Attraction of Coffee Bean Weevil, <Emphasis Type="Italic">Araecerus fasciculatus</Emphasis>, to Volatiles from the Industrial Yeast <Emphasis Type="Italic">Kluyveromyces lactis</Emphasis>

The coffee bean weevil (CBW), Araecerus fasciculatus (De Geer, 1775) (Coleoptera: Anthribidae) is an important pest of stored products such as grains, coffee beans, cassava, and traditional Chinese medicine materials. In China, CBW causes large losses of Daqu, a traditional Chinese liquor fermentation starter, and, unfortunately, the use of conventional insecticides against CBW is not suitable in Daqu storage. We found CBW to be highly attracted to fermenting yeast cultures, such as Kluyveromyces lactis. Eight volatile compounds, produced by fermenting cultures and not by sterile samples, were identified by gas chromatography coupled with mass spectrometry. Five of these substances elicited significant responses in Y-tube behavioral bioassays. Field trapping experiments revealed 2-phenylethanol and 2-phenylethyl acetate to be crucial for attraction of CBW. Results show that yeast volatiles play an important role in host location, and that 2-phenylethanol and 2-phenylethyl acetate could be utilized as potential attractants in monitoring and control systems against this important pest.     

Influence of Two Acyclic Homoterpenes (Tetranorterpenes) on the Foraging Behavior of <Emphasis Type="Italic">Anthonomus grandis</Emphasis> Boh

Previous studies have shown that the boll weevil, Anthonomus grandis, is attracted to constitutive and conspecific herbivore-induced cotton volatiles, preferring the blend emitted by cotton at the reproductive over the vegetative stage. Moreover, this preference was paralleled by the release of the acyclic homoterpenes (tetranorterpenes) (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene (TMTT) in Delta Opal cotton being higher at the vegetative than at the reproductive stage. Here, we evaluated whether this difference in release of acyclic homoterpenes also occurred in other cotton varieties, and if boll weevils could recognize these compounds as indicators of a specific cotton phenological stage. Results showed that cotton genotypes CNPA TB-90, BRS-293 and Delta Opal all produced higher levels of DMNT and TMTT at the vegetative stage than at the reproductive stage and that these homoterpenes allowed for principal component analysis separation of volatiles produced by the two phenological stages. Electroantennograms confirmed boll weevil antennal responses to DMNT and TMTT. Behavioral assays, using Y-tube olfactometers, showed that adding synthetic homoterpenes to reproductive cotton volatiles (mimicking cotton at the vegetative stage in terms of homoterpene levels) resulted in reduced attraction to boll weevils compared to that to unmodified reproductive cotton. Weevils showed no preference when given a choice between plants at the vegetative stage and the vegetative stage-mimicked plant. Altogether, the results show that DMNT and TMTT are used by boll weevils to distinguish between cotton phenological stages.     

Attractiveness of Host Plant Volatile Extracts to the Asian Citrus Psyllid, <Emphasis Type="Italic">Diaphorina citri,</Emphasis> is Reduced by Terpenoids from the Non-Host Cashew

Diaphorina citri is a vector of the bacterial causative agent of Huanglongbing (HLB?=?Citrus greening), a severe disease affecting citrus crops. As there is no known control for HLB, manipulating insect behaviour through deployment of semiochemicals offers a promising opportunity for protecting citrus crops. The behavioural responses of D. citri to plant volatiles, and the identity of these plant volatiles were investigated. Volatiles were collected from host plants Murraya paniculata, Citrus sinensis, C. reshni, C. limettioides, Poncirus trifoliata, and from non-host plants Psidium guajava, Mangifera indica, Anacardium occidentale. In behavioural assays, female D. citri spent more time in the arms containing volatiles from either M. paniculata or C. sinensis compared to the control arms. When D. citri was exposed to volatiles collected from A. occidentale, they preferred the control arm. Volatiles emitted from the other studied plants did not influence the foraging behaviour of D. citri. Chemical analyses of volatile extracts from C. sinensis, M. paniculata, and A. occidentale revealed the presence of the terpenoids (E)-4,8-dimethylnona-1,3,7–triene (DMNT) and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene (TMTT) in higher amounts in A. occidentale. In further behavioural bioassays, female D. citri spent less time in arms containing a synthetic blend of DMNT and TMTT compared to the control arms. Female D. citri also spent less time in arms containing the synthetic blend in combination with volatile extracts from either M. paniculata or C. sinensis compared to the control arms. Results suggest that higher release of the two terpenoids by A. occidentale make this species unattractive to D. citri, and that the terpenoids could be used in reducing colonisation of citrus plants and therefore HLB infection.     

