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Grazing and mowing constitute two important ways of reducing vegetation structure, which causes mechanical injuries in plants. In response to these injuries, plants emit herbivore-induced plant volatiles (HIPVs) that can act as recruitment signals for arthropod predators. Among these arthropods, spiders have been suggested to respond to HIPVs. It is unknown, however, if spiders make microhabitat choice based on the detection of those HIPVs or based solely on the availability of vegetal structure. In this study, we investigated microhabitat choice of the orb-weaver spider Argiope trifasciata (Forsskål, 1775) and its potential relationship with impacted and not impacted vegetation structure availability. Our major results corroborate other findings that microhabitat choice in orb-weaver spiders is driven not by HIPVs, but rather by vegetation structure. Habitat structure influences a variety of ecological factors such as predation risk, prey availability, and mate finding in orb-weavers. The mechanisms underlying assessment by A. trifasciata of the vegetative structure remains unknown, and future studies might investigate their capacity to perceive light and shade and/or their assessment of vertical positioning. Practically, our results can be useful in evaluating the impact of land management on spider populations and their resilience to these impacts. [ABSTRACT FROM AUTHOR]

Avian species were historically thought to have a very limited sense of smell. However, recent studies suggest that odor plays an important role in many areas of avian life, including foraging and navigation. It has been shown that insectivorous birds can interact in a tritrophic fashion with plants and their herbivores by cuing in on herbivore-induced plant volatiles (HIPVs), important signaling compounds released by plants in response to herbivorous damage. This phenomenon has been observed in a number of plant species, including complex HIPV blends in corn (Zea mays). However, in other species, simpler single-compound HIPVs can act as phytohormones, causing the release of additional HIPVs, and have also been shown to be attractive to birds. Here we test if 2 single-compound general HIPVs, methyl jasmonate and methyl salicylate, attract avian predators to insect prey on corn plants using clay caterpillar models. We observed appreciable levels of bird attacks on our models across 10 experimental sites. However, we did not observe any difference between HIPV and control treatments. Interestingly, we did find that several weather variables, including wind speed and temperature, were significant or near significant predictors of avian predation activity, respectively. Together with previous studies, our results add to a nuanced picture of how birds may be using HIPVs to locate insect prey. Additionally, the potential for birds to act as a natural form of biocontrol in agricultural settings may be affected by physical location and local climate. On pensait historiquement que les espèces aviaires avaient une olfaction très limitée. Cependant, des études récentes suggèrent que l'odeur joue un rôle important dans de nombreux domaines de la vie aviaire, y compris la recherche de nourriture et la navigation. Les oiseaux insectivores peuvent interagir à travers trois niveaux trophiques avec les plantes et leurs herbivores par les signaux des substances volatiles végétales induites par les herbivores (HIPV), les composés de signalisation importants libérés par les plantes en réponse aux dommages causés par les herbivores. Ce phénomène a été observé chez plusieurs espèces végétales, comme le maïs (Zea mays) et ses mélanges complexes d'HIPV. Chez d'autres espèces, les HIPV plus simples et mono-composés peuvent agir comme des phytohormones, provoquant l'émission d'autres HIPV, qui se sont également avérés attrayants pour les oiseaux. Ici, nous testons si deux HIPV à un seul composé, le jasmonate de méthyle et le salicylate de méthyle, attirent les prédateurs aviaires vers les insectes proies sur les plants de maïs en utilisant des modèles de chenilles en argile. Nous observâmes des niveaux appréciables d'attaques d'oiseaux sur nos modèles dans dix sites expérimentaux. Cependant, nous ne trouvâmes aucune différence entre les traitements d'HIPV et les témoins. Il est intéressant de noter que nous constatâmes que plusieurs variables météorologiques, notamment la vitesse du vent et la température, étaient des prédicteurs significatifs ou presque significatifs de l'activité de prédation aviaire, respectivement. Nos résultats, combinés à des études précédentes, décrivent comment les oiseaux peuvent utiliser les HIPV pour localiser les proies d'insectes. De plus, le potentiel des oiseaux à agir comme une forme naturelle de lutte biologique dans les milieux agricoles peut être affecté par l'environnement physique et le climat local. [ABSTRACT FROM AUTHOR]

