                                                      [@ref-78], [@ref-120]
  Ayurvedic leaves                                                                                                                                       Burning                                      Sri Lanka                                                                [@ref-82]
  *Laurus nobilis* (L.) (bay leaves)                                                                                                                     Burning                                      USA                                                                      
  Coconut husks                                                                                                                                          Burning                                      USA, Australia                                                           [@ref-71]
  Coconut shell with dhuna                                                                                                                               Burning                                      India                                                                    [@ref-71]
  *Coffea Arabica* (L.) (coffee)                                                                                                                         Burning                                      Europe, Brazil, USA, Africa                                              [@ref-103]
  *Larrea tridentate* (de Candolle) (Creosote)                                                                                                           Burning                                      USA                                                                      [@ref-53]
  Dhup-an                                                                                                                                                Burning                                      Bangladesh                                                               [@ref-108]
  Dried *Chrysanthemum spp.* plants                                                                                                                      Burning                                      Kenya                                                                    [@ref-60]
  Dry *Vitex negundo* (L.) (Nochi) leaves                                                                                                                Burning                                      India                                                                    [@ref-12]
  Dry powdered rhizomes of certain plants                                                                                                                Burning                                      India                                                                    [@ref-32]
  *Eucalyptus globulus* (Labillardiere) (Tasmanian bluegum) leaves                                                                                       Burning                                      Brazil, USA                                                              [@ref-79]
  *Formes fomentarius* (L.) (tinder fungus)                                                                                                              Burning                                      Sweden                                                                   
  *Poaceae* (L.) (grass)                                                                                                                                 Burning                                      Canada                                                                   [@ref-131]
  Lemon scented candles                                                                                                                                  Burning                                      Netherlands                                                              [@ref-61]
  *Prosopis juliflora* (DC.) (mesquite)                                                                                                                  Burning                                      USA                                                                      [@ref-118]
  Mixture of diesel fuel & malathion                                                                                                                     Burning                                      USA                                                                      [@ref-1]
  *Citrus sinensis* (L.) (orange) peel or dried rind                                                                                                     Burning                                      Europe, Africa, USA, Canada Brazil                                       [@ref-9]
  *Citrus sinensis* (L.) (orange) peel with *Syzygium aromaticum* (L.) (clove)                                                                           Burning                                      USA                                                                      [@ref-133]
  Peat                                                                                                                                                   Burning                                      Sweden                                                                   [@ref-68]
  *Schinus terebinthifolius* (Raddi) (pepper tree)                                                                                                       Burning                                      Namibia                                                                  [@ref-67]
  *Salvia officinalis* (L.) (sage)                                                                                                                       Burning                                      USA                                                                      [@ref-57]
  *Tamarix* (L.) (salt cedar)                                                                                                                            Burning                                      USA                                                                      [@ref-54]
  *Santalum album* (L.) (sandalwood)                                                                                                                     Burning                                      Australia                                                                [@ref-8]
  Spices such as *Cinnamomum* (Schaffer) (cinnamon), *Mentha* (L.) (mint), *Salvia officinalis* (L.) (sage), *Petroselinum crispum* (Miller) (parsley)   Burning                                      USA                                                                      [@ref-58]
  *Nicotiana tabacum* (L.) (tobacco) *or Cannabis sativa* (L.) (marijuana)                                                                               Burning                                      USA                                                                      [@ref-52]
  Vanilla candles                                                                                                                                        Burning                                      USA                                                                      
  Cigar smoke                                                                                                                                            Burning, Topical                             USA, Ireland, Hungary                                                    [@ref-63]
  Kerosene                                                                                                                                               Burning, Unspecified                         USA, Bangladesh, New Zealand                                             [@ref-91]
  Brewer's yeast                                                                                                                                         Ingestion                                    Canada, New Zealand, USA                                                 [@ref-21]
  Capsaicin                                                                                                                                              Ingestion                                    USA                                                                      [@ref-100]
  *Pelargonium citrosum* (Citronella) tea                                                                                                                Ingestion                                    Brazil, Mexico (herbal tea)                                              [@ref-79]
  Dill pickles and *Allium sativum* (L.) (garlic)                                                                                                        Ingestion                                    Unknown                                                                  
  Gin and tonic                                                                                                                                          Ingestion                                    Chile, New Zealand, South Africa                                         
  *Zingiber officinale* (Roscoe) (ginger) tea                                                                                                            Ingestion                                    USA                                                                      [@ref-132]
  *Citrus paradise* (Macfad.) (grapefruit) juice                                                                                                         Ingestion                                    USA                                                                      [@ref-131]
  Iron pills                                                                                                                                             Ingestion                                    USA                                                                      
  Local honey                                                                                                                                            Ingestion                                    USA                                                                      
  Marmite                                                                                                                                                Ingestion                                    New Zealand                                                              [@ref-21]
  *Citrus sinensis* (L.) (oranges)                                                                                                                       Ingestion                                    Canada, USA                                                              [@ref-9]
  *Origanum vulgare* (L.) (oregano) oil                                                                                                                  Ingestion                                    Canada                                                                   [@ref-76]