<Emphasis Type="Italic">n</Emphasis>-Pentacosane Acts as both Contact and Volatile Pheromone in the tea Weevil, <Emphasis Type="Italic">Myllocerinus aurolineatus</Emphasis>

Insect cuticular hydrocarbons (CHCs) play important roles in chemical communication, as well as having ecological and physiological roles. The use of CHCs for mate recognition has been shown in many insect genera, but little is known about their use in the tea weevil Myllocerinus aurolineatus. Here, we provide evidence that CHCs on the surface of sexually mature M. aurolineatus females act as contact sex pheromones, facilitating mate recognition and eliciting copulatory behavior in male weevils. Using gas chromatography-mass spectrometry, we identify n-pentacosane and n-heptacosane as two potential contact pheromone components. Results from arena bioassays showed that n-pentacosane is a component of a contact pheromone of M. aurolineatus. Further results from the Y-tube olfactometer bioassays showed that n-pentacosane also acts as a volatile attractant. Our results greatly improve our understanding of the chemical ecology of M. aurolineatus.     

Methyl Jasmonate-Induced Monoterpenes in Scots Pine and Norway Spruce Tissues Affect Pine Weevil Orientation

In large parts of Europe, insecticide-free measures for protecting conifer plants are desired to suppress damage by the pine weevil Hylobius abietis (L.). Treatment with methyl jasmonate (MeJA), a chemical elicitor already used in crop production, may enhance expression of chemical defenses in seedlings in conifer regenerations. However, in a previous experiment, MeJA treatment resulted in substantially better field protection for Scots pine (Pinus sylvestris L.) than for Norway spruce (Picea abies (L.) Karst.). Hypothesizing that the variations may be at least due partly to volatiles released by MeJA-treated seedlings and their effects on pine weevil orientation, we examined tissue extracts of seedlings (from the same batches as previously used) by two-dimensional GC-MS. We found that the MeJA treatment increased contents of the monoterpene (?)-β-pinene in phloem (the weevil’s main target tissue) of both tree species, however, the (?)-β-pinene/(?)-α-pinene ratio increased more in the phloem of P. sylvestris. We also tested the attractiveness of individual monoterpenes found in conifer tissues (needles and phloem) for pine weevils using an arena with traps baited with single-substance dispensers and pine twigs. Trap catches were reduced when the pine material was combined with a dispenser releasing (?)-β-pinene, (+)-3-carene, (?)-bornyl acetate or 1,8-cineole. However, (?)-α-pinene did not have this effect. Thus, the greater field protection of MeJA-treated P. sylvestris seedlings may be due to the selective induction of increases in contents of the deterrent (?)-β-pinene, in contrast to strong increases in both non-deterrent (?)-α-pinene and the deterrent (?)-β-pinene in P. abies seedlings.     

Aggregation Pheromone of the Bearded Weevil, <Emphasis Type="Italic">Rhinostomus barbirostris</Emphasis> (Coleoptera: Curculionidae): Identification,Synthesis, Absolute Configuration and Bioactivity

