Attraction Of Natural Enemies Research Articles

The Belowground–Aboveground Interactions of Zucchini: The Effects of Trichoderma afroharzianum Strain T22 on the Population and Behavior of the Aphid Aphis gossypii Glover and Its Endoparasitoid Aphidius colemani Viereck

Fungi belonging to the genus Trichoderma have received high consideration in agriculture due to their beneficial effects on crops from their plant promotion effects and protection from disease. A role of Trichoderma fungi in triggering plant defense mechanisms against insect pests, either directly or by natural enemy attraction, has been proposed, even if the results in different studies are controversial. In this present study, using zucchini plants as a model species, we investigated the effects of Trichoderma afroharzianum strain T22 plant inoculation on the cotton aphid Aphis gossypii and its endoparasitoid Aphidius colemani. Our results showed that the inoculation with T. afroharzianum T22 promotes A. gossypii population growth and makes zucchini more attractive to the aphid. The higher abundance of aphids on Trichoderma-inoculated zucchini was compensated for by a higher presence of the mummies of Aphidius colemani. In this present study, we recorded a higher zucchini biomass, thereby confirming that Trichoderma can act as a plant growth inducer.

Cultivars and Method of Application Influences the Effect of Silicon on Incidence and Damage of Phloem Feeders, Induction of Defense Reaction, Attraction of Natural Enemies and Yield in Black Gram (Vigna mungo L.)

Cultivars and Method of Application Influences the Effect of Silicon on Incidence and Damage of Phloem Feeders, Induction of Defense Reaction, Attraction of Natural Enemies and Yield in Black Gram (Vigna mungo L.)

Aphid-Induced Volatiles and Subsequent Attraction of Natural Enemies Varies among Sorghum Cultivars.

The production of herbivore-induced plant volatiles (HIPVs) is a type of indirect defense used by plants to attract natural enemies and reduce herbivory by insect pests. In many crops little is known about genotypic variation in HIPV production or how this may affect natural enemy attraction. In this study, we identified and quantified HIPVs produced by 10 sorghum (Sorghum bicolor) cultivars infested with a prominent aphid pest, the sorghum aphid (Melanaphis sorghi Theobald). Volatiles were collected using dynamic headspace sampling techniques and identified and quantified using GC-MS. The total amounts of volatiles induced by the aphids did not differ among the 10 cultivars, but overall blends of volatiles differed significantly in composition. Most notably, aphid herbivory induced higher levels of methyl salicylate (MeSA) emission in two cultivars, whereas in four cultivars, the volatile emissions did not change in response to aphid infestation. Dual-choice olfactometer assays were used to determine preference of the aphid parasitoid, Aphelinus nigritus, and predator, Chrysoperla rufilabris, between plants of the same cultivar that were un-infested or infested with aphids. Two aphid-infested cultivars were preferred by natural enemies, while four other cultivars were more attractive to natural enemies when they were free of aphids. The remaining four cultivars elicited no response from parasitoids. Our work suggests that genetic variation in HIPV emissions greatly affects parasitoid and predator attraction to aphid-infested sorghum and that screening crop cultivars for specific predator and parasitoid attractants has the potential to improve the efficacy of biological control.

Atmospheric Degradation of Ecologically Important Biogenic Volatiles: Investigating the Ozonolysis of (E)-β-Ocimene, Isomers of α and β-Farnesene, α-Terpinene and 6-Methyl-5-Hepten-2-One, and Their Gas-Phase Products.