  Selenium supplements                                                                                                                                   Ingestion                                    USA                                                                      [@ref-10]
  Tonic water with quinine                                                                                                                               Ingestion                                    USA, South Africa, Malaysia, France, New Zealand, Australia              
  Alcohol                                                                                                                                                Ingestion, Avoidance                         USA, Canada, Denmark, Hungary, Ireland                                   [@ref-74]
  Apple cider vinegar                                                                                                                                    Ingestion, Spray, Topical                    USA, Europe                                                              
  Aloe vera                                                                                                                                              Ingestion, Topical                           South Africa, Italy, Germany, Norway, Australia                          [@ref-111]
  *Cinnamomum* (Schaeff.) (cinnamon)                                                                                                                     Ingestion, Topical, Unspecified              USA, South Korea, Canada                                                 [@ref-8]
  Car Mobil                                                                                                                                              Larvicide                                    India                                                                    
  Charcoal tabs in standing water                                                                                                                        Larvicide                                    USA                                                                      [@ref-17]
  Clorox                                                                                                                                                 Larvicide                                    USA                                                                      [@ref-13]
  Coffee disposal granules                                                                                                                               Larvicide, Spray                             USA, Brazil                                                              [@ref-103]
  Diesel                                                                                                                                                 Larvicide, Spray                             Egypt, USA                                                               [@ref-75]
  Cut a *Solanum lycopersicum* (L.) (tomato) in half and leave it next to the bed                                                                        Other                                        South Africa                                                             [@ref-22]
  Cut *Syzygium aromaticum* (L.) (lemon)                                                                                                                 Other                                        USA, Malaysia                                                            [@ref-46]
  Hanging dried *Eucalyptus globulus* (Labill.) (eucalyptus) branches                                                                                    Other                                        USA                                                                      [@ref-93]
  Hanging Ziploc bag of water with penny or lavender inside                                                                                              Other                                        USA                                                                      
  Jar of sugar water away from people                                                                                                                    Other                                        USA                                                                      
  Keep cut *Syzgium aromaticum* (L.) (lemon) in all the rooms                                                                                            Other                                        Malaysia                                                                 [@ref-46]
  *Tagetes minuta* (L.) (Khakibos) under mattress.                                                                                                       Other                                        South Africa                                                             [@ref-25]
  Moth balls                                                                                                                                             Other                                        USA                                                                      [@ref-56]
  *Allium cepa* (L.) (onion) by side of the bed                                                                                                          Other                                        USA                                                                      [@ref-123]
  *Pteridium aquilinum* (L.) (Bracken fern)                                                                                                              Plant                                        Canada                                                                   [@ref-40]
  *Chrysathemum* (L.) (chrysathemums)                                                                                                                    Plant                                        USA                                                                      [@ref-64]
  *Eupatorium capillifolium* (Lamarck) (dog fennel)                                                                                                      Plant                                        USA                                                                      [@ref-114]
  *Equisetum* (L.) (horse tail)                                                                                                                          Plant                                        USA                                                                      [@ref-26]
  *Monarda punctata* (L.) (horsemint)                                                                                                                    Plant                                        USA                                                                      [@ref-113]
  *Lippia javanica* (Musudzungwane)                                                                                                                      Plant                                        South Africa                                                             [@ref-70]
  *Achillea millefolium* (L.) (yarrow)                                                                                                                   Plant                                        Canada                                                                   [@ref-86]
  *Tagetes* (L.) (Marigolds)                                                                                                                             Plant, Larvicide                             USA, Canada                                                              [@ref-93]
  *Solanum lycopersicum* (L.) (tomato plant)                                                                                                             Plant, Other                                 Austria, Switzerland, South Africa                                       [@ref-22]
  *Melissa officinalis* (L.) (lemon balm)                                                                                                                Plant, Topical                               USA                                                                      [@ref-8]
  *Rosmarinus officinalis* (L.) (rosemary)                                                                                                               Plant, Topical, Burning                      USA, Australia, Hungary, Canada                                          [@ref-60]
  *Nepeta cataria* (L.) (catnip)                                                                                                                         Plant, Topical, Other                        USA                                                                      [@ref-6]
  *Lavandula* (L.) (lavender)                                                                                                                            Plant, Topical, Spray, Unspecified           USA, Germany, Canada, Australia                                          [@ref-8]
  *Ocimum basilica* (L.) (basil)                                                                                                                         Plant, Topical, Unspecified                  USA, Australia, Ireland                                                  [@ref-36]
  *Pelargonium* (L.) (geraniums)                                                                                                                         Plants                                       USA, Switzerland, Canada, Eritrea                                        [@ref-113]
  *Callicarpa americana* (L.) (Beauty berry)                                                                                                             Plants, Topical, Unspecified                 USA, UK                                                                  [@ref-28]
  Beer, mouthwash, Epsom salt solution                                                                                                                   Spray                                        USA                                                                      [@ref-74]
  Boric acid (1%) and 10% sucrose solution                                                                                                               Spray                                        USA                                                                      [@ref-50]
  Coconut oil and Dettol disinfectant                                                                                                                    Spray                                        New Zealand                                                              [@ref-110]