The bearded weevil, Rhinostomus barbirostris (Coleoptera: Curculionidae: Dryophthorinae), attacks coconut trees, oil palms and other species of Arecaceae. Besides direct damage, R. barbirostris may be a vector of diseases in coconut and oil palms, such as stem bleeding (resinosis) and red ring disease. Currently, the only method to control this weevil is by visual observation of damage and removal of infected plants. Semiochemical-based trapping could improve the effectiveness of monitoring and management of R. barbirostris. In comparisons of volatiles released by R. barbirostris males and females by gas chromatography (GC) two male-specific compounds were observed. GC-mass spectrometry (MS) and GC-Fourier transform-infrared (FTIR) analyses of the natural compounds suggested these were diastereoisomers of 5-hydroxy-4-methylheptan-3-one, also known as sitophilure, a pheromone component of other dryophthorine species. Synthesis of the mixture of all four stereoisomers of sitophilure was performed in two steps, and the chemical structures were confirmed by comparing GC retention times and MS and FTIR spectra of natural and synthetic compounds. The absolute configurations of the two male-specific compounds were elucidated by enantioselective GC; the major component was the (4S,5R)-isomer, and the minor component (4S,5S)-sitophilure. In analyses by GC-electroantennography (EAG) the antennae of male and female R. barbirostris only responded to the (4S,5R)-isomer of the synthetic sitophilure. The stereoisomeric mixture of sitophilure was attractive to both sexes of R. barbirostris in laboratory experiments in the presence of sugar cane volatiles, and a similar result was obtained in a preliminary field trapping test.     

Feeding Experience Affects the Behavioral Response of Polyphagous Gypsy Moth Caterpillars to Herbivore-induced Poplar Volatiles

Plant volatiles influence host selection of herbivorous insects. Since volatiles often vary in space and time, herbivores (especially polyphagous ones) may be able to use these compounds as cues to track variation in host plant quality based on their innate abilities and previous experience. We investigated the behavioral response of naïve (fed on artificial diet) and experienced (fed on poplar) gypsy moth (Lymantria dispar) caterpillars, a polyphagous species, towards constitutive and herbivore-induced black poplar (Populus nigra) volatiles at different stages of herbivore attack. In Y-tube olfactometer assays, both naïve and experienced caterpillars were attracted to constitutive volatiles and volatiles released after short-term herbivory (up to 6 hr). Naïve caterpillars also were attracted to volatiles released after longer-term herbivory (24–30 hr), but experienced caterpillars preferred the odor of undamaged foliage. A multivariate statistical analysis comparing the volatile emission of undamaged plants vs. plants after short and longer-term herbivory, suggested various compounds as being responsible for distinguishing between the odors of these plants. Ten compounds were selected for individual testing of caterpillar behavioral responses in a four-arm olfactometer. Naïve caterpillars spent more time in arms containing (Z)-3-hexenol and (Z)-3-hexenyl acetate than in solvent permeated arms, while avoiding benzyl cyanide and salicyl aldehyde. Experienced caterpillars avoided benzyl cyanide and preferred (Z)-3-hexenyl acetate and the homoterpene (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) over solvent. Only responses to DMNT were significantly different when comparing experienced and naïve caterpillars. The results show that gypsy moth caterpillars display an innate behavioral response towards constitutive and herbivore-induced plant volatiles, but also that larval behavior is plastic and can be modulated by previous feeding experience.     

Volatile and Contact Chemical Cues Associated with Host and Mate Recognition Behavior of <Emphasis Type="Italic">Sphenophorus venatus</Emphasis> and <Emphasis Type="Italic">Sphenophorus parvulus</Emphasis> (Coleoptera: Dryophthoridae)

Beetles in the genus Sphenophorus Schönherr, or billbugs, potentially utilize both volatile and non-volatile behavior-modifying chemical signals. These insects are widely distributed across North America, often occurring in multi-species assemblages in grasses. However, details about their host- and mate-finding behavior are poorly understood. This study tested the hypothesis that volatile organic compounds from host-plants and conspecifics direct the dispersal behavior of hunting billbug S. venatus Say. Further, we characterized the cuticular hydrocarbon profiles of two widespread pest species, S. venatus and bluegrass billbug S. parvulus Gyllenhaal, to assess the potential role of contact pheromones in mate-recognition. In Y-tube olfactometer bioassays, S. venatus males were attracted to a combination of conspecifics and Cynodon dactylon host-plant material, as well as C. dactylon plant material alone. S. venatus females were attracted to a combination of male conspecifics and host-plants but were also attracted to male conspecifics alone. Field evaluation of a putative male-produced aggregation pheromone, 2-methyl-4-octanol, identified from two congeners, S. levis Vaurie and S. incurrens Gyllenhaal, did not support the hypothesis that S. venatus and S. parvulus were also attracted to this compound. Gas chromatography-mass spectrometry analysis of S. venatus and S. parvulus whole-body cuticular extracts indicated a series of hydrocarbons with qualitative and quantitative interspecific variation in addition to intraspecific quantitative variation between males and females. This study provides the first evidence that S. venatus orients toward host- and insect-derived volatile organic compounds and substantiates the presence of species-specific cuticular hydrocarbons that could serve as contact pheromones for sympatric Sphenophorus species.     

