Behavior Of Natural Enemies Research Articles

The effect of blue and UV light-emitted diodes (LEDs) on the disturbance of the whitefly natural enemies Macrolophus pygmaeus and Encarsia formosa

Recent studies demonstrated that blue and UV light effectively disturb greenhouse whiteflies (Trialeurodes vaporariorum) from a host plant (“push”), enhancing their capture on attractive traps after dispersal (“pull”). This push–pull technique could contribute to whitefly biocontrol and lead to the development of mass trapping. However, the impact of these wavelengths on the behavior of whitefly natural enemies, commonly deployed for biocontrol, remains underexplored. This study investigated the response of two important whitefly biocontrol agents, Macrolophus pygmaeus and Encarsia formosa, to blue and UV light. Initial experiments were conducted under artificial conditions (no prey/host and plant present) to isolate their visual behavior to these lights, excluding other stimuli. In follow up experiments, the effect of these lights was assessed in a more complex scenario, involving prey/host (whitefly nymphs) on tomato leaves. Results revealed that both M. pygmaeus and E. formosa exhibited avoidance behavior under blue and UV LEDs in the artificial setup, irrespective of ambient light or dark conditions. Contrastingly, in presence of prey/host on tomato leaves, only M. pygmaeus was significantly disturbed by UV light, whereas in all other scenarios there was little to no effect of blue and UV LEDs on the behavior of these natural enemies.. These findings enhance our understanding on the visual behavior of crucial biocontrol agents and highlight the importance of refining targeted whitefly control techniques that minimize impacts on beneficial insects and optimize the use of LEDs in integrated pest management (IPM).

Effects of Elevated CO2 and O3 on Aboveground Brassicaceous Plant-Insect Interactions.

Atmospheric gases, such as carbon dioxide (CO2) and ozone (O3), influence plant-insect interactions, with variable effects. The few studies that have investigated the direct effects of elevated CO2 (eCO2; 750-900 ppm) or elevated O3 (eO3; 60-200 ppb) on insects have shown mixed results. Instead, most research has focused on the indirect effects through changes in the host plant. In general, the lower nitrogen levels in C3 brassicaceous plants grown at eCO2 negatively affect insects and may result in compensatory feeding. Phytohormones involved in plant resistance may be altered by eCO2 or eO3. For example, stress-related jasmonate levels, which lead to induced resistance against chewing herbivores, are weakened at eCO2. In general, eCO2 does not affect herbivore-induced plant volatiles, which remain attractive to natural enemies. However, floral volatiles and herbivore-induced plant volatiles may be degraded by O3, affecting pollination and foraging natural enemy behavior. Thus, eCO2 and eO3 alter plant-insect interactions; however, many aspects remain poorly understood.

Biological reinforcement learning simulation for natural enemy -host behavior: Exploring deep learning algorithms for population dynamics

This study introduces a simulation of biological reinforcement learning to explore the behavior of natural enemies in the presence of host pests, aiming to analyze the population dynamics between natural enemies and insect pests within an ecological context. The simulation leverages on Q-learning, a reinforcement learning algorithm, to model the decision-making processes of both parasitoids/predators and pests, thereby assessing the impact of varying parasitism and predation rates on pest population growth. Simulation parameters, such as episode count, duration in months, steps, learning rate, and discount factor, were set arbitrarily. Environmental and reward matrices, representing climatic conditions, crop availability, and the rewards for different actions, were established for each month. Initial Q-tables for parasitoids/predators and pests, along with population arrays, were used to track population dynamics.•The simulation, illustrated through the Aphid-Ladybird beetle interaction case study over multiple episodes, includes a sensitivity analysis to evaluate the effects of different predation rates.•Findings reveal detailed population dynamics, phase relationships between predator and pest populations, and the significant influence of predation rates.•These insights contribute to a deeper understanding of ecological systems and inform potential pest management strategies.