Biogenic volatile organic compounds (bVOCs), synthesised by plants, are important mediators of ecological interactions that can also undergo a series of reactions in the atmosphere. Ground-level ozone is a secondary pollutant generated through sunlight-driven reactions between nitrogen oxides (NOx) and VOCs. Its levels have increased since the industrial revolution and reactions involving ozone drive many chemical processes in the troposphere. While ozone precursors often originate in urban areas, winds may carry these hundreds of kilometres, causing ozone formation to also occur in less populated rural regions. Under elevated ozone conditions, ozonolysis of bVOCs can result in quantitative and qualitative changes in the gas phase, reducing the concentrations of certain bVOCs and resulting in the formation of other compounds. Such changes can result in disruption of bVOC-mediated behavioural or ecological interactions. Through a series of gas-phase experiments using Gas Chromatography Mass Spectrometry (GC-MS) and Proton Transfer Reaction Mass Spectrometry (PTR-MS), we investigated the products and their yields from the ozonolysis of a range of ubiquitous bVOCs, which were selected because of their importance in mediating ecological interactions such as pollinator and natural enemy attraction and plant-to-plant communication, namely: (E)-β-ocimene, isomers of α and β-farnesene, α-terpinene and 6-methyl-5-hepten-2-one. New products from the ozonolysis of these compounds were identified, and the formation of these compounds is consistent with terpene-ozone oxidation mechanisms. We present the degradation mechanism of our model bVOCs and identify their reaction products. We discuss the potential ecological implications of the degradation of each bVOC and of the formation of reaction products.

Infestation with chewing (Spodoptera frugiperda) and piercing-sucking (Tetranychus urticae) arthropod lead to differential emission and biosynthesis of HIPVs underscoring MeSA and terpenoids in chrysanthemum foliage

Many volatiles that are induced in plant foliage as a result of herbivorous insect infestation can act as cues for natural enemy attraction or for priming defense mechanisms. However, the qualitative and quantitative differences in volatile emissions in chrysanthemum plants that are fed upon by pests with different mouthparts have not been explored. In this study, Tetranychus urticats (TEU) with piercing-sucking mouthparts and Spodoptera frugiperda larvae (FAW) with chewing mouthparts were selected to infest the Chrysanthemum morifolium leaves to determine the response of volatile emission and production induced by herbivore feeding with different mouthparts. Our results showed that FAW-infestation significantly increased the emission rate of monoterpenes and specifically induced the emission of β-pinene. In contrast, TEU-infested plants significantly enhanced the emission rate of sesquiterpenes and phenylpropanoids compared to the control group. In particular, β-funebrene and methyl salicylate (MeSA) were exclusively induced in TEU-infested plants. CmSAMTs responsible for the elicited emission of MeSA, were functionally characterized. Additionally, multiple CmTPSs with strikingly elevated expression induced by TEU and FAW-infestation were subjected to enzymatic assay for the identification of their biochemical function. The products (β-pinene, α-copaene, germacrene D, β-caryophyllene, β-funebrene and β-ylangene) of two pivotal CmTPSs covered the major terpene profiles elicited by TEU and FAW feeding. Overall, these results could deepen our understanding of the corresponding defensive strategies against herbivores feeding with different mouthparts in chrysanthemum plants and provide theoretical basis for the biological control of pests in the cultivation and production of chrysanthemum.

Enhancing Coccinella Beetle Biological Pest Control via a Floral Approach in Cucumber Greenhouse.

Flower-rich habitats are crucial for promoting biodiversity and ecosystem services within agricultural ecosystems, such as pollination and pest control. The present study investigates the efficacy of employing floral structures as a criterion for the selection of plant species in order to enhance the attraction of natural enemies within cucumber greenhouses, consequently augmenting floral resources. The results of our study provide evidence that flower strips have a beneficial effect on the fitness of critical natural predators, while not facilitating the proliferation of detrimental insect species. These findings exhibit potential for enhancing pest-management services in the agricultural sector. The findings of our study demonstrate that pest levels within greenhouse environments closely resemble those observed in real-world commercial cropping systems. As a result, the introduction of Coccinella septempunctata and Menochilus sexmaculatus biocontrol agents is confirmed to be a reliable and efficient method for pest management. The phenomenon of predator-prey density dependency is recognized as a crucial element in the implementation of biological control strategies. Furthermore, we investigate the impact of floral resources on the reproductive capacity of indigenous predators. The impact of Coriandrum sativum on fertility is substantial, indicating that the presence of a varied plant assortment with overlapping flowering periods can prolong the availability of floral resources. This study highlights the significance of flower-rich habitats and deliberate plant selection in augmenting biodiversity, ecosystem services, and pest management within agricultural settings. The implementation of conservation biological control technologies presents supplementary ecological advantages, thus offering practical implications for the promotion of sustainable agricultural practices.

