Attraction Of Wasps Research Articles

Plant-derived monoterpene S-linalool and β-ocimene generated by CsLIS and CsOCS-SCZ are key chemical cues for attracting parasitoid wasps for suppressing Ectropis obliqua infestation in Camellia sinensis L.

Insect-induced plant volatile organic compounds (VOCs) may function as either direct defence molecules to deter insects or indirect defence signals to attract the natural enemies of the invading insects. Tea (Camellia sinensis L.), an important leaf-based beverage crop, is mainly infested by Ectropis obliqua which causes the most serious damage. Here, we report a mechanistic investigation of tea plant-derived VOCs in an indirect defence mechanism against E. obliqua. Parasitoid wasp Parapanteles hyposidrae, a natural enemy of E. obliqua, showed strong electrophysiological response and selection behaviour towards S-linalool and β-ocimene, two monoterpenes with elevated emission from E. obliqua-damaged tea plants. Larvae frass of E. obliqua, which also released S-linalool and β-ocimene, was found to attract both mated female or male Pa. hyposidrae according to gas chromatography-electroantennogram detection and Y-tube olfactometer assays. In a field setting, both S-linalool and β-ocimene were effective in recruiting both female and male Pa. hyposidrae wasps. To understand the molecular mechanism of monoterpenes-mediated indirect defence in tea plants, two novel monoterpene synthase genes, CsLIS and CsOCS-SCZ, involved in the biosynthesis of S-linalool or β-ocimene, respectively, were identified and biochemically characterised. When the expression of these two genes in tea plants was inhibited by antisense oligodeoxynucleotide, both volatile emission and attraction of wasps were reduced. Furthermore, gene expression analysis suggested that the expression of CsLIS and CsOCS-SCZ is regulated by the jasmonic acid signalling pathway in the tea plant.

Oviposition substrate location by the invasive woodwasp Sirex noctilio: the combined effect of chemical cues emitted by its obligate symbiont Amylostereum areolatum and different host-tree species.

Sirex noctilio is an invasive forest wasp that affects pines and can result in severe economic losses. The use of semiochemicals offers an opportunity to develop sensitive and specific capturing systems to mitigatenegative impacts. Previous research showed that female S. noctilio would use volatiles emitted by its fungal symbiont, Amylostereum areolatum, but little is known about how these modulate behaviour when combined with pine-wood emissions. Our aim was to understand the relevance of fungal volatiles grown on artificial media and wood from two hosts trees, Pinus contorta and Pinus ponderosa, on behavioural and electroantennographic responses of wasp females. Because background odours can modify an insect's response towards resource-indicating semiochemicals, we propose that the behaviour towards the symbiont (resource) will be modulated by host pine emissions (background odours). Olfactometric assays showed that both host species with fungus were attractive when contrasted against air (P. contorta versus Air, χ2 = 12.19, P < 0.001; P. ponderosa versus Air, χ2 = 20.60, P < 0.001) and suggest a clear hierarchy in terms of female preferences towards the tested stimuli, with response highest towards the fungus grown on P. contorta (olfactory preference index: 5.5). Electrophysiological analyses indicate that females detect 62 volatile compounds from the tested sources. Results indicate a strong synergy between symbiont and host semiochemicals, suggesting that the pine species could play a fundamental role in the interaction. Further understanding of the chemical basis of this, could guide the development of specific and attractive lures, in order to maximize attraction of wasps in surveillance programmes. © 2023 Society of Chemical Industry.

Maintenance of specificity in sympatric host-specific fig/wasp pollination mutualisms.

