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.

Egg parasitoids have a short time frame in which their host eggs are suitable for parasitism, and in several systems these parasitoids respond to plant volatiles induced by oviposition on the plant (either in isolation or in combination with feeding damage) as a means of finding suitable hosts. It is known that the parasitoid of pentatomid eggs Telenomus podisi responds to damage done to soybeans by female Euschistus heros, its preferred host. In this study our aim was to determine the type of E. heros damage to soybean (herbivory, oviposition or a combination of both) necessary for attraction of T. podisi. In a Y-tube olfactometer the parasitoid has shown to respond to the undamaged plant over clean air and herbivory-damaged plants over undamaged plants. However, the parasitoids did not respond to the treatments where oviposition occurred, either in isolation or in combination with herbivory. Analysis of volatile blends revealed that herbivory plus oviposition damage to soybean induced a volatile blend different to those induced when herbivory or oviposition occurred separately. These results, along with other results from this system, suggest that T. podisi uses plant volatile cues associated with female E. heros damage in order to be present when E. heros lays its eggs, and thus ensure its resource is optimal for parasitism.

The boll weevil, Anthonomus grandis, has been monitored through deployment of traps baited with aggregation pheromone components. However, field studies have shown that the number of insects caught in these traps is significantly reduced during cotton squaring, suggesting that volatiles produced by plants at this phenological stage may be involved in attraction. Here, we evaluated the chemical profile of volatile organic compounds (VOCs) emitted by undamaged or damaged cotton plants at different phenological stages, under different infestation conditions, and determined the attractiveness of these VOCs to adults of A. grandis. In addition, we investigated whether or not VOCs released by cotton plants enhanced the attractiveness of the aggregation pheromone emitted by male boll weevils. Behavioral responses of A. grandis to VOCs from conspecific-damaged, heterospecific-damaged (Spodoptera frugiperda and Euschistus heros) and undamaged cotton plants, at different phenological stages, were assessed in Y-tube olfactometers. The results showed that volatiles emitted from reproductive cotton plants damaged by conspecifics were attractive to adults boll weevils, whereas volatiles induced by heterospecific herbivores were not as attractive. Additionally, addition of boll weevil-induced volatiles from reproductive cotton plants to aggregation pheromone gave increased attraction, relative to the pheromone alone. The VOC profiles of undamaged and mechanically damaged cotton plants, in both phenological stages, were not different. Chemical analysis showed that cotton plants produced qualitatively similar volatile profiles regardless of damage type, but the quantities produced differed according to the plant's phenological stage and the herbivore species. Notably, vegetative cotton plants released higher amounts of VOCs compared to reproductive plants. At both stages, the highest rate of VOC release was observed in A. grandis-damaged plants. Results show that A. grandis uses conspecific herbivore-induced volatiles in host location, and that homoterpene compounds, such as (E)-4,8-dimethylnona-1,3,7-triene and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene and the monoterpene (E)-ocimene, may be involved in preference for host plants at the reproductive stage.

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.

