**Using Semiochemicals for Coleopterean Pests in Sustainable Plant Protection**

Maria Pojar-Fenesan and Ana Balea

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/64278

#### **Abstract**

Since the early twentieth century, chemical industry provides farmers large amounts of synthetic chemicals used as fertilizers and pest control products. Agriculture became intensive and the crop yields and the profit increased dramatically. Tons of toxic material for crop protection and fertilization were scattered through the gardens, fields, and orchards. But all these chemicals affect the environment, with serious negative consequences for humanity, today and tomorrow. Since 1959 until today many researchers observed and discussed the disadvantages of chemical methods of combating harmful insects and misapplied their disruptive action on cultivated ecosystems. Integrated pest management (IPM) is a process used to solve pest problems with minimum risks to people and environment. The objective of the researches presented in this chapter is to obtain and testing "*semio*chemicals"—pheromones, involved in intraspecific communication, into environmentally compatible strategies, to reduce pest populations under economic damage thresholds. Insect that are monitored and mass trapped in proposed IPM strategies are potato pest, Colorado potato beetle, *Lepidoptera decemlineata* Say (Coleoptera, Chrisomelidae); corn pests, West Corn Rootworm *Diabrotica virgifera virgifera* (Coleoptera, Chrisomelidae); and sixspined bark beetle *Pityogenes chalcographus* (Coleoptera, Scolitydae) pest in coniferous forests.

**Keywords:** semiochemicals, sexual, aggregation pheromones, kairomones, control, pest, Coleoptera, Colorado potato beetle (*Leptinotarsa decemlineata* SAY), western corn rootworm (*Diabrotica virgifera virgifera*), bark beetle, *Pityogenes chalcographus*

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

## **1. Introduction**

The care forthe next generations involves the resources protection, keeping soil, air, and waters clean. In agriculture, for a sustainable future, scientists and farmers must develop the environ‐ mentally friendly, economically viable, and socially responsible technologies [1]. Intensive agriculture uploads environment with pollutants such as pesticides, herbicides, and fertilizer. IntheEuropeanUnion, 38% of birdspecies and45% oflepidopteranspecies are threatened with extinction. It is true that the high populations of insects' pests could destroy the human food sources, and therefore need to be maintained under economic damage level, but each organ‐ ism has its role in the ecosystem to which it belongs.

The concept of integrated protection or integrated pest management (IPM) appeared at the end of the sixth decade of twentieth century by the works of Dutch researcher, Briejer [2] and Americans: Smith and Hagen [3] and Stern and van den Bosch [4]. The disadvantages of chemical methods of combating harmful insects and misapplied their disruptive action on cultivated ecosystems were discussed recently by Gill and Garg [5].

Modern ecofriendly crop protection strategies are discussed in symposiums organized by Food and Agriculture Organization of the United Nations (FAO) and IOBC/WPRS (Interna‐ tional Organization for Biological and Integrated Control of Noxious Animals and Plants/West Regional Paleartic Section). According to the FAO, IPM means considering all available pest control techniques and other measures that reduce the development of pest populations, with minimum risks to human health and the environment.

Development of pest management alternatives based on mediators' chemicals has been necessitated by the loss of traditional pesticides, insect pest resistance, pest resurgences, and secondary pest outbreaks often due to the effect of pesticides on all environments [5].

Semiochemicals, defined as behavior-modifying chemicals, are volatile organic compounds that transmit chemical messages, "words" in organism "language" and are used by insects for intra- and interspecies communication. The term "*semio*chemical" derived from the Greek word "semeon," which means "sign" or "signal" [6]. Insects detect volatiles semiochemicals directly from the air with olfactory receptors located in sensilla hairs on the antennae and the effect is a change in insect behavior. Semiochemicals can be classified as pheromones or allelochemicals based on how they are used and who benefits [7].

The intraspecific communication language have as "words" volatile signals, so called phero‐ mones , emitted by an organism that produces on the receptors of the same species a behavioral change. The term "pheromone" is derived from the Greek words "pherein" (to carry) and "hormone" (to stimulate), and was introduced by Karlson and Butenandt [8]. Based on their effect, pheromones categories are as follows:

**•** Aggregation pheromones: signaling an important place for the life, e.g., where insects' species could find the "food" or could lay eggs.

**1. Introduction**

are the pollinators such as honeybees.

The care forthe next generations involves the resources protection, keeping soil, air, and waters clean. In agriculture, for a sustainable future, scientists and farmers must develop the environ‐ mentally friendly, economically viable, and socially responsible technologies [1]. Intensive agriculture uploads environment with pollutants such as pesticides, herbicides, and fertilizer. IntheEuropeanUnion, 38% of birdspecies and45% oflepidopteranspecies are threatened with extinction. It is true that the high populations of insects' pests could destroy the human food sources, and therefore need to be maintained under economic damage level, but each organ‐ ism has its role in the ecosystem to which it belongs. The pesticides kill not only harmful insects butalsobeneficialorganisms,andthus theecosystemequilibriumismodified.Themostaffected

The concept of integrated protection or integrated pest management (IPM) appeared at the end of the sixth decade of twentieth century by the works of Dutch researcher, Briejer [2] and Americans: Smith and Hagen [3] and Stern and van den Bosch [4]. The disadvantages of chemical methods of combating harmful insects and misapplied their disruptive action on

Modern ecofriendly crop protection strategies are discussed in symposiums organized by Food and Agriculture Organization of the United Nations (FAO) and IOBC/WPRS (Interna‐ tional Organization for Biological and Integrated Control of Noxious Animals and Plants/West Regional Paleartic Section). According to the FAO, IPM means considering all available pest control techniques and other measures that reduce the development of pest populations, with

Development of pest management alternatives based on mediators' chemicals has been necessitated by the loss of traditional pesticides, insect pest resistance, pest resurgences, and

Semiochemicals, defined as behavior-modifying chemicals, are volatile organic compounds that transmit chemical messages, "words" in organism "language" and are used by insects for intra- and interspecies communication. The term "*semio*chemical" derived from the Greek word "semeon," which means "sign" or "signal" [6]. Insects detect volatiles semiochemicals directly from the air with olfactory receptors located in sensilla hairs on the antennae and the effect is a change in insect behavior. Semiochemicals can be classified as pheromones or

The intraspecific communication language have as "words" volatile signals, so called phero‐ mones , emitted by an organism that produces on the receptors of the same species a behavioral change. The term "pheromone" is derived from the Greek words "pherein" (to carry) and "hormone" (to stimulate), and was introduced by Karlson and Butenandt [8]. Based on their

**•** Aggregation pheromones: signaling an important place for the life, e.g., where insects'

secondary pest outbreaks often due to the effect of pesticides on all environments [5].

cultivated ecosystems were discussed recently by Gill and Garg [5].

allelochemicals based on how they are used and who benefits [7].

effect, pheromones categories are as follows:

species could find the "food" or could lay eggs.

minimum risks to human health and the environment.

130 Integrated Pest Management (IPM): Environmentally Sound Pest Management

The allelochemicals are classified as allomones, kairomones, or synomones [7]. Allomones are a class of compounds that benefit the producer, but not the receiver. Allomones are often used for defense, such as toxic insect secretions. Predators also use allomones to lure prey. Kairo‐ mones are a class of compounds that are advantageous for the receiver. Kairomones are the volatiles emitted by plants that benefit many predators by guiding them to prey or potential host insects.

Synomones ("with" or "together") are compounds that are beneficial to both the receiver and the sender such as volatiles emitted by flowers that attract bees for pollination.

The practical goal of semiochemical research is to develop techniques and methods for insects' pest control. Semiochemical research is placed in Pasteur's Quadrant of the Stokes model. It is based on the research in fine synthetic organic chemistry, but the final goal is still to develop solutions for agricultural problems, insects' pest population control, through applied research in the experimental field.

Since 1880s scientists used female insects to lure males into traps. Since the 1950s up until today, more than 3000 semiochemicals connected to the chemical communication of insects have been identified. Research on semiochemicals involves continued molecular mapping, synthesis, and studies of biosynthesis. Biologist and entomologist try to understand the neurophysiological sensory functions of insects and how hormonal regulation in insects affects pheromone biosynthesis and release.

Synthetic pheromones represent a new breeding prevention method for crop pest control. In sustainable agriculture using pheromones to control pests could drastically reduce the use of pesticides. The idea is to use an artificially synthesized scent, synthetic pheromones, to "attract and kill" into a trap the pests or to disrupt mating communication between male and female pests, thus preventing them from mating and lowering the population density of the next generation of the pests. These pheromones are specific and selective, have no effect on beneficial insects, such as pests' natural enemies or on other living organisms. Synthetic pheromones mimic the natural pheromones. Fascinating and somehow ironic is that the substances involved in perpetuation of the insects species can be used to control insect pest.

"Pheromonists," chemist researchers' team from "Raluca Ripan" Institute for Research in Chemistry Cluj – Napoca, Romania, is working to develop a variety of organic synthetic insects' pheromones and with multidisciplinary teams, biologists, entomologists, agronomists as partners in projects, develop new IPM friendly environmental techniques and technologies for insects' pest control.

Synthesis of pheromones and proposed IPM environmentally compatible strategies as monitoring or mass trapping of some coleopterean species (beetles), with the aim to reduce pest populations under economic damage thresholds are presented below.

The overall objective of research presented in this chapter is to find a technique using phero‐ mones for protect : (1) maize crop against the West Corn Rootworm (WCR), *Diabrotica virgifera virgifera* LeConte (Coleoptera, Chrisomelidae); (2) potato crops against Colorado potato beetle (CPB), *Lepidoptera decemlineata* Say (Coleoptera, Chrisomelidae); (3) coniferous forests against six-spined spruce bark beetle, *Pityogenes chalcographus* (Coleoptera, Scolytidae).

## **2. Colorado potato beetle aggregation pheromones in IPM techniques for potato plant protection**

## **2.1. Chemical ecology of Colorado potato beetle**

The CPB, *Leptinotarsa decemlineata* (Say), Coleoptera, Chrisomelidae, native from Mexico, identified as major pest of potato plants first time in America in 1824, arrived in Europe in 1922, via cargo ships during World War I and subsequently colonizing all of Europe except for the British Isles and Scandinavia. Then, CPB continued to expand into eastern Europe and then central Asia and western China [9].

CPB (*L. decemlineata*) attacks potatoes (*Solanum tuberosum* L.) and various other cultivated crops such as tomatoes (*Solanum lycopersicum*) and aubergines (*Solanum melongena*). It also attacks wild solanaceous plants, which occur widely and can act as a reservoir for infestation. The adults feed on the tubers of host plants in addition to the leaves, stems, and growing points [10, 11] (**Figure 1**). Both adults and larvae feed on foliage and may skeletonize the crop.

**Figure 1.** *Leptinotarsa decemlineata* (Say) adult on potato leaves (own photo on experimental plots).

CPB overwinter in the soil as an adult. The beetles become active in the spring. Females lay 800 of orange colored eggs in groups of two or several dozens for a period of 4–5 weeks. Larvae hatch after 4–9 days. Larval stage lasts 2–3 weeks and then the larvae hide in the ground. During their complete larval stage (3–4 weeks), CPB larvae consume approximately 40 cm2 of potato leaves while adults can eat up to 10 cm2 /day [12]. It is well known in Europe, where the CPB population increased dramatically during and immediately following World War II and spread eastward.

Insecticides are currently the main method of beetle control on commercial farms. However, many chemicals are often unsuccessful when used against this pest because of the beetle's ability to rapidly develop insecticide resistance. The Colorado potato beetle has developed resistance to all major insecticide classes, although not every population is resistant to every chemical. The secret of Colorado potato beetle's success as a pest is its diverse and flexible life history coupled with a remarkable adaptability.

Now because of the inevitable decline of effective insecticide treatments, research should focus even more on the development of new control methods and approaches. Some methods such as cultivating GM plants are not seen positively by consumers, and farmers have abandoned them due to lack of buyers [13]. Researches for better understanding of insect's biology and lifestyle could permit entomologists and chemists to devise new control techniques.

The use of semiochemical attractants to improve insecticide treatments should be considered as an innovative approach of CPB management. Chewing insects are indeed more sensitive to volatile organic compounds (VOCs) released by their host plants because the damage they induce in plant tissues increases the release of these compounds [14].

It is necessary but very difficult to find the cocktail of natural odors within which the quanti‐ tative proportion of each compound is as close as possible to that of the naturally emitted blend [15]. The challenge consists in finding the appropriate molecules and their ratio, instead of trying to include as many compounds in the mixture as possible [14].

Researchers from Université de Liège and from ARS-USDA Beltsville, Maryland, USA review alternative strategies to control CPB populations [16]:

Synthesis of pheromones and proposed IPM environmentally compatible strategies as monitoring or mass trapping of some coleopterean species (beetles), with the aim to reduce

The overall objective of research presented in this chapter is to find a technique using phero‐ mones for protect : (1) maize crop against the West Corn Rootworm (WCR), *Diabrotica virgifera virgifera* LeConte (Coleoptera, Chrisomelidae); (2) potato crops against Colorado potato beetle (CPB), *Lepidoptera decemlineata* Say (Coleoptera, Chrisomelidae); (3) coniferous forests against

**2. Colorado potato beetle aggregation pheromones in IPM techniques for**

The CPB, *Leptinotarsa decemlineata* (Say), Coleoptera, Chrisomelidae, native from Mexico, identified as major pest of potato plants first time in America in 1824, arrived in Europe in 1922, via cargo ships during World War I and subsequently colonizing all of Europe except for the British Isles and Scandinavia. Then, CPB continued to expand into eastern Europe and

CPB (*L. decemlineata*) attacks potatoes (*Solanum tuberosum* L.) and various other cultivated crops such as tomatoes (*Solanum lycopersicum*) and aubergines (*Solanum melongena*). It also attacks wild solanaceous plants, which occur widely and can act as a reservoir for infestation. The adults feed on the tubers of host plants in addition to the leaves, stems, and growing points [10,

11] (**Figure 1**). Both adults and larvae feed on foliage and may skeletonize the crop.