The homoterpenes 4,8‐dimethyl‐1,3,7‐nonatriene (DMNT) and 4,8,12‐trimethyl‐1,3,7,11‐tridecatetraene (TMTT) are volatile products of plant metabolism reported from diverse plant taxa and multiple plant tissues. As such, they have a range of potential ecological functions. Here, we review the key literature to assess evidence for roles in contrasting plant–arthropod interactions. TMTT, and DMNT especially, have been reported as sometimes dominant constituents of floral scents from angiosperm taxa ranging from primitive Magnoliales to more advanced, taxonomic orders of economic significance such as Fabales and Sapindales. Although all taxa producing TMTT and DMNT in floral scents are entomophilous ('insect pollinated'), experimental evidence for an assumed role of these homoterpenes in pollinator attraction is limited. Representing a trade‐off, in some cases, homoterpenes in floral scents have been shown to act as kairomones, attracting herbivores. Additionally, both TMTT and DMNT are released by plant foliage in response to arthropod feeding, mechanical damage simulating feeding, or even egg deposition. Evidence for a functional role in herbivore‐induced plant volatile (HIPV) blends comes from a wide range of angiosperm orders, including anemophilous ('wind pollinated') taxa, as well as from gymnosperms. We conclude by considering how TMTT and DMNT function in community‐level interactions and highlighting research priorities that will reveal how plants avoid trade‐offs from contrasting ecological functions of DMNT and TMTT release and how homoterpene production might be exploited to develop improved crop varieties. [ABSTRACT FROM AUTHOR]

Plants developed a series of defence mechanisms to counteract the attack of herbivores. These can impact on food‐webs at various trophic levels, in both natural and managed ecosystems, such as crops. The biochemical and ecological bases behind these processes are reviewed here by highlighting the differences in direct and indirect, constitutive and induced defences. In integrated pest management (IPM), several pest control tools are applied in an economically sound way in order to increase the crop resilience and reduce reliance on synthetic pesticides. Plant resistance is thus a crucial aspect of preventive pest control strategies in several agroecosystems, including tomato. In this context, we review the current literature dealing with the physiology and biochemistry of tomato plants in terms of metabolite pathways and multitrophic interactions. We also describe recent advances in plant defence‐based control tools obtained by studying the multitrophic interactions between pests and plants in the tomato system. [ABSTRACT FROM AUTHOR]

In mite communities, behavioral and foraging decisions of individuals rely on semiochemicals that they gather from the environment, which contain odors from plants, herbivores, and predators. Because herbivorous mites commonly co-occur with several species of phytoseiid predatory mites, which may engage in intraguild predation (IGP), predator mite decision-making relies on their ability to recognize odors signaling the presence of the herbivore but also that of potential competitors/predators. Here the odor-related foraging decisions of three predatory mites, Euseius stipulatus (AthiasHenriot), Neoseiulus californicus (McGregor) and Phytoseiulus persimilis (Athias-Henriot) (Mesostigmata: Phytoseiidae), which co-occur in citrus, compete for the herbivore Tetranychus urticae Koch (Prostigmata: Tetranychidae), and can engage in IGP were investigated. The composition of the volatile blends associated with the three predators was characterized. Moreover, the effect of these odors on the predators foraging decisions was measured. Results revealed that (1) the volatile signature of the three predatory mites is species specific, (2) the predators’ foraging behavior is affected by heterospecific predator odors, and (3) predator responses strongly depend on the host plant: mutual attraction and mutual repellence occurred in Cleopatra mandarin and sour orange, respectively. These findings have important consequences for the management of systems where these species occur. The odor blends that make predators that share pest species as prey avoid each other could be used to improve pest control by minimizing undesired negative interactions among predator species, and by locally increasing predation risk on herbivore pest species. [ABSTRACT FROM AUTHOR]

Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae) is a common polyphagous mite in tropical and subtropical areas and is considered as an important citrus pest.To understand the response of citrus to P. latus infestation, we have characterized the volatile profile and the molecular defence mechanisms of two citrus genotypes, namely sour orange (Citrus aurantium) and Cleopatra mandarin (Citrus reshni), to P. latus infestation. These two species are important rootstocks for the citrus industry and display differential resistance to Tetranychus urticae Koch (Acari: Tetranychidae), with sour orange showing elevated levels of constitutive and induced resistance associated with the jasmonic acid (JA) pathway compared with Cleopatra mandarin.P. latus infestation activated both the JA‐ and the salicylic acid‐dependent pathways in sour orange but not in Cleopatra mandarin. However, this differential activation resulted in the production of similar volatile blends (a mixture of green leaf volatiles and aromatic compounds).Contrary to T. urticae infestation, sour orange supported larger densities of P. latus than Cleopatra mandarin with similar injury levels.Therefore, sour orange may be more tolerant to P. latus than Cleopatra mandarin. [ABSTRACT FROM AUTHOR]