Reviews on the Strategies Employed in Implementing the 'Push-Pull' Approach to Integrated Pest Management

Abstract: For small-holder maize farmers in Africa, the push-pull strategy is outlined as an alternate ecological management technique to traditional insecticide-based integrated pest management for the control of the spotted stem borer Chilo partellus and the autumn armyworm Spodoptera frugiperda. Push-Pull Technology (abbreviated PPT) is a unique integrated pest management method developed by the International Centre of Insect Physiology and Ecology (ICIPE) and its partners. This tactic involves influencing the behavior of natural enemies and insect pests by strategically deploying stimuli that make the resource under protection unappealing or inappropriate for the pests (the "push"). Additionally, the pests are drawn to an alluring source the pull, from which they are then eliminated

Perception and kairomonal response of the coccinellid predator (Harmonia axyridis) to the fall armyworm (Spodoptera frugiperda) sex pheromone.

Pheromone cues released from hosts or prey are of crucial importance to natural enemies for prey and habitat location. The use of herbivorous insect sex pheromones has long been considered as a potential pest control alternative that is non-toxic and harmless to beneficials. We hypothesized that Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), a major predatory coccinellid beetle of the devastating migratory pest Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), could perceive and use the sex pheromone of S. frugiperda to locate its habitat. Here we tested the electrophysiological and behavioral responses of H. axyridis to the two components Z7-12:Ac and Z9-14:Ac of S. frugiperda sex pheromone by using electroantennography (EAG) and Y-tube bioassay. The 3D modeling of H. axyridis odorant-binding proteins (HaxyOBPs) and molecular docking were also performed. The results showed that both female and male H. axyridis exhibited significantly higher electrophysiological and behavioral responses to Z9-14:Ac at the concentrations of 0.001, 0.01, and 0.1μg/μL, while no significant electrophysiological and behavioral responses of H. axyridis were observed to Z7-12:Ac. The blend of Z7-12:Ac and Z9-14:Ac at the ratio of 1:100 had a significant attraction to both male and female H. axyridis at the concentrations of 0.01 and 0.1μg/μL based on electrophysiological and behavioral assays, but no significant behavioral responses were observed at the ratios of 1:9. According to the 3D modeling of HaxyOBPs and molecular docking, HaxyOBP12 has a good affinity with Z9-14:Ac. Z9-14:Ac is bound to the HaxyOBP12 by hydrogen bonding and hydrophobic interactions. However, there were no credible docking results between HaxyOBPs and Z7-12:Ac. Our findings revealed that H. axyridis can perceive Z9-14:Ac and could use it as a chemical cue to locate prey habitat. We speculated that Z7-12:Ac, which showed some antagonistic effect toward the response of H. axyridis to Z9-14:Ac, could improve the adaptability of S. frugiperda in the presence of predators. This study provides new insights into the application of pheromones to manipulate natural enemy behavior for pest control.

UNDERSTANDING THE SEARCHING BEHAVIOUR OF PREDATOR AND PARASITOID INSECTS: A REVIEW

The aim of this review is to understand whether the searching behaviour of natural enemies (parasitoids and predators) is affected by complex odour mixtures and if there are differences between specialist and generalist natural enemies. To accomplish this objective, a literature review of several research papers related to the topic was done. Natural enemies of herbivores mainly use herbivore induced plant volatiles (HIPVs) to find their prey or host. However, the chemical information conveyed through HIPVs toward natural enemies might be unreliable or sometimes undetectable for them (odour masking), thereby influencing their searching behaviour. Many factors influence the reliability and detectability of HIPVs such as: plant diversity, intensity of the herbivore attack, if one or more herbivore species attack the plant at the same time or sequentially, and environmental conditions like light intensity, fertilization levels, soil moisture, and high concentrations of ozone, hydroxyl, and nitrate radicals. Nevertheless, in order to overcome reliability and detectability problems of HIPVs, natural enemies have the ability to learn by association and use these HIPVs to find their prey or host. Further field experiments supported by laboratory assessments should be carried out to understand how the searching behaviour of natural enemies is affected in a multitrophic level context, where known biodiversity (above and below ground) and environmental conditions have the possibility to interact.