Potential of Silicon to Improve Biological Control of Fall Armyworm, Spodoptera frugiperda on Maize

Silicon (Si) accumulation in plants confers a mechanical barrier to insect herbivory and may alter plant chemistry to increase the attraction of natural enemies to host insect herbivores on Si−treated plants. The fall armyworm (FAW), Spodoptera frugiperda, is a major insect pest of grain crops, including maize (Zea mays L.). This study examined whether Si supplementation alters maize volatile compounds that mediate host location in Euthyrhynchus floridanus, a generalist predator of FAW. A four-arm olfactometer was used to test the olfactory preference of nymphs and adults of E. floridanus to the odor of maize leaf materials from plants that were; Si−treated and infested, Si−treated without infestation, Si−deprived and infested, and Si−deprived without infestation. The probabilities of individual insects choosing between the four treatments were estimated using a multinomial generalized linear mixed model. There were no statistical differences in the olfactory preference of E. floridanus between Si−treated and Si−deprived maize leaf materials. However, the median estimate showed that nymphs were almost twice likely to be attracted to Si−supplemented leaf material, indicating a potential positive effect of Si. However, a more robust follow-up study is needed to further assess the impact of Si on E. floridanus.

Physiological Differences Between Seasonal Dimorphs of Agonoscena pistaciae (Hemiptera: Aphalaridae) Elicit Distinct Host Plant Responses, Informing Novel Pest Management Insights.

We examined differences in the physiology and life history between dimorphs of the common pistachio psyllid, Agonoscena pistaciae (Burckhardt and Lauterer) (Hemiptera: Aphalaridae), and how they differ in elicitating host plant production of key metabolites and volatile compounds involved in the recruitment of herbivores and natural enemies. Summer morphs had higher activities of glutathione S-transferase, carboxylesterase, acetylcholinesterase, and cytochrome P450 monooxygenase, superoxide dismutase, catalase, peroxidase, phenoloxidase, and a higher total protein content compared to winter morphs, whereas the latter had higher amounts of lipid, carbohydrate, and glycogen. Winter morphs were heavier, with a higher chitin content and longer preoviposition period, but greater fecundity and longevity than summer morphs. A lower LC50 to thiamethoxam for winter morphs resulted in higher mortality following exposure to the recommended rate of this insecticide in a greenhouse trial. Feeding by winter morphs elicited more strongly the release of volatile compounds known to be attractive to other herbivores, whereas feeding by summer morphs elicited more strongly the release of volatiles implicated in the attraction of natural enemies. Feeding by psyllids increased the concentrations of nitrogenous compounds, carbohydrates, vitamins, and amino acids in plants, the winter morph eliciting larger changes and more improved host plant quality. We conclude that winter morphs are more vulnerable targets for chemical control in early spring, whereas management of summer morphs could rely more on conservation biological control.

Molecular basis of (E)-β-farnesene-mediated aphid location in the predator Eupeodes corollae

(E)-β-farnesene (EBF) is an important chemical cue mediating interactions between plants, aphids, and natural enemies. This chemical has two origins, being secreted by aphid as an alarm pheromone and also produced by the attacked plants as a semiochemical attracting natural enemies. Despite the important role of this volatile chemical, little is known on the molecular mechanisms mediating the attraction of natural enemies to EBF. Here, we first verified that the larvae and adults of aphid predator hoverfly Eupeodes corollae detect and are attracted to EBF. Then, we found a neuron housed in type III basiconic sensilla of adult antenna responding to EBF. We further verified that in both adults and larvae odorant receptor EcorOR3 and odorant-binding protein EcorOBP15 mediate detection of EBF and structurally similar volatiles. Finally, we provide evidence that larvae of E.corollae may use aphid-derived EBF for prey location in the short-range, whereas adults could detect plant-derived EBF to find attacked plants from longer distances. Thus, while dissecting the molecular basis for attraction to EBF produced by two different sources, our results may find potential applications in integrated aphid management approaches.