Response of a Predatory ant to Volatiles Emitted by Aphid- and Caterpillar-Infested Cucumber and Potato Plants

In response to herbivory by insects, various plants produce volatiles that attract enemies of the herbivores. Although ants are important components of natural and agro-ecosystems, the importance of herbivore-induced plant volatiles (HIPVs) as cues for ants for finding food sources have received little attention. We investigated responses of the ant Formica pratensis to volatiles emitted by uninfested and insect-infested cucumber (Cucumis sativus) and potato (Solanum tuberosum) plants. Cucumber plants were infested by the phloem-feeding aphid Aphis gossypii, the leaf chewer Mamestra brassicae or simultaneously by both insects. Potato plants were infested by either Aphis gossypii, by the leaf chewer Chrysodeixis chalcites or both. In olfactometer experiments, ants preferred volatile blends emitted by cucumber plants infested with M. brassicae caterpillars alone or combined with A. gossypii to volatiles of undamaged plants or plants damaged by A. gossypii only. No preference was recorded in choice tests between volatiles released by aphid-infested plants over undamaged plants. Volatiles emitted by potato plants infested by either C. chalcites or A. gossypii were preferred by ants over volatiles released by undamaged plants. Ants did not discriminate between potato plants infested with aphids and caterpillars over plants infested with aphids only. Plant headspace composition showed qualitative and/or quantitative differences between herbivore treatments. Multivariate analysis revealed clear separation between uninfested and infested plants and among herbivore treatments. The importance of HIPVs in indirect plant defence by ants is discussed in the context of the ecology of ant-plant interactions and possible roles of ants in pest management.     

Plant Volatiles Increase Sex Pheromone Attraction of <Emphasis Type="Italic">Holotrichia parallela</Emphasis> (Coleoptera: Scarabaeoidea)

Holotrichia parallela (Coleoptera: Scarabaeoidea) is a notorious pest of many crops. To improve the effectiveness of its female-produced sex pheromone (L-isoleucine methyl ester:(R)-(?)-linalool = 6:1), 14 plant volatiles, including dodecanoic acid, dodecanal, farnesol, α-farnesene, (Z)-3-hexen-1-ol, (E)-2-hexen-1-ol, (Z)-3-hexenyl acetate, (E)-2-hexenyl acetate, (R)-(+)-limonene, α-phellandrene, α-pinene, ocimene, methyl benzoate, and benzaldehyde, were individually evaluated using electroantennography and olfactometer assays. (E)-2-Hexenyl acetate and (Z)-3-hexenyl acetate were found to elicit the strongest responses in both males and females. Further testing of these two compounds in mixtures with the sex pheromone indicated that (E)-2-hexenyl acetate had a stronger synergistic effect than (Z)-3-hexenyl acetate. Field evaluations showed that mixtures of (E)-2-hexenyl acetate and the sex pheromone resulted in significantly higher catches than the sex pheromone alone. Using a 5:1 mixture of the sex pheromone and (E)-2-hexenyl acetate, the maximum number of females per trap per day was 14, showing a synergistic effect of a factor of four. For males, a 3:1 mixture of the sex pheromone and (E)-2-hexenyl acetate yielded a maximum number of 310 individuals per trap per day, equivalent to a synergistic effect of 175%. These results may provide the basis for the development of efficient pest management systems against H. parallela using plant volatiles and insect sex pheromones.     