• Nesidiocoris tenuis : highly efficient as biological control agent but damages tomato plants. • Tomato plant defenses are activated by the GLV (Z)-3-HP. • Increasing plant defenses reduces N. tenuis damage. • Reduced callose deposition limits tissue damage. Although Nesidiocoris tenuis is highly effective as a biological control agent, it can also damage tomato plants due to its zoophytophagous behavior. When N. tenuis pierces the stems and petioles of tomato plants with its stylets, it triggers callose deposition and subsequent cell death, resulting in blocked nutrient transport, floral abortions, or wilting of tender shoots. Recently, it has been shown that exposure of tomato plants to the green leaf volatile (Z)-3-hexenyl propanoate [(Z)-3-HP] activates defensive mechanisms, including the regulation of genes involved in the synthesis and degradation of callose. In this study, conducted under greenhouse conditions, we tested the hypothesis that damage caused by N. tenuis could be reduced by exposing tomato plants to (Z)-3-HP through polymeric dispensers. Tomato plants exposed to (Z)-3-HP and non-exposed control plants were inoculated with N. tenuis. Nesidiocoris tenuis established in both groups with no significant differences between the two treatments. However, as hypothesized, the damage caused by N. tenuis was significantly lower in the plants exposed to (Z)-3-HP. Gene expression analysis of salicylic, jasmonic, and abscisic acids, along with histochemical staining methods, was used to compare the defensive responses of tomato plants infested solely with N. tenuis versus those infested with N. tenuis and exposed to (Z)-3-HP. Our findings confirm the influence of (Z)-3-HP exposure on differential defensive activation between treatments and reduced callose deposition in (Z)-3-HP-exposed plants. These results pave the way for improved management of N. tenuis by enhancing the plant's defenses based on inter-plant communication. [ABSTRACT FROM AUTHOR]

Summary: Herbivore‐induced plant volatiles (HIPVs) are widely recognized as an ecologically important defensive response of plants against herbivory. Although the induction of this 'cry for help' has been well documented, only a few studies have investigated the inhibition of HIPVs by herbivores and little is known about whether herbivores have evolved mechanisms to inhibit the release of HIPVs.To examine the role of herbivore effectors in modulating HIPVs and stomatal dynamics, we conducted series of experiments combining pharmacological, surgical, genetic (CRISPR‐Cas9) and chemical (GC‐MS analysis) approaches.We show that the salivary enzyme, glucose oxidase (GOX), secreted by the caterpillar Helicoverpa zea on leaves, causes stomatal closure in tomato (Solanum lycopersicum) within 5 min, and in both tomato and soybean (Glycine max) for at least 48 h. GOX also inhibits the emission of several HIPVs during feeding by H. zea, including (Z)‐3‐hexenol, (Z)‐jasmone and (Z)‐3‐hexenyl acetate, which are important airborne signals in plant defenses.Our findings highlight a potential adaptive strategy where an insect herbivore inhibits plant airborne defenses during feeding by exploiting the association between stomatal dynamics and HIPV emission. [ABSTRACT FROM AUTHOR]

Parasitoids need to find their plant-feeding hosts in complex environments that contain multiple other plant and insect species. They usually rely on herbivore-induced plant volatiles to locate herbivore-infested plants from a distance and their foraging efficiency may be reduced when volatile information is not available. Downwind foraging during times when high wind speeds prevent odour-guided upwind flights may create foraging situations with limited accessibiliy to volatile information. We hypothesized that parasitoids forage less efficiently by landing on nonhost-damaged or undamaged plants when they are forced to fly downwind and tested this in a wind tunnel experiment. We released the parasitoid Cotesia glomerata (Hymenoptera, Braconidae) either upwind or downwind of a plant stand and observed their foraging behaviour. During downwind foraging, parasitoids were less successful in host finding and needed more time until they managed to oviposit in a host caterpillar compared to the upwind foraging situation. The observed increase in foraging time was caused by prolonged foraging on nonhost-infested and undamaged plants in the downwind situation, indicating that parasitoids leave an unprofitable patch that does not contain host caterpillars earlier, when they perceive volatiles from other herbivore-infested plants located upwind. Volatile information on the availability of herbivore-infested plants within a plant stand seems to be crucial for efficient foraging in plant stands that contain a mixture of host-infested, nonhost-infested and undamaged plants. Parasitoid foraging efficiency may thus be strongly reduced when high wind speed prevents odour-guided upwind flight. • Downwind-flying parasitoids foraged less efficiently than upwind-flying parasitoids. • Upwind-flying parasitoids had access to HIPVs from all herbivore-infested plants. • Low HIPV availability reduced between-plant movement of downwind-flying parasitoids. • Downwind-flying parasitoids foraged more intensively on nonhost-infested plants. • Intensive foraging on nonhost-infested plants delayed host finding. [ABSTRACT FROM AUTHOR]