Endophytic Colonization by the Entomopathogenic Fungus Beauveria Bassiana Affects Plant Volatile Emissions in the Presence or Absence of Chewing and Sap-Sucking Insects.

Entomopathogenic fungi are gaining acceptance in Integrated Pest Management (IPM) systems as effective and environmental safety biological control agents to protect a great variety of crops against pest insects. Many of these insect-pathogenic fungi can establish themselves as endophytes and thereby may induce the plant immune system. The activation of plant defenses by the fungal endophytic colonization can have a direct impact on herbivores and plant pathogens. An integral component of many plant defense responses is also the release of volatile organic compounds, which may serve as an indirect defense by attracting the natural enemies of herbivores. Here we investigated the effect of endophytic colonization by the entomopathogenic fungus Beauveria bassiana on the volatile emission by melon and cotton plants, either unharmed or after being damaged by sap-sucking aphids or leaf chewing caterpillars. We found that when the plants are colonized by B. bassiana they emit a different blend of volatile compounds compared to uncolonized control plants. Some of the emitted compounds have been reported previously to be released in response to herbivory and have been implicated in natural enemy attraction. Several of the compounds are also known to have antimicrobial properties. Therefore, endophytic colonization by B. bassiana might help to not only direct control insect pests but also increase the resistance of plants against agronomically important pests and phytopathogens.

Silica nanoparticles as pesticide against insects of different feeding types and their non-target attraction of predators

The agricultural use of silica (SiO2) nanoparticles (NPs) has the potential to control insect pests while the safety and tritrophic effects on plants and beneficial natural enemies remains unknown. Here, we evaluate the effects of silica NPs on insect pests with different feeding niches, natural enemies, and a plant. Silica NPs were applied at different concentrations (75–425 mg/L) on field-cultivated faba bean and soybean for two growing seasons. The faba bean pests, the cowpea aphid Aphis craccivora and the American serpentine leafminer Liriomyza trifolii, and the soybean pest, the cotton leafworm Spodoptera littoralis, were monitored along with their associated predators. Additional laboratory experiments were performed to test the effects of silica NPs on the growth of faba bean seedlings and to determine whether the rove beetle Paederus fuscipes is attracted to cotton leafworm-infested soybean treated with silica NPs. In the field experiments, silica NPs reduced the populations of all three insect pests and their associated predators, including rove beetles, as the concentration of silica NPs increased. In soybean fields, however, the total number of predators initially increased after applying the lowest concentration. An olfactometer-based choice test found that rove beetles were more likely to move towards an herbivore-infested plant treated with silica NPs than to a water-treated control, suggesting that silica NPs enhance the attraction of natural enemies via herbivore-induced plant volatiles. In the laboratory, while silica NPs inhibited the development of faba bean roots at 400 mg/L, they did not affect germination percentage, germination time, shoot length, or vigor index compared to the control.

Silicon suppresses a ubiquitous mite herbivore and promotes natural enemy attraction by altering plant volatile blends

Silicon (Si) accumulation in plants is widely recognised as an effective physical defence against chewing herbivores. However, its effects on some feeding guilds such as cell-content feeders are understudied despite being severe economic pests (e.g. Tetranychus urticae). Moreover, most studies focus on direct impacts of Si, but there is growing evidence that Si also impacts indirect defence. We examined the effects of Si on French bean, Phaseolus vulgaris, defences against the two-spotted spider mite, T. urticae. We grew plants hydroponically with (+ Si) or without (–Si) silicon, assessed T. urticae performance and tested the preference of the predatory mite, Phytoseiulus persimilis, for volatiles from T. urticae-infested (+ M) or uninfested (–M) plants. The provision of Si to plants suppressed T. urticae egg-laying, population growth and leaflet damage, and partially ameliorated T. urticae-induced reductions in stomatal conductance and net photosynthesis. Furthermore, T. urticae infestation increased foliar Si accumulation. Predatory mites were more attracted (64%) to volatiles from + Si plants experiencing herbivory than to –Si plants. The relative emissions (%) of volatile compounds, viz. E-2-hexanyl benzoate, hexanal, E-trans-β-ocimene, D-limonene, β-caryophyllene and methyl salicylate were elevated from + Si + M plants, while the relative emissions of 3-hexanol, trans-calamenene, o-xylene and o-cymene were lowered compared to –Si + M plants. Our results show, for the first time, that Si defences are inducible and effective even in low Si-accumulating plants against T. urticae and suggest that Si could play a role in pest biocontrol.