  Pinol (Mexican version of pinsol)                                                                                                                      Spray                                        USA                                                                      [@ref-13]
  *Thymus vulgaris* (L.) (thyme) leaf tea mixed with *Pelargonium citrosum* (L.) (citronella) oil                                                        Spray                                        USA                                                                      [@ref-60]
  Water soaked *Fragaria ananassa* (Duchene) (strawberry)                                                                                                Spray                                        Brazil                                                                   [@ref-30]
  Listerine/mouth wash                                                                                                                                   Spray, Topical, Unspecified                  USA, South Africa, Canada                                                [@ref-7]
  Avon Skin So Soft                                                                                                                                      Topical                                      USA, Europe, Australia, South Africa                                     [@ref-99]
  Baby oil                                                                                                                                               Topical                                      USA                                                                      [@ref-4]
  Baby wipes                                                                                                                                             Topical                                      USA                                                                      [@ref-4]
  Bounce dryer sheet                                                                                                                                     Topical                                      USA, Saudi Arabia                                                        
  Cigarette butts soaked in alcohol                                                                                                                      Topical                                      USA                                                                      [@ref-85]
  *Syzygium aromaticum* (L.) (clove) in alcohol solution                                                                                                 Topical                                      Brazil                                                                   [@ref-95]
  *Cocos nucifera* (L.) (coconut) oil                                                                                                                    Topical                                      USA, Australia, Denmark, UK                                              [@ref-35]
  Cream with *Melaleuca alternifolia* (Maiden & Betche) (tea tree) oil, *Eucalyptus globulus* (Labill.) (eucalyptus) oil, and bees wax                   Topical                                      USA                                                                      [@ref-129]
  Crushed dried *Carica papaya* (L.) (papaya) leaves                                                                                                     Topical                                      USA                                                                      [@ref-97]
  Crushed *Hyptis suaveolens* (L.) (pignut)                                                                                                              Topical                                      Australia                                                                [@ref-129]
  Crushed *Mentha* (L.) (mint)                                                                                                                           Topical                                      USA, Australia                                                           [@ref-65]
  Crushed seeds of *Lepidium sativum* (L.) (chandrashura), *Brassica nigra* (L.) (black mustard), and *Ricinus communis* (L.) (castorbean)               Topical                                      USA                                                                      [@ref-14]
  Deer tallow                                                                                                                                            Topical                                      Alaska                                                                   [@ref-44]
  Deodorant                                                                                                                                              Topical                                      New Zealand, USA                                                         [@ref-124]
  Diatomaceous earth                                                                                                                                     Topical                                      USA                                                                      [@ref-59]
  Diluted fabric softener                                                                                                                                Topical                                      USA                                                                      
  Fresh aromatic leaves of *Myrtaceae* (Juss.) plants                                                                                                    Topical                                      Australia                                                                [@ref-128]
  Germix                                                                                                                                                 Topical                                      USA                                                                      
  Lemon/lime juice                                                                                                                                       Topical                                      USA, Pakistan, Denmark                                                   [@ref-8]
  Local bear bread (a tree fungus, pollypore)                                                                                                            Topical                                      Alaska                                                                   
  Mixture of baby oil and *Citronella* oil                                                                                                               Topical                                      Australia                                                                [@ref-79]
  Mixture of fresh or dried *Petroselinum crispum* (Mill.) (parsley) and apple cider vinegar                                                             Topical                                      Unknown                                                                  
  Mixture of garlic juice and crushed peels of limes and lemons                                                                                          Topical                                      USA                                                                      
  Mixture of vodka and citronella, geranium, and other essential oils                                                                                    Topical                                      USA                                                                      [@ref-101]
  Mud                                                                                                                                                    Topical                                      USA, Canada, Australia                                                   
  *Ananas comosus* (L.)(pineapple plant)                                                                                                                 Topical                                      Canada                                                                   
  Shampoo (as repellent)                                                                                                                                 Topical                                      Mexico, Malaysia, Britain, USA                                           
  South African camphor oil ointment, called Zambuk                                                                                                      Topical                                      South Africa                                                             [@ref-106]
  SPF 30 sunscreen                                                                                                                                       Topical                                      USA                                                                      [@ref-107]
  Talcum powder                                                                                                                                          Topical                                      USA                                                                      [@ref-83]
  *Tanacetum vulgare* (L.) (tansey) leaves                                                                                                               Topical                                      Canada                                                                   [@ref-106]
  *Melaleuca alternifolia* (Maiden & Betche) (tea tree) oil                                                                                              Topical                                      Ireland, USA, Norway, France, Australia                                  [@ref-3]
  Thiamine patch                                                                                                                                         Topical                                      USA                                                                      [@ref-42]
  Tiger balm                                                                                                                                             Topical                                      USA, Cambodia, Australia, Malaysia                                       [@ref-102]
  Vanilla extract                                                                                                                                        Topical                                      USA                                                                      
  Vaseline                                                                                                                                               Topical                                      South Africa, USA                                                        [@ref-77]