Electrophysiological and Oviposition Responses of <Emphasis Type="Italic">Tuta absoluta</Emphasis> Females to Herbivore-Induced Volatiles in Tomato Plants

In response to attack by herbivorous insects, plants produce semiochemicals for intra- and interspecific communication. The perception of these semiochemicals by conspecifics of the herbivore defines their choice for oviposition and feeding. We aimed to investigate the role of herbivore-induced plant volatiles (HIPVs) by Tuta absoluta larvae on the oviposition choice of conspecific females on tomato plants. We performed two- choice and non-choice bioassays with plants damaged by larvae feeding and intact control plants. We also collected headspace volatiles of those plants and tested the response of female antennae on those blends with Gas Chromatography- Electro-Antennographical Detection (GC-EAD). In total 55 compounds were collected from the headspace of T. absoluta larvae-infested plants. Our results show that female moths preferred to oviposit on intact control plants instead of damaged ones. Herbivory induced the emission of hexanal, (Ζ)-3-hexen-1-ol, (E)-β-ocimene, linalool, (Z)-3-hexenyl butanoate, methyl salicylate, indole, nerolidol, guaidiene-6,9, β-pinene, β-myrcene, α-terpinene, hexenyl hexanoate, β-elemene, β-caryophyllene and (Ε-Ε)- 4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT), one unidentified sesquiterpene and three unknown compounds. In Electroantennographic (EAG) assays, the antennae of T. absoluta females responded to hexanal, (Ζ)-3-hexen-1-ol, methyl salicylate and indole. The antennae of T. absoluta females exhibited a dose-response in EAG studies with authentic samples. Strong EAG responses were obtained for compounds induced on damaged tomato plants, as well as in nonanal, a compound emitted by both infested and control plants. These compounds could be utilized in integrated pest management of T. absoluta.     

Attraction of Three Mirid Predators to Tomato Infested by Both the Tomato Leaf Mining Moth <Emphasis Type="Italic">Tuta absoluta</Emphasis> and the Whitefly <Emphasis Type="Italic">Bemisia tabaci</Emphasis>

Plants emit volatile compounds in response to insect herbivory, which may play multiple roles as defensive compounds and mediators of interactions with other plants, microorganisms and animals. Herbivore-induced plant volatiles (HIPVs) may act as indirect plant defenses by attracting natural enemies of the attacking herbivore. We report here the first evidence of the attraction of three Neotropical mirid predators (Macrolophus basicornis, Engytatus varians and Campyloneuropsis infumatus) toward plants emitting volatiles induced upon feeding by two tomato pests, the leaf miner Tuta absoluta and the phloem feeder Bemisia tabaci, in olfactometer bioassays. Subsequently, we compared the composition of volatile blends emitted by insect-infested tomato plants by collecting headspace samples and analyzing them with GC-FID and GC-MS. Egg deposition by T. absoluta did not make tomato plants more attractive to the mirid predators than uninfested tomato plants. Macrolophus basicornis is attracted to tomato plants infested with either T. absoluta larvae or by a mixture of B. tabaci eggs, nymphs and adults. Engytatus varians and C. infumatus responded to volatile blends released by tomato plants infested with T. absoluta larvae over uninfested plants. Also, multiple herbivory by T. absoluta and B. tabaci did not increase the attraction of the mirids compared to infestation with T. absoluta alone. Terpenoids represented the most important class of compounds in the volatile blends and there were significant differences between the volatile blends emitted by tomato plants in response to attack by T. absoluta, B. tabaci, or by both insects. We, therefore, conclude that all three mirids use tomato plant volatiles to find T. absoluta larvae. Multiple herbivory did neither increase, nor decrease attraction of C. infumatus, E. varians and M. basicornis. By breeding for higher rates of emission of selected terpenes, increased attractiveness of tomato plants to natural enemies may improve the effectiveness of biological control.     