**Figure 1.** *Leptinotarsa decemlineata* (Say) adult on potato leaves (own photo on experimental plots).

pest populations under economic damage thresholds are presented below.

132 Integrated Pest Management (IPM): Environmentally Sound Pest Management

six-spined spruce bark beetle, *Pityogenes chalcographus* (Coleoptera, Scolytidae).

**2.1. Chemical ecology of Colorado potato beetle**

**potato plant protection**

then central Asia and western China [9].

**•** the potato plant recognizes the presence of CPB through chemical signals. By genetic manipulations increase the natural capacity of the plant to trigger defense mechanisms [16].

## **2.2. Experimental research using synthetically CPB aggregation pheromones**

Our research is related to biotechnology that uses "chemical messengers" sending or receiving information for pest control in potato crops. Such "chemical mediators," which induce a certain behavior, are aggregation pheromones—intraspecific messengers and kairomones—interspe‐ cific messengers—chemical signals emitted by the host plants.A male-produced aggregation pheromone was identified for the Colorado potato beetle, *L. decemlineata* (Say) in 2002 by Dickens et al. [17] (**Figure 2**).

**Figure 2.** (*S*)-3,7-Dimethyl-2-oxo-6-octene-1,3-diol, aggregation pheromone of CPB [(*S*)-CPB].

The biological effect of (*S*)-CPB was first evaluated in a Y-olfactometer on male and female CPB, both of which were highly attracted. The (*R*)-enantiomer and the racemic mixture were not attractive [17]. CPB larvae also seem capable of perceiving the aggregation pheromone produced by adults, but further studies are needed to characterize larval behavior [18].

#### *2.2.1. Synthesis of CPB aggregation pheromone*

The synthetized (*S*)-CPB by route presented below (**Figures 3** and **4**) was analyzed and used in the field tests with extracts from potato plants (leaves) contain substances which function as kairmones.

**Figure 3.** The way to prepare in ICCRR laboratory synthetic pheromone (*S*)-CPB.

behavior, are aggregation pheromones—intraspecific messengers and kairomones—interspe‐ cific messengers—chemical signals emitted by the host plants.A male-produced aggregation pheromone was identified for the Colorado potato beetle, *L. decemlineata* (Say) in 2002 by

The biological effect of (*S*)-CPB was first evaluated in a Y-olfactometer on male and female CPB, both of which were highly attracted. The (*R*)-enantiomer and the racemic mixture were not attractive [17]. CPB larvae also seem capable of perceiving the aggregation pheromone produced by adults, but further studies are needed to characterize larval behavior [18].

The synthetized (*S*)-CPB by route presented below (**Figures 3** and **4**) was analyzed and used in the field tests with extracts from potato plants (leaves) contain substances which function

**Figure 2.** (*S*)-3,7-Dimethyl-2-oxo-6-octene-1,3-diol, aggregation pheromone of CPB [(*S*)-CPB].

**Figure 3.** The way to prepare in ICCRR laboratory synthetic pheromone (*S*)-CPB.

*2.2.1. Synthesis of CPB aggregation pheromone*

as kairmones.

Dickens et al. [17] (**Figure 2**).

134 Integrated Pest Management (IPM): Environmentally Sound Pest Management

**Figure 4.** (EI) GC-MS analysis (Hewlett-Packard 5972 GC-MSD, capillary column HP-5MS (30 m × 0.25 mm × 0.25 μm) synthons and *S*-(CPB) aggregation pheromone.

#### *2.2.2. Testing S-CPB attractivity for L. decemlineata: field experiments*

Field experiments were conducted in three different locations from Transylvania area, Romania: Research-Development for Potato Station Targu-Secuiesc (**Figure 5**), University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, USAMV Research Station situated in Jucu-Cluj county, and Agricole Research-Development Station Turda (**Figure 6**).

**Figure 5.** Experimental plots from RDPS Targu-Secuiesc (own photo on experimental plots).

**Figure 6.** Adult CPB migration dynamic on potato plants in two plots (blank and experimental) ARDS Turda, Cluj, România.

 Baits were placed on potato plants, close to the pitfall trap, "attract and kill" technique. The pheromonal baits are 0, 1 g (*S)-3,7-dimethyl-2-oxo-6-octen-1,3-ol* and *2-phenyl-ethan-1-ol* [(*S*)-CPB] impregnated on rubber stopper (**Figure 7**).

Experiments and observations from Research Development for Potato Station (RDPS) Targu-Secuiesc are presented below.

The experimental plots were artificially colonized with CPB. Each plot have 28 rows spacing 0.75 m and a distance between plants 0.30 m. Thirty CPB adults, collected from elsewhere, were placed on potato plants row nos. 13 and 14. The pitfall with kairomone (potato lives extract) and baits with pheromones are located on row no. 4 from the edge of the plot. In days 1, 3, 5, 7, and 10, CPB migration from row no. 14 ("start point") to row no. 4 "finish point" was observed. After day 10, 13 CPB adults were found on row no. 4, area with pheromonal baits.

**Figure 7.** Pheromonal baits and pitfall traps with kairomones.

**Figure 5.** Experimental plots from RDPS Targu-Secuiesc (own photo on experimental plots).

136 Integrated Pest Management (IPM): Environmentally Sound Pest Management

**Figure 6.** Adult CPB migration dynamic on potato plants in two plots (blank and experimental) ARDS Turda, Cluj,

Considering aggregation pheromone as attractant we try to get out the pest from potato field attract CPB a pitfall trap, a container with potato leaves alcoholic extract. Baits were placed on potato plants, close to the pitfall trap, "attract and kill" technique. The pheromonal baits are 0, 1 g (*S)-3,7-dimethyl-2-oxo-6-octen-1,3-ol* and *2-phenyl-ethan-1-ol* [(*S*)-CPB] impregnated on

Experiments and observations from Research Development for Potato Station (RDPS) Targu-

The experimental plots were artificially colonized with CPB. Each plot have 28 rows spacing 0.75 m and a distance between plants 0.30 m. Thirty CPB adults, collected from elsewhere, were placed on potato plants row nos. 13 and 14. The pitfall with kairomone (potato lives

România.

rubber stopper (**Figure 7**).

Secuiesc are presented below.

The experiment conclusions are as follows: aggregation pheromone bait attracts beetle, but CPB did not reach into the trap, pitfall with kairomone is not efficient, probably the trap design is inadequate, to capture CPB must be used another type of trap such as a small wing trap (**Figure 20**).

## *2.2.3. Field experiments in USAMV Research Station situated in Jucu-Cluj county*

In the field, the Colorado beetles were observed on potato plants. The experimental plots were located at 200 m distance from the blank plot. Pitfall traps and pheromone baits were placed in 40 m2 area each, the experimental plot was at 20 m distance. A significantly number of CPB adults were identified by counting, crowded around traps, relative to the place where no pheromone traps were placed. The adults were aggregate, during egg lying, around traps in an area of about 18 m2 , with a circle radius of 2.5 m. This result shows that the behavior induced by this pheromone attract the beetles into the area, but these beetles do not try to touch the pheromone source, as occurs if the attractants are the sexual pheromone. Noteworthy, there was a higher concentration of adults in plots' edges and especially an affinity for plants infected with viruses.

## *2.2.4. Experimental research in the field of Agricola Research-Development Station Turda*

At this location, the traps were placed on 0.8 ha potato plants' experimental plot, located at 20 m distance between them. Data placement of traps were made from June 5, following the evolution of both generations of the pest. Observations were made from June 10, and continued until September. Dynamic observation was performed each 5 days. Besides the abundance of adults, an observation on attack frequency (%) in each variant (experimental and blank) was performed. In 2008, the abundance of adults was lower compared to previous years, around 80 adults in the period between June 10 and late July, untreated version. In the experimental lot, the abundance was 19 adults in the mentioned period in the six traps.

Because the abundance of adults was lower this year, the frequency of attacks was insignificant. Thus, in the untreated lot, the attack rate was of about 40% and in the experimental lot it was 10%.

Pitfall with (*S*)-CPB as bait-attractant compositions was placed in the potato plant field. The effect of aggregation pheromone has been a migration, colonization beetles of both sexes, for "frontier" where they were installed traps and dispensers. In all the experiments, in the pitfall were found other insects of the same order as CPB, and many CPB adults were found around, but not in trap. The above results show a good aggregation capacity of the pheromone, but the traps still have to be perfection, because not all pests attracted by the pheromone are also captured.

By capturing their pest population, the results show a fall below economic threshold without affecting the potato crop or ecosystem.

It is necessary to continue to explore alternative control methods using semiochemicals and studying to better understand behaviors generated by these semiochemicals. The chemical ecology of CPB is not yet completely understood and this incomplete knowledge makes semiochemical-based approaches inefficient when compared to traditional insecticide treatments. The management strategies for CPB control must be flexible and adaptable to everchanging circumstances [16].

## **3. Pheromones for maize crop protection**

## **3.1. Chemical ecology of western corn rootworm (***D. virgifera virgifera* **LeConte)**

*Pest description*: Class: Insect; Order: Coleoptera; Family: Chrisomelidae; Genus: Diabrotica.

Western corn rootworm (WCR) *D. virgifera virgifera* LeConte infests corn crops in North America and since 1992 has been reported in Europe [19]. In Romania, WCR was first reported in 1996 at Nadlac (Arad County), near the Hungarian border and this quarantine pest migrates eastward.

The WCR beetles are about 5–7 mm long. Adults have a dark head, a yellow pronotum, and a yellow abdomen. The legs covered with short hairs are dark brown in males and brown in females. Male's body color is greenish-yellow and female's body has a yellow color [20] (**Figure 8**).

*2.2.4. Experimental research in the field of Agricola Research-Development Station Turda*

138 Integrated Pest Management (IPM): Environmentally Sound Pest Management

lot, the abundance was 19 adults in the mentioned period in the six traps.

10%.

captured.

eastward.

affecting the potato crop or ecosystem.

**3. Pheromones for maize crop protection**

changing circumstances [16].

At this location, the traps were placed on 0.8 ha potato plants' experimental plot, located at 20 m distance between them. Data placement of traps were made from June 5, following the evolution of both generations of the pest. Observations were made from June 10, and continued until September. Dynamic observation was performed each 5 days. Besides the abundance of adults, an observation on attack frequency (%) in each variant (experimental and blank) was performed. In 2008, the abundance of adults was lower compared to previous years, around 80 adults in the period between June 10 and late July, untreated version. In the experimental

Because the abundance of adults was lower this year, the frequency of attacks was insignificant. Thus, in the untreated lot, the attack rate was of about 40% and in the experimental lot it was

Pitfall with (*S*)-CPB as bait-attractant compositions was placed in the potato plant field. The effect of aggregation pheromone has been a migration, colonization beetles of both sexes, for "frontier" where they were installed traps and dispensers. In all the experiments, in the pitfall were found other insects of the same order as CPB, and many CPB adults were found around, but not in trap. The above results show a good aggregation capacity of the pheromone, but the traps still have to be perfection, because not all pests attracted by the pheromone are also

By capturing their pest population, the results show a fall below economic threshold without

It is necessary to continue to explore alternative control methods using semiochemicals and studying to better understand behaviors generated by these semiochemicals. The chemical ecology of CPB is not yet completely understood and this incomplete knowledge makes semiochemical-based approaches inefficient when compared to traditional insecticide treatments. The management strategies for CPB control must be flexible and adaptable to ever-

**3.1. Chemical ecology of western corn rootworm (***D. virgifera virgifera* **LeConte)**

*Pest description*: Class: Insect; Order: Coleoptera; Family: Chrisomelidae; Genus: Diabrotica.

Western corn rootworm (WCR) *D. virgifera virgifera* LeConte infests corn crops in North America and since 1992 has been reported in Europe [19]. In Romania, WCR was first reported in 1996 at Nadlac (Arad County), near the Hungarian border and this quarantine pest migrates

The WCR beetles are about 5–7 mm long. Adults have a dark head, a yellow pronotum, and a yellow abdomen. The legs covered with short hairs are dark brown in males and brown in

**Figure 8.** WCR (Diabrotica virgifera virgifera LeConte) adult (own photo on experimental plots).

The main damage is caused by WCV larva which lives in the soil and feed the roots and the adults feeding damage on corn silk and the maize in the milk stage, sometime on maize leaves or other species of plants from the spontaneous flora, but the multiplication of this species is assured by the maize crop [21] WCR (cucurbits, bean). Adults lay eggs in the soil and WCR larvae become active in May, attacking the roots of corn plants in development by drilling the cortical parenchyma, create tunnels in the central vascular tissue, which lead to the fall of the plant in windy day.