  *Azadirachta indica* (Juss.) (neem)                                                                                                                    Topical, Burning, Plant                      India, USA, Bangladesh, Eritrea, Brazil, West Indies, Germany, Nigeria   [@ref-60]
  Vicks Vaporub/menthol                                                                                                                                  Topical, Other                               USA, Canada, Australia, South Africa, Namibia                            [@ref-5]
  *Mentha piperita* (L.) (peppermint) lotion/oil                                                                                                         Topical, Other (camping tent)                USA, Unknown                                                             [@ref-48]
  Mixture of baby oil, menthol, and Dettol                                                                                                               Topical, Spray, Unspecified                  Australia, New Zealand                                                   [@ref-27]
  Crushed *Backhousia citriodora* (F.Muell.) (lemon myrtle) or *Eucalyptus globulus* (Labill.) (eucalyptus) leaves                                       Topical, Spray, Unspecified                  Australia                                                                [@ref-79]
  Vinegar/vinegar based solutions                                                                                                                        Topical, Spray, Unspecified                  USA                                                                      [@ref-96]
  Crushed up leaves of the *Myrica cerifera* (L.) (Wax Myrtle tree)                                                                                      Topical, Unspecified                         USA, Australia                                                           [@ref-33]
  *Aleurites moluccanus* (L.) (Kukui nut) oil                                                                                                            Topical, Unspecified                         USA (Hawaii)                                                             [@ref-88]
  Rubbing alcohol                                                                                                                                        Topical, Unspecified                         USA, South Korea                                                         [@ref-51]
  Witch hazel                                                                                                                                            Topical, unspecified                         USA, Canada                                                              
  Baking soda                                                                                                                                            Unspecified                                  USA                                                                      [@ref-20]
  *Citrus bergamia* (Risso.) (bergamot) oil                                                                                                              Unspecified                                  USA                                                                      [@ref-94]
  *Actaea racemose* (L.) (black cohosh)                                                                                                                  Unspecified                                  USA                                                                      
  *Plantago major* (L.) (broadleaf plaintain)                                                                                                            Unspecified                                  Germany                                                                  
  Broken liquid aspirin                                                                                                                                  Unspecified                                  USA                                                                      [@ref-6]
  *Melaleuca cajuputi* (Thomas Powell) (cajuput) oil                                                                                                     Unspecified                                  Indonesia                                                                [@ref-8]
  *Calendula officinalis* (L.) (English marigold) oil                                                                                                    Unspecified                                  Canada                                                                   [@ref-115]
  *Capsicum annuum* (L.) (cayenne)                                                                                                                       Unspecified                                  USA                                                                      [@ref-125]
  Chlorine                                                                                                                                               Unspecified                                  USA                                                                      [@ref-81]
  Copper pins                                                                                                                                            Unspecified                                  Germany                                                                  [@ref-15]
  Diluted Raw Armor's starch                                                                                                                             Unspecified                                  USA                                                                      
  Hairspray                                                                                                                                              Unspecified                                  USA                                                                      
  *Jasminum* (L.) (jasmine)                                                                                                                              Unspecified                                  Ireland, Spain                                                           [@ref-8]
  Key lime                                                                                                                                               Unspecified                                  USA                                                                      
  Mixture of *Cymbopogon* (Kurt Sprengel) (lemongrass) oil, mouthwash, and *Prunus dulcis* (Mill.) (almond) oil                                          Unspecified                                  USA                                                                      [@ref-11]
  Mixture of Listerine and witch hazel                                                                                                                   Unspecified                                  USA                                                                      [@ref-11]
  Mixture of *Melaleuca alternifolia* (Maiden & Betche) (tea tree) oil, apple cider vinegar, and water                                                   Unspecified                                  USA                                                                      [@ref-38]
  Mixture of WD-40, camphor/phenol, and mineral oil                                                                                                      Unspecified                                  New Zealand, USA                                                         
  Nail polish                                                                                                                                            Unspecified                                  USA                                                                      [@ref-51]
  Oil paint                                                                                                                                              Unspecified                                  Pakistan                                                                 [@ref-66]
  *Pogostemon cablin* (Blanco) (patchouli) oil                                                                                                           Unspecified                                  USA, Canada                                                              [@ref-79]
  *Pinus sylvestris* (L.) (pine) oil                                                                                                                     Unspecified                                  USA                                                                      [@ref-79]
  Pine tar                                                                                                                                               Unspecified                                  USA                                                                      [@ref-117]
  *Sesamum indicum* (L.) (sesame) oil                                                                                                                    Unspecified                                  USA                                                                      [@ref-121]
  *Mentha spicata* (L.) (spearmint) oil                                                                                                                  Unspecified                                  USA                                                                      [@ref-11]
  Sulphur                                                                                                                                                Unspecified                                  USA, Canada                                                              [@ref-45]
  Thieves oil                                                                                                                                            Unspecified                                  USA                                                                      [@ref-42]
  Toothpaste                                                                                                                                             Unspecified                                  USA                                                                      [@ref-48]
  Trader Joe's Tea Tree Tingle                                                                                                                           Unspecified                                  USA                                                                      [@ref-3]
  Windex                                                                                                                                                 Unspecified                                  USA                                                                      [@ref-84]