Innate and Learned Prey-Searching Behavior in a Generalist Predator

Early colonization by Zyginidia scutellaris leafhoppers might be a key factor in the attraction and settling of generalist predators, such as Orius spp., in maize fields. In this paper, we aimed to determine whether our observations of early season increases in field populations of Orius spp. reflect a specific attraction to Z. scutellaris-induced maize volatiles, and how the responses of Orius predators to herbivore-induced volatiles (HIPVs) might be affected by previous experiences on plants infested by herbivorous prey. Therefore, we examined the innate and learned preferences of Orius majusculus toward volatiles from maize plants attacked by three potential herbivores with different feeding strategies: the leafhopper Z. scutellaris (mesophyll feeder), the lepidopteran Spodoptera littoralis (chewer), and another leafhopper Dalbulus maidis (phloem feeder). In addition, we examined the volatile profiles emitted by maize plants infested by the three herbivores. Our results show that predators exhibit a strong innate attraction to volatiles from maize plants infested with Z. scutellaris or S. littoralis. Previous predation experience in the presence of HIPVs influences the predator’s odor preferences. The innate preference for plants with cell or tissue damage may be explained by these plants releasing far more volatiles than plants infested by the phloem-sucking D. maidis. However, a predation experience on D. maidis-infested plants increased the preference for D. maidis-induced maize volatiles. After O. majusculus experienced L3-L4 larvae (too large to serve as prey) on S. littoralis-infested plants, they showed reduced attraction toward these plants and an increased attraction toward D. maidis-infested plants. When offered young larvae of S. littoralis, which are more suitable prey, preference toward HIPVs was similar to that of naive individuals. The HIPVs from plants infested by herbivores with distinctly different feeding strategies showed distinguishable quantitative differences in (Z)-3-hexenal, (E)-2-hexenal, and methyl salicylate. These compounds might serve as reliable indicators of prey presence and identity for the predator. Our results support the idea that feeding by Z. scutellaris results in the emission of maize’s HIPVs that initially recruit Orius spp. into maize fields.     

Qualitative and Quantitative Differences in Herbivore-Induced Plant Volatile Blends from Tomato Plants Infested by Either <Emphasis Type="Italic">Tuta absoluta</Emphasis> or <Emphasis Type="Italic">Bemisia tabaci</Emphasis>

Plants release a variety of volatile organic compounds that play multiple roles in the interactions with other plants and animals. Natural enemies of plant-feeding insects use these volatiles as cues to find their prey or host. Here, we report differences between the volatile blends of tomato plants infested with the whitefly Bemisia tabaci or the tomato borer Tuta absoluta. We compared the volatile emission of: (1) clean tomato plants; (2) tomato plants infested with T. absoluta larvae; and (3) tomato plants infested with B. tabaci adults, nymphs, and eggs. A total of 80 volatiles were recorded of which 10 occurred consistently only in the headspace of T. absoluta-infested plants. Many of the compounds detected in the headspace of the two herbivory treatments were emitted at different rates. Plants damaged by T. absoluta emitted at least 10 times higher levels of many compounds compared to plants damaged by B. tabaci and intact plants. The multivariate separation of T. absoluta-infested plants from those infested with B. tabaci was due largely to the chorismate-derived compounds as well as volatile metabolites of C₁₈-fatty acids and branched chain amino acids that had higher emission rates from T. absoluta-infested plants, whereas the cyclic sesquiterpenes α- and β-copaene, valencene, and aristolochene were emitted at significantly higher levels from B. tabaci-infested plants. Our findings imply that feeding by T. absoluta and B. tabaci induced emission of volatile blends that differ quantitatively and qualitatively, providing a chemical basis for the recently documented behavioral discrimination by two generalist predatory mirid species, natural enemies of T. absoluta and B. tabaci employed in biological control.     

Volatiles Emitted by Calling Males of Burying Beetles and <Emphasis Type="Italic">Ptomascopus morio</Emphasis> (Coleoptera: Silphidae: Nicrophorinae) Are Biogenetically Related