Factors that influence the pest propagation are as follows:

*Soil*: With good physical, chemical, and biological properties, loose and rich in humus, slightly acidic or alkaline, moist on top, favoring the breeding. Sandy soil is unfavorable for larvae, especially for the young during drought.

*Climate*: Gentle winter, with snow, free of strong winds; moistly spring; high air temperature for adult activity (until 30°C), favors the breeding.

*Host plant*: Larvae can feed on 22 species of plants, but they prefer maize and soybean. *Human intervention*—early seeding, the high density of the maize plants, excess nitrogen fertilization, irrigation, all these technologies contribute to the pest breeding.

*Monitoring*: Pheromone traps and yellow sticky traps were used.

*Control*: From nonpollutant methods it can be mentioned: pheromone traps, color traps, autochthonous natural enemies, and biological product Spinosad 240 SC (based on filamen‐ tous bacteria *Saccharopolyspora spinosa*) [22].

In the establishing of the pest's control strategy, an important part it has the prognosis of its appearance, which is based on the number of adults/plant (sticky traps with sexual phero‐ mones baits), the number of larva and eggs/sample, the intensity of the caused damage to the silk of the corn cobs.

The reduction of the adult population is an important part in the reduction of the larva population of the next year and in the reduction of the damage to the cobs, which influences the production of beans and the quality of the seeds. It is recommended the control of adults, because their act by of destruction on the silk and implicitly compromise the pollination process when it is registered a density of more than 10 adults/plant at the commercial hybrids and five adults/plant at corn for seed [23].

## **3.2. Experimental research using synthetically sexual pheromone for WCR**

Sexual pheromone of the *D. virgifera virgifera* Le Conte was identified by Guss et al., from virgin females of the WCR as 8-methyl-2-decanol propanoate (1,7-dimethyl-nonan-1-yl propanoate) [24].

The way of synthesis proposed and carried out in "Raluca Ripan" Institute for Research in Chemistry Laboratory is described in **Figure 9** and have five stages [25]. On this way, the racemic mixture of the four enantiomers was obtained [26].

The reaction yields for each stage was >74% and the intermediary and reaction products were identified through GC-MS, IR, and NMR [26].

In the case of the 1,7-dimethyl-nonan-1-yl propanoate there are four optically active forms or four optical isomers afferent to the two asymmetric carbon atoms C1 and C7. The four isomers, respectively: 1*R*, 7*R*; 1*S*, 7*S*; 1*R*, 7*S*; 1*S*, 7*R*; form two pairs of enantiomers (the **A** pair: 1*R*, 7*R*; 1*S*, 7*S*, the B pair: 1*R*, 7*S*; 1*S*, 7*R*) The GC-MS analysis carried out this time with a chiral column separates two pairs of diastereoisomers without separating each isomer (**Figure 10**, **Figure 11**).

*Monitoring*: Pheromone traps and yellow sticky traps were used.

140 Integrated Pest Management (IPM): Environmentally Sound Pest Management

tous bacteria *Saccharopolyspora spinosa*) [22].

and five adults/plant at corn for seed [23].

silk of the corn cobs.

[24].

*Control*: From nonpollutant methods it can be mentioned: pheromone traps, color traps, autochthonous natural enemies, and biological product Spinosad 240 SC (based on filamen‐

In the establishing of the pest's control strategy, an important part it has the prognosis of its appearance, which is based on the number of adults/plant (sticky traps with sexual phero‐ mones baits), the number of larva and eggs/sample, the intensity of the caused damage to the

The reduction of the adult population is an important part in the reduction of the larva population of the next year and in the reduction of the damage to the cobs, which influences the production of beans and the quality of the seeds. It is recommended the control of adults, because their act by of destruction on the silk and implicitly compromise the pollination process when it is registered a density of more than 10 adults/plant at the commercial hybrids

Sexual pheromone of the *D. virgifera virgifera* Le Conte was identified by Guss et al., from virgin females of the WCR as 8-methyl-2-decanol propanoate (1,7-dimethyl-nonan-1-yl propanoate)

The way of synthesis proposed and carried out in "Raluca Ripan" Institute for Research in Chemistry Laboratory is described in **Figure 9** and have five stages [25]. On this way, the

The reaction yields for each stage was >74% and the intermediary and reaction products were

**3.2. Experimental research using synthetically sexual pheromone for WCR**

racemic mixture of the four enantiomers was obtained [26].

**Figure 9.** 1,7-Dimethyl-nonan-1-yl propanoate, WCR sexual pheromone synthesis.

identified through GC-MS, IR, and NMR [26].

**Figure 10.** GC analysis of the 1,7-dimethyl-nonan-1-yl propanoate (GC Hewlett-Packard 5972 GC-MSD, capillary col‐ umn HP-5MS (30 m × 0.25 mm × 0.25 μm).

**Figure 11.** (EI)-MS spectrum of the 1,7-dimethyl-nonan-1-yl propanoate: GC-MS: tr = 13.91 min; *m*/*z*: 171 (M+ −COEt), 154 (M+ −OCOEt), 136, 125, 112, 101, 97, 83, 74, 70, 57 (100%), 43.

In the WCR, adults monitoring tests were carried out in the fields of Agricole Research and Developments Station (ARDS) Turda-Cluj county, Romania, the baits with racemic mixture using sticky traps showed a good attractivity.

The data from the graphic confirm both the existence of the attack of *D. virgifera virgifera* in the corn culture at the Turda Station, and the efficiency of the Romanian pheromone in comparison with others type of traps (**Figure 12**).

**Figure 12.** The efficiency of the Romanian pheromone in comparison with the imported one.

In 2005, at ARDS Turda, WCR was monitoring in field conditions, in two crop rotations: beanwheat-corn and soy-wheat-corn, using sticky traps with bait sexual pheromones prepared in "Raluca Ripan" Institute for Research in Chemistry Cluj-Napoca.

The observations were carried out between July 12 and September 7, the number of WCR adults in this period being quite high: 921 WCR adults in the soy-wheat-corn crop rotation and 680 adults in the bean-wheat-corn crop rotation.

This pest can also develop in the soy culture, as shown in WCR adults numbers in the crop rotation with soy, as compared to the other one. The massive appearance of adults took place starting from the end of July and until the end of August, with a large number of adults in the second decade of August, when, in the traps with sexual pheromones were registered 100–248 adults/week.

The total number of adults of *D. virgifera virgifera* captured in the traps with pheromones, in the mentioned period, was of 1601 (**Figure 13**).

In Romania, start with July 1996, western corn rootworm (*D. virgifera virgifera*) was quarantine pest. In Transylvania, adults were monitored in the corn fields, e.g., 2002–2005 in ARDS Turda (**Figure 14**).

**Figure 14.** WCR pest "fly" dynamic in ARDS Turda fields (2002–2005).

**Figure 12.** The efficiency of the Romanian pheromone in comparison with the imported one.

"Raluca Ripan" Institute for Research in Chemistry Cluj-Napoca.

142 Integrated Pest Management (IPM): Environmentally Sound Pest Management

adults in the bean-wheat-corn crop rotation.

**Figure 13.** WCR males captured in two different crops.

adults/week.

In 2005, at ARDS Turda, WCR was monitoring in field conditions, in two crop rotations: beanwheat-corn and soy-wheat-corn, using sticky traps with bait sexual pheromones prepared in

The observations were carried out between July 12 and September 7, the number of WCR adults in this period being quite high: 921 WCR adults in the soy-wheat-corn crop rotation and 680

This pest can also develop in the soy culture, as shown in WCR adults numbers in the crop rotation with soy, as compared to the other one. The massive appearance of adults took place starting from the end of July and until the end of August, with a large number of adults in the second decade of August, when, in the traps with sexual pheromones were registered 100–248

As bait in sticky traps are 1,7-dimethyl-nonyl propanoate (WCR sexual pheromones) synthe‐ tized in "Raluca Ripan" Institute for Research in Chemistry (RRIRC) (**Figures 15** and **16**).

**Figure 15.**

**Figure 16.** RRIRC sticky traps (own photo on experimental plots).

#### **3.3. Recommended biotech corn crop protection using pheromone traps**

Together with other measures to reduce *D. virgifera virgifera* larval population (crop rotation, the seeding, and seed treatments), using synthetic sex pheromone traps is a recommended option for the pest management.

Traps used for western corn rootworm *Diabrotica virgifera virgifera* are placed on a stick in the ground or in more vigorous corn plant at the height of 1 m, usually 1–2 weeks before pre‐ sumptive appearance of the pest (in June).

Adults begin to emerge, usually in late June, when the corn plant already has silk (the beetle's favorite food). If used for monitoring, 9 traps/ha have to be installed at the edge of the maize lot. The traps are inspected twice a week when count the captured beetles and clean the trap by removing butterflies, insects or leaves that accidentally entered on the sticky surface. Sticky plate is replaced twice per month, pheromone bait once per month, and observations are made in 5–7 days. Depending on the number of adults captured, the chemical treatment is indicated or not. So, monitoring and treatments recommended are as follows:

The field tests show how important are traps with pheromonal baits for monitoring the appearance of WCR adults in crops and for decreased adult populations during mating season so that generations of larvae in the next year are reduced.

## **4. Aggregation pheromones used in pine forest protection**

**Figure 16.** RRIRC sticky traps (own photo on experimental plots).

144 Integrated Pest Management (IPM): Environmentally Sound Pest Management

option for the pest management.

sumptive appearance of the pest (in June).

**3.3. Recommended biotech corn crop protection using pheromone traps**

or not. So, monitoring and treatments recommended are as follows:

year), only ground treatment is insufficient.

corn for sowing, treatment is required for adults.

Together with other measures to reduce *D. virgifera virgifera* larval population (crop rotation, the seeding, and seed treatments), using synthetic sex pheromone traps is a recommended

Traps used for western corn rootworm *Diabrotica virgifera virgifera* are placed on a stick in the ground or in more vigorous corn plant at the height of 1 m, usually 1–2 weeks before pre‐

Adults begin to emerge, usually in late June, when the corn plant already has silk (the beetle's favorite food). If used for monitoring, 9 traps/ha have to be installed at the edge of the maize lot. The traps are inspected twice a week when count the captured beetles and clean the trap by removing butterflies, insects or leaves that accidentally entered on the sticky surface. Sticky plate is replaced twice per month, pheromone bait once per month, and observations are made in 5–7 days. Depending on the number of adults captured, the chemical treatment is indicated

**-** If the number of catches is 5–8 WCR adults/trap in next year. If corn is sown on the same plots, the roots will be attacked by larvae. It is necessary either seed treated with insecticide or treatment ground for larvae. Treatment with granular soil insecticide is done either when seeding or at first diggings. If there are larvae (i.e., eggs deposited in the previous

**-** If the number of capture is 10 adults/trap—corn for consumption or five adults/trap—

## **4.1. Chemical ecology of six-spined spruce bark beetles** *P. chalcographus* **L.**

*Pest description*: Class: insect; Order: Coleoptera; Family: Scolytidae; Genus: Pityogenes.

*P. chalcographus* infests Norway spruce [*Picea abies*], especially the younger trees or, in compe‐ tition with another bark beetles *Ips typographus*, the upper regions of older trees. Bark beetles (Coleoptera, Scolytidae) must compete for food and space in which to reproduce within the relatively thin phloem layer of their host tree [27]. *P. chalcographus* is rather small for bark beetles, being only 2 mm long and weighing 1.2 g, the color is dark brown almost black [28].

*Biology*: In the Nordic countries, *P. chalcographus* has a single generation in a year. Romania had two flights per year. The first flight was in April-June (76–94% from the flight on all growing season), the second flight was in July-August (6–24% from the flight on all growing season) [29].

*Damage*: Both sexes are aggregated through male pheromone released. The attracted males want to join the attack and secure an area for his and several female's young. The female deposits their eggs in galleries excavated in the vascular cambium and secondary phloem. The phloem layer is only about 2–4 mm thick and rich in nutrients; successful breeding is depend‐ ent on the death of these tissues. Larval galleries have a length of 2–4 cm, are dense, well printed on bark and wood weak [30]. Aggressive bark beetle species like *P. chalcographus* are associated with pathogenic blue stain fungi, which help them to overcome the defense reaction of the host tree. Some of the fungi in this group are pathogenic and may play an important role in the death of the tree by blocking water conduction [31] or indirectly by overstimulating tree defense mechanisms that may exhaust the host [32, 33].

*Host*: Norway spruce is the preferred but not the only host. Bark beetles belong to the family of ypids. Usually, these insects are attracted to and breed on trees felled or broken by wind, on trees affected by fire or sunstroke, on trees severely debilitated by drought or pollution, and the trees having lost defense capability. Most of the time, these beetles live under the bark of trees, feeding inner part of the bark, and leave this place just to seek new sources of food.

*Monitoring*: At the temperature of 16.8–17°C, beetles *P. chalcographus* become active and could be monitored [34].

*Control*: Pest control is carried out by pheromone traps. The use of pheromones by "mass trapping" technique is one of the few ways to protect the forest ecosystem.

## **4.2. Experimental research using synthetically aggregation pheromone for bark beetle** *P. chalcographus*

#### *4.2.1. Chemical synthesis of the main component*

The bark beetle *P. chalcographus* aggregation pheromone is a "cocktail" with four components: 2-ethyl-1,6-dioxaspiro-[4,4]-nonane (Chalcogran)—the main component [35] and secondary components: methyl-*E*2,*Z*4-decadienoate; α-pinene and ipsdienol.

