Several studies have shown that herbivore-induced plant volatiles act directly on herbivores and indirectly on their natural enemies. However, little is known about the effect of herbivore damage on resistant and susceptible plant cultivars and its effect on their natural enemies. Thus, the aim of this study was to evaluate the attraction of the herbivorous pentatomid bug Euschistus heros and its egg parasitoid Telenomus podisi to two resistant and one susceptible soybean cultivars with different types of damage (herbivory, herbivory+oviposition, and oviposition). In a Y-tube olfactometer, the parasitoids were attracted to herbivory and herbivory+oviposition damaged soybean plants when compared to undamaged soybean plants for the resistant cultivars, but did not show preference for the susceptible cultivar Silvânia in any of the damage treatments. The plant volatiles emitted by oviposition-damaged plants in the three cultivars did not attract the egg parasitoid. In four-arm-olfactometer bioassays, E. heros females did not show preference for odors of damaged or undamaged soybean plants of the three cultivars studied. The Principal Response Curves (PRC) analysis showed consistent variability over time in the chemical profile of volatiles between treatments for the resistant cultivar Dowling. The compounds that most contributed to the divergence between damaged soybean plants compared to undamaged plants were (E,E)-α-farnesene, methyl salicylate, (Z)-3-hexenyl acetate, and (E)-2-octen-1-ol.

After herbivore attack or chemical activation, plants release a blend of volatile organic compounds (VOCs) that is qualitatively or quantitatively different to the blend emitted by an undamaged plant. The altered blend of VOCs is then usually attractive to the herbivore's natural enemies. Soybean, Glycine max (L.) (Fabaceae), when damaged by stink bug herbivory, has been shown to emit a blend of VOCs that attracts the stink bug egg parasitoid Telenomus podisi (Ashmead) (Hymenoptera: Scelionidae) to the plant. In this study, our aim was to investigate changes in the VOC profile of soybean (var. BR16) elicited by the naturally occurring plant activator cis‐jasmone, and to determine whether these changes elicited the attraction of T. podisi. cis‐Jasmone elicited chemical defence in soybean similar to that previously reported for stink bug damage. The main components induced by cis‐jasmone were camphene, myrcene, (E)‐ocimene, methyl salicylate, and (E,E)‐4,8,12‐trimethyltrideca‐1,3,7,11‐tetraene. In Y‐tube behavioural bioassays, T. podisi preferred cis‐jasmone treated plants over untreated plants. Thus, cis‐jasmone appears to induce defence pathways in soybean similar to those induced by stink bug damage, and this phenomenon appears to be a promising tool for the manipulation of beneficial natural enemies in future sustainable stink bug control strategies. The delay in response demonstrates that cis‐jasmone treatment is not directly causing the response, but, more importantly, that it is causing activation of induced defence, long after initial treatment.

During host selection, physical and chemical stimuli provide important cues that modify search behaviours of natural enemies. We evaluated the influence of volatiles released by eggs and egg extracts of the stink bug Euschistus heros and by soybean plants treated with the eggs and egg extracts on Telenomus podisi foraging behaviour. Responses to volatiles were evaluated in Y-tube olfactometers after exposure to (1) one egg cluster for 24 h; (2) plants with eggs laid by the stink bug, tested at 24, 48, and 72 h after treatment; (3) plants with eggs laid artificially, tested at 24, 48, and 72 h after treatment; and (4) plants treated with acetone or hexane extracts of eggs. Telenomus podisi was attracted to volatiles emitted by one egg cluster and to acetone extracts of one egg cluster, but not to air or acetone controls. There were no responses to odours of plants treated with eggs or egg extracts. Analysis of acetone extracts of egg clusters by gas chromatography revealed the major components were saturated and unsaturated fatty acids, including hexadecanoic acid, linoleic acid, and (Z)-9-octadecenoic acid. Our results suggest that one egg cluster and the acetone extract of one egg cluster contain volatile compounds that can modify T. podisi foraging behaviour, and that the amounts of these compounds, probably together with some minor compounds, are important for host recognition by T. podisi. Also, the oviposition damage or egg extracts on the plant did not elicit indirect defences that attracted Telenomus podisi.

2019. Variability in herbivore-induced defence signalling across different maize genotypes impacts significantly on natural enemy foraging behaviour.