Herbivore-induced plant volatiles (HIPVs) are important cues for natural enemies to find their hosts. HIPVs are usually present as blends and the effects of combinations of individual components are less studied. Here, we investigated plant volatiles in a tritrophic system, comprising the parasitoid wasp Lytopylus rufipes Nees (Hymenoptera: Braconidae), the Oriental fruit moth Grapholita molesta (Busck) (Lepidoptera: Tortricidae), and Japanese pear, Pyrus pyrifolia 'Kosui', so as to elucidate the effects of single components and blends on wasp behaviors. Bioassays in a four-arm olfactometer, using either shoots or their isolated volatiles collected on adsorbent, revealed that female wasps preferred volatiles from host-infested shoots over those from intact shoots. Analyses identified (Z)-3-hexenyl acetate (H), linalool (L), (E)-β-ocimene (O), (E)-3,8-dimethyl-1,4,7-nonatriene (D), and (E,E)-α-farnesene (F). Among them, only F was induced by infestation with G. molesta. When tested singly, only O and D elicited positive responses by L. rufipes. Binary blends of HO and DF elicited a positive response, but that of HD elicited a negative one, even though D alone elicited a positive response. Remarkably, wasps did not prefer either the ODF or HL blends, but showed a highest positive response to a quinary blend (HLODF). These results show that synergism among volatiles released from host-infested plants is necessary for eliciting high behavioral responses in L. rufipes, enabling L. rufipes to find its host efficiently. [ABSTRACT FROM AUTHOR]

Sour orange, Citrus aurantium, displays higher constitutive and earlier inducible direct defenses against the two-spotted spider mite, Tetranychus urticae, than Cleopatra mandarin, Citrus reshni. Moreover, herbivore-induced plant volatiles (HIPVs) produced by sour orange upon infestation can induce resistance in Cleopatra mandarin but not vice versa. Because the role of these HIPVs in indirect resistance remains ignored, we have carried out a series of behavioral assays with three predatory mites with different levels of specialization on this herbivore, from strict entomophagy to omnivory. We have further characterized the volatile blend associated with T. urticae, which interestingly includes the HIPV methyl salicylate, as well as that produced by induced Cleopatra mandarin plants. Although a preference for less defended plants with presumably higher prey densities (i.e., C. reshni) was expected, this was not always the case. Because predators' responses changed with diet width, with omnivore predators responding to both HIPVs and prey-related odors and specialized ones mostly to prey, our results reveal that these responses depend on plant genotype, prey presence and predator diet specialization. As the different volatile blends produced by infested sour orange, induced Cleopatra mandarin and T. urticae itself are attractive to T. urticae natural enemies but not to the herbivore, they may provide clues to develop new more sustainable tools to manipulate these agriculturally relevant species. [ABSTRACT FROM AUTHOR]

Plants synthesize variable mixtures of herbivore-induced plant volatiles (HIPVs) as part of their evolutionary conserved defense. To elucidate the impact of chewing herbivores with different level of adaptation on HIPV profiles in rice, we measured HIPVs released from rice seedlings challenged by either the generalist herbivore Mythimna loreyi (MYL) or the specialist Parnara guttata (PAG). Both herbivores markedly elicited the emission of HIPVs, mainly on the second and third days after attack compared to control plants. In addition, side-by-side HIPV comparisons using MYL and PAG caterpillars revealed that generalist feeding induced comparably more HIPVs relative to specialist, particularly on day two as highlighted by multivariate analysis (PLS-DA) of emitted HIPVs, and further confirmed in mimicked herbivory experiments. Here, mechanically wounded plants treated with water (WW) released more VOCs than untreated controls, and on top of this, oral secretions (OS) from both herbivores showed differential effects on volatile emissions from the wounded plants. Similar to actual herbivory, MYL OS promoted higher amounts of HIPVs relative to PAG OS, thus supporting disparate induction of rice indirect defenses in response to generalist and specialist herbivores, which could be due to the differential composition of their OS. (196 words). [ABSTRACT FROM AUTHOR]