Sublethal effects of some insecticides on the functional response of Aenasius bambawalei Hayat, 2009 (Hymenoptera: Encyrtidae)

Aenasius bambawalei Hayat, 2009 is one of the most effective natural enemies of Phenacoccus solenopsis Tinsley, 1898. The sublethal effects of dimethoate, imidacloprid, and thiodicarb on the functional response of A. bambawalei to different densities of third instar nymphs of P. solenopsis were evaluated under laboratory conditions. Young females were exposed to the insecticides and then introduced to the host densities of 2, 4, 8, 16, 32, and 64 for 24 h. The results revealed a type III functional response in control and insecticide treatments. The handling time and maximum attack rates of A. bambawalei females were adversely affected by insecticides. The longest handling time and the lowest value of maximum attack rate were observed in thiodicarb treatment, 5.03 h and 4.76, respectively. Therefore, for the simultaneous application of biological and chemical control of P. solenopsis, the influence of insecticides on the functional response behavior of natural enemies must be evaluated.

Integrated Volatile Metabolomics and Transcriptomics Analyses Reveal the Influence of Infection TuMV to Volatile Organic Compounds in Brassica rapa

Turnip mosaic virus (TuMV), which is distributed almost all over the world and has a wide range of hosts, mainly brassica crops, was first described in Brassica rapa in the USA. Plant volatile compounds play an important role in the host searching behavior of natural enemies of herbivorous insects. In this study, TuMV-inoculated resistant and susceptible B. rapa lines were tested using volatile metabolome and transcriptome analyses. In volatile metabolome analysis, the volatile organic compounds (VOCs) were different after inoculation with TuMV in resistant B80124 and susceptible B80461, and the degree of downregulation of differentially expressed metabolites was more obvious than the degree of upregulation. Through transcriptome analysis, 70% of differentially expressed genes were in biological process, especially focusing on defense response, flavonoid biosynthetic process, and toxin metabolic process, which indicates that TuMV stress maybe accelerate the increase of VOCs. Integrating the metabolome and transcriptome analyses, after inoculating with TuMV, auxin regulation was upregulated, and ARF, IAA and GH3 were also upregulated, which accelerated cell enlargement and plant growth in tryptophan metabolism. The different genes in zeatin biosynthesis pathways were downregulated, which reduced cell division and shoot initiation. However, the metabolite pathways showed upregulation in brassinosteroid biosynthesis and α-linolenic acid metabolism, which could cause cell enlargement and a stress response. This study determined the difference in volatiles between normal plants and infected plants and may lay a foundation for anti-TuMV research in B. rapa.

Neonicotinoid Exposures that Stimulate Predatory Stink Bug, Podisus maculiventris (Hemiptera: Pentatomidae), Reproduction Do Not Inhibit Its Behavior.

Exposure to sublethal amounts of pesticide can compromise life-history traits and behavior of natural enemies thereby reducing their effectiveness as predators. However, sublethal exposures to pesticides and other stressors may also stimulate insects, a dose-response phenomenon known as hormesis. We previously reported stimulatory effects on reproduction in the beneficial insect predator Podisus maculiventris (Say) (Hemiptera: Pentatomidae) following exposure to sublethal concentrations of imidacloprid. Here we examined whether these same treatments stimulated behavior and/or predation of P. maculiventris. Stimulation of some behaviors occurred at a reproductively hormetic concentration and two additional sublethal concentrations, depending upon bioassay design and sex. We observed no substantial inhibition of behavior or predation at a reproductively hormetic concentration, demonstrating that reproductive fitness in P. maculiventris may be stimulated without compromising behaviors important in its effectiveness as a natural enemy.