The proposed synthesis *for 2-ethyl-1,6-dioxaspiro-*[4,4]*-nonanne* is represented in (**Figure 17**, **Figure 18**), it has four steps with 1,6-hexanediol as starting substance. It is an original reaction path except for the last stage, where the reaction conditions used by Cekovic and Bosnjak [36] at the cyclization of 1,7-nonanediol were modified [37, 38].

**Figure 17.** The reaction path which was proposed and carried out in laboratory.

**Figure 18.** The mass spectra of the main product of reaction: 2-ethyl-1,6-dioxaspiro-[4,4]-nonane (**1**).

The 2-ethyl-1,6-dioxaspiro-[4,4]-nonane (**1**), having two asymmetric centers, has two pairs of optical diastereoisomers: **A** (2*R*,5*S*-**1**; 2*R*,5R-**1**) and **B** (2*S*,5*S*-**1**; 2*S*,5*R*-**1**) (**Figure 19**). The natural pheromone contains the pair of diastereoisomers (2*S***,**5*R*)-**1**—biologically active and (2*S*,5*S*)-**1** —biologically inactive [39, 40].

**Figure 19.** Enantiomers and diastereomers for 2-ethyl-1,6-dioxaspiro-[4,4]-nonane.

All the four stereoisomers were obtained by synthesis and this racemic was tested.

#### *4.2.2. Field experiments*

**4.2. Experimental research using synthetically aggregation pheromone for bark beetle** *P.*

The bark beetle *P. chalcographus* aggregation pheromone is a "cocktail" with four components: 2-ethyl-1,6-dioxaspiro-[4,4]-nonane (Chalcogran)—the main component [35] and secondary

The proposed synthesis *for 2-ethyl-1,6-dioxaspiro-*[4,4]*-nonanne* is represented in (**Figure 17**, **Figure 18**), it has four steps with 1,6-hexanediol as starting substance. It is an original reaction path except for the last stage, where the reaction conditions used by Cekovic and Bosnjak [36]

*chalcographus*

*4.2.1. Chemical synthesis of the main component*

146 Integrated Pest Management (IPM): Environmentally Sound Pest Management

components: methyl-*E*2,*Z*4-decadienoate; α-pinene and ipsdienol.

at the cyclization of 1,7-nonanediol were modified [37, 38].

**Figure 17.** The reaction path which was proposed and carried out in laboratory.

**Figure 18.** The mass spectra of the main product of reaction: 2-ethyl-1,6-dioxaspiro-[4,4]-nonane (**1**).

The biological activity, respectively the efficiency of the Romanian pheromone baits is tested in comparison with other imported compound. All the tests were obtained in Brasov area (Romania) between 2001 and 2004 (**Tables 1** and **2**).

**Table 1.** Experimental results in Romanian forests, 2001–2004.

**Table 2.** Experimental results , Romanian forests, 2002–2003.

**Figure 20.** *Pityogenes chalcographus* wing trap installed in forest (own photo on experimental plots).

#### *4.2.3. Conclusions*

(1) In 2001 and 2004, tests show the increased attractiveness of baits with the Romanian pheromone—Atrachalc, compared to another baits (import), irrespective of the type of trap used.

(2) In 2002 and 2003, the tests carried out with the Atrachalc baits and wing traps show in the same location different no captured beetles according to the period of time when the traps were placed and the observations were made. Besides the time factor, weather conditions or other elements from the ecosystem could influence catches

(3) 2009 comparative tests in Brasov area with different lures obtained higher level of the captured beetles using Atrachalc—Romanian baits. Wing traps with Atrachalc lure are recommended by experts for Romanian forests [41].

## **4.3. Recommended biotechnique:** *P. chalcographus* **"mass-trapping"**

For monitoring and control bark beetles, pheromone lures are placed in wing-type trap (**Figure 20**). The traps are placed at the forest edge at about 5 m in the case of old forests and about 15 m in the case of young forests. Between the traps, distance is 30–50 m. To a high infestation, 2–3 traps/ha are used and for low infested forest one trap/ha is used. Traps are installed in late April to late August usual on a tree already attacked by bark beetles. Phero‐ mone baits are replaced at no more than 6 weeks.

## **5. Conclusions**

**Year Location of the experiments**

2002 Gârcin

2003 Gârcin

(OS Săcele)

(OS Săcele)

*4.2.3. Conclusions*

used.

**The type of Trap**

**Table 2.** Experimental results , Romanian forests, 2002–2003.

**The type of bait**

148 Integrated Pest Management (IPM): Environmentally Sound Pest Management

Wing Atrachalc 5 21.05–28.07

Wing Atrachalc 3 19.05–1.07

**Figure 20.** *Pityogenes chalcographus* wing trap installed in forest (own photo on experimental plots).

other elements from the ecosystem could influence catches

recommended by experts for Romanian forests [41].

(1) In 2001 and 2004, tests show the increased attractiveness of baits with the Romanian pheromone—Atrachalc, compared to another baits (import), irrespective of the type of trap

(2) In 2002 and 2003, the tests carried out with the Atrachalc baits and wing traps show in the same location different no captured beetles according to the period of time when the traps were placed and the observations were made. Besides the time factor, weather conditions or

(3) 2009 comparative tests in Brasov area with different lures obtained higher level of the captured beetles using Atrachalc—Romanian baits. Wing traps with Atrachalc lure are

**No. of traps**

**The period and duration of observation (days)**

(68 days)

(43 days)

**The number of captures**

35.531 104.5

35.679 276.5

**The intensity of the attraction**

> A changing climate with higher growing season temperatures and altered rainfall patterns make control of native and invasive insects an increasingly urgent challenge. Treatments with increasing amounts of insecticides are not a solution; it is time to intensify interdisciplinary research on semiochemicals based on a scientifically sound understanding of pest biology to provide the urgently needed and cost-effective technical solutions for sustainable insect management worldwide [42].

> Using pheromones in order to protect the above-mentioned crops is first of all an ecofriendly method, avoiding these ways the overloading environment with insecticides. The ecosystem remains unaffected due to the high selectivity and specificity of the semiochemicals. Sex pheromone baits in sticky traps attract insects very selective, only the species that emitted for mating the natural sex pheromons.

> This method does not affect another components of the ecosystem such as soil, air, water, or animals. The insect pest population falls below the economic damage threshold. In the case of the bark beetle is the most efficient combating method, because this pest lives (acts) underneath the bark, a place where insecticides cannot be applied.

> The same happen in the case of WCR because it is very difficult to use pesticides in the maize crop. Because Colorado potato beetles develop rapidly resistance to insecticides using aggregation pheromone as bait in a proper trap could be a solution to control this pest.

> All studies and experimental reviews above-mentioned have enhanced knowledge of chemical communication in and highlight the potential of semiochemicals as a component of future integrated management strategies.

## **Acknowledgements**

The original researches were supported by PN II grants financed by MEN-ANCS CeEx— BIOTECH 116, INVENT 160, grant CNCSIS-MEN Romania. We thank Dr Felicia Muresanu— Agricola Research Development Station Turda, Prof. Dr Gavrila Morar—University of Agricultural Sciences and Veterinary Medicine Cluj, Dr Daniela Popa—Research-Develop‐ ment for Potato Station Targu-Secuiesc for testing in the fields ICCRR-synthetic Pheromones.

## **Author details**

Maria Pojar-Fenesan\* and Ana Balea

\*Address all correspondence to<EMAIL_ADDRESS>
Babes-Bolyai University, "Raluca Ripan" Institute for Research in Chemistry, Cluj-Napoca, Romania

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[1] Allen P, Dusen DV, Lundy J, Gliessman S. Expanding the definition of sustainable

[2] Briejer CJ. The growing resistance of insect to insecticides. Atlantic Naturalist.

[3] Smith RF, Hagen KS. Impact of commercial insecticide treatments. HILGARDIA.

[4] Stern VM, van den Bosch R. Field experiments on the effects of insecticides, HILGAR‐ DIA. Journal of Agricultural Science, California University. 1959;29(2):1–80

[5] Gill HK, Garg H. Pesticide: environmental impacts and management strategies. In: Solenski S, Larramenday ML, editors. Pesticides—Toxic Effects. Rijeka, Croatia: Intech;

[6] Edward M. Barrows,. Animal Behaviour Desk Reference: A Dictionary of Animal Behaviour, Ecology, and Evolution, 2rd ed., CRC Press; Boca Raton London, New York

[7] Norin T. Semiochemicals for insect pest management. Pure and Applied Chemistry.

[8] Karlson P, Butenandt A. Pheromones (ectohormones) in insects. Annual Review of

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[25] Pojar-Fenesan M, Pop L, Oprean I, Balea A. Synthesis of racemic 8-methyl-2-decyl propanoate, the sex pheromone of western corn rootworm *Diabrotica virgifera virgifera* LeConte (Cleoptera, Chrisomelidae). Revue Roumaine de Chimie. 2001;45(3):263–266.

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[31] Paine TD, Raffa KF, Harrington TC. Interactions among scolytid bark beetles, their associated fungi, and live host conifers. Annual Review of Entomology. 1997;42:176–

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## **Detergents and Soaps as Tools for IPM in Agriculture**

Tomislav Curkovic S.

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/64343

#### **Abstract**

This chapter presents extensive and updated knowledge from scientific and technical reports on the management of agriculture pests using detergents and soaps (D + S), with emphasis on their utility in integrated pest management (IPM) schemes. It includes a review on their environmental, ecological, and toxicological impacts, and their possibilities to become important tools for pest control, especially for those D + S having minimum risk, considering both current and newer products. The present knowledge of their modes of action on arthropods is addressed, revealing the need to better identify the mechanisms to optimize their use against crop pests. Their disadvantages are also analyzed, mainly the lack of residual effect and the potential toxicity to plants.  A comparison of the direct costs of the use of conventional pesticides versus D + S, achieving statistically similar levels of control, is discussed, and scenarios where detergents are competitive (representing lower costs) are presented. There is also a review of the type of com‐ pounds reported in the specific literature, which leads to highlight the opportunities to develop agriculture detergents and soaps suited to local agriculture needs. New findings on D + S as co-adjuvants for conventional and biological pesticides, and their potential utilization as safe postharvest treatments against pest, are also presented. Finally, the authorization for soaps and detergents is also discussed, highlighting the need for a joint effort (state agencies, producers, researchers, etc.), in order to increase the offer and the use of detergents and soaps, partially replacing conventional pesticides, to take advantage of their potential as sustainable pest management tools, particularly for IPM programs, but also for organic and conventional productive schemes.

**Keywords:** detergents, IPM, soaps, surfactants, sustainability, toxicity

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

## **1. Introduction**

## **1.1. Chemical control in integrated pest management (IPM) programs and detergents and soaps**

Integrated pest management is a strategy developed to control agricultural pests and, at the same time solve problems derived from the extensive and intensive implementation of chemical control in conventional agriculture, where broad spectrum, specific action site, and persistent pesticides are used. Compounds with this profile have been called "conventional pesticides" and are responsible for causing resistance in pest populations, destruction of beneficial arthropods, and presence of pesticide residues in foods, soils, water, and air [1]. In order to obtain an economic, environmental, and ecologically sustainable food production, IPM encompasses several components, including cultural, biological, and chemical control [2]. Therefore, the use of pesticides is not excluded from IPM programs, for instance, when there is no other available tools to avoid economic damage [3], synergy occurs between chemical and biological control [4], or a diverse pest complex affects the crop [5]. Under those circum‐ stances, the products used should target several sites and mechanisms (multisite), be shortly persistent in the environment and crops (non-residual), and have both a narrow spectrum (selective) and low toxicity to mammals. Many compounds having these attributes have been called "alternative pesticides", including oils, pheromones, botanicals, entomopathogens, and soaps and detergents, among the most frequently used [6, 7]. For definition purposes, agriculture detergents and soaps, from now on "D + S", correspond to surfactants from either natural or synthetic origin, formulated specifically for pest control or other uses in crops. Within these options, D + S have additional particularities, being relatively inexpensive, easy to produce and apply, versatile (controlling juvenile and adults), allowed as postharvest treatment, etc. [8, 9].

#### *1.1.1. Resistance management*

Resistance is a consequence of the elimination of susceptible genotypes and selection, over time, of the tolerant part of the population by the frequent and wide use of pesticides with specific sites of action that lose afterwards their capability to control pests [1]. The alternating use of conventional products with different action sites has been one way to face resistance, but a more holistic approach is necessary to provide a sustainable solution [10]. That is why IPM was developed during the second half of the twentieth century, attempting to either avoid or reverse resistance by replacing chemical control by other strategies, and/or by using several different chemicals with multiple modes of action, as D + S that, therefore, should become useful tools for IPM [8, 11].