BackgroundFig/wasp pollination mutualisms are extreme examples of species-specific plant-insect symbioses, but incomplete specificity occurs, with potentially important evolutionary consequences. Why pollinators enter alternative hosts, and the fates of pollinators and the figs they enter, are unknown.MethodsWe studied the pollinating fig wasp, Ceratosolen emarginatus, which concurrently interacts with its typical host Ficus auriculata and the locally sympatric alternative host F. hainanensis, recording frequencies of the wasp in figs of the alternative hosts. We measured ovipositor lengths of pollinators and style lengths in female and male figs in the two host species. Volatile organic compounds (VOCs) emitted by receptive figs of each species were identified using GC-MS. We tested the attraction of wasps to floral scents in choice experiments, and detected electrophysiologically active compounds by GC-EAD. We introduced C. emarginatus foundresses into figs of both species to reveal the consequences of entry into the alternative host.ResultsC. emarginatus entered a low proportion of figs of the alternative host, and produced offspring in a small proportion of them. Despite differences in the VOC profiles of the two fig species, they included shared semiochemicals. Although C. emarginatus females prefer receptive figs of F. auriculata, they are also attracted to those of F. hainanensis. C. emarginatus that entered male figs of F. hainanensis produced offspring, as their ovipositors were long enough to reach the bottom of the style; however, broods were larger and offspring smaller than in the typical host. Female figs of F. hainanensis failed to produce seeds when visited by C. emarginatus. These findings advance our current understanding of how these species-specific mutualisms usually remain stable and the conditions that allow their diversification.

Attraction of Trichogramma Wasps to Butterfly Oviposition-Induced Plant Volatiles Depends on Brassica Species, Wasp Strain and Leaf Necrosis

Within the Brassicaceae, wild as well as crop species are challenged by specialist herbivores including cabbage white butterflies (Pieris spp.). The wild crucifer Brassica nigra responds to oviposition by Pieris butterflies by the synergistic expression of two egg-killing traits. Genotypes that express a hypersensitive response (HR)-like necrosis (direct egg-killing) also emit oviposition-induced plant volatiles (OIPVs) attracting Trichogramma egg parasitoids (indirect egg-killing). This so-called double defense line can result in high butterfly egg mortalities. It remains unknown whether this strategy is unique to B. nigra or more common in Brassica species. To test this, we examined the response of different Trichogramma evanescens lines to OIPVs emitted by B. nigra and three close relatives (Brassica napus, Brassica rapa, and Brassica oleracea). Furthermore, we evaluated whether HR-like necrosis played a role in the attraction toward plant volatiles. Our results show a specificity in wasp attraction to different plant species. Three out of four plant species attracted a specific T. evanescens strain, including the crops B. rapa and B. napus. Parasitoid attraction was positively affected by presence of HR-like necrosis in one plant species. Our findings imply that, despite being a true generalist in terms of host range, T. evanescens shows intraspecific variation during host searching, which should be taken into account when selecting parasitoid lines for biocontrol of certain crops. Finally, we conclude that also crop plants within the Brassicaceae family possess egg-killing traits and can exert the double-defense line which may enable effective selection of egg-killing defense traits by cabbage breeders.

The Role of Color Traps and Attractive Baits in Reducing Damage of Red Wasp Vespa orientalis L. on Honeybee Colonies in Khabat/Erbil-Iraq

In the present study which carried out in the Khabat Technical Institute for the spring and autumn seasons during the period from 1/4/2014 to 3/10/2014 by applying special techniques for hunting wasps that attack honey bee colonies in the apiary, in order to know the attraction of red wasps (Vespa orientalis L.). Study result found that the techniques used in capturing and hunting wasps all serve to reduce the severity of red wasps attacks. The results indicated the superiority of the data for the averages annual numbers of traps were (pink, yellow, green, and comparison) was (78.9), (110.8), (80.1) and (30) respectively. The average number of wasps trapped (84.8), (98.1), (79.4) and (79.2) by taste traps (pear juice, date palms juice, grape juice and control (the sugar solution)), respectively. The efficiency of colored traps on attracting wasps from transparent traps (without color), the mean of yellow traps significantly different from other by (110.8) wasps/trap however the efficiency of the rest of color traps adhesively better than control, as well as the taste of dates palm juice significantly on average (98.1) wasp / trap higher compare to the rest of the juice traps.&nbsp;

Whitefly-induced tomato volatiles mediate host habitat location of the parasitic wasp Encarsia formosa, and enhance its efficacy as a bio-control agent.