Exploring the Kairomone-Based Foraging Behaviour of Natural Enemies to Enhance Biological Control: A Review

Kairomones are chemical signals that mediate interspecific interactions beneficial to organisms that detect the cues. These attractants can be individual compounds or mixtures of herbivore-induced plant volatiles (HIPVs) or herbivore chemicals such as pheromones, i.e., chemicals mediating intraspecific communication between herbivores. Natural enemies eavesdrop on kairomones during their foraging behaviour, i.e., location of oviposition sites and feeding resources in nature. Kairomone mixtures are likely to elicit stronger olfactory responses in natural enemies than single kairomones. Kairomone-based lures are used to enhance biological control strategies via the attraction and retention of natural enemies to reduce insect pest populations and crop damage in an environmentally friendly way. In this review, we focus on ways to improve the efficiency of kairomone use in crop fields. First, we highlight kairomone sources in tri-trophic systems and discuss how these attractants are used by natural enemies searching for hosts or prey. Then we summarise examples of field application of kairomones (pheromones vs. HIPVs) in recruiting natural enemies. We highlight the need for future field studies to focus on the application of kairomone blends rather than single kairomones which currently dominate the literature on field attractants for natural enemies. We further discuss ways for improving kairomone use through attract and reward technique, olfactory associative learning, and optimisation of kairomone lure formulations. Finally, we discuss why the effectiveness of kairomone use for enhancing biological control strategies should move from demonstration of increase in the number of attracted natural enemies, to reducing pest populations and crop damage below economic threshold levels and increasing crop yield.

Adverse weather conditions impede odor-guided foraging of parasitoids and reduce their host-finding success

Biological pest control depends on the ability of natural enemies to find herbivore-infested plants, which is often guided by herbivore-induced plant volatiles (HIPVs). While foraging behavior of natural enemies has been extensively studied under controlled conditions, little is known on how odor-guided foraging behavior is influenced by fluctuating weather conditions in the field.Here we investigated how HIPV-guided foraging of Cotesia glomerata parasitoids is influenced by prevailing weather conditions in the field. C. glomerata females were released in 5 m radius circles of cabbage plants infested with Pieris brassicae caterpillars, and host finding success and direction of foraging activity was assessed by recapturing parasitoids on the host-infested plants. Wind speed and direction, humidity, barometric pressure and temperature was recorded and related to parasitoid foraging activity. Parasitoid foraging behavior was studied in more detail by observing individually released parasitoids in 0.5 m circles with host-infested cabbages.Recapture rates and movement direction of parasitoids was influenced by an interaction between humidity, wind speed, temperature and change in barometric pressure. High humidity and low wind speed was generally positively associated with host finding success. Direct observations of parasitoid flight behavior confirmed the influence of humidity and wind speed. Successful host finding in upwind direction was only observed at wind speeds below 3 m/s.Our study highlights the complex ways in which weather variables moderate parasitoid foraging behavior under field conditions. Since unfavorable weather conditions result in a strong reduction in parasitoid foraging efficiency, weather conditions are an important factor in the effectiveness of parasitoids as biocontrol agents.

No evidence of modulation of indirect plant resistance of Brassica rapa plants by volatiles from soil‐borne fungi