Temporal changes in the pre- and post-alighting responses of mated female diamondback moth, Plutella xylostella L. ( Lepidoptera: Plutellidae), to two species of Brassica ( Brassicaceae) host plants induced by larval feeding were studied using olfactometer and oviposition assays. Females displayed strong olfactory and oviposition preferences for herbivore-induced common cabbage ( Brassica oleracea var. capitata L. cv. sugarloaf) plants over intact plants; these preferences decreased with time and disappeared by the 7th day after induction. In herbivore-induced common cabbage plants, eggs were clustered near feeding damage on the younger leaves (leaves 5-7), whereas in intact plants, eggs were clustered on the stem and lower leaves (leaves 1-4) . However, as the time interval between larval feeding and oviposition increased, more eggs were laid on the lower leaves of induced plants. This demonstrates a change in egg distribution from the pattern associated with induced plants to that associated with intact plants. In contrast, females displayed strong olfactory and oviposition preferences for intact Chinese cabbage [ Brassica rapa ssp. pekinensis (Lour.) Hanelt cv. Wombok] plants over induced plants; these preferences decreased with time and disappeared by the 5th day after induction. More eggs were laid on the upper leaves (leaves 4-6) than on the lower leaves (leaves 1-3) of intact Chinese cabbage plants at first, but the distribution changed over time until there were no significant differences in the egg count between upper and lower leaves by the 4th day post induction. For both host plant species, pre-alighting responses of moths were reliable indicators of post-alighting responses on the first 2 days post induction. The results suggest that temporal changes in a plant's profile (chemical or otherwise) following herbivory may influence attractiveness to an insect herbivore and be accompanied by changes in olfactory and oviposition preferences. [ABSTRACT FROM AUTHOR]

We compared the attractiveness of a mixture of cis-3-hexen-1-ol, cis-3-hexenyl acetate, and methyl salicylate (MeSA), and of each of these compounds singly, to a predacious ladybird beetle, Stethorus punctum picipes (Casey), to make it clear whether mixture of several volatiles may attract more natural enemies at different spatial scales. In an olfactometer experiment, S. p. picipes females were attracted to the volatile mixture, but not to single volatiles. Male S. p. picipes were not attracted to the mixture. In a small-scale open-field test using sticky cards, S. p. picipes were attracted to the volatile mixture and to MeSA alone. In a vineyard trapping test, significantly more S. p. picipes were trapped on sticky cards baited with a mixture of volatiles than on single-volatile-baited cards. [ABSTRACT FROM AUTHOR]

Volatile organic compounds emitted by plants (pVOCs) protect themselves from abiotic and biotic stresses. Plants are under constant threats from biotic stress especially herbivores which facilitate plants to emit herbivore-induced plant volatiles (HIPVs), an inducible defense in plants against herbivores by communicating to herbivores' natural enemies and neighboring plants. HIPVs are reported to act as feeding and/or oviposition deterrents to herbivores, belonging to four major groups including terpene/terpenoids, benzenoids and phenylpropanoids, the volatile fatty acid derivatives, and the volatile aminoacid derivatives. However, the plant volatile profiles induced by herbivores have been reported to be altered by silicon (Si)-fertilization, priming of plants with chemical elicitors and climate change which can induce plants to produce and emit novel plant volatiles that are not expressed by plants in response to damage by herbivory. Transgenic crops and/or sentinel crops with enhanced pVOCs emission profiles have been proposed to improve plant resistance, health and yields. Currently several technological advances in devices including field-portable electronic devices (e-Nose) and hand-held smartphone-based biosensors for in situ early detection of pVOCs profiles which are now available and supported by artificial intelligence (AI), to increase detection accuracy of these systems. The present review highlights the multi-dimension approaches emerging in pVOCs research for early and rapid detection of specific VOCs indicators as markers with associated plant biotic stressors. [Display omitted] • Biotic and abiotic factors induce plants to emit volatile organic compounds (pVOCs), belonging to four major groups. • Herbivore induced plant volatiles (HIPVs) rescue plants from their herbivores by attracting herbivores' natural enemies. • Allelopathy effects of pVOCs smother non-economical crops. • Exogenous application of Silicon, chemical elicitors and climate change significantly modify the HIPV profiles. • Companion/transgenic crops can be employed to enhance pVOCs emissions for IPM. • pVOCs repository can be raw material for development of plant phenotyping tools including e-Nose, biosensors etc. [ABSTRACT FROM AUTHOR]

We studied the role of methyl salicylate as an important part of volatile blends in searching behaviour of the predatory mite,Phytoseiulus persimilis(Athias-Henriot). We showed that Methyl Salicylate (MeSa) attracted the predatory mites (1 h starved) in a dose range of 0.02–20??g. The highest attraction was recorded at the dose of 0.2??g. The dose of 0.002??g was considered under the detection level of the predator.P. persimiliscould not detect the extra amount of MeSa (100 and 200??g). The probable effect of starvation period on the predator response is discussed. [ABSTRACT FROM PUBLISHER]