Whitefly Bemisia tabaci is a phloem-feeding insect and causes extensive agricultural damage around the world. Although the parasitic wasp Encarsia formosa is widely used to control B. tabaci on glasshouse tomatoes, low efficiency and discontinuity are frequently recorded. It has been well-documented that herbivore-induced plant volatiles (HIPVs) are important cues in the foraging behavior of the natural enemies of herbivores. However, the volatiles emitted from tomatoes infested by different developmental stages of B. tabaci (nymphs versus adults) have not been compared in terms of their effects on E. formosa attraction. Olfactometer assays with four tomato cultivars revealed that the E. formosa wasps showed a significant attraction to the volatiles from adult-infested plants (except for cv. Castlemart), but not to those from nymph-infested plants. In a close-range habitat, however, the wasps appeared to use visual or tactile cues derived from nymphs for host location. Volatile analyses and behavioral assays showed that wasp attraction was correlated with enhanced β-myrcene and β-caryophyllene emissions from adult-infested plants. Furthermore, the use of B. tabaci adult-induced plant cues under glasshouse conditions resulted in a higher parasitism rate by this parasitoid. Our findings confirm that E. formosa uses the HIPVs resulting from feeding of B. tabaci adults to locate host habitat. Release of β-myrcene and β-caryophyllene from dispensers may enhance the efficacy of E. formosa as a biological control agent against B. tabaci in glasshouse production systems.

Isolation and identification of attractants from the pupae of three lepidopteran species for the parasitoid Chouioia cunea Yang.

Chouioia cunea Yang (Hymenoptera: Eulophidae) is a parasitic wasp and natural enemy of several lepidopteran pests during their pupal stage. The volatiles from pupae of three hosts, Hyphantria cunea (Arctiidae), Antheraea pernyi (Saturniidae) and Lymantria dispar (Erebidae), were analyzed and compared to elucidate the chemical cues used by C. cunea to locate its hosts. The attraction of C. cunea to H. cunea pupae has no obvious association with the types of plant leaves consumed by H. cunea before pupation. C. cunea exhibited the strongest attraction to the pupae of H. cunea, followed by those of A. pernyi and L. dispar based on behavioral experiments. Gas chromatography-mass spectrometry and GC-electroantennography (GC-EAD) analyses showed that these three host pupae consisted of essentially the same active volatile components but at different relative amounts. Active components derived from these pupae by GC-EAD were alkanes from C12 to C27, and C. cunea showed different levels of attraction to different single compounds. Host location by C. cunea primarily depends on common compounds emanating from the pupae of several host species. The relative amount of each component varies across host species, guiding host preferences by C. cunea. Optimal blends of several components were identified. Understanding the chemical cues used by C. cunea to locate its host could increase the possibility of developing attractants for parasitic wasps and subsequently increasing the parasitism rate of C. cunea on various hosts. © 2019 Society of Chemical Industry.

DISPERSAL OF SPICEBUSH (CALYCANTHUS OCCIDENTALIS, CALYCANTHACEAE) BY YELLOW JACKETS (GENUS VESPULA; HYMENOPTERA: VESPIDAE)

Carnivorous wasps of the family Vespidae are known to seek out and disperse the diaspores of at least two North American and two Asian plant species. Attraction of the wasps to the diaspores is likely due to the release of volatile compounds that signal availability of an eliaiosome rich in protein and fat, which the wasps remove before releasing the diaspore. It is thought that this interaction between carnivorous wasps and plants is rare, occurring in just a few plant species. Here, we present our findings on dispersal of spicebush (Calycanthus occidentalis Hook. & Arn.) achenes by carnivorous wasps of the genus Vespula. Observations and experiments were performed with the goals of discovering: how geographically widespread this interaction is; what the reward system is, if any; and, how wasps detect the achenes. Eight populations of C. occidentalis in northern California were used to observe wasps and plants, and to perform experiments on wasp attraction to the achenes. In all examined populations, workers of western yellowjacket (Vespula pensylvanica [de Saussure, 1857]) were observed entering mature Calycanthus receptacles, removing achenes, taking flight with them, and successfully transporting achenes through the air. Receptacles were found to open upward at an average angle of 45° (SD = 29°), preventing the achenes from falling to the ground when mature. No animals other than wasps were observed visiting the receptacles during the observations. Experiments suggest that wasps are attracted to an elaiosome-like organ of the achene. Nutritional analysis shows that this organ is high in fat and protein. Further experiments using solvent extracts of the achenes suggest that the attraction is likely mediated by volatile compounds.