Upon herbivory, plants emit specific herbivore‐induced plant volatiles (HIPVs) that can attract natural enemies of the herbivore thus serving as indirect plant resistance. Not only insect herbivores, but microorganisms may also affect HIPV emission before or after plant colonisation, which in turn can affect behaviour of natural enemies of the herbivore. Yet, it remains elusive whether volatiles from microorganisms influence HIPV emission and indirect plant resistance. In this study, we investigated whether exposure of Brassica rapa roots to volatiles from soil‐borne fungi influence HIPV emission and the recruitment of natural enemies of Pieris brassicae larvae. Using a two‐compartment pot system, we performed greenhouse and common‐garden experiments, and we profiled plant HIPV emission. We found that exposure of plant roots to fungal volatiles did not affect the number of P. brassicae larvae recollected from the plants, suggesting a neutral effect of the fungal volatiles on natural predation. Likewise, in a greenhouse, similar numbers of larvae were parasitised by Cotesia glomerata wasps on control plants as on fungal volatile‐exposed plants. Additionally, chemical analysis of HIPV profiles revealed no qualitative and quantitative differences between control plants and fungal volatile‐exposed plants that were both infested with P. brassicae larvae. Together, our data indicate that root exposure to fungal volatiles did not affect indirect plant resistance to an insect herbivore. These findings provide new insight into the influence of indirect plant resistance by fungal volatiles that are discussed together with the effects of fungal volatiles on direct plant resistance.

Natural enemies in alternative plants during the soybean and corn offseason in Cruz Alta, Rio Grande do Sul

Identifying the behavior of natural enemies during the crop offseason is a key tool for integrated pest management. The objective of this work was to evaluate the population density of natural enemies of the plants Chloris distichophylla, Andropogon bicornis, and Erianthus angustifolium and to analyze the influence of the structural complexity of these plants on the present population. During the offseasons of 2014, 2015, and 2016, 150 plants of each species were evaluated and subdivided into different clump diameters. The species Lycosa spp., Eriops connexa, Cicloneda sanguinea, Coleomegilla quadrifasciata, Lebia concinna, and Harmonia axyridis were identified. A. bicornis was the plant with the highest population density, followed by C. distichophylla and E. angustifolium. Plants with greater structural complexities sheltered a higher population density of natural enemies.

Manipulating natural enemy behavior to improve biological control: attractants and repellents of a weaver ant

Farmers may not want certain natural enemies of insect pests to be present in their fields all year round, due to the detrimental effects they might have on themselves or on their crop. We explored the potential for manipulating the behavior of the African weaver ant, Oecophylla longinoda, which may bite humans while being a major natural enemy against the invasive fruit fly, Bactrocera dorsalis, in Africa. Our aim was to find repellents that might help to protect farmers when working in the fields, while also coming up with ways of increasing weaver ant populations, by finding carbohydrate sources from local cultivated plants (attractant). To that end, we carried out behavioral experiments in the laboratory which revealed (i) that oily repellents were the most efficient of all those tested, (ii) that the extra floral nectar of a legume crop, such as cowpea, was consumed by weaver ants, but in quite small amounts and also differently depending on the varieties. This approach, tackling these two aspects at the same time, was based on and shaped by the reality faced by farmers. The results are key to breaking down obstacles to using weaver ants in Africa and are discussed in this respect.

Keep your enemies closer: enhancing biological control through individual movement rules to retain natural enemies inside the field

Abstract. Biological control of pests aims at lowering population levels of pest species by favouring natural enemies, in order to reduce the use of pesticides. The movement behaviour of natural enemies is decisive in the success of biological control: when low habitat quality hinders the diffusion of natural enemies from the border, the density of natural enemies may frequently be heterogeneous inside agricultural plots. We hypothesise that the specific relationship between habitat quality and movement behaviour may allow the improvement of biological control by means of a careful allocation of habitat qualities inside and around the plot. We used three tested individual-based movement models, with different levels of complexity ranging from simple cell-to-cell movements to complex strategies including the sinuosity of the path, boundary crossings, perceptual range, and directional persistence. We used the models to explore how the manipulation of habitat quality may allow significant improvements to the residence time of natural enemies inside the field. We suggest that existing field designs are generally inadequate to retain natural enemies. Mechanistic explanations leading to the highest and lowest residence times are used to draw specific management recommendations.