#### *1.1.2. Environmental, ecological, and toxicological issues*

Environmental contamination, diversity threatening, and toxic effects on mammals and other animal species are well known and severe impacts from the use of conventional pesticides. Environmental toxicity by soaps, on the other hand, is considered very low [12], but detergents in wastewater (sometimes in large concentrations) are considered important pollutants when they reach rivers and streams, where they form foam layers and affect the aquatic fauna. However, the greater biodegradability of current surfactants has significantly reduced those problems [13]. Besides, sprays in farms should not massively reach water courses, therefore minimizing the potential impact in surface and groundwater. Based on studies of wastewater used for irrigation [14], some surfactants alter physical, chemical, and biological properties of some types of soils [15]. However, linear alkylbenzene sulfonates (LAS, widely used in detergents) are considered not to be a threat to terrestrial ecosystems on a long-term basis because of biodegradation [16], although nonylphenol has been questioned [17]. Thus, their impact depends largely on the type of surfactant chemistry, providing room for testing, selecting, and using those less hazardous products.

**1. Introduction**

156 Integrated Pest Management (IPM): Environmentally Sound Pest Management

treatment, etc. [8, 9].

*1.1.1. Resistance management*

useful tools for IPM [8, 11].

*1.1.2. Environmental, ecological, and toxicological issues*

**soaps**

**1.1. Chemical control in integrated pest management (IPM) programs and detergents and**

Integrated pest management is a strategy developed to control agricultural pests and, at the same time solve problems derived from the extensive and intensive implementation of chemical control in conventional agriculture, where broad spectrum, specific action site, and persistent pesticides are used. Compounds with this profile have been called "conventional pesticides" and are responsible for causing resistance in pest populations, destruction of beneficial arthropods, and presence of pesticide residues in foods, soils, water, and air [1]. In order to obtain an economic, environmental, and ecologically sustainable food production, IPM encompasses several components, including cultural, biological, and chemical control [2]. Therefore, the use of pesticides is not excluded from IPM programs, for instance, when there is no other available tools to avoid economic damage [3], synergy occurs between chemical and biological control [4], or a diverse pest complex affects the crop [5]. Under those circum‐ stances, the products used should target several sites and mechanisms (multisite), be shortly persistent in the environment and crops (non-residual), and have both a narrow spectrum (selective) and low toxicity to mammals. Many compounds having these attributes have been called "alternative pesticides", including oils, pheromones, botanicals, entomopathogens, and soaps and detergents, among the most frequently used [6, 7]. For definition purposes, agriculture detergents and soaps, from now on "D + S", correspond to surfactants from either natural or synthetic origin, formulated specifically for pest control or other uses in crops. Within these options, D + S have additional particularities, being relatively inexpensive, easy to produce and apply, versatile (controlling juvenile and adults), allowed as postharvest

Resistance is a consequence of the elimination of susceptible genotypes and selection, over time, of the tolerant part of the population by the frequent and wide use of pesticides with specific sites of action that lose afterwards their capability to control pests [1]. The alternating use of conventional products with different action sites has been one way to face resistance, but a more holistic approach is necessary to provide a sustainable solution [10]. That is why IPM was developed during the second half of the twentieth century, attempting to either avoid or reverse resistance by replacing chemical control by other strategies, and/or by using several different chemicals with multiple modes of action, as D + S that, therefore, should become

Environmental contamination, diversity threatening, and toxic effects on mammals and other animal species are well known and severe impacts from the use of conventional pesticides. Environmental toxicity by soaps, on the other hand, is considered very low [12], but detergents in wastewater (sometimes in large concentrations) are considered important pollutants when In general, D + S have low acute toxicity [18], particularly non-ionic or anionic detergents, which are, by far, less dangerous than conventional insecticides [19]. For instance, the soap Safer has an oral LD50 of 16.500 ppm (= median lethal dose, i.e., the amount of active substance per body weight required to kill half of an exposed population), which is by far less dangerous than conventional insecticides, including botanicals [12]. The risk should be even lower considering both the necessary dilution and the small chance of ingestion. Conventional pesticides on the foliage are an important risk for applicators by dermal exposure, making necessary reentry intervals after their application, which are not needed when D + S are used. Detergents can cause dermal [20] or eye irritation, but in general this type of exposure represents a very low risk to agriculture workers wearing the basic personal protective equipment, although some respiratory disorders have been reported to detergent exposure, mainly on asthma sufferers [21, 22]. There are some concerns regarding specific housecleaning products (e.g., those containing alkyl phenols), which have been related to breast cancer [23], although under normal exposure in the field the risks are reduced, since no systemic toxicity is expected for most D + S and several components of their formulations [18, 19, 24], but this issue needs a case-by-case analysis. Another important issue is the persistence of conventional pesticide residues in/on the marketable part of the crop that makes necessary to establish regulations of MRLs (maximum residue limits) for foods. Thus, PHIs (preharvest intervals) are established to comply with the law, whereas most D + S are not subjected to this type of restrictions. In fact, some D + S are applied right before harvest [9] and others are authorized for postharvest treatments [25], being easily washed off from the epidermis of fruits and vegetables by rinsing before consumption, having minimum risk and being therefore exempt of MRLs [26].

Regarding the impact on beneficial fauna in crops, D + S have been considered more selective than conventional insecticides, being compatible with biological control due to their low adverse impact on not sprayed insect and mites and the lack of residual activity [4, 27]. The only threat occurs by the direct spray or when the solution persists on the foliage, usually for short periods, killing predators and parasitoids. Therefore, the release of beneficial arthropods after a spray, once deposits are dry, allows them to survive. Available EIQ (environmental impact quotient that considers environmental and ecological threats) values for soaps indicate their low impact (e.g., 19.45 for M-Pede), close to most botanicals or IGRs (insecticide growth regulators), and smaller than those of horticulture oils [28]. However, no data on detergents were available. Therefore, research to identify efficient (current or new), but also nontoxic and ecologically safe D + S for pest control is required.

## *1.1.3. Legal and economic issues*

Conventional pesticides are subject to a complex and expensive registration process where, after agronomic and toxicological reviews, they might obtain legal authorization to be used on crops. On the other hand, D + S are not necessarily subjected to registration, since some products are not labeled as pesticides, but as tree cleaners. However, it is important to transparent the real purpose of its use in agriculture [11]. Even when explicitly recommended to control pests, D + S should be easier to register after considering their risk assessment due to their low acute and chronic toxicity and, in some cases, their status as food additives or edible surfactants [29]. Considering the growing demand for residue-free foods, the eventual replacement of conventional pesticides for D + S will make those foods preferred by customers, increasing their value and making their trade easier. Therefore, all the actors involved should deeply assess D + S uses for pest control.

## **1.2. Modes of action of detergents and soaps as pesticides**

The modes of action for D + S against pests have not been well understood yet [30, 31]. In fact, D + S are not considered on the IRAC (Insecticide Resistance Action Committee) lists that classify the pesticides mode of action for those with known specific target sites [32]. This is because D + S are not known to act at specific target sites, but at multiple sites [11]. Despite that, wax removal, arthropod dislodging, and drowning have been mentioned as lethal mechanism in D + S.

#### *1.2.1. Wax removal*

The arthropod epicuticle is mainly made of lipids. The outermost part is a wax layer constituted mostly by hydrocarbons, serving mainly for waterproofing to avoid dehydration [33]. This is a serious threat for small insects and mites, particularly those sessile and exposed individuals. It has been proposed that when arthropods are sprayed with detergent, lipids are removed from the epicuticle, losing its waterproof ability, which in turn causes important water losses and, finally, the death of treated pests [34]. In fact, a significant reduction in both residual epicuticular lipids and body weight (assumed to occur mainly due to water losses) on the obscure mealybug *Pseudococcus viburni* Signoret (Hemiptera: Pseudococcidae) sprayed with detergent solutions was measured ([35], **Table 1**). After the spray, water losses reached up to 3% of body weight 7 h after exposure, and residual waxes were 88–73% below when compared with the control (check) at 24 h. Mortality was positively related with both water losses and wax removal when the agriculture detergent TS 20135 was used, but no significant relationship was found when the surfactants alone (excluding the co-adjuvants from the formulation) were tested.

Santibáñez [35] proposed that mealybug mortality by exposure to detergents might be caused by several mechanisms, including the initial wax removal that might lead to further damage of the integument, but this was not demonstrated. Many reports of pest management with D + S reveal that individuals present a degreased and dehydrated aspect after exposure, sug‐ gesting that water losses might be involved in mortality. For instance, the cotton aphid *Aphis gossypii* Glover (Hemiptera: Aphididae) nymphs and adults were strongly dehydrated and their bodies collapsed when evaluated 48 h after the spray with an agricultural detergent [9]. Wax removal (assumed to lead to dehydration) is also evident after exposure to detergents, causing dramatic changes in mealybugs, even a few minutes after the spray ([8, 11], **Figure 1** shows effects on hemipterans either sprayed or immersed in solutions).

1 LC = lethal concentration estimated by Probit analysis; study conducted using a Potter tower, control sprayed with water.

2 Active ingredient, the sum of surfactants formulated in TS 2035 (see **Table 3**)

3 Difference between initial (before) and final weight.

were available. Therefore, research to identify efficient (current or new), but also nontoxic and

Conventional pesticides are subject to a complex and expensive registration process where, after agronomic and toxicological reviews, they might obtain legal authorization to be used on crops. On the other hand, D + S are not necessarily subjected to registration, since some products are not labeled as pesticides, but as tree cleaners. However, it is important to transparent the real purpose of its use in agriculture [11]. Even when explicitly recommended to control pests, D + S should be easier to register after considering their risk assessment due to their low acute and chronic toxicity and, in some cases, their status as food additives or edible surfactants [29]. Considering the growing demand for residue-free foods, the eventual replacement of conventional pesticides for D + S will make those foods preferred by customers, increasing their value and making their trade easier. Therefore, all the actors involved should

The modes of action for D + S against pests have not been well understood yet [30, 31]. In fact, D + S are not considered on the IRAC (Insecticide Resistance Action Committee) lists that classify the pesticides mode of action for those with known specific target sites [32]. This is because D + S are not known to act at specific target sites, but at multiple sites [11]. Despite that, wax removal, arthropod dislodging, and drowning have been mentioned as lethal

The arthropod epicuticle is mainly made of lipids. The outermost part is a wax layer constituted mostly by hydrocarbons, serving mainly for waterproofing to avoid dehydration [33]. This is a serious threat for small insects and mites, particularly those sessile and exposed individuals. It has been proposed that when arthropods are sprayed with detergent, lipids are removed from the epicuticle, losing its waterproof ability, which in turn causes important water losses and, finally, the death of treated pests [34]. In fact, a significant reduction in both residual epicuticular lipids and body weight (assumed to occur mainly due to water losses) on the obscure mealybug *Pseudococcus viburni* Signoret (Hemiptera: Pseudococcidae) sprayed with detergent solutions was measured ([35], **Table 1**). After the spray, water losses reached up to 3% of body weight 7 h after exposure, and residual waxes were 88–73% below when compared with the control (check) at 24 h. Mortality was positively related with both water losses and wax removal when the agriculture detergent TS 20135 was used, but no significant relationship was found when the surfactants alone (excluding the co-adjuvants from the formulation) were

Santibáñez [35] proposed that mealybug mortality by exposure to detergents might be caused by several mechanisms, including the initial wax removal that might lead to further damage

ecologically safe D + S for pest control is required.

158 Integrated Pest Management (IPM): Environmentally Sound Pest Management

*1.1.3. Legal and economic issues*

deeply assess D + S uses for pest control.

mechanism in D + S.

*1.2.1. Wax removal*

tested.

**1.2. Modes of action of detergents and soaps as pesticides**

4 Residual waxes extracted with chloroform from 20 P. *viburni* adult females after detergent spray.

5 Means with different letters in a column are significantly different (p ≤ 0.05) according to Tukey's test. Data extracted from Santibáñez [35].

**Table 1.** *Pseudococcus viburni* water losses and residual waxes after detergent sprays.

**Figure 1.** Healthy hemipterans before (left column) and either minutes or a few hours after exposure in 1–2% detergent solutions (right), presenting symptoms of dehydration, browning, body collapse, and wax removal. A, *Pseudococcus longispinus* Targioni and Tozzetti (Pseudococcidae); B, *P. longispinus* after 5-s immersion in SU 120 (see details in **Ta‐ ble 3**); C, *Aphis gossypii* Glover (Aphididae); D, effect of TS 2035 on *A. gossypii*; E, *Eriosoma lanigerum* (Hausmann) (Erio‐ somatidae); F, effect of TS 2035 on *E. lanigerum;* G, *Siphoninus phillyreae* (Haliday) (Aleyrodidae); H, *S. phillyreae* a few days after sprayed.

1 Quix solutions (see **Table 3**).

2 Individuals found after immersion for 5 s + filtration.

3 Tap water. Data extracted from Curkovic and Araya [37].

**Table 2.** *Panonychus citri* dislodgement (D), mortality (M) at 24 h, and contribution of dislodgement (CD) to the control (D + M), after immersion of infested lemon leaves in the laboratory.

#### *1.2.2. Arthropod dislodgement*

Detergents and soaps contain surfactants, that is, compounds that reduce the surface tension of solutions, enhancing their capability to wet and wash arthropods off. Thus, sprays can dislodge motile forms of phytophagous pests, as nymphs and adults of mites, thrips, etc. (particularly when the solution runoffs on the leaves). Even not necessarily all removed individuals die, and dislodgement causes significant reductions of populations infesting the foliage. Dislodgement has been highlighted as an anti-herbivore trait [36] that reduces their phytophagous performance on the plant. In a laboratory study, up to 22% dislodgment of the citrus red mite *Panonychus citri* McGregor (Acari:Tetranychidae) infesting lemon (*Citrus × limon* (L.) Burm.f.) leaves occurred after immersion in a detergent solution at 1% (v/v), significantly greater than water alone [37]. Mite mortality was also greater along with detergent concentration, but the relative contribution of dislodgment to total control (dislodgment + mortality) was even greater (44.5%) when the lower concentration (0.25%, v/v) was used (**Table 2**). In another study, 22% of the Chilean false red mite *Brevipalpus chilensis* Baker (Acari: Tenuipalpidae) were washed off vine leaves after immersion in a detergent (see **Table 3** for details) solution, but lower concentrations contributed less to total control [38], suggesting that dislodgement depends on the type of detergent and/or the mite species.