Volatiles released by damaged leaves of Piper mollicomum (Piperaceae) act as cues for predaceous wasps: evidence using plasticine dummies as herbivore model

Volatiles released by damaged plants are used as cues by predators and parasitoids to find their herbivorous prey. Here, we assessed whether odor cues released by simulated herbivore-damaged leaves in Piper mollicomum attract predaceous wasps. We applied plasticine dummy caterpillars as an herbivore model to evaluate predation risk on undamaged and artificially damaged leaves by the mandible marks left by foraging wasps. Despite observing a tendency of a visual component in the wasp attraction (more marks on dummies under old naturally damaged leaves), we observed that chemical cues play a crucial role, with recent artificial damage and leaves baited with volatile essential oils of P. mollicomum attracting more wasps for the dummies than those untreated. Headspace analysis by GC–MS showed that undamaged leaves released small amounts of compounds, while damaged ones released 63 times more volatiles, which consisted of a blend containing mostly mono- and sesquiterpenoids. Histochemical tests revealed that terpenoids are located in oil cells spread among the leaf tissue, and may be released by the disruption of such cells when herbivores are feeding on leaves. We suggest that signals of disrupted plants differ from the mosaic of odor blends emitted by the background environment and may provide a detectable, although not necessarily specific, cue for prey presence. Such detectable cues are important for generalist foraging predaceous wasps, since they spend time searching for prey in different host plants.

Effects of single or combined water deficit and aphid attack on tomato volatile organic compound (VOC) emission and plant-plant communication

Plants release a broad spectrum of volatile organic compounds (VOCs). The composition of the released VOC blend is dependent on the physiological status and, consequently, is affected by biotic and abiotic stresses. Stress-related VOCs can be perceived by different organisms, including natural enemies of herbivores and neighboring plants. Here, the responses of tomato plants (emitters) to single or combined abiotic (water stress) and biotic (aphid attack) stresses, and the effect of VOC released by emitters on neighboring unstressed plants (receivers), have been investigated. Emissions of α-pinene and methyl salicylate from plants exposed to single or combined stress, and of camphene from plants exposed to water or combined stress were significantly higher than in unstressed plants. In receivers, only the release of methyl salicylate increased when companion emitters were stressed. The expression of genes related to VOC biosynthesis and plant defense responses was unaffected or declined in water-stressed emitters, and was generally higher in receivers than in emitters. The gene coding for methyl salicylate biosynthesis was particularly active in aphid-attacked emitters and in receivers that were conditioned by the infested emitters. In addition, VOCs emitted by stressed plants induce VOC emission in unstressed receivers, and this increases attraction of parasitic wasps, which may improve protection against aphid attacks under conditions of reduced water availability.

Priming of cowpea volatile emissions with defense inducers enhances the plant's attractiveness to parasitoids when attacked by caterpillars.

The manipulation of herbivore-induced volatile organic compounds (HI-VOCs) via the application of the inducers benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester (BTH) and laminarin (β-1,3-glucan) is known to enhance the attractiveness of caterpillar-damaged cotton and maize plants to parasitoids. To test if this is also the case for legumes, we treated cowpea (Vigna unguiculata var. unguiculata) with these inducers and studied the effects on HI-VOC emissions and the attraction of three generalist endoparasitoids. After the inducers had been applied and the plants subjected to either real or mimicked herbivory by Spodoptera littoralis caterpillars, females of the parasitoids Campoletis sonorensis and Microplitis rufiventris showed a strong preference for BTH-treated plants, whereas Cotesia females were strongly attracted to both BTH- and laminarin-treated plants with real or mimicked herbivory. Treated plants emitted more of certain HI-VOCs, but considerably less indole and linalool and less of several sesquiterpenes. Multivariate data analysis revealed that enhanced wasp attraction after treatment was correlated with high relative concentrations of nonanal, α-pinene, (E)-β-ocimene and (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), and with low relative concentrations of indole, (S)-linalool and (E)-β-farnesene. Inducer treatments had no significant effect on leaf consumption by the caterpillars. Our findings confirm that treating cowpea plants with inducers can enhance their attractiveness to biological control agents. © 2017 Society of Chemical Industry.