The role of herbivore-induced plant volatiles (HIPVs) as indirect plant defense mechanism in a diverse plant and herbivore species; a review

When plants are attacked by herbivores, they release plant volatiles called herbivore-induced plant volatiles (HIPVs) to the environment to communicate with higher trophic levels. HIPVs play different ecological roles such as plant-plant interaction, plant-herbivore interaction, tritrophic interaction and other related interactions. Attractiveness of HIPVs to natural enemies in a tritrophic interaction varies depending on species diversity. Under natural and multiple cropping systems, tritrophic interaction is expected to be more complex than single tritrophic interaction with one species per trophic level. In complex tritrophic interaction, diversity of different trophic levels affects attractiveness of HIPVs to natural enemies. From plant diversity point of view, HIPVs mixture emanating from herbivore-damaged multiple plant species are reported to affect behavioral responses and foraging behavior of natural enemies under laboratory and field conditions. Similarly, from herbivore diversity point of view, in nature, plants are commonly attacked by more than one herbivore species. Constituents of HIPVs vary between plants infested by multiple and single herbivore species and this affects the behavioral responses and foraging behavior of natural enemies. This paper reviews recent findings on the role of HIPVs as indirect plant defense in systems with simple tritrophic interaction, and in diverse plants species and diverse herbivore species.

Intercropping hampers the nocturnal biological control of aphids

AbstractIncreasing plant diversity in agroecosystems (i.e. intercropping) has been widely accepted as a means of promoting conservation biological control of mites and insect pests. Nevertheless, the contribution from underlying mechanisms such as the provision of non‐prey alternative food (i.e. pollen and nectar) and shelter have not been properly disentangled; and additionally, it remains unexplored whether the performance of nocturnal and diurnal natural enemies is improved when provided with diverse plant communities. Using open field experiments and a greenhouse microcosm, we investigated whether intercropping collards with parsley could create shelter for natural enemies in the lower stratum (parsley), and whether or not nocturnal and diurnal natural enemies would carry out aphid biological control equally well in this increased plant diversity scenario (intercropping). The results showed that the shelter alone provided by the lower stratum/companion plants (parsley) mediated an increase in the abundance of natural enemies without involving the provision of non‐prey alternative food. However, the biological control of aphids exerted by nocturnal predators was negatively affected by intercropping. The lower stratum (parsley) appeared to hamper the ability of nocturnal predators to reach aphids more quickly on the collard host plants (higher stratum). In total, our findings indicate that intercropping non‐flowering companion plants is likely enough to mediate an increase of natural enemies via shelter provision. In addition, the results suggest that nocturnal predators, or non‐flying predators for that matter, are hampered by complex lower stratum vegetation. Thus, considering natural enemy behaviour and plant characteristics when designing polyculture systems are vital for attaining conservation biological control success.

Identification and functional analysis of two P450 enzymes of Gossypium hirsutum involved in DMNT and TMTT biosynthesis

SummaryThe homoterpenes (3E)‐4,8‐dimethyl‐1,3,7‐nonatriene (DMNT) and (E,E)‐4,8,12‐trimethyl‐1,3,7,11‐tridecatetraene (TMTT) are major herbivore‐induced plant volatiles that can attract predatory or parasitic arthropods to protect injured plants from herbivore attack. In this study, DMNT and TMTT were confirmed to be emitted from cotton (Gossypium hirsutum) plants infested with chewing caterpillars or sucking bugs. Two CYP genes (GhCYP82L1 and GhCYP82L2) involved in homoterpene biosynthesis in G. hirsutum were newly identified and characterized. Yeast recombinant expression and enzyme assays indicated that the two GhCYP82Ls are both responsible for the conversion of (E)‐nerolidol to DMNT and (E,E)‐geranyllinalool to TMTT. The two heterologously expressed proteins without cytochrome P450 reductase fail to convert the substrates to homoterpenes. Quantitative real‐time PCR (qPCR) analysis suggested that the two GhCYP82L genes were significantly up‐regulated in leaves and stems of G. hirsutum after herbivore attack. Subsequently, electroantennogram recordings showed that electroantennal responses of Microplitis mediator and Peristenus spretus to DMNT and TMTT were both dose dependent. Laboratory behavioural bioassays showed that females of both wasp species responded positively to DMNT and males and females of M. mediator could be attracted by TMTT. The results provide a better understanding of homoterpene biosynthesis in G. hirsutum and of the potential influence of homoterpenes on the behaviour of natural enemies, which lay a foundation to study genetically modified homoterpene biosynthesis and its possible application in agricultural pest control.