In burying beetles, Nicrophorus spp. (Coleoptera: Silphidae: Nicrophorinae) mate finding is mediated by male produced volatile compounds. To date, pheromone components of only two species have been identified. In an attempt to better understand the evolution of male pheromone signaling in burying beetles, we investigated the male released volatiles of ten Nicrophorus species and one closely related nicrophorine species, Ptomascopus mori. Volatiles emitted by calling males were collected in the laboratory by means of solid phase micro extraction and analyzed using gas chromatography coupled with mass spectrometry. Identified volatiles included short chain esters of 4-methylcarboxylic acids, terpenoids, and some other aliphatic compounds. The long-range volatile signals of the burying beetle species included in this study are blends of two to seven components. We found that methyl or ethyl esters of 4-methylheptanoic acid and 4-methyloctanoic acid are produced by eight of the ten investigated Nicrophorus species. These esters may play a key role in chemical communication. Their widespread occurrence suggests that these compounds did not evolve recently, but appeared relatively early in the phylogeny of the genus. Although Ptomascopus is considered the sister genus of Nicrophorus, P. morio males do not produce any of the Nicrophorus compounds, but release 3-methylalkan-2-ones, which are absent in Nicrophorus. A better understanding of the evolution of burying beetle pheromones, however, will only be possible once more species have been studied.     

The Fungus <Emphasis Type="Italic">Raffaelea lauricola</Emphasis> Modifies Behavior of Its Symbiont and Vector,the Redbay Ambrosia Beetle (<Emphasis Type="Italic">Xyleborus Glabratus</Emphasis>), by Altering Host Plant Volatile Production

The redbay ambrosia beetle Xyleborus glabratus is the vector of the symbiotic fungus, Raffaelea lauricola that causes laurel wilt, a highly lethal disease to members of the Lauraceae family. Pioneer X. glabratus beetles infect live trees with R. lauricola, and only when tree health starts declining more X. glabratus are attracted to the infected tree. Until now this sequence of events was not well understood. In this study, we investigated the temporal patterns of host volatiles and phytohormone production and vector attraction in relation to laurel wilt symptomology. Following inoculations with R. lauricola, volatile collections and behavioral tests were performed at different time points. Three days after infection (DAI), we found significant repellency of X. glabratus by leaf odors of infected swamp bay Persea palustris as compared with controls. However, at 10 and 20 DAI, X. glabratus were more attracted to leaf odors from infected than non-infected host plants. GC-MS analysis revealed an increase in methyl salicylate (MeSA) 3 DAI, whereas an increase of sesquiterpenes and leaf aldehydes was observed 10 and 20 DAI in leaf volatiles. MeSA was the only behaviorally active repellent of X. glabratus in laboratory bioassays. In contrast, X. glabratus did not prefer infected wood over healthy wood, and there was no associated significant difference in their volatile profiles. Analyses of phytohormone profiles revealed an initial increase in the amount of salicylic acid (SA) in leaf tissues following fungal infection, suggesting that the SA pathway was activated by R. lauricola infection, and this activation caused increased release of MeSA. Overall, our findings provide a better understanding of X. glabratus ecology and underline chemical interactions with its symbiotic fungus. Our work also demonstrates how the laurel wilt pathosystem alters host defenses to impact vector behavior and suggests manipulation of host odor by the fungus that attract more vectors.     

Volatiles of <Emphasis Type="Italic">Solena amplexicaulis</Emphasis> (Lam.) Gandhi Leaves Influencing Attraction of Two Generalist Insect Herbivores

Epilachna vigintioctopunctata Fabr. (Coleoptera: Coccinellidae) and Aulacophora foveicollis Lucas (Coleoptera: Chrysomelidae) are important pests of Solena amplexicaulis (Lam.) Gandhi (Cucurbitaceae), commonly known as creeping cucumber. The profiles of volatile organic compounds from undamaged plants, plants after 48 hr continuous feeding of adult females of either E. vigintioctopunctata or A. foveicollis, by adults of both species, and after mechanical damaging were identified and quantified by GC-MS and GC-FID analyses. Thirty two compounds were detected in volatiles of all treatments. In all plants, methyl jasmonate was the major compound. In Y-shaped glass tube olfactometer bioassays under laboratory conditions, both insect species showed a significant preference for complete volatile blends from insect damaged plants, compared to those of undamaged plants. Neither E. vigintioctopunctata nor A. foveicollis showed any preference for volatiles released by heterospecifically damaged plants vs. conspecifically damaged plants or plants attacked by both species. Epilachna vigintioctopunctata and A. foveicollis showed attraction to three different synthetic compounds, linalool oxide, nonanal, and E-2-nonenal in proportions present in volatiles of insect damaged plants. Both species were attracted by a synthetic blend of 1.64 μg linalool oxide?+?3.86 μg nonanal?+?2.23 μg E-2-nonenal, dissolved in 20 μl methylene chloride. This combination might be used as trapping tools in pest management strategies.     