Corrigendum

Functional EcologyVolume 31, Issue 8 p. 1670-1670 CorrigendumFree Access Corrigendum This article corrects the following: Compatible and incompatible pathogen–plant interactions differentially affect plant volatile emissions and the attraction of parasitoid wasps Camille Ponzio, Berhane T. Weldegergis, Marcel Dicke, Rieta Gols, Sergio Rasmann, Volume 30Issue 11Functional Ecology pages: 1779-1789 First Published online: June 28, 2016 First published: 10 July 2017 https://doi.org/10.1111/1365-2435.12931Citations: 1AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Ponzio, C., Weldegergis, B.T., Dicke, M. & Gols, R. (2016) Compatible and incompatible pathogen–plant interactions differentially affect plant volatile emissions and the attraction of parasitoid wasps. Functional Ecology, 30, 1779–1789. https://doi.org/10.1111/1365-2435.12689. After publication of this article the authors carried out some further symptom development and PCR analyses of the bacterial strains used. Based on these analyses the authors have found that the virulent pathogen used in the article was in fact Xanthomonas campestris pathovar raphani, (formerly known as Xanthomonas campestris pathovar armoraciae), not Xanthomonas campestris pathovar campestris as listed in the article. The journal editors and authors are satisfied that this error does not affect the results or conclusions of the article. The authors apologise for any confusion or inconvenience caused by this error. Reference Ponzio, C., Weldegergis, B.T., Dicke, M., & Gols, R. (2016) Compatible and incompatible pathogen–plant interactions differentially affect plant volatile emissions and the attraction of parasitoid wasps. Functional Ecology, 30, 1779– 1789. https://doi.org/10.1111/1365-2435.12689 Citing Literature Volume31, Issue8August 2017Pages 1670-1670 ReferencesRelatedInformation

Floral signals and filters in a wasp- and a bee-pollinated Gomphocarpus species (Apocynaceae: Asclepiadeae)

Floral traits may function as attractants for some flower visitors and also as mechanisms that filter out non-beneficial flower visitors. Our current understanding of floral filter mechanisms is limited as this particular aspect of floral function has received less attention than floral attractants. Here we report on a case of two closely related Gomphocarpus species, G. physocarpus and G. fruticosus, that are similar in their general floral shape and architecture but differ in their main pollinators, which are vespid wasps and honeybees, respectively. To identify the floral traits that best explain the observed pollinators we analysed and compared the floral scent composition, the flower colour, flower morphology, and nectar sugar composition of the two species. Furthermore, the response to floral scent was tested in behavioural experiments with Belanogaster and Polistes vespid wasps. The floral scent composition differed significantly between the plant species. Acetic acid was a main component in the wasp-pollinated G. physocarpus, which is highly unusual for a floral scent bouquet. Choice experiments suggest that the species-specific odour might be responsible for the selective attraction of either wasps or bees. Furthermore, wasp-pollinated G. physocarpus flowers offer relatively large amounts of nectar that is freely accessible to insect visitors, whereas in G. fruticosus the site of nectar accumulation is covered by a specific morphological structure that makes it difficult for short-tongued insects such as wasps to access the nectar. Altogether, pollinator specialisation in the two Gomphocarpus species seem to be due to a combination of floral filter mechanisms and olfactory cues that cause flower visitors to learn to differentiate between the two species.

A cry for help or sexual perfumes? An alternative hypothesis for wasp attraction to the scent of caterpillar-wounded plants.

This article comments on: Combined use of herbivore-induced plant volatiles and sex pheromones for mate location in braconid parasitoids.

Discovery and Development of Chemical Attractants Used to Trap Pestiferous Social Wasps (Hymenoptera: Vespidae).

Chemical attractants for trapping temperate social wasps have been discovered during the screening of chemicals as attractants for flies, the study of pentatomid bug pheromones, and the testing of volatiles of fermented sweet baits. Wasp attraction to these chemicals seems to be related to either food-finding or prey-finding behavior. Of these attractive chemicals, commercial lures marketed in North America for trapping wasps generally contain heptyl butyrate, or the combination of acetic acid and 2-methyl-1-butanol. Heptyl butyrate is a very good attractant for two major pest wasp species in North America and minor wasp pests in the Vespula rufa species group. The combination of acetic acid with isobutanol attracted nearly all North American pest species of social wasps, including yellowjackets (Vespula and Dolichovespula), a hornet (Vespa crabro), and several paper wasps (Polistes spp.). The testing of wasp chemical attractants in different geographic areas demonstrated responses of many wasp taxa and showed a broad potential scope for the marketing of trap lures. Comparisons of compounds structurally similar to isobutanol revealed similar activity with 2-methyl-1-butanol, which is now used commercially because of a vapor pressure that is more favorable than isobutanol for formulations and dispensers. Doses and concentrations needed for good wasp catches were determined for heptyl butyrate, acetic acid, isobutanol, and 2-methyl-1-butanol, either formulated in water or dispensed from a controlled release device. Trap designs were developed based on consumer considerations; visual appeal, ease and safety of use, and low environmental impact. The resultant lures and traps are marketed in numerous physical and on-line retail outlets throughout the United States and southern Canada.

