Volatile infochemicals used in host and host habitat location byCotesia flavipes Cameron andCotesia sesamiae (Cameron) (Hymenoptera: Braconidae), larval parasitoids of stemborers on graminae

FemaleCotesia flavipes Cameron andCotesia sesamiae (Cameron) were attracted to odors in a Y-tube olfactometer from uninfested maize (Zea mays L.), sorghum [Sorghum bicolor (L.)], and napier grass (Pennisetum purpureum Schumach). In dual choice tests,Cotesia flavipes showed a preference for maize over sorghum, while maize and napier grass were equally attractive. In contrast,Cotesia sesamiae preferred volatiles from sorghum and napier grass over those from maize. The two parasitoids were significantly more attracted to maize infested with the stemborers,Chilo partellus (Swinhoe),Chilo orichalcociliellus Strand,Sesamia calamistis Hampson, andBusseola fusca (Fuller), than uninfested maize. In dual choice tests,Cotesia flavipes andCotesia sesamiae were unable to discriminate between odors from plants infested by the different species of stemborers.     

Plant-natural enemy association in tritrophic system,Cotesia rubecula-Pieris rapae-brassicaceae (Cruciferae). III: Collection and identification of plant and frass volatiles

To elucidate the identity of the volatile compounds that could be involved in the searching behavior of the parasitoidCotesia rubecula Marshall (Hymenoptera: Braconidae), the volatiles released by cabbage and frass of Lepidoptera feeding on cabbage were collected and analyzed using a gas chromatograph-mass spectrometer. The volatiles emitted by intact cabbage were -pinene, -pinene, myrcene, 1,8-cineole,n-hexyl acetate,cis-3-hexen-1-yl acetate, and dimethyl trisulfide. Mechanical damage on an intact plant induced the release of two more compounds,trans-2-hexenal and 1-methoxy-3-methylene-2-pentanone. Current feeding by larvae ofPieris rapae L. (Pieridae) induced the plant to release all the compounds released after mechanical damage and additionally 4-methyl-3-pentenal and allyl isothiocyanate. Current feeding by larvae ofPlutella xylostella L. (Plutellidae) induced the plant to release all the compounds present after mechanical damage and additionally allyl isothiocyanate. The volatiles emitted after feeding by the lepidopterans had ceased were the same as those emitted by cabbage damaged by mechanical means. The blend of volatiles emitted by frass was comprised of plant chemicals, mainly sulfur compounds. Frass ofP. rapae emitted allyl isothiocyanate, methyl isothiocyanate, methyl propyl sulfide, dimethyl trisulfide,S-methyl methane thiosulfinate, 4-methyl-3-pentenal,trans-2-hexenal, and 2,3-dihydro-4-methyl furan. Frass ofP. xylostella emitted only dimethyl trisulfide andS-methyl methane thiosulfinate. The blend of volatiles emitted by frass is herbivore-species specific.     

Mechanism of aggregation behavior inMaladera matrida Argaman (Coleoptera: Scarabaeidae)

AdultMaladera matrida Argaman (Coleoptera: Scarabaeidae: Melolonthinae) males emerge from soil for an active period at dusk, a few minutes before the females. Adults are found during most of the active hours on the foliage in aggregations composed of an equal sex ratio. The mechanism of aggregation behavior ofM. matrida beetles was studied in a Y-shaped olfactometer. No evidence was found for the existence of an aggregation pheromone released either by males or by females, but behavior tests indicate that adultM. matrida beetles, males as well as females, are attracted to volatiles of an injured host plant. The following scenario is suggested: Males emerge daily from soil at dusk, a few minutes before the females, and immediately start feeding. Additional males are attracted to the injured host's volatiles and form aggregations. When females emerge from soil, the attractant volatiles are concentrated in spots, and the females join the aggregations, forming an equal sex ratio.     

Impact of Botanical Pesticides Derived from Melia azedarach and Azadirachta indica Plants on the Emission of Volatiles that Attract Parasitoids of the Diamondback Moth to Cabbage Plants