Olfactory perception of herbivore‐induced plant volatiles elicits counter‐defences in larvae of the tobacco cutworm

Abstract Herbivore attack leads to increased emission of herbivore‐induced plant volatiles (HIPVs) that protect plants by eliciting direct anti‐herbivore defences and indirect defences via attraction of natural enemies. Whether herbivorous insects can develop counter‐defences against host plants in response to HIPVs is largely unexplored. Using a directed airflow apparatus, we investigated the influence of HIPVs emitted from tobacco cutworm Spodoptera litura‐infested tomatoes on larval performance on herbivore‐pretreated tomatoes versus untreated tomatoes or on trypsin inhibitor‐amended artificial diets versus unamended diets, as well as the transcriptional responses of HIPV‐exposed larvae. Spodoptera litura larval feeding on tomato plants led to increased emission of HIPVs. The HIPV‐exposed larvae showed significantly increased survival rates and weight gains on both herbivore‐pretreated tomato leaves and trypsin inhibitor‐supplemented diet but not on untreated tomato leaves and control diets, nor when they had been exposed to HIPVs emitted from spr8 mutant plants which barely emit terpenes. These results suggest that larval exposure to HIPVs from wild‐type plants enhanced their ability to cope with plant‐induced defences. The latter is supported by the observation that larval exposure to HIPVs led to enhanced transcript levels of eight genes encoding cuticle proteins, and seven genes encoding cytochrome P450s, an important class of detoxification enzymes. Our studies revealed a mechanism by which larval olfactory perception of HIPVs elicits counter‐defences that enhance the ability of insect herbivores to withstand host plant chemical defences.

Seed-to-seedling transitions exhibit distance-dependent mortality but no strong spacing effects in a Neotropical forest.

Patterns of seed dispersal and seed mortality influence the spatial structure of plant communities and the local coexistence of competing species. Most seeds are dispersed in proximity to the parent tree, where mortality is also expected to be the highest, because of competition with siblings or the attraction of natural enemies. Whereas distance-dependent mortality in the seed-to-seedling transition was often observed in tropical forests, few studies have attempted to estimate the shape of the survival-distance curves, which determines whether the peak of seedling establishment occurs away from the parent tree (Janzen-Connell pattern) or if the peak attenuates but remains at the parent location (Hubbell pattern). In this study, we inferred the probability density of seed dispersal and two stages of seedling establishment (new recruits, and seedlings 20cm or taller) with distance for 24 tree species present in the 50-ha Forest Dynamics Plot of Barro Colorado Island, Panama. Using data from seed traps, seedling survey quadrats, and tree-census records spanning the 1988-2014 period, we fit hierarchical Bayesian models including parameters for tree fecundity, the shape of the dispersal kernel, and overdispersion of seed or seedling counts. We combined predictions from multiple dispersal kernels to obtain more robust inferences. We find that Hubbell patterns are the most common and Janzen-Connell patterns are very rare among those species; that distance-dependent mortality may be stronger in the seed stage, in the early recruit stage, or comparable in both; and that species with larger seeds experience less overall mortality and less distance-dependent mortality. Finally, we describe how this modeling approach could be extended at a community scale to include less abundant species.

Methyl Salicylate Increases Attraction and Function of Beneficial Arthropods in Cranberries.