Not many reports have demonstrated dislodgment when soaps and detergents are used for pest control, although surfactants have been mentioned as useful tools to wash out arthropods plant substrates (including plant organs) for cleaning produce or pest sampling purposes [39]. For instance, ca. 28% of the western flower thrips, *Frankliniella occidentalis* (Pergande), were removed after the immersion in a 0.1% surfactant solution (see **Table 3**) from infested Coleus shoots (*Lamiaceae*), but the thrips were apparently not harmed [40].

#### *1.2.3. Drowning*

Arthropod respiratory system is formed by a net of conducts (traqueae) that allow direct gas exchange with tissues. It is connected to the exterior by spiracles that regulate opening by muscles [33]. The surfactant properties of detergents and soaps allow the solutions to enter the spiracles [41, 42]. The solutions fill the traqueae, causing drowning and death. No reports have been found describing this mechanism for pest control, but several papers have mentioned drowning as a mortality factor after surfactant sprays on insects and mites [43, 44]. In larger insects, this seems to be a lethal mechanism after exposure to D + S [43].

## *1.2.4. Other mechanisms*

**Detergents1**

Quix solutions (see **Table 3**).

*1.2.2. Arthropod dislodgement*

*1.2.3. Drowning*

1

2

3

 **(%, v/v) % dislodgment2**

160 Integrated Pest Management (IPM): Environmentally Sound Pest Management

Individuals found after immersion for 5 s + filtration.

Tap water. Data extracted from Curkovic and Araya [37].

(D + M), after immersion of infested lemon leaves in the laboratory.

1.00% 22.2 59.4 27.2 0.50% 21.7 32.6 40.0 0.25% 14.1 17.6% 44.5 Control3 3.2 18.8% 14.5

dislodgement depends on the type of detergent and/or the mite species.

shoots (*Lamiaceae*), but the thrips were apparently not harmed [40].

**Table 2.** *Panonychus citri* dislodgement (D), mortality (M) at 24 h, and contribution of dislodgement (CD) to the control

Detergents and soaps contain surfactants, that is, compounds that reduce the surface tension of solutions, enhancing their capability to wet and wash arthropods off. Thus, sprays can dislodge motile forms of phytophagous pests, as nymphs and adults of mites, thrips, etc. (particularly when the solution runoffs on the leaves). Even not necessarily all removed individuals die, and dislodgement causes significant reductions of populations infesting the foliage. Dislodgement has been highlighted as an anti-herbivore trait [36] that reduces their phytophagous performance on the plant. In a laboratory study, up to 22% dislodgment of the citrus red mite *Panonychus citri* McGregor (Acari:Tetranychidae) infesting lemon (*Citrus × limon* (L.) Burm.f.) leaves occurred after immersion in a detergent solution at 1% (v/v), significantly greater than water alone [37]. Mite mortality was also greater along with detergent concentration, but the relative contribution of dislodgment to total control (dislodgment + mortality) was even greater (44.5%) when the lower concentration (0.25%, v/v) was used (**Table 2**). In another study, 22% of the Chilean false red mite *Brevipalpus chilensis* Baker (Acari: Tenuipalpidae) were washed off vine leaves after immersion in a detergent (see **Table 3** for details) solution, but lower concentrations contributed less to total control [38], suggesting that

Not many reports have demonstrated dislodgment when soaps and detergents are used for pest control, although surfactants have been mentioned as useful tools to wash out arthropods plant substrates (including plant organs) for cleaning produce or pest sampling purposes [39]. For instance, ca. 28% of the western flower thrips, *Frankliniella occidentalis* (Pergande), were removed after the immersion in a 0.1% surfactant solution (see **Table 3**) from infested Coleus

Arthropod respiratory system is formed by a net of conducts (traqueae) that allow direct gas exchange with tissues. It is connected to the exterior by spiracles that regulate opening by muscles [33]. The surfactant properties of detergents and soaps allow the solutions to enter the spiracles [41, 42]. The solutions fill the traqueae, causing drowning and death. No reports have

 **(D) % mortality (M) CD = 100×D/[D + M])**

Interference with cellular metabolism [41], repellency [30], breakdown of cell membranes [42], abnormal juvenile development [12], caustic activity, uncoupling oxidative phosphorylation, and/or even nervous system disruption [45] have been also indicated as possible modes of action of D + S, but further details have not been found. Interestingly, in nature, surfactants have been highlighted as a mechanism of defense developed by some insects against their predators by producing oral secretions containing surfactants that, for instance, stop ants attacking beet armyworm, *Spodoptera exigua* (Hübner) caterpillars (Lepidoptera: Noctuidae). After exposure, the ants covered by the secretion are engaged in intensive grooming that persisted for a few minutes, enough to save the caterpillar. Besides, after cleaning, ants were reluctant to attack a second time [46]. In fact, the author has regularly poured pure dishwashing detergents (~5 mL on their path) to successfully stop ant columns at home.

## **1.3. Detergents and soaps used for pest control in agriculture**

## *1.3.1. Formulations*

**Table 3** presents the characteristics and origin of 16 detergents and soaps used for pest control, or as co-adjuvants, reported in here. Many are liquids that perform better as insecticides and miticides [47], and a few are bars or powders. All were mixed in water to be applied, but bars needed, additionally, chipping and boiling before dilution. Several of the main world pro‐ ducers of cleaning products are represented in the list. About 44% of the products listed in **Table 3** correspond to either dishwashing, housecleaning, or personal cleaning products tested or used as alternatives to conventional pesticides. Thus, most products were not registered for pest control or agriculture use, but the results from research led later, in some cases, to the development of agriculture detergents (e.g., TS 2035 or SU 120 in Chile). Some D + S are produced locally, by relatively small producers, with raw materials easy to obtain, making suppliers and growers, particularly in developing countries, more independent from foreign surfactant producers. Information on D + S formulae was not always readily available and their components were not completely described, indicating only generically the type of compound (no chemical names given) or giving the range of the total surfactant content, but not precise figures. In fact, in many scientific publications reporting on the topic, there are no details on the specific inert ingredients or the surfactants (considered the active ingredients), or their respective proportions [47, 48].

1 Not an exhaustive web search, thus, the characteristics were not found for all products; some of them can have different commercial names elsewhere.

2 Liquid (L), powder (P) or bars (B).

3 Fabricant or distributor at the time the original paper was published or current owner of the product.

4 Either % w/v or v/v of surfactant(s) (considered the active ingredient) reported in the commercial product (c.p.) when available

5 Reported use, housecleaning (HC), personal cleaning (PC), agriculture (A), horticulture (H), detergent (D), soap (So), or surfactant (Su) used as co-adjuvant (Co) or dishwashing (Di) detergent; bibliographical references where the product was cited

6 Anionic surfactant.

7 Non-ionic surfactant.

**Table 3.** Characteristic1 and origin of some of the detergents and soaps reported herein.

#### *1.3.2. Surfactants*

**Commercial names and**

Acco Highway Plant Spray Soap, L

**Companies3**

Acme Chemical Company, PA, USA

162 Integrated Pest Management (IPM): Environmentally Sound Pest Management

Disolkyn, L Bramell Ltda., Chile Sodium disoctyl

Proctor and Gamble,

**countries**

Break, L BASF, Chile Trisiloxane7

OH, USA

USA

S.A., Chile

Quix, L Lever S.A., Chile Sodium benzene-

Safer, L Agro-Chem, CA, USA Potassium salts of

Tecsa fruta, L Protecsa, Chile Xylene sulfonate6

Triton X, L Sigma, MO, USA Octyl-phenol hydrophobe

TS 2035, L Pace Intl., Chile 15-17% sodium dodecyl

Unilever, Ghana LAS6

M-Pede, L Mycogen Corp., CA,

Nobla, P Johnson and Diversey, Chile

SU 120, L Johnson and Diversey, Chile

different commercial names elsewhere.

Liquid (L), powder (P) or bars (B).

Sunlight Dishwashing

Detergent, L

1

2

3

4

6

7

available 5

product was cited

Anionic surfactant.

Non-ionic surfactant.

**Table 3.** Characteristic1

Palmolive, L Colgate-Palmolive

 **and**

**Surfactants (a.i.) and %4**

Coconut oil soap6

sulfosuccinate6

Key soap, B Unilever, Ghana Not provided PCSo, Asiedu et al. [48] LK dishwashing, P Biotec S.A., Chile Not provided DiD, Arias et al. [47]

sulfonate6

sulfonate6

fatty acids6

sulpfnate6

sulfate6

sulfate6

Not an exhaustive web search, thus, the characteristics were not found for all products; some of them can have

Either % w/v or v/v of surfactant(s) (considered the active ingredient) reported in the commercial product (c.p.) when

 Reported use, housecleaning (HC), personal cleaning (PC), agriculture (A), horticulture (H), detergent (D), soap (So), or surfactant (Su) used as co-adjuvant (Co) or dishwashing (Di) detergent; bibliographical references where the

and origin of some of the detergents and soaps reported herein.

Fabricant or distributor at the time the original paper was published or current owner of the product.

nonylphenol7

Acids salts of coconut oil and tallow6

Potassium salts of fatty acids6

Total fatty acids6

(49)

(5-15)

(15-30%)

(50)

Sulfonates (14.9); lauryleter

(17.8)

(5-10)

(10-20) + sodium lauryl ether

+

(1.5-2)

series Polyethylene glycol ether7

, 4-6 ethoxilated alcohol%7

Sodium alkyl benzene-

(70)

 **in c.p. Declared uses5**

(38.5) ASo, Moore et al. [63]

(71) PCSo, Arias et al. [47]

[40]

Su, Sazo et al. [66]

HCD, Sclar et al. [69]

ASo, Butler et al. [30]

HCD, Curkovic et al. [57]

HCD, Curkovic et al. [34]

ASo, Osborne and Petit [65]

AD, Ripa et al. [55]

DiD, Asiedu et al. [48]

AD, Curkovic et al. [38]

AD, Curkovic et al. [9]

ASu, Warnock and Loughner

(75) Co, Sazo et al. [54]

 **and references**

**formulations2**

Ivory Clear detergent, L The first synthesized surfactants were soaps, molecules with a relatively long hydrocarbon hydrophobic chain in one extreme, capable of binding lipids, and a hydrophilic carboxylic group in the other extreme bonded to either sodium or potassium [49]. Soaps are relatively easy to produce from natural raw materials (animal fat or vegetable oils). They were used in pest control as far back as the eighteenth century [50]. However, soaps did not perform efficiently in hard water (where they precipitate) or at low temperatures. Therefore, and also considering the shortage of raw materials in Europe after World War I, detergents were developed in the 1930s, overcoming the limitations of soaps [20], mainly by substituting the carboxylic end by a sodium sulfate or sulfonate, or other hydrophilic group. The main uses of both types of compounds worldwide are housecleaning (laundry and dishwashing), personal care (body washers, shampoos), but also in agriculture, food processing, etc. Today, the main raw materials used to produce surfactants are petroleum-based materials and plant oils (mainly from soybean and palm). The latter has an increasing production due to, among other factors, its low cost and toxicity, and natural origin. In fact, from the point of view of their use in agriculture, detergents, unlike soaps, cannot be used in organic farms because they are synthetic, nonnatural products. The recent changes in surfactant markets (including the need for safer, environmentally friendly, and economical products) have stimulated the production of new compounds. For instance, food and pharmaceutical processing surfactants or edible surfactants are available, providing alternatives that need to be tested as pesticides, besides older compounds [29, 51]. Surfactants in D + S reported herein are described in **Table 3**. In solution, surfactants tend to adsorb to the surface or interphase of materials, reducing hydrogen bridges between water molecules, thus improving their wetting capabilities. Besides, in contact with water, surfactants form micelles or small spheres, usually having the hydrophobic end inside, binding lipids, and the hydrophilic end outside. In this way, lipids are removed (degreasing effect) from the substrate and get diluted (solubilized). The electric charge of the hydrophilic end in solution can be neutral (non-ionic surfactants), negative (anionic, the most common among the D + S reported herein), positive (cationic), or both (negative and positive) [49]. Ionic surfactants can modify the pH of the solution. For instance, anionic surfactants tend to slightly acidify the pH, but they perform better at basic pH; therefore, the detergent formulae include some buffer agents. In fact, it was found that agriculture detergents (including all co-adjuvants) tend to alkalinize the solution in distilled water (pH: 7.8–8.9, depending on the concentration) [35], but only when above 1% (v/v) was prepared, maintaining the pH neutral otherwise [52]. In many cases, the surfactants vary between D + S formulations (in their chemistry and/or proportions), affecting their insecticide/ miticide performance [38, 53]. Therefore, the activity of D + S needs some standardizing procedure in order to compare their activities as pesticides, for instance, comparing the proportion of surfactants (see below the case of some mealybugs), although differences can also be due to the particular type of surfactant, so this issue needs further research. Besides the house or personnel cleaning products, and some agriculture detergents, other sources for pest control are the co-adjuvants commercialized for specific functions, for example, wetting agents when mixed with pesticides or fertilizers in agriculture. Some of them have been individually or in mixtures tested as insecticides and miticides [52, 54].