Responses of Parasitoids to Volatiles Induced by <Emphasis Type="Italic">Chilo partellus</Emphasis> Oviposition on Teosinte,a Wild Ancestor of Maize

Maize, a genetically diverse crop, is the domesticated descendent of its wild ancestor, teosinte. Recently, we have shown that certain maize landraces possess a valuable indirect defense trait not present in commercial hybrids. Plants of these landraces release herbivore-induced plant volatiles (HIPVs) that attract both egg [Trichogramma bournieri Pintureau & Babault (Hymenoptera: Trichogrammatidae)] and larval [Cotesia sesamiae Cameron (Hymenoptera: Braconidae)] parasitoids in response to stemborer egg deposition. In this study, we tested whether this trait also exists in the germplasm of wild Zea species. Headspace samples were collected from plants exposed to egg deposition by Chilo partellus Swinhoe (Lepidoptera: Crambidae) moths and unexposed control plants. Four-arm olfactometer bioassays with parasitic wasps, T. bournieri and C. sesamiae, indicated that both egg and larval parasitoids preferred HIPVs from plants with eggs in four of the five teosinte species sampled. Headspace samples from oviposited plants released higher amounts of EAG-active compounds such as (E)-4,8-dimethyl-1,3,7-nonatriene. In oviposition choice bioassays, plants without eggs were significantly preferred for subsequent oviposition by moths compared to plants with prior oviposition. These results suggest that this induced indirect defence trait is not limited to landraces but occurs in wild Zea species and appears to be an ancestral trait. Hence, these species possess a valuable trait that could be introgressed into domesticated maize lines to provide indirect defense mechanisms against stemborers.     

Electrophysiological and behavioral responses of female African rice gall midge, <Emphasis Type="Italic">Orseolia oryzivora</Emphasis> Harris and Gagné, to host plant volatiles

African rice gall midge, Orseolia oryzivora Harris and Gagné, is a major pest of rice in Africa. Depsite its economic importance, its chemical ecology is not well understood. Here, we assessed behavioral and electrophysiological responses of O. oryzivora to host plant volatiles. In olfactometer bioassays, mated female O. oryzivora were attracted to volatiles emitted from intact rice plants but were repelled by volatiles collected from plants infested by conspecifics. In a choice test, there was a preference for volatiles from uninfested plants over those from infested plants. Coupled gas chromatography-electroantennography analyses of panicle volatiles isolated four electrophysiologically active components: (S)-linalool, 4,8-dimethyl-1,3,7-nonatriene, (E)-caryophyllene, and (R/S)-(E)-nerolidol. A synthetic blend of volatiles at the same concentration and ratio as that from an intact plant was attractive to mated females, whereas a blend based on the ratio of volatiles from an infested plant was repellent. This suggests that O. oryzivora uses olfaction for host plant recognition. The identification of blends of volatiles emitted by plants that can both attract and repel O. oryzivora may aid the development of sustainable control measures.     

An Attractant of the Aphidophagous Gall Midge <Emphasis Type="Italic">Aphidoletes aphidimyza</Emphasis> From Honeydew of <Emphasis Type="Italic">Aphis gossypii</Emphasis>

Many natural enemies of insects use honeydew as a volatile cue to locate hosts or prey, as an oviposition stimulant, and as an arrestant for foraging. The aphidophagous gall midge Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) has predacious larval stages and can be used to control aphid populations, especially in greenhouses. Previous studies have shown that the honeydew, excreted by the aphid Myzus persicae, attracts A. aphidimyza, but the crucial attractants have not been identified. Using an olfactometer, we studied behavioral responses of female A. aphidimyza to volatiles emitted from honeydew excreted by the aphid Aphis gossypii on eggplants. The volatiles attracted female midges and induced oviposition. Moreover, using gas chromatography coupled with mass spectrometry (GC/MS), we identified phenylacetaldehyde as the attractant compound in the honeydew, although it did not induce oviposition in olfactometer experiments.