Unconventional mosquito repellent methods
-----------------------------------------

The major goal of this study was to collect information on unconventional mosquito repellent and control methods. In one of the last survey questions, participants were asked to list additional repellent methods that were not previously mentioned. [Table 1](#table-1){ref-type="table"} shows 167 of the unconventional methods that survey participants listed. The table is organized into the type of survey responses, followed by the application/preparation of the product mentioned, and the regions from where the participants that listed it reside at the time of the survey. The last column shows scientific references for this particular method. If the product mentioned was used in multiple ways, the most commonly listed application was listed first. In general, we documented the use of various plants, smokes, personal hygiene products, household chemicals, softeners, diets, supplements, and other behaviors. Within this collection of mosquito repellent strategies, the most commonly listed method was topical application of various substrates including personal hygiene products, plant rubs, and household chemicals. The second most listed unconventional strategy was the use of smoke produced by incineration of various materials encompassing specific local plants, tobacco products, and candles. Following the burning strategy was ingestion of various food items and supplements. Using live plants as a spatial repellent was the fourth most commonly listed method we documented as unconventional. Many of these plants are known as sources for essential oils.

For some items we documented several ways of use. For example, garlic was used either by ingestion, applying to the skin, or creating a spray that was used as an outdoor spatial repellent. In some cases we documented conflicting attitudes toward certain interventions; for example both the ingestion, as well as the avoidance of ingestion of bananas as well as alcohol were listed as mosquito-avoidance strategies.