Plant secondary metabolites play an important role in mediating interactions with insect herbivores and their natural enemies. Metabolites stored in plant tissues are usually investigated in relation to herbivore behaviour and performance (direct defence), whereas volatile metabolites are often studied in relation to natural enemy attraction (indirect defence). However, so-called direct and indirect defences may also affect the behaviour and performance of the herbivore's natural enemies and the natural enemy's prey or hosts, respectively. This suggests that the distinction between these defence strategies may not be as black and white as is often portrayed in the literature. The ecological costs associated with direct and indirect chemical defence are often poorly understood. Chemical defence traits are often studied in two-species interactions in highly simplified experiments. However, in nature, plants and insects are often engaged in mutualistic interactions with microbes that may also affect plant secondary chemistry. Moreover, plants are challenged by threats above- and belowground and herbivory may have consequences for plant-insect multitrophic interactions in the alternative compartment mediated by changes in plant secondary chemistry. These additional associations further increase the complexity of interaction networks. Consequently, the effect of a putative defence trait may be under- or overestimated when other interactions are not considered. [ABSTRACT FROM AUTHOR]

Plants respond to herbivory with the emission of plant volatiles, which can be used by the herbivores' natural enemies to locate their hosts or prey. In nature, plants are often simultaneously confronted with insect herbivores and phytopathogens, potentially interfering with the attraction of the herbivores' enemies as a result of modifications of the induced volatile blend. Here, we investigated parasitoid ( C otesia glomerata) attraction to volatiles of plants challenged by different attackers, either alone or in combination with P ieris brassicae caterpillars, hosts of C . glomerata. We used a natural system consisting of B rassica nigra plants, eggs and larvae of P . brassicae, B revicoryne brassicae aphids and the bacterial phytopathogen X anthomonas campestris pv. campestris. In all cases, parasitoids successfully located host-infested plants, and wasp foraging behaviour was unaffected by the simultaneous presence of a non-host attacker or host eggs. Analysis of the volatile emissions show that the volatile blends of caterpillar-infested treatments were different from those without caterpillars. Furthermore, dually attacked plants could not be separated from those with only caterpillars, regardless of non-host identity, supporting the behavioural data. Our results suggest that, in this system, indirect plant defences may be more resistant to interference than is generally assumed, with volatiles induced during dual attack remaining reliable indicators of host presence for parasitoids. [ABSTRACT FROM AUTHOR]

Parasitoid foraging decisions are often affected by community characteristics such as community diversity and complexity. As part of a complex habitat, the presence of unsuitable hosts may affect foraging behaviour of parasitoids. First, unsuitable herbivores may affect the localization of patches where hosts are present. Second, encounters with unsuitable herbivores in the food plant patch may affect parasitoid decisions during their searching behaviour in the patch. In this review, we outline the importance of the presence of unsuitable herbivores on the behavioural responses of parasitoids during both these foraging phases. Nonhosts feeding on a neighbouring plant or on the same plant individual the host is feeding from may affect odour-based searching by parasitoids in a way specific for the species combination studied. Feeding by specific host and nonhost–herbivore combinations may induce volatiles that are more, less or equally attractive compared to those from plants infested by the host only. Within the food patch, mixed presence of host and nonhost may reduce the number of hosts parasitized per time unit and reduce parasitoid foraging efficiency. Importantly, we show that a single nonhost species may have contrasting effects in terms of its effects on odour-based searching and patch residence decisions. We conclude that studying host searching behaviour at both phases of foraging is essential for our understanding of parasitoid foraging behaviour in natural and agricultural settings. We further speculate on the ecological context in which unsuitable herbivores affect either of the two phases of parasitoid foraging. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

As studies demonstrating attraction of natural enemies to synthetic herbivore-induced plant volatiles ( HIPVs) accumulate, it is becoming increasingly important to investigate how deployment of these compounds influences arthropod behavior and distribution in the field. There is currently an unexplained dichotomy in the literature regarding the distance over which HIPVs are thought to be effective. It is assumed that these compounds increase recruitment of natural enemies into fields, whereas experiments have found the effects of attraction to dissipate as little as 1.5 m from lures. Through the use of the common HIPV phenylethyl alcohol in soybean [ Glycine max ( L.) Merr ( Fabaceae)] fields, we used replicated mini plots to test the spatial scale and consequences of attraction by analyzing the response of a complex arthropod community to HIPVs along a distance gradient from the HIPV source. Although repellent effects were more common than attractive ones, we found that insect responses to HIPVs are generally consistent out to a range of 8 m, corroborating the idea that volatiles can influence a wide area and are capable of increasing arthropod recruitment at a field scale. Evidence of redistribution (i.e., depletion of patches surrounding HIPV-augmented plots) was found for a single taxon, braconid wasps, for which augmentation occurred around the lure, but with a reciprocal decline in abundance at greater distances from the emission site. These results are both encouraging and cautionary. Although broad-scale diffusion of HIPVs appears to be common, redistribution of key predators and/or parasitoids may complicate natural enemy management on a landscape scale by aggravating pest outbreaks in areas robbed of their normal carnivore assemblage. [ABSTRACT FROM AUTHOR]