Herbivorous and carnivorous arthropods use chemical information from plants during foraging. Aqueous leaf extracts from the syringa tree Melia azedarach and commercial formulations from the neem tree Azadirachta indica, Neemix 4.5^®, were investigated for their impact on the flight response of two parasitoids, Cotesia plutellae and Diadromus collaris. Cotesia plutellae was attracted only to Plutella xylostella-infested cabbage plants in a wind tunnel after an oviposition experience. Female C. plutellae did not distinguish between P. xylostella-infested cabbage plants treated with neem and control P. xylostella-infested plants. However, females preferred infested cabbage plants that had been treated with syringa extract to control infested plants. Syringa extract on filter paper did not attract C. plutellae. This suggests that an interaction between the plant and the syringa extract enhances parasitoid attraction. Diadromus collaris was not attracted to cabbage plants in a wind tunnel and did not distinguish between caterpillar-damaged and undamaged cabbage plants. Headspace analysis revealed 49 compounds in both control cabbage plants and cabbage plants that had been treated with the syringa extract. Among these are alcohols, aldehydes, ketones, esters, terpenoids, sulfides, and an isothiocyanate. Cabbage plants that had been treated with the syringa extract emitted larger quantities of volatiles, and these increased quantities were not derived from the syringa extract. Therefore, the syringa extract seemed to induce the emission of cabbage volatiles. To our knowledge, this is the first example of a plant extract inducing the emission of plant volatiles in another plant. This interesting phenomenon likely explains the preference of C. plutellae parasitoids for cabbage plants that have been treated with syringa extracts.     

Electroantennogram responses of the mediterranean fruit fly,Ceratitis capitata,to a spectrum of plant volatiles

Electroantennograms (EAGs) were recorded from unmated, laboratory-reared, male and femaleCeratitis capitata (medfly) in response to a range of C₁ and C₂ to C₁₂ carbon chain-length aliphatic alcohols, aldehydes, acetates, and acids, and lactones, some of which are known volatiles from leaves and fruits. A large degree of EAG response uniformity between the sexes was observed, with only eight of the 70 compounds tested eliciting significantly larger amplitude EAG responses from female than male antennae. In general, for the five functional-group series tested, aldehydes and alcohols elicited greater responses than acetates, lactones, and acids. The unsaturated alcohols, aldehydes, acetates, and acids elicited equal or larger amplitude EAG responses than their comparable saturated compounds. For four of the functional-group series tested, the EAG response amplitude was significantly greater for a particular carbon chain length, with responsiveness to primary alcohols and aldehydes peaking at C₆, acids peaking at C_5–6, and acetates peaking at both C₅ and C₈. The EAG responses to both the 2- and 3-position monoenic alcohols peaked at C₆ and C₈, while the secondary alcohols peaked at C₇. The greatest EAG responses of all compounds tested were elicited by monoenic C₆ alcohols and aldehydes that are constituents of the general green-leaf odor that emanates from most plants. The potential adaptive benefit of selective sensitivity to green-leaf volatiles is discussed in regard to foraging behavior of medflies.     

Herbivore-Induced Volatile Production by Arabidopsis thaliana Leads to Attraction of the Parasitoid Cotesia rubecula: Chemical, Behavioral, and Gene-Expression Analysis

Many plant species defend themselves against herbivorous insects indirectly by producing volatiles in response to herbivory. These volatiles attract carnivorous enemies of the herbivores. Research on the model plant Arabidopsis thaliana (L.) Heynh. has contributed considerably to the unraveling of signal transduction pathways involved in direct plant defense mechanisms against pathogens. Here, we demonstrate that Arabidopsis is also a good candidate for studying signal transduction pathways involved in indirect defense mechanisms by showing that: (1) Adult females of Cotesia rubecula, a specialist parasitic wasp of Pieris rapae caterpillars, are attracted to P. rapae-infested Arabidopsis plants. (2) Arabidopsis infested by P. rapae emits volatiles from several major biosynthetic pathways, including terpenoids and green leaf volatiles. The blends from herbivore-infested and artificially damaged plants are similar. However, differences can be found with respect to a few components of the blend, such as two nitriles and the monoterpene myrcene, that were produced exclusively by caterpillar-infested plants, and methyl salicylate, that was produced in larger amounts by caterpillar-infested plants. (3) Genes from major biosynthetic pathways involved in volatile production are induced by caterpillar feeding. These include AtTPS10, encoding a terpene synthase involved in myrcene production, AtPAL1, encoding phenylalanine ammonia-lyase involved in methyl salicylate production, and AtLOX2 and AtHPL, encoding lipoxygenase and hydroperoxide lyase, respectively, both involved in the production of green leaf volatiles. AtAOS, encoding allene oxide synthase, involved in the production of jasmonic acid, also was induced by herbivory.     

Electroantennogram responses of the cabbage seed weevil,Ceutorhynchus assimilis,to oilseed rape,Brassica napus ssp.Oleifera,volatiles

Electroantennograms (EAGs) were recorded from male and female cabbage seed weevils (Ceutorhynchus assimilis Payk.) in response to volatiles isolated and identified from the odor of oilseed rape (Brassica napus ssp.oleifera DC. cv. Ariana). Relatively large EAGs were obtained on stimulation with volatiles produced by the oilseed rape crop at the time when seed weevils were actively searching for host plants. Artificial rape odor without certain key volatile compounds was in most cases significantly less stimulatory than odor containing these volatiles. There were significant differences in the EAG response of the sexes ofC. assimilis to the green leaf volatiles of oilseed rape and several terpenes present in rape flower odor. The importance of the qualitative and quantitative composition of host-plant odor in host location byC. assimilis is discussed.     