Parasitoids use herbivore‐induced plant volatiles (HIPVs) to locate their hosts. However, there are few studies in soybean showing the mechanisms involved in the attraction of natural enemies to their hosts and prey. The objective of this study was to evaluate the influence of volatile organic compounds (VOCs) of soybean, Glycine max (L.) Merr. (Fabaceae) (cv. Dowling), that were induced after injury caused by Euschistus heros (Fabricius) (Hemiptera: Pentatomidae), on the searching behavior of the egg parasitoid Telenomus podisi Ashmead (Hymenoptera: Scelionidae). Four HIPVs from soybean, (E,E)‐α‐farnesene, methyl salicylate, (Z)‐3‐hexenyl acetate, and (E)‐2‐octen‐1‐ol, were selected, prepared from standards at various concentrations (10−6 to 10−1 m), and tested individually and in combinations using a two‐choice olfactometer (type Y). Telenomus podisi displayed a preference only for (E,E)‐α‐farnesene at 10−5 m when tested individually and compared to hexane, but they did not respond to the other compounds tested individually at any concentration or when combinations of these compounds were tested. However, the parasitoids stayed longer in the olfactometer arm with the mixture of (E,E)‐α‐farnesene + methyl salicylate at 10−5 m than in the arm containing hexane. The results suggest that (E,E)‐α‐farnesene and methyl salicylate might help T. podisi to determine the presence of stink bugs on a plant. In addition, bioassays were conducted to compare (E,E)‐α‐farnesene vs. the volatiles emitted by undamaged and E. heros‐damaged plants, to evaluate whether (E,E)‐α‐farnesene was the main cue used by T. podisi or whether other minor compounds from the plants and/or the background might also be used to locate its host. The results suggest that minor volatile compounds from soybean plants or from its surroundings are involved in the host‐searching behavior of T. podisi.

1 Despite the importance of Leucoptera coffeella (Gue´rin-Me`neville) in coffee production worldwide, there is a lack of information on its reproduction. This knowledge will help in mass rearing, and support the development of behavioural control techniques for this insect. The present study determined the effects of delayed mating and previous matings of male L. coffeella on fecundity, egg viability and frequency of female remating. 2 The highest levels of fecundity and egg viability were obtained from matings of 1-3-day-old females. When females mated at 5 days of age, there were reductions of 40% in oviposition and of 43% in egg viability. 3 Females mated with 2-day-old virgin males were more fecund than those mated with older males; egg viability was also low (18%) from females mated with older males. 4 Virgin females that mated with virgin males laid a greater number of eggs than those mated with previously copulated males. Egg viability decreased with the increase in the number of previous male matings. 5 Five-day-old females remated in greater proportion than 2-3-day-old females.Females that copulated with males that had previously mated three times had higher rates of remating than those that copulated with virgin males. 6 The results obtained indicate that 1-3 days after emergence is the optimum age for mating. The implications of these findings for the control of L. coffeella by synthetic sex pheromone are discussed.

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-The objective of this review was to summarize the current information about semiochemicals with potential to be applied in insect pest management in agroecosystems. One of the great challenges to Neotropical agriculture is to reduce the indiscriminate use of pesticides, which can be minimized by using semiochemicals, a tool that can be applied in the field to manage pests and their natural enemies. In addition, small lipophilic molecules from insects and from the secondary metabolism of plants play a fundamental role in the chemical communication of different species that are present in important crops.Index terms: chemical communication, herbivore-induced plant volatiles (HIPVs), oviposition-induced plant volatiles (OIPVs), pest control, pheromone, synomone. Semioquímicos de plantas e insetos no comportamento de busca de parasitoides de ovos PlatygastridaeResumo -O objetivo deste artigo de revisão foi reunir informações atuais sobre semioquímicos com potencial para serem aplicados no manejo de insetos-praga em agroecossistemas. Um dos grandes desafios para a agricultura Neotropical é reduzir o uso indiscriminado de pesticidas, que pode ser minimizado pelo uso de semioquímicos, uma ferramenta que pode ser aplicada no campo para o manejo de pragas e de seus inimigos naturais. Além disso, pequenas moléculas lipofílicas dos insetos e do metabolismo secundário de plantas desempenham papel fundamental na comunicação química das diferentes espécies que estão presentes em importantes culturas.Termos para indexação: comunicação química, voláteis de planta induzidos pela herbivoria (HIPVs), voláteis de planta induzidos pela oviposição (OIPVs), controle de pragas, feromônios, sinomônios.