Using herbivore-induced plant volatiles (HIPVs) to attract specific natural enemies in the field has proven challenging, partly because of a poor understanding of: (i) which compound(s) to manipulate to attract specific taxa, and (ii) the ecological conditions over which HIPVs are effective. To address these issues, we quantified the response of a complex arthropod community to three common HIPVs (methyl salicylate, cis-3-hexen-1-ol, and phenylethyl alcohol) as individual compounds and equal part blends in corn and soybean fields. Of 119 arthropod taxa surveyed, we found significant responses by four species in corn fields (2 parasitoids, 1 herbivore, and 1 detritivore) and 16 in soybean fields (8 parasitoids, 3 predators, 4 herbivores, and 1 detritivore), with both attractive and repellent effects of the HIPVs observed. For example, tachinid flies were highly attracted to cis-3-hexen-1-ol (ca. 3-fold increase), but repelled by methyl salicylate (ca. 60 % decrease). Surprisingly, we found very few cases in which HIPVs acted synergistically; only two arthropod groups (ichneumonid wasps and phorid flies) were more attracted by a blend of the HIPVs than by the individual compounds composing the blend. Crop type, however, had a strong impact on the strength of arthropod responses to HIPVs. A few arthropod species were broadly affected across both crops (i.e., the herbivore Halticus bractatus was repelled by most of our treatments, regardless of crop background), but overall more arthropod groups responded to HIPVs released in soybean fields compared with corn. This was true despite the fact that taxa responding to HIPVs were present and abundant in both systems, suggesting that crop-based outcomes were likely driven by the plant matrix rather than mere differences in taxonomic composition of the arthropod community in corn vs. soybean fields. As a whole, these results suggest that: (i) repellent effects of HIPVs on natural enemies of herbivorous insects can be observed as frequently as attractive effects; (ii) odor blends may be no more effective than single-compound lures for some taxa; and (iii) crop background alters the magnitude of attraction to HIPVs, depending on the species being targeted. [ABSTRACT FROM AUTHOR]

Herbivore-induced plant volatiles (HIPV) provide important information that influences host location behaviour for insect natural enemies, such as parasitoid wasps, that develop in the bodies of herbivorous insects. The dietary breadth of both the parasitoid and its host may affect the extent to which a searching parasitoid relies on HIPV. Specialist species are expected to rely on specific volatile cues to which they respond innately, whereas generalists are expected to show a higher degree of phenotypic plasticity that depends on foraging experience in the parasitoid. We compared the response to HIPV emitted by different plant species damaged by host and nonhost caterpillars for two congeneric parasitoid species, the specialist Diadegma semiclausum and the generalist Diadegma fenestrale, attacking caterpillars of the diamondback moth, Plutella xylostella. For the three tested plant species, Brassica oleracea, a feral Brassica population and Sinapis alba, both parasitoid species preferred volatiles from host-infested plants over those produced by undamaged plants. However, both parasitoid species only distinguished between volatiles induced by host and nonhosts when the caterpillars had been feeding on B. oleracea, the plant on which they had been reared. Chemical analysis of the volatile blends could not explain volatile preferences of the parasitoids. Despite the difference in their dietary breadth, the two parasitoids responded similarly to HIPV and experience treatments. A flexible response to a wide array of volatile blends by parasitoids is probably important in nature, given that different generations of the host and the parasitoid probably develop on different food plants. [ABSTRACT FROM AUTHOR]