Antennal responses of the two host races of the larch bud moth,Zeiraphera diniana,to larch and cembran pine volatiles

The larch bud moth (LBM) Zeiraphera diniana Guenée causes defoliation on larch in the Alps at 8- to 10-year intervals, after which populations crash. There are two LBM host races, one on larch and the other on cembran pine. These host races are morphologically indistinguishable as adults but they differ genetically in larval color types. Furthermore, females of each host race produce distinct pheromone blends and show oviposition preferences for their respective hosts. It is not clear to what extent host choice contributes to assortative mating in the LBM. Here, we compare the olfactory sensitivities of the two host races to the odors of fresh foliage of the host plants using the electroantennogram (EAG) technique, and the responses of the two host races to volatiles collected from the two host plants as analyzed by gas-chromatography-linked antennographic detection (GC-EAD). Both sexes of the larch and cembran host races show the same EAG responses to vapors of fresh larch and cembran pine foliage. Fifteen plant volatiles identified as chemostimuli by GC-EAD from larch and cembran pine odors elicited the same antennogram responses from the two host races. However, the GC-EAD analyses indicate that the number and quantity of chemostimuli emanating from each host plant is different. It is, therefore, most probably the array of olfactory receptors responding to the bouquet of volatiles unique to each host plant that underlies the host preferences of the two races. What remains open is the extent to which the similarity of the olfactory systems may contribute to cross-attraction. The fact that LBM individuals with intermediate characteristics between the two host races exist, suggests that olfactory perception does not hinder gene flow and contributes to sustained genetic diversity within the species Z. diniana.     

Fecal volatiles as part of the aggregation pheromone complex of the desert locust,Schistocerca gregaria (Forskal) (Orthoptera: Acrididae)

Olfactometric bioassays showed that nymphs of crowded desert locusts,Schistocerca gregaria, aggregated in response to volatiles derived from their feces and to volatiles emitted from the feces of young adults, but were indifferent to volatiles emitted by older adult feces. On the other hand, young and older adults were not only responsive to their own fecal volatiles but also cross-responsive to each other's and that of the nymphs. Charcoal-trapped volatiles from the feces and synthetic blends of the fecal volatiles also elicited similar responses. Young adults responded moderately to a blend of nymphal volatiles and those derived from nymphal feces. GC-EAD and GC-MS analysis of the trapped volatiles revealed the presence of guaiacol and phenol as predominant electrophysiologically active components of nymphal and young adult feces. Fecal volatiles of older adult contained phenylacetonitrile in addition to guaiacol and phenol, which were present in relatively lower proportion. These results suggest that fecal volatiles are part of the aggregation pheromone complex of the desert locust, which includes the pheromone blends produced by nymphs and older adults, respectively.     

Effect of volatiles collected above fecal pellets on behavior of the rabbit,Oryctolagus cuniculus,tested in an experimental chamber

The fecal pellets of rabbits,Oryctolagus cuniculus, are coated with secretion from the anal gland, the odor from which functions as a territorial marker. The total volatiles collected from above fecal pellets and three different fractions prepared by washing the volatiles through either distilled water, 1 M sodium hydroxide, or 1 M hydrochloric acid were tested for their effect on the territorial confidence of individual animals. Tests were based on the neutral pen paradigm used in previous studies but employed a specially designed test chamber, the internal odor environment of which could be fully controlled. In the four series of bioassays a total of 140 separate tests were performed and 64 adult male rabbits were used. The results showed that the presence of the total volatiles influences the outcome of territorial competitions in pairs of male rabbits in favor of the individual from which they were derived. They were comparable with those obtained in earlier studies when fecal pellets were presented in the test pen. The effects of the different washing reagents on the total odor are illustrated by gas chromatograms, and the components most likely to be removed by the different treatments are suggested. The volatiles remaining after passing through distilled water had less effect on the rabbit's behavior than the total odor. Since the washing process not only removed water-soluble compounds but also led to a reduction in the concentrations of water-insoluble components introduced into the test chamber, either of these factors could have been responsible for the weakened effect. Fractions of the odor obtained by washing with either sodium hydroxide or hydrochloric acid did not influence the results of the tests. This suggests that the essential components of the olfactory signal include both basic and acidic compounds.     