Invasive insect herbivores as disrupters of chemically-mediated tritrophic interactions: effects of herbivore density and parasitoid learning

Invasive insect herbivores have the potential to interfere with native multitrophic interactions by affecting the chemical cues emitted by plants and disrupting the attraction of natural enemies mediated by herbivore-induced plant volatiles (HIPVs). In a previous study, we found that the presence of the exotic herbivore Spodoptera littoralis on Brassica rapa plants infested by the native herbivore Pieris brassicae makes these dually-infested plants unattractive to the main parasitoid of P. brassicae, the braconid wasp Cotesia glomerata. Here we show that this interference by S. littoralis is strongly dependent on the relative densities of the two herbivores. Parasitoids were only deterred by dually-infested plants when there were more S. littoralis larvae than P. brassicae larvae on a plant. Furthermore, the blend of HIPVs emitted by dually-infested plants differed the most from HIPVs emitted by Pieris-infested plants when S. littoralis density exceeded P. brassicae density. We further found that associative learning by the parasitoid affected its preferences: attraction to dually-infested plants increased after parasitoids were presented a P. brassicae caterpillar (rewarding experience) in presence of the odor of a dually-infested plant, but not when presented a S. littoralis caterpillar (non-rewarding experience). A non-rewarding experience prior to the bioassays resulted in a general decrease in parasitoid motivation to respond to plant odors. We conclude that herbivore density and associative learning may play an important role in the foraging behavior of natural enemies in communities, and such effects should not be overlooked when investigating the ecological impact of exotic species on native food webs.

Methyl jasmonate induction of cotton: a field test of the 'attract and reward' strategy of conservation biological control.

Natural or synthetic elicitors can affect plant physiology by stimulating direct and indirect defence responses to herbivores. For example, increased production of plant secondary metabolites, a direct response, can negatively affect herbivore survival, development and fecundity. Indirect responses include increased emission of plant volatiles that influence herbivore and natural enemy behaviour, and production of extrafloral nectar that serves as a food source for natural enemies after their arrival on induced plants. Therefore, the use of elicitors has potential for the study of basic aspects of tritrophic interactions, as well as application in biorational pest control, i.e. an 'attract and reward' strategy. We conducted a field study to investigate the effects of methyl jasmonate, an elicitor of plant defence responses, on three trophic levels: the plant, herbivores and natural enemies. We made exogenous applications of methyl jasmonate to transgenic cotton and measured volatile emission, extrafloral nectar production and plant performance (yield). We also assessed insect abundance, insect performance, and parasitism and predation of brown stink bug, Euschistus servus, eggs in methyl jasmonate-treated and untreated control plots. Application of methyl jasmonate increased emission of volatiles, in particular, (+)-limonene and (3E)-4,8-dimethyl-1,3,7-nonatriene, and production of extrafloral nectar, but not yield, compared with the control treatment. Despite increased volatile and extrafloral nectar production, methyl jasmonate application did not affect plant bug performance, or mortality of E. servus egg masses, and only marginally influenced insect abundance. Mortality of E. servus eggs varied over the course of the study. Overall, methyl jasmonate treatment affected cotton plant-induced responses, but not the insects that inhabit the plants. Our results were probably influenced by reduced natural enemy colonization of cotton from adjacent non-crop habitats, and subsequent low within-field population recruitment. Much remains to be learned about the effects of exogenous application of plant-produced 'enhancers' on the behaviour of natural enemies before crop physiology can be manipulated to enhance pest control.