Methyl salicylate (MeSA) is an herbivore-induced plant volatile (HIPV) known to attract the natural enemies of herbivores in agro-ecosystems; however, whether this attraction leads to an increase in natural enemy functioning, i.e., predation, remains largely unknown. Here, we monitored for 2 years (2011–2012) the response of herbivores and natural enemies to MeSA lures (PredaLure) by using sticky and pitfall traps in cranberry bogs. In addition, European corn borer, Ostrinia nubilalis, egg masses were used to determine whether natural enemy attraction to MeSA leads to higher predation. In both years, MeSA increased adult hoverfly captures on sticky traps and augmented predation of O. nubilalis eggs. However, MeSA also attracted more phytophagous thrips and, in 2012, more plant bugs (Miridae) to sticky traps. Furthermore, we used surveillance cameras to record the identity of natural enemies attracted to MeSA and measure their predation rate. Video recordings showed that MeSA lures increase visitation by adult lady beetles, adult hoverflies, and predatory mites to sentinel eggs, and predation of these eggs doubled compared to no-lure controls. Our data indicate that MeSA lures increase predator attraction, resulting in increased predation; thus, we provide evidence that attraction to HIPVs can increase natural enemy functioning in an agro-ecosystem.

Volatile extraction from soybean plants infested with several herbivores

The oral secretion of herbivores triggers chemical defenses in plants. When subjected to simultaneous or se­quential attack by herbivores, plants emit volatile compounds of varying chemical nature, which can interfere with the attraction of natural enemies. This study investigates the profile of volatile compounds emitted by transgenic soybean (Bt M6210 IPRO) plants infested with Tetranychus urticae Koch (Acari: Tetranychidae) and Anticarsia gemmatalis Hubner (Lepidoptera: Noctuidae). To this end, we used a method without leaf maceration. For plant infestation, 100 T. urticae mites per plant were used for one day and, subsequently, 2 A. gemmatalis caterpillars for 36 hours. Volatile compounds produced after infestation were analyzed by gas chromatography coupled with mass spectrometry. Principal component analysis showed differences between groups of compounds and explained 77.5% of the variation in volatiles. There are chemical differences between the emission of compounds according to the type of herbivory. It is concluded that soybean plants infested in a single ( T. urticae ) or multiple ( T. urticae followed by A. gemmatalis ) way trigger the production of volatile compounds that can be used as chemical traces to direct the foraging of natural enemies. The possible functions of volatiles produced after herbivory are discussed.

Silicon and Plant Natural Defenses against Insect Pests: Impact on Plant Volatile Organic Compounds and Cascade Effects on Multitrophic Interactions.

Environmental factors controlling silicon (Si) accumulation in terrestrial plant are key drivers to alleviate plant biotic stresses, including insect herbivory. While there is a general agreement on the ability of Si-enriched plant to better resist insect feeding, recent studies suggest that Si also primes biochemical defense pathways in various plant families. In this review, we first summarize how soil parameters and climate variables influence Si assimilation in plants. Then, we describe recent evidences on the ability of Si to modulate plant volatile emissions, with potential cascade effects on phytophagous insects and higher trophic levels. Even though the mechanisms still need to be elucidated, Si accumulation in plants leads to contrasting effects on the levels of the three major phytohormones, namely jasmonic acid, salicylic acid and ethylene, resulting in modified emissions of plant volatile organic compounds. Herbivore-induced plant volatiles would be particularly impacted by Si concentration in plant tissues, resulting in a cascade effect on the attraction of natural enemies of pests, known to locate their prey or hosts based on plant volatile cues. Since seven of the top 10 most important crops in the world are Si-accumulating Poaceae species, it is important to discuss the potential of Si mobility in soil-plant systems as a novel component of an integrated pest management.

Mycorrhizae Alter Constitutive and Herbivore-Induced Volatile Emissions by Milkweeds.