Abstract: Methyl salicylate (MeSA) is a herbivore-induced plant volatile that has shown potential in attracting natural enemies. Here, we conducted a meta-analysis to evaluate the magnitude of natural enemy response to MeSA in the field, and tested its attractiveness to insect predators in commercial cranberry bogs. Eighteen experiments from 14 publications were used in the meta-analysis, resulting in 91 total observations. Of these, 41 documented significant attraction and the magnitude of this attraction response was not significantly different across predator and parasitoid taxa. Insect predators were monitored in cranberries using MeSA (PredaLure)-baited and unbaited yellow sticky traps. MeSA-baited traps caught greater numbers of adult hoverfly, Toxomerus marginatus, lady beetles, and green lacewings compared with unbaited traps. In another field experiment, predator abundance was monitored using traps placed near the MeSA lure (0m), as well as at 2.5, 5, and 10m away from the lure. Adult T. marginatus, the dominant predator species, showed a clear attraction to the point source but not to the other distances. In complementary studies we showed that MeSA emissions from PredaLures dropped quickly soon after deployment in the field but remained relatively high for over 4weeks; flowering, but not vegetative, vines were a primary source of MeSA in cranberries; and, exposure to PredaLures triggered elevated MeSA emissions from vegetative vines. In conclusion, we find strong evidence that insect predators are broadly attracted to MeSA in agricultural fields, including cranberries; yet, whether this behavior can be manipulated to improve biological control needs further investigation. [Copyright &y& Elsevier]

Despite a large number of studies on herbivore-induced plant volatiles (HIPVs), little is known about which specific compounds are used by natural enemies to locate prey- or host- infested plants. In addition, the role of HIPVs in attracting natural enemies has been restricted largely to agricultural systems. Differences in volatile blends emitted by cultivars and plants that originate from wild populations may be attributed to potentially contrasting selection regimes: natural selection among the wild types and artificial selection among cultivars. A more realistic understanding of these interactions in a broader ecological and evolutionary framework should include studies that involve insect herbivores, parasitoids, and wild plants on which they naturally interact in the field. We compared the attractiveness of HIPVs emitted by wild and cultivated cabbage to the parasitoid Cotesia rubecula, and determined the chemical composition of the HIPV blends to elucidate which compounds are involved in parasitoid attraction. Wild and cultivated cabbage differed significantly in their volatile emissions. Cotesia rubecula was differentially attracted to the wild cabbage populations and preferred wild over cultivated cabbage. Isothiocyanates, which were only emitted by the wild cabbages, may be the key components that explain the preference for wild over cultivated cabbage, whereas terpenes may be important for the differential attraction among the wild populations. Volatile analysis revealed that parasitoid attraction cannot be explained by simple linear relationships. Our results suggest that unraveling which compound(s) are innately attractive to parasitoids of cabbage pests should include wild Brassicaceae. [ABSTRACT FROM AUTHOR]

Abstract: We evaluated five herbivore-induced plant volatiles plus a male-produced pheromone as attractants for adult green lacewings in Washington apple orchards in 2008. We found at least five attractants or combinations of attractants were attractive to the three most abundant green lacewing species in our trials. Chrysopa nigricornis and Chrysopa oculata were attracted to the combination of methyl salicylate and iridodial with iridodial alone being the second best attractant. Chrysoperla plorabunda was found in lower numbers than C. nigricornis and C. oculata, but did exhibit a significant attraction to benzaldehyde. In mid-summer, we added the herbivore-induced plant volatile squalene to the study and found it to be exceedingly attractive, but only to male C. nigricornis. Whether alone or in combination, squalene attracted 4–5-fold more C. nigricornis than any other compound tested. Our data have revealed C. nigricornis to be an abundant orchard predator that can be readily monitored with squalene-baited traps. Despite the obvious promise of HIPVs in biological control programs, we urge caution in their deployment as large-scale attractants, at least until further studies have investigated potential disruption of natural enemy population dynamics. [ABSTRACT FROM AUTHOR]

Purpose The issue of continued oral contraceptive use among women with abnormal Pap smears may be controversial due to reported evidence of an increased risk of cervical cancer among long term oral contraceptive users. This article reviews the evidence concerning oral contraception and cervical cancer risk. The role of Human Papilloma virus (HPV) and proposed mechanisms for the development of cervical cancer are explained. Evidence from World Health Organization (WHO) studies and additional research evidence are discussed. Implications tor clinical practice are included. Data Sources WHO commissioned studies, additional relevant studies searchable from an EBSCO database, and texts that describe the natural history of HPV. Conclusions Epidemiological studies and biomedical research suggest 3 role for steroid hormones, such as oral contraceptives, in facilitating the action of HPV. However, a majority of HPV infections resolve spontaneously, despite widespread use of oral contraception. Oral contraception does not appear to increase incident HPV infection or persistence of HPV infection. The benefits of oral contraceptives appear to outweigh the risks associated with HPV facilitation. Implications for Practice NPs inform patients of abnormal Pap smears, manage the clinical care of women at risk of cervical cancer, and provide educational counseling regarding contraceptive choices. Ethical considerations include clear disclosure of potential risk. However, a risk-benefit analysis supports continued use of oral contraception among women who have abnormal Pap smears but also have access to clinical surveillance. [ABSTRACT FROM AUTHOR]