One of the most reoccurring responses was the use of dryer sheets. Over 200 participants have used dryer sheets of some sort as a repellent device. Not listed as frequently as dryer sheets but having participants from a diversity of regions mention it, were products of the Neem tree (*Azadirachta indica (Jussieu)*) and coffee. Neem products were used by either burning or topically and their use was stated by people from Brazil, USA, India, Nigeria, Eritrea, and Bangladesh. Coffee was listed as either being burned or used grounded on lawns or as a larvicide. Coffee was listed by participants that resided in Greece, South Africa, Brazil, United Kingdom, Canada, or the United States. Burning sage and planting and/or topical application of catnip were listed only by respondents currently residing in the US.

Discussion
==========

The data that we collected from this survey were acquired with the intent to find unconventional methods of mosquito control or repellency. We were able to identify 167 different methods.

Unconventional mosquito control methods
---------------------------------------

Some of the unconventional methods reported include *Aloe vera* (L.) and grapefruit, both of which have been previously studied. *Aloe vera* (L.) in combination with bio-control agent *B. sphaericus* has shown strong larvicidal effects against *A. aegypti (L.) larvae* ([@ref-111]). Grapefruit oil was tested as a repellent against the adult rice weevil, *Sitophilus oryzae (L.)* ([@ref-130]). Other methods warrant efficacy tests such as key lime, sugar consumption, and iron pills. Many of these unconventional methods can be further analyzed in order to identify the chemical component(s) that make them a repellent such as analyzing the chemical ingredients in specific toothpastes or Windex for their repellency effects.

Many of our respondents used DEET and citronella candles which is interesting because DEET is a very effective mosquito repellent while citronella candles are not ([@ref-98]; [@ref-99]). These popular methods could be used as controls in future studies. Picaridin and other commercial insect repellent products were mentioned but not as often as DEET and citronella.

The participants listed many different methods which were used at varying degrees in different regions. This may be due to the regional availability of certain mosquito repellent products or regional preferences for a certain method. It was unexpected to find a high number of participants from North America listing bed nets as a method that they've used. Interestingly, many of the North American bed nets users noted that they used them abroad.

Limitations of this study
-------------------------

Despite the fact that the survey was available in three different languages---English, Spanish, and Portuguese---the overwhelming numbers of answers were received from English-speaking survey respondents. A higher percentage---around 75%---of the survey respondents held some sort of academic degree (associates, bachelors, or graduate) ([Fig. 1](#fig-1){ref-type="fig"}). Also, we received a total of 5,209 responses with 3,645 of those responses from people currently residing in the United States. Therefore, our respondent pool was strongly biased towards English-speaking academics residing in the US (see [Supplemental Information 3](#supp-3){ref-type="supplementary-material"}). This suggests that we were unable to successfully plant "community-based seeds" both in the US and other countries in which the survey would be shared outside the academic community. The high number of female participants in this survey study could indicate that the topic of mosquito control appeals more to females than to males. An alternative explanation is that females are more likely to respond to online surveys in general which is supported by other studies like the one done by [@ref-104], where both paper and online surveys were more heavily answered by females than males.