Compatible and incompatible pathogen–plant interactions differentially affect plant volatile emissions and the attraction of parasitoid wasps

Summary The effects of multiple insect attacks on herbivore‐induced plant volatiles and carnivorous arthropods are increasingly studied. Phytopathogens also represent an important threat to plants, and plant defence strategies against pathogens and insects are strongly interconnected, yet the potential impact of pathogens on insect‐induced volatiles has been largely overlooked, and degree of pathogenicity is rarely considered. We investigated how pathogen challenge, with virulent and avirulent strains of Xanthomonas campestris either alone or with simultaneous Pieris brassicae caterpillar herbivory, affected the volatile emissions of Brassica nigra plants. The impact of these volatiles on the foraging behaviour of Cotesia glomerata parasitoids wasps was then assessed. Pathogens themselves induced volatiles that were highly attractive to parasitoids, and enhanced the attractiveness of host‐infested plant volatiles. Chemical analyses revealed that virulent and avirulent strains differentially induced plant volatiles, with primarily sesquiterpene, homoterpene and green leaf volatile compounds contributing to the differences. Strong similarities were found in the blends induced by the virulent strain and caterpillar herbivory. Challenge by either virulent or avirulent pathogens has a significant impact on plant chemistry and its interactions with other community members, demonstrating the importance of integrating pathogen‐ and insect‐based research to broaden our knowledge of plant defences under conditions of increasing complexity. A lay summary is available for this article.

Comparing the attraction of two parasitoids to herbivore-induced volatiles of maize and its wild ancestors, the teosintes

Artificial selection of crop plants for desired traits such as increased yield and improved seed or fruit quality has been hypothesized to have had a cost for other potentially useful traits, including resistance to herbivores. Besides direct defences, such as the production of toxins, plants may also indirectly protect themselves by emitting volatile organic compounds (VOCs) that attract the natural enemies of herbivores. Parasitoid wasps are known to use these VOCs to localize hosts for their offspring. However, domestication and selective breeding of crop plants have reportedly led to the loss of such signals. The aim of this study was to identify possible differences in the attraction of parasitoid wasps by modern maize and its wild ancestors, the teosintes. In a six-arm olfactometer, we compared the capacity of teosintes and maize to attract the parasitoid wasps Cotesia marginiventris (Hymenoptera: Braconidae) and Campoletis sonorensis (Hymenoptera: Ichneumonidae). We studied the attractiveness of plants in which VOC emission was induced by the application of artificial damage and caterpillar regurgitant, as well as the attractiveness of extracts of volatiles that we collected from plants exposed to herbivory. C. sonorensis did not distinguish between the odours of maize and teosintes, whereas C. marginiventris showed a significant preference for the odours of teosintes over the odours of maize. The fact that we obtained very similar results with extracts of collected volatiles implies that we could use these extracts to identify the key compounds that are responsible for wasp attraction. Restoring and/or enhancing such key parasitoid attractants in cultivated plants could be an effective way to increase natural pest control.