Os Voláteis Químicos (Semioquímicos) Produzidos pelos Percevejos Neotropicais Hemiptera: Pentatomidae) RESUMO -Nos últimos anos tem sido crescente a preocupação com as mudanças climáticas e com a utilização auto-sustentável dos recursos naturais, estimulando cada vez mais os estudos para a prospecção de novos produtos naturais visando minimizar o uso de pesticidas. Os percevejos produzem uma variedade de compostos químicos com potencial para o seu manejo. A composição química dos compostos defensivos dos percevejos Chinavia impicticornis (Stål), C. ubica (Rolston), Dichelops melacanthus (Dallas), Euschistus heros (F.), Piezodorus guildinii (Westwod), Thyanta perditor (Westwood) e Tibraca limbativentris (Stål) foi avaliada. Os principais compostos nas glândulas dos percevejos foram: 2-alcenais, principalmente o isômero E, hidrocarbonetos alifáticos saturados; e 4 oxo-(E)-2-alcenal. O primeiro feromônio sexual de percevejo identifi cado no Brasil foi do Nezara viridula L., que consiste na mistura dos isômeros cis e trans epóxi-bisabolenos; na sequência, o percevejo praga da soja E.. heros também teve seu feromônio sexual identifi cado. Os machos desta espécie produzem três ésteres: 2,6,10-trimetildecanoato de metila, 2,6,10 trimetildodecanoato de metila e 2E,4Z decadienoato de metila. Recentemente, mais três espécies de percevejos neotropicais tiveram a composição da mistura feromonal elucidada. Machos de T. perditor produzem o éster, 2E,4Z,6Z-decatrienoato de metila. O percevejo P. guildinii tem como feromônio sexual o -sesquifelandreno, e o percevejo praga do arroz T. limbativentris tem também como feromônio sexual um sesquiterpenóide, o zingiberenol. Nessa revisão serão abordados os avanços obtidos no estudo do comportamento e identifi cação de feromônios sexuais e de alarme de várias espécies do complexo de percevejos praga da agricultura brasileira. A aplicação desses conhecimentos é discutida. PALAVRAS-CHAVE: Feromônio, aleloquímico, agregação, comportamento, soja ABSTRACT -In recent years the growing concern about environmental changes and how we are using the natural resources have triggered a search for natural products as alternatives to synthetic pesticides. The stink bugs produce a wide variety of chemical compounds (semiochemicals) that show potential to manage these insects. The stink bugs Chinavia impicticornis (Stål), C. ubica (Rolston), Dichelops melacanthus (Dallas), Euschistus heros (F.), Piezodorus guildinii (Westwood), Thyanta perditor (Westwood) and Tibraca limbativentris (Stål) had their blends of defensive compounds evaluated both qualitative and quantitatively. The main compounds identifi ed on the glands of Brazilian stink bugs are: 2-alkenals, mainly the E isomer; saturated aliphatic hydrocarbons; and 4 oxo-(E)-2-alkenals. The fi rst sex attractant determined from a stink bug was obtained from Nezara viridula L., and consists on a mix of two isomers cis -and trans bisabolene-epoxides. Later the soybean stink bug E. heros was also studied and its sex attractant was identifi ed as three es...

The stink bugs Acrosternum impicticorne, Euschistus heros, Piezodorus guildinii and Thyanta perditor (Heteroptera: Pentatomidae) feed and mate on the same host plants and constitute major components of the soybean pest complex in Brazil. During mating, they communicate with species and sex-specific vibratory signals whose spectral properties are characteristic of the subfamily Pentatominae. Songs differ between species in the time structure and amplitude modulation of their units. The repertoire of A. impicticorne, E. heros and T. perditor fits into the scheme described for most investigated stink bugs: females call with a sequence of pulses that differ between species in their duration and repetition rate, and males respond with courtship songs of species-specific temporal structure and amplitude modulation of complex pulse trains. Female calling and male courtship songs are the main constituents of vibratory communication between sexes in the mating period. The other vibratory emissions appear to represent either transitional songs, support recognition during close-range courtship, or are involved in male rivalry. The first recorded vibratory emissions of P. guildinii confirm that the genus Piezodorus represents an exception within the Pentatominae. Irregularly repeated female vibratory signals of P. guildinii do not trigger typical male courtship responses as they would in the small stink bugs Holcostethus strictus and Murgantia histrionica. On the other hand, complex rivalry with extensive frequency modulation of pulses, as also described in Piezodorus lituratus, opens a new insight into the role of vibratory communication in stink bugs.

The silverleaf whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is one of the most important pest insects in tomato crop systems worldwide. It has been previously demonstrated that intercropping tomato [Solanum lycopersicum L. Mill. (Solanaceae)] with coriander [Coriandrum sativum L. (Apiaceae)] reduces the incidence and severity of damage caused by B. tabaci. However, it is not yet known how coriander affects the insect′s behaviour. We evaluated the attractiveness of tomato constitutive volatiles to B. tabaci and what effect coriander constitutive volatiles have on the insect′s behaviour. To this end, we conducted three bioassays in a multiple‐choice four‐arm olfactometer (‘×’ type), measuring B. tabaci behaviour when offered tomato and coriander constitutive volatiles presented alone as well as together. We also evaluated the colonisation and establishment of B. tabaci in experimental plots with only single tomato plants and tomatoes intercropped with coriander in a greenhouse. Bemisia tabaci males and females recognised tomato constitutive volatiles as a positive stimulus (kairomonal effect), indicating that semiochemicals from this plant can play an important role in the insect’s host plant selection. Coriander constitutive volatiles reduced the attractiveness of tomato volatiles but no repellency to these volatiles was observed. Greater numbers of adults and nymphs of B. tabaci per plant were observed in tomato monoculture plots than in tomato intercropped with coriander. We suggest that coriander constitutive volatiles have an odour masking effect on tomato volatiles, thus interfering in the host plant selection of B. tabaci.

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