Plants use volatile organic compounds (VOCs) to cue natural enemies to their herbivore prey on plants. Simultaneously, herbivores utilize volatile cues to identify appropriate hosts. Despite extensive efforts to understand sources of variation in plant communication by VOCs, we lack an understanding of how ubiquitous belowground mutualists, such as arbuscular mycorrhizal fungi (AMF), influence plant VOC emissions. In a full factorial experiment, we subjected plants of two milkweed (Asclepias) species under three levels of AMF availability to damage by aphids (Aphis nerii). We then measured plant headspace volatiles and chemical defenses (cardenolides) and compared these to VOCs emitted and cardenolides produced by plants without herbivores. We found that AMF have plant species-specific effects on constitutive and aphid-induced VOC emissions. High AMF availability increased emissions of total VOCs, two green leaf volatiles (3-hexenyl acetate and hexyl acetate), and methyl salicylate in A. curassavica, but did not affect emissions in A. incarnata. In contrast, aphids consistently increased emissions of 6-methyl-5-hepten-2-one and benzeneacetaldehyde in both species, independent of AMF availability. Both high AMF availability and aphids alone suppressed emissions of individual terpenes. However, aphid damage on plants under high AMF availability increased, or did not affect, emissions of those terpenes. Lastly, aphid feeding suppressed cardenolide concentrations only in A. curassavica, and AMF did not affect cardenolides in either plant species. Our findings suggest that by altering milkweed VOC profiles, AMF may affect both herbivore performance and natural enemy attraction.

Genotypic Variation and Phenotypic Plasticity in Gene Expression and Emissions of Herbivore-Induced Volatiles, and their Potential Tritrophic Implications, in Cranberries.

Herbivorous insects are important problems in cranberry (Vaccinium macrocarpon Ait.) production. The use of chemical pesticides is common practice, but beneficial insects such as natural enemies of herbivores (e.g. predators and parasitoids) could be affected as well. Therefore, we studied the defensive mechanisms that cranberry plants use to combat pests, focusing on herbivore-induced plant volatiles (HIPVs), which can be used to recruit predators and parasitoids foraging for prey or hosts. Then, we used synthetic HIPVs to test the attraction of natural enemies. In a greenhouse, we assessed nine cranberry genotypes for expression of genes involved in HIPV biosynthesis and/or emission of HIPVs. In an experimental field, we assessed whether baiting traps with individual or combinations of HIPVs increased attractiveness to natural enemies. The results showed that different cranberry genotypes vary in their emission of monoterpenes and sesquiterpenes but not in their expression of two genes associated with terpene biosynthesis, α-humulene/β-caryophyllene synthase and (3S,6E)-nerolidol/R-linalool synthase. Induction with methyl jasmonate or herbivore (gypsy moth, Lymantria dispar L.) feeding increased the expression of these genes and emission of HIPVs. The HIPV methyl salicylate (MeSA), alone or in combination with other HIPVs, increased syrphid attraction by 6-fold in the field, while (Z)-3-hexenyl acetate and MeSA repelled ladybeetles and megaspilids, respectively. Linalool and β-caryophyllene elicited no behavioral responses of natural enemies. Elucidating the mechanisms of pest resistance, as well as experimentally augmenting plant defenses such as HIPVs, may contribute to the development of more sustainable pest management practices in crops, including cranberries.

Cascading effects of combining synthetic herbivore-induced plant volatiles with companion plants to manipulate natural enemies in an agro-ecosystem.

Whether tactics to manipulate natural enemies in agro-ecosystems enhance their ecosystem function and services remains debatable. We conducted field experiments in 2015-2016 to test the hypothesis that attraction of natural enemies to herbivore-induced plant volatiles (HIPVs), alone or in combination with companion plants, increases crop productivity. Our treatments consisted of bean plants alone or baited with methyl salicylate (MeSA; an HIPV), or combined with coriander (a companion plant), or with both MeSA and coriander. Numbers of arthropods were visually sampled in each treatment. Sentinel aphids were used to measure ecosystem function (i.e. predation). Plant damage and biomass, and the number and weight of pods and seeds, were measured as a proxy for ecosystem services. MeSA and coriander, when alone or combined, increased the abundance of insect predators from six families, reduced herbivore (e.g. spider mite and thrips) populations, and increased aphid predation. MeSA and coriander also reduced damage by spider mites. MeSA with or without coriander did not, however, increase crop biomass or any yield parameters. MeSA alone or combined with coriander attracted different predator communities, altered pest communities, and reduced damage; however, these results did not cascade down to improve crop productivity. © 2018 Society of Chemical Industry.