#### *1.3.3. Efficacy as insecticides or miticides*

Most reports of pest control with D + S state relatively high levels of control (measured as either density reduction or mortality) against target pests. Those levels were usually achieved with the highest concentration tested, in most cases under or equal to 2%, either w/v or v/v, and considering the largest number of sprays [31]. The efficacy was directly related to coverage (the volume of water/ha used) and the stage of the pest (younger instars, except eggs, are the more susceptible ones, see **Table 4**) [11, 55]. In a few reports, however, the level of control obtained with soaps was poor [31, 56] or not significant when compared to some standard treatments (a recommended conventional pesticide). Maximum control was frequently measured when evaluations were conducted about a week after application, presumably due to a slower activity on arthropods than conventional pesticides [9], but some rapid stop-feeding response was also reported for insecticidal soaps, although mortality was achieved more slowly [12]. A few formulations include insecticides (e.g., pyrethrins are added in small amounts, [12]) for uses as agriculture soaps or louse shampoos [45], increasing their biocidal activity because of the addition of the natural neurotoxicant, but this is not the case of the products reported herein.

1 LC50 obtained by Probit analysis of data from commercial products in solutions (%, v/v) applied with a Potter tower (SU 120) or immersed 3 s in a solution (Tecsa fruta), values at 24 h after exposure.

2 Means with different letters are significantly different based on Curkovic et al. [68].

3 LC90, values calculated from unpublished data, LC90 were 3–6× greater than the LC50.

4 No data are provided because maximum observed mortality was <50%.

**Table 4.** LC501 and LC90 for *Myzus persicae* nymphs and adult females exposed to two agriculture detergent solutions.

#### **1.4. Challenges and opportunities of detergents and soaps for pest control**

#### *1.4.1. Phytotoxicity*

Toxicity to plants is a risk associated to the use of D + S, particularly at concentrations above 1–2% (v/v), but this effect should be a function of the proportion and type of surfactant(s) in the commercial formulation. It also depends on the plant species (its specific susceptibility or tolerance), their physiological condition, morphology, and growth stage. Phytotoxicity affects mainly leaves, flowers, and fruits [27, 57]; symptoms on the

foliage range from yellowing to bronzing, and wilting or curling, up to necrosis and defoliation, whereas in fruits they range from small brown spots or massive epidermal browning to fruit dropping (**Figure 2**). Petal flowers can become brown or even necrotic when D + S are applied during flower bud appearance and blooming. These symptoms are also observed after repeated sprays with high concentrations (usually above 1%) of detergents [58] or when plants are under some type of stress (e.g., shaded plants, see below the case of *E. lanigerum*). It is believed that epicuticle wax removal in plants, at least in part, is responsible for this type of damage [34, 35]. Plant external cuticle is mainly made of cutin (one of two waxy polymers of long-chain fatty acids that are the main components of the plant cuticle, which covers all aerial surfaces of plants), and waxes that offer strong resistance to evaporation from the underlying cells [59]. These compounds can be removed by D + S, depending on the type and concentration [60], significantly increasing evaporation. Water losses can also occur through the stomata that have an opening regulated by guard cells [59] that are affected by some soaps, getting through their membranes [42]. Phytotoxicity has been observed more frequently in plants with pubescent surfaces (leaves), where the droplets act as lens causing burning [12], and lesser in those with heavily waxed leaves, limiting the use of D + S depending on the plant species and leaf anatomy. Regarding the pH of the sprayed solution, we have presented examples of data indicating only small changes not expected to be hazardous for plants when 1% or lower concentrations are used. In **Figure 2** (left picture), a recently set olive fruit (cv. Sevillana) presents browning on the lower half after exposure to an agricultural detergent (**Table 3**, [27]), even at 0.5% c.p. (v/v). The fruit later aborted, and the same happened in several other table (Kalamata, Manzanilla) and olive oil varieties (Arbequina). In fact, because of phytotoxicity, detergents (and horticultural oils) should not be applied to olive trees from flower bud to stone hardening (about 1-cm fruit diameter) [27]. Similar results have been observed in grapes at blossom and fruit set. These examples demonstrate specific susceptibility to surfactant sprays, since D + S can be applied at the same or even greater concentrations, on other fruit species during fruit set, without phytotoxic effects (e.g., apples and citrus). However, **Figure 2** (right picture) presents apple leaves damaged by weekly detergent sprays (*n* = 4, at 0.5% (v/v), see **Table 5**), probably due to the abnormal susceptibility of plants maintained for a long time (above a year) at a greenhouse covered by a shade mesh, before the trial was conducted. This condition might reduce the thickness of the cuticle layer and make the plant more susceptible to damage (sun burnt) or water losses [61]. In fact, foliage of apple trees in orchards sprayed with the same detergents (at 1%, v/v) did not present phytotoxic symptoms at all. Therefore, it is necessary to test at a small scale detergent and soap sprays, case by case, before being sure to conduct a larger-scale application. To do this, the evaluation should be conducted within a week or less after the spray for symptoms to be observed [27, 31], thus selecting tolerant species or adequate plant growth stages. On the other hand, phytotoxicity caused by D + S can be considered useful in crop protection, since some can be used directly as either herbicides or herbicide co-adjuvants [42].

*1.3.3. Efficacy as insecticides or miticides*

164 Integrated Pest Management (IPM): Environmentally Sound Pest Management

products reported herein.

Tecsa fruta 1.4 b2

1

2

3

4

**Table 4.** LC501

*1.4.1. Phytotoxicity*

**Detergents LC50 on LC903**

(SU 120) or immersed 3 s in a solution (Tecsa fruta), values at 24 h after exposure.

No data are provided because maximum observed mortality was <50%.

Means with different letters are significantly different based on Curkovic et al. [68].

LC90, values calculated from unpublished data, LC90 were 3–6× greater than the LC50.

**1.4. Challenges and opportunities of detergents and soaps for pest control**

SU 120 1.2 c (nymphs) 7.5 (nymphs)

Most reports of pest control with D + S state relatively high levels of control (measured as either density reduction or mortality) against target pests. Those levels were usually achieved with the highest concentration tested, in most cases under or equal to 2%, either w/v or v/v, and considering the largest number of sprays [31]. The efficacy was directly related to coverage (the volume of water/ha used) and the stage of the pest (younger instars, except eggs, are the more susceptible ones, see **Table 4**) [11, 55]. In a few reports, however, the level of control obtained with soaps was poor [31, 56] or not significant when compared to some standard treatments (a recommended conventional pesticide). Maximum control was frequently measured when evaluations were conducted about a week after application, presumably due to a slower activity on arthropods than conventional pesticides [9], but some rapid stop-feeding response was also reported for insecticidal soaps, although mortality was achieved more slowly [12]. A few formulations include insecticides (e.g., pyrethrins are added in small amounts, [12]) for uses as agriculture soaps or louse shampoos [45], increasing their biocidal activity because of the addition of the natural neurotoxicant, but this is not the case of the

(nymphs) 4.2 (nymphs)

and LC90 for *Myzus persicae* nymphs and adult females exposed to two agriculture detergent solutions.

2.5 a (adults) 9.7 (adults)

1.4 b (adults) n/d4

LC50 obtained by Probit analysis of data from commercial products in solutions (%, v/v) applied with a Potter tower

Toxicity to plants is a risk associated to the use of D + S, particularly at concentrations above 1–2% (v/v), but this effect should be a function of the proportion and type of surfactant(s) in the commercial formulation. It also depends on the plant species (its specific susceptibility or tolerance), their physiological condition, morphology, and growth stage. Phytotoxicity affects mainly leaves, flowers, and fruits [27, 57]; symptoms on the

 **on**

(adults)

**Figure 2.** Symptoms of phytotoxicity on recently set olives during the spring (October, left), and on apple foliage in the middle of the summer (February, right), after a spray with detergents (0.5% or 1%, v/v, respectively).

1 Lorsban 75 WG was applied once on February 12, 2014 (= day 0), at 80 g c.p./hL.

2 Tap water was applied every time.

3 Total number of sprays during the 2-week period.

4 Days after first spray (dafs) the successive applications were conducted.

5 Means with different letters are significantly different (p≤0.05) according to Tukey's test.

**Table 5.** Mortality of *Eriosoma lanigerum* adults and nymphs infesting potted apple trees, with up to 3 weekly sprays of an agriculture detergent (at two concentrations) versus one spray of chlorpyrifos.

#### *1.4.2. Lack of residual activity*

Some reports state that insecticidal soaps are not persistent since they suffer rapid degradation [12]. However, some other studies on detergents or surfactants have demonstrated that their residues persist on the substrate after application. Triton X and Tween 80 (see **Table 3** for details), two surfactants used as co-adjuvants, produced persistent residues, at least a week after the spray on tomato fruits or tobacco leaves, respectively [60, 62]. Despite that, D + S residues do not have residual activity in terms of protection over time [31], which occurs only in solution [45], thus they are considered strictly contact pesticides (spray or topic exposure), some affecting the pest quickly [12]. Some soaps have been incorporated into a diet causing a slight mortality in the laboratory [56], showing some ingestion activity, but only at high concentrations (5× the recommended field rate). There is, however, some "residual" activity shortly after the application of D + S, if the solution lasts as either droplets or a liquid layer on the foliage and contacts the arthropod [47]. There is also the possibility of re-hydration if, for instance, relative humidity increases enough and shortly (after the spray) during fog events, to re-dilute D + S residues. It has been proposed to conduct repeated and frequent sprays of D + S to counteract their lack of residual activity on recurrent pests (see **Tables 5** and **6** for successful examples), but some concerns have been mentioned about the potential buildup of surfactants in the soil [63], although specific studies have not been conducted, except for some co-adjuvants [64]. On the other hand, the lack of residual effect turns out to be an advantage, preventing mortality of beneficial arthropods released after residues, which are dry, making D + S compatible with biological control and IPM programs.

1 At 0.5% c.p. (v/v).

**Figure 2.** Symptoms of phytotoxicity on recently set olives during the spring (October, left), and on apple foliage in the

middle of the summer (February, right), after a spray with detergents (0.5% or 1%, v/v, respectively).

**Treatments # sprays Dafs3 % mortality** TS 2035 0.5% 1 (0) 15.2% e4 " 2 (0 and 7) 38.0% de " 3 0, 7, and 14 62.8% bcd TS 2035 1.0% 1 (0) 61.1% cd " 2 (0 and 7) 84.4% abc " 3 (0, 7, and 14) 90.5% ab Chlorpyrifos1 1 (0) 94.4% a Control2 3 (0, 7, and 14) 0.0% f

166 Integrated Pest Management (IPM): Environmentally Sound Pest Management

Lorsban 75 WG was applied once on February 12, 2014 (= day 0), at 80 g c.p./hL.

an agriculture detergent (at two concentrations) versus one spray of chlorpyrifos.

Means with different letters are significantly different (p≤0.05) according to Tukey's test.

**Table 5.** Mortality of *Eriosoma lanigerum* adults and nymphs infesting potted apple trees, with up to 3 weekly sprays of

Some reports state that insecticidal soaps are not persistent since they suffer rapid degradation [12]. However, some other studies on detergents or surfactants have demonstrated that their residues persist on the substrate after application. Triton X and Tween 80 (see **Table 3** for details), two surfactants used as co-adjuvants, produced persistent residues, at least a week after the spray on tomato fruits or tobacco leaves, respectively [60, 62]. Despite that, D + S residues do not have residual activity in terms of protection over time [31], which occurs only in solution [45], thus they are considered strictly contact pesticides (spray or topic exposure), some affecting the pest quickly [12]. Some soaps have been incorporated into a diet causing a slight mortality in the laboratory [56], showing some ingestion activity, but only at high concentrations (5× the recommended field rate). There is, however, some "residual" activity shortly after the application of D + S, if the solution lasts as either droplets or a liquid layer on

Days after first spray (dafs) the successive applications were conducted.

1

2

3

4

5

Tap water was applied every time.

*1.4.2. Lack of residual activity*

Total number of sprays during the 2-week period.

2 Confidor 350 SC applied once on January 24, 2013 (day 0), at 60 cc c.p./hL.

3 Total number of sprays/treatment.

4 Days after first spray (dafs) the successive applications were done.

5 Means with different letters are significantly different (p ≤ 0.05) according to Tukey's test. Unpublished data.

**Table 6.** Mortality of *Parthenolecanium corni* nymphs infesting vines, with one to four sprays (every 10 days) of TS 2035 at 0.5% versus one spray of imidacloprid.