Attraction of Encyrtid wasps (Hymenoptera, Chalcidoidea: Encyrtidae) to a peach orchard agrocenosis in the Republic of Moldova

A total of 26 species from 19 genera of Encyrtidae were recorded in peach orchards in the environs of Chisinau, Moldova. The species affecting the numbers of such peach pests as the Oriental fruit moth Grapholita molesta Busck, the peach twig borer Anarsia lineatella Z., the San Jose scale Diaspidiotus perniciosus Comst., and the gooseberry scale Eulecanium coryli L., are listed. The encyrtid parasites of the potential peach pests in Moldova, and also the hyperparasites and parasites of beneficial predatory insects, are considered. Proteincarbohydrate mixture (PCM) and methyl salicylate (MeSA) were most effective for attraction of encyrtid wasps in April and the first half of May, providing 7.0- and 3.2-fold increase in the parasite numbers as compared with the control. In the second decade of May and in June, the increase was 3.6 times on PCM, 1.8 times on MeSA, and 2.6 times on nectariferous plants. From the end of June the efficiency of PCM and MeSA only slightly exceeded the control level while nectariferous plants were most effective, yielding a more than twofold increase in the numbers of encyrtids.

Invasive Vespula Wasps Utilize Kairomones to Exploit Honeydew Produced by Sooty Scale Insects, Ultracoelostoma.

Vespula wasps are widely distributed invasive alien species that are able to reach high population densities in the 1.2 M ha of beech forests (Fuscospora spp.) of New Zealand's South Island. These endemic temperate forests have an abundance of carbohydrate-rich honeydew produced by native scale insects (Ultracoelostoma spp.). A characteristic aroma is associated with the honeydew in beech forests, which we hypothesized is the signal used by wasps to harvest the vast resources previously exploited by birds and other insects. Volatile collections were taken of black beech tree trunks with honeydew and sooty mold present, and analyzed with a gas chromatograph-mass spectrometer. Eleven compounds (benzaldehyde, benzyl alcohol, 2-phenylethyl acetate, 2-phenylethanol, phenylacetaldehyde, methyl 2-phenylacetate, ethyl 2-phenylacetate, methyl salicylate, n-octanol, octan-3-ol, and 1-octen-3-ol) were positively identified from the headspace, and were shown to elicit an electrophysiological response from Vespula vulgaris worker antennae by using electroantennography (EAG). Field trials with delta traps individually baited with these compounds confirmed wasp attraction to 8 of the 11 compounds tested, with 2-phenylethyl acetate, methyl salicylate, and octan-3-ol capturing the same numbers of wasps as the control. In later trials, attraction to a 1:1 blend of benzaldehyde and n-octanol was significantly higher (45%) than to any other treatment. Many of the chemicals identified are known to be associated with fermenting sugars, or with fungal aroma. Benzaldehyde and n-octanol are common compounds produced by many different species in nature. The ability to respond to generic signals emanating from sugar resources is likely to contribute to the success of V. vulgaris as an invasive species.

Attraction of egg-killing parasitoids toward induced plant volatiles in a multi-herbivore context

In response to insect herbivory, plants emit volatile organic compounds which may act as indirect plant defenses by attracting natural enemies of the attacking herbivore. In nature, plants are often attacked by multiple herbivores, but the majority of studies which have investigated indirect plant defenses to date have focused on the recruitment of different parasitoid species in a single-herbivore context. Here, we report our investigation on the attraction of egg parasitoids of lepidopteran hosts (Trichogramma brassicae and T. evanescens) toward plant volatiles induced by different insect herbivores in olfactometer bioassays. We used a system consisting of a native crucifer, Brassica nigra, two naturally associated herbivores [the butterfly Pieris brassicae (eggs and caterpillars) and the aphid Brevicoryne brassicae] and an alien invasive herbivore (eggs and caterpillars of the moth Spodoptera exigua). We found that Trichogramma wasps were attracted by volatiles induced in the plants by P. brassicae eggs, but not by those induced in the plants by S. exigua eggs, indicating the specificity of the plant responses toward lepidopteran herbivores. The results of the chemical analysis revealed significant differences between the volatile blends emitted by plants in response to attack by P. brassicae and S. exigua eggs which were in agreement with the behavioural observations. We investigated the attraction of Trichogramma wasps toward P. brassicae egg-induced volatiles in plants simultaneously attacked by larvae and nymphs of different non-hosts. The two chewing caterpillars P. brassicae and S. exigua, but not the phloem-feeding aphid B. brassicae, can disrupt the attraction of Trichogramma species toward P. brassicae egg-induced volatiles. Indirect plant defenses are discussed in the context of multiple herbivory by evaluating the importance of origin, dietary specialization and feeding guild of different attackers on the recruitment of egg-killing parasitoids.