Challenges and future directions
--------------------------------

Survey research presents some challenges for fully understanding how alternative repellents are used ([@ref-69]). Our survey responses tended to include ingredients rather than practices. Some responses may have left out specific actions or ingredients that respondents did not consider important. Future research may further explore these uses through collaboration with anthropologists and other field researchers who can observe and document actual practices as well as interview key informants with particular expertise in these alternative practices, including traditional healers and community elders. The intent of this study was to identify potential affordable, accessible, and culturally relevant mosquito control practices that can be made widely available to the public. However, one ethical issue that will need to be addressed in the future research is the protection of traditional knowledge and the potential for exploitation of that knowledge for commercial gain ([@ref-87]).

Availability, choice, use, and effectiveness of repellents and other mosquito avoidance strategies are also important variables for mathematical models predicting mosquito-borne disease dynamics. The concept of 'One Heath' integrates human, animal and environmental health. This multidisciplinary approach is relevant for veterinarians, ecologists, biologists, and others to understand and predict the spread of disease among people, animals, and within the environment ([@ref-37]). One Health approaches will benefit from solid knowledge on local repellent use, and its efficacy. Thus, knowing how different people in different regions defend themselves against mosquitos, and knowing the efficacy of these methods, can be combined with other data to contribute to disease outbreak predictions ([@ref-18]).

In conclusion, we identified several understudied mosquito repellent methods that may or may not be more effective and practical across diverse global settings. In many cases the efficacy of these methods has not been evaluated in scientific experiments. This study offers opportunities for further research into unconventional mosquito repellent methods to determine their effectiveness. Those that prove to be effective may be taken up more quickly by populations at risk for contracting mosquito-borne diseases because local populations may have better access to them and they may fit better into the context of people's daily lives.

Supplemental Information
========================

10.7717/peerj.5151/supp-1

###### Survey questions

###### 

Click here for additional data file.

10.7717/peerj.5151/supp-2

###### Raw data

This file contains the individual answers of the survey participants.

###### 

Click here for additional data file.

10.7717/peerj.5151/supp-3

###### Geographic distribution of all survey responses

This file shows the number of responses from all the countries from which there were responses.

###### 

Click here for additional data file.

The authors would like to thank all participants of their survey study for volunteering their time to fill out the survey and sharing their experiences. The authors would like to thank Ms. Alora Garibay for her help conducting the survey.

Additional Information and Declarations
=======================================

The authors declare there are no competing interests.

[Emily Lucille Moore](#author-1){ref-type="contrib"} performed the experiments, analyzed the data, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.

[Mary Alice Scott](#author-2){ref-type="contrib"} conceived and designed the experiments, performed the experiments, contributed reagents/materials/analysis tools, authored or reviewed drafts of the paper, approved the final draft.

[Stacy Deadra Rodriguez](#author-3){ref-type="contrib"} conceived and designed the experiments, performed the experiments, analyzed the data, authored or reviewed drafts of the paper, approved the final draft.

[Soumi Mitra](#author-4){ref-type="contrib"}, [Julia Vulcan](#author-5){ref-type="contrib"}, [Joel Javierla Cordova](#author-6){ref-type="contrib"}, [Hae-Na Chung](#author-7){ref-type="contrib"} and [Kristina Kay Gonzales](#author-9){ref-type="contrib"} performed the experiments, approved the final draft.

[Debora Linhares Lino de Souza](#author-8){ref-type="contrib"} performed the experiments, approved the final draft, translated the survey into Portuguese.

[Immo Alex Hansen](#author-10){ref-type="contrib"} conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, authored or reviewed drafts of the paper, approved the final draft.

The following information was supplied relating to ethical approvals (i.e., approving body and any reference numbers):

The study was approved by the NMSU Institutional Review Board (IRB \#15378).

The following information was supplied regarding data availability:

The raw data are provided in the [Supplemental Files](#supplemental-information){ref-type="supplementary-material"}.