#### *1.4.3. Legal restrictions and registration*

Authorization is an obligatory requirement to legally utilize D + S as pesticides in agriculture. It implies the demonstration of no toxicological risks (including ecotoxicology) and agronomic efficiency, based on science, excluding compounds that do not comply. The process requires a large effort, and it is slow and expensive, making the agrochemical industry to proceed only when the economic return is attractive. There are a few cases of registered D + S as insecticides and/or miticides for agriculture, a few in the United States [30, 65]. In Chile, there has been one registration (Disolkyn, see **Table 3**) for a few years during the mid-2000s [66], but it was not renewed, so there are no legally available D + S for pest control currently in this country. Despite that, non-registered D + S have been used in Chile for pest control, suggesting that they do not cause problems. Their use with no sanctions has occurred because this is an issue not regulated specifically, since the products can be declared as used, for instance, as tree cleaners (an authorized use in some agricultural detergents), pest control being the real purpose [11]. However, growers subjected to the certification process do not use D + S. This causes a serious bottleneck for registration and development for these compounds as tools for pest management. Besides, the chemical and agrochemical industry have not made large efforts for detergent registration as pesticides, in part for a low market expectative in economic terms (low profit), and also due to the difficulty and elevated costs involved. For D + S, government agencies require the same requisite used for the registration of conventional pesticides, making even more difficult for the industry to spend efforts in a registration process for these types of compounds. However, as mentioned before, many surfactants, detergents, and soaps are safe for the environment and the users, and some are even food additives or edible surfactants, so there is room for pesticide development to identify and select those D + S with very low risks. Similar to the case of horticulture oils, pheromones, or biological pesticides [12, 13, 18], D + S should be developed as safe products, obviously excluding those questioned and dangerous [15, 17]. Therefore, authorization for D + S must be addressed by all the actors involved: government (registration agency, Departments of Health and of Agriculture), producers (the surfactants industry and agrochemical companies, suppliers, and distributors), the academic sector (researchers from the agronomic, chemistry, and toxicology areas), and even grower and consumer organizations (particularly those advocated to consumption of safer foods). Only by acting jointly, the analysis, selection, and development will lead to register and use D + S in pest management. Once available, these compounds will serve in IPM, but also to conventional or organic production schemes, and serve in many complex scenarios (e.g., used very close to harvest with no other management options).

#### *1.4.4. Spray conditions*

Since D + S work strictly by direct contact, application should maximize the exposure of the pest as much as possible. Spray equipment must be adapted, for instance, modifying nozzles orientation in order to apply from underneath the leaves or fruits, where mealybugs, spider mites, or whiteflies use to feed [9]. Air-blast or powered backpack sprayers have been preferred for D + S applications, since better coverage and smaller droplets are achieved [9, 27]. If possible, trees might be pruned before spraying surfactants in order to increase pest exposure and air circulation that will help in the dehydration of treated insects and mites [9]. Solutions should be applied considering whole coverage of infested organs, using high volumes of water/ha and high-pump pressure during the spray [8, 63]. Besides, sprays should be done early in the morning or late in the evening to increase the duration of the wet layer and extend their insecticide lifetime [31].

#### *1.4.5. Pest biology and ecology*

The habits, biology, and morphology of the pest should also be considered to maximize exposure by D + S sprays. For instance, nocturnal pests (armyworms (Lepidoptera: Noctuidae) or snails (Mollusca: Pulmonata, Helicidae)) should be sprayed at night for direct exposure. In fact, some noctuids have not been controlled efficiently by diurnal soap sprays in the field [56]. For the greenhouse whitefly *Trialeurodes vaporariorum* (Westwood), nocturnal sprays were also recommended, since evaporation is low and adults are less mobile, being more likely reached by the solution [47], but diurnal application is efficient against the sessile stages (older nymphs). In pests known as susceptible to D + S, however, some specific instars are less (or not) vulnerable (e.g., spider mite eggs are less susceptible than mobile forms). In fact, in one report only slight activity against overwintering eggs of the European red mite *P. ulmi* (Koch) was found [67], while significantly greater summer eggs LC50 (1.5–2.3×) than adult females of the two-spotted spider mite, *Tetranychus urticae* Koch (both Acari: Tetranychidae), were observed in another study [68]. In the case of whiteflies, eggs and pupae are less susceptible, whereas nymphs or adults are severely affected by detergent sprays [27]. Mealybugs (pseu‐ dococcids) are difficult to reach by either contact or systemic insecticides in the field when they colonize fruit cavities, woodcuts, or roots [9]. In general, therefore, it is necessary to find the vulnerability for each pest species to be controlled with D + S.

## **2. Review of agriculture pests controlled with detergents and soaps**

## **2.1. Hemiptera**

causes a serious bottleneck for registration and development for these compounds as tools for pest management. Besides, the chemical and agrochemical industry have not made large efforts for detergent registration as pesticides, in part for a low market expectative in economic terms (low profit), and also due to the difficulty and elevated costs involved. For D + S, government agencies require the same requisite used for the registration of conventional pesticides, making even more difficult for the industry to spend efforts in a registration process for these types of compounds. However, as mentioned before, many surfactants, detergents, and soaps are safe for the environment and the users, and some are even food additives or edible surfactants, so there is room for pesticide development to identify and select those D + S with very low risks. Similar to the case of horticulture oils, pheromones, or biological pesticides [12, 13, 18], D + S should be developed as safe products, obviously excluding those questioned and dangerous [15, 17]. Therefore, authorization for D + S must be addressed by all the actors involved: government (registration agency, Departments of Health and of Agriculture), producers (the surfactants industry and agrochemical companies, suppliers, and distributors), the academic sector (researchers from the agronomic, chemistry, and toxicology areas), and even grower and consumer organizations (particularly those advocated to consumption of safer foods). Only by acting jointly, the analysis, selection, and development will lead to register and use D + S in pest management. Once available, these compounds will serve in IPM, but also to conventional or organic production schemes, and serve in many complex scenarios (e.g., used very close to harvest with no other management options).

168 Integrated Pest Management (IPM): Environmentally Sound Pest Management

Since D + S work strictly by direct contact, application should maximize the exposure of the pest as much as possible. Spray equipment must be adapted, for instance, modifying nozzles orientation in order to apply from underneath the leaves or fruits, where mealybugs, spider mites, or whiteflies use to feed [9]. Air-blast or powered backpack sprayers have been preferred for D + S applications, since better coverage and smaller droplets are achieved [9, 27]. If possible, trees might be pruned before spraying surfactants in order to increase pest exposure and air circulation that will help in the dehydration of treated insects and mites [9]. Solutions should be applied considering whole coverage of infested organs, using high volumes of water/ha and high-pump pressure during the spray [8, 63]. Besides, sprays should be done early in the morning or late in the evening to increase the duration of the wet layer and extend

The habits, biology, and morphology of the pest should also be considered to maximize exposure by D + S sprays. For instance, nocturnal pests (armyworms (Lepidoptera: Noctuidae) or snails (Mollusca: Pulmonata, Helicidae)) should be sprayed at night for direct exposure. In fact, some noctuids have not been controlled efficiently by diurnal soap sprays in the field [56]. For the greenhouse whitefly *Trialeurodes vaporariorum* (Westwood), nocturnal sprays were also recommended, since evaporation is low and adults are less mobile, being more likely reached by the solution [47], but diurnal application is efficient against the sessile stages (older

*1.4.4. Spray conditions*

their insecticide lifetime [31].

*1.4.5. Pest biology and ecology*

Most examples of pest species controlled with D + S belong to this insect Order. They are the main target group because of their (a) size, being small (most), therefore highly dependent on their protective wax layer; (b) exposure on plant tissues, many being relatively easy to reach and/or remove from the foliage by the spray; (c) type of cuticle, being either soft or thin, thus more susceptible to D + S; (d) damage, as most species cause it when reaching high populations, thus, a significant reduction (but maybe not eradication) is enough to secure satisfactory yields, as expected for surfactants; and (e) null development of resistant populations as with conven‐ tional insecticides, thus, management with multisite D + S helps to avoid or reverse the problem, etc. The following review presents the most important hemipteran groups controlled with these types of compounds.

#### *2.1.1. Aleyrodidae*

Whiteflies are plant-sucking pests, having many generations per crop cycle, which infest mainly the foliage (usually the underside of leaves) of vegetables, tree fruit orchards, and ornamentals. They affect plant growth and yield by sap sucking, transmission of some diseases during feeding, and release of honeydew on the foliage and fruits, allowing the colonization by sooty mold. This fungus reduces both photosynthetic capacity and the value of the produce (downgrading the price of fruits and vegetables). Honeydew also serves as food for attendant ants that disturb biological control agents. Whiteflies have externally a conspicuous whitedusting wax layer to protect them from dehydration, also serving to reduce insecticide exposure. Detergent and soap sprays have been widely used to target the underside of the leaves and control whiteflies, despite some limitations against these pests as the lack of both systemic activity and residual effect. To counteract these narrowing factors, sprays require to be frequent, to cover the whole population. Besides, as whiteflies have several generations lasting about a month per crop cycle, each one should receive sprays. Butler et al. [30] were one of the first researchers in testing 16 D + S (e.g., M-Pede, Palmolive, etc.; see details in **Table 3**) on the control of the sweet-potato whitefly, *Bemisia tabaci* (Gennadius), 48 h after spraying several vegetable and ornamental species under greenhouse conditions. The production of honeydew by nymphs was measured as an evidence of nymph survival. In fact, there was a significant and inverse regression between the number of honeydew droplets (trapped on sensitive paper placed below infested leaves) and D + S concentration. The authors also found above 85% mortality (against the control sprayed with water) with 13 D + S at 1% either v/v or w/v, even under heavy infestation. Besides, adult whiteflies were removed from the leaves by the sprays and some ended adhered to the lower foliage and died. This is an additional control effect when using these types of compounds and it probably explains the reduction in adult's captures in traps after the application. D + S have also been tested on the greenhouse whitefly, *T. vaporariorum* (Westwood), but with dissimilar results. For instance, D + S were sprayed on infested seedling tomatoes (less than 10-leaf stage), and yield, plant toxicity, and nymph reduction were measured. Slight but significant nymph reduction (compared to the control) was observed when M-Pede insecticidal soap was sprayed at 2% (v/ v), not causing yield losses. Weekly applications were suggested to control *T. vaporariorum* in tomato greenhouses, without plant toxicity risk [69]. Several other detergents (e.g., Ivory Clear detergent) used at 2% significantly reduced nymph density, but they also caused damage on the plant and yield reduction. In another study evaluating 12 D + S, only one product (LK dishwashing at 4–5% c.p. v/v) provided a bit over 50% adult *T. vaporariorum* mortality 24 h after the spray on infested bean plants (nymph mortality was not evaluated). Solid and liquid soaps caused similar results (below 35% mortality), except for Palmolive, that reached ~42% mortality using a 4% solution, but the lethal effect was dependent on the presence of liquid residues on the foliage [47]. High levels of control of the ash whitefly, *Siphoninus phillyreae* (Haliday), in olive trees sprayed with agriculture detergents (TS 2035 and *Tecsa fruta*) at 1–2% v/v, were reported [58]. Best results were obtained when detergents were applied on younger nymph stages (particularly nymph I) infesting potted plants, easier to cover with the spray. In another study in a pomegranate orchard, it was found that *S. phillyreae* nymphs I–III were easier to control whereas eggs and pupae (nymph IV) were far more difficult to kill with the same concentrations; thus, adults can emerge after the spray, not being a good predictor of whiteflies control [9]. Detergents at 0.5% (v/v) and above used against *S. phillyreae* produced toxic effects in Chilean olive orchards when used between flower bud and recently set fruits, precluding its use between those phenology stages, but pomegranates, on the other hand, were highly tolerant to 1% detergent (see **Table 3**) solution, and did not suffer either fruit or foliage damage. Results from other reports [9, 27] confirm that whiteflies are good targets to be controlled by D + S.

#### *2.1.2. Aphidoidea*

Aphids (*Aphididae*) are also very important plant-sucking pests, having impacts similar to whiteflies. Aphids tend to congregate on the buds and leaves, and also have several genera‐ tions per season, but they tend to infest the foliage, twigs, and flowers during the spring, late in the season (close to harvest). Some cause the leaves to curl, forming refuges, being harder to reach with contact insecticide sprays, although this is easier with D + S due to its surfactant properties. Their bodies have less conspicuous wax layers than whiteflies. Because of that, sprays with contact insecticide target directly the colonies. D + S have been widely used to control aphids, with similar considerations as in whiteflies. Puritch [70], one of the oldest reports in recent times, found that soaps and their respective fatty acids (at 0.5% v/v) were active against the balsam woolly aphid, *Adelges piceae* (Ratz.) (*Adelgidae*), in Canada. The soap was more effective than the corresponding fatty acid, but both had neither ovicidal nor residual effect. Moore et al. [63] published one of the first reports of housecleaning products (D + S) used against three Aphididae species (the green peach aphid, *Myzus persicae* Sulzer; the spirea aphid, *A. spiraecola* [=*citricola*] (Patch), and the black bean aphid, *A. fabae* Scopoli), infesting several species of ornamentals. They found that Ivory liquid dishwashing at 1–2% (v/v) sprayed until runoff notably reduced populations immediately after the application. Plant toxicity was observed, particularly on plants with pubescent epidermis. In another report [69], the activity of two detergents on *M. persicae* nymphs and adults was evaluated by spraying (SU 120) or immersion (Tecsa fruta), in the laboratory. The last detergent was significantly more active (having a smaller LC50, considering the smaller amount of active ingredients, that is, surfactants in the formulation) regardless of the aphid instar. Nymphs were more suscep‐ tible (**Table 4**: LC50 for adults was 1.2–1.8× greater).