Effect of volatiles collected above fecal pellets on behavior of the rabbit,Oryctolagus cuniculus,tested in an experimental chamber

Gas chromatographic techniques were used to trap and fractionate the volatile substances emanating from the fecal pellets of wild rabbits,Oryctolagus cuniculus, which incorporate the odor of the anal gland secretion. The volatiles were bubbled through water, trapped on Chromosorb 105, transferred to Silicone SF96 traps, passed through a GC capillary column, and retrapped on SF96. The behavioral effect of trapped and fractionated volatiles was determined in four series of bioassays involving 51 adult, male, wild-type rabbits in 112, ten-minute tests. The bioassay was based on the demonstration of territorial confidence by the rabbits under the influence of their own odor. In the bioassays of the unfractionated volatiles eluted from Chromosorb 105 and SF96 traps the animals were significantly more confident in the presence of the volatiles from their own fecal pellets. One of the two fractions of the total volatiles was ineffective while the effect of the other was less than that of the unfractionated odor. The results demonstrate that the gas chromatographic techniques can be used to manipulate complex mammalian odors with precision. Combined with a discriminative bioassay, this opens up the possibility of identifying the specific combinations of volatile substances involved in the formation of olfactory signals.     

Field evaluation of herbivore-induced plant volatiles as attractants for beneficial insects: methyl salicylate and the green lacewing,Chrysopa nigricornis

Synthetic methyl salicylate (MeSA), a herbivore-induced plant volatile (HIPV), was demonstrated to be an attractant for the green lacewing, Chrysopa nigricornis, in two field experiments conducted in a Washington hop yard. Significantly greater numbers of C. nigricornis were trapped on MeSA-baited sticky cards (mean: 2.8 ± 0.4/card/week) than on unbaited cards (0.45 ± 0.15) during June–September. Cards baited with two other HIPVs, hexenyl acetate and dimethyl nonatriene, did not attract more C. nigricornis than did unbaited traps (0.30 ± 0.10, 0.44 ± 0.15, respectively). MeSA-baited Unitraps captured 1.9 ± 0.5 C. nigricornis/trap/week during July–August compared to 0.20 ± 0.20/trap/week in methyl eugenol-baited traps and 0.03 ± 0.03/trap/week in unbaited traps. The potential use of MeSA in enhancing C. nigricornis populations in Washington hop yards as an aid to conservation biological control of aphids and mites is discussed.     

Oviposition stimulants for the black swallowtail butterfly: Identification of electrophysiologically active compounds in carrot volatiles

Headspace volatiles were collected from undamaged foliage of carrot,Daucus carota, a host-plant species of the black swallowtail butterfly,Papilio polyxenes. The volatiles were fractionated over silica on an open column, and the fractions were tested in behavioral assays withP. polyxenes females in laboratory experiments. The polar fractions, as well as the total mixture of volatiles, increased the landing frequency and the number of eggs laid on model plants with leaves bearing contact-oviposition stimulants. The nonpolar fraction, containing the most abundant compounds in carrot odor, was not stimulatory. Gas Chromatographic (GC) separation of the fractions was coupled with electroantennogram (EAG) recordings to identify the compounds perceived byP. polyxenes females. The EAG activity corresponded to the behavioral activity of the fractions. None of the nonpolar compounds, identified as various monoterpenes, evoked a major EAG response, but several constituents of the polar fractions elicited high EAG responses. Sabinene hydrate (both stereoisomers), 4-terpineol, bomyl acetate, and (Z)-3-hexenyl acetate were identified by GC-MS as active compounds.     

Ovipositional behavior ofBracon mellitor Say,a parasitoid of the boll weevil (Anthonomus grandis Boheman) III. Isolation and identification of natural releasers of ovipositor probing

The chemical cues in the frass of larvae of the boll weevil,Anthonomus grandis Boheman, that elicit an ovipositional response in females ofBracon mellitor Say were isolated by a combination of column, thin-layer, and gas-liquid chromatography. Derivatization, analytical tests, and mass spectrometry were used to identify the biologically active materials as long-chain fatty acid esters of cholesterol. Bioassays with natural and synthetic cholesteryl esters were used to confirm activity. The activity of the cholesteryl esters was also confirmed by using females that had not been previously exposed to hosts.Hymenoptera: Braconidae.Mention of a proprietary or commercial product in this paper does not constitute an endorsement of this product by the U.S. Department of Agriculture.Approved for publication in TA 12593 by the Director, Texas Agricultural Experiment Station.This study was supported, in part, by the National Science Foundation and the International Biological Program (NSF-SC-0030) to the University of California. The findings are those of the authors and not necessarily those of the University of California or NSF.     

Effects on behavior ofApanteles melanoscelus females caused by modifications in extraction,storage, and presentation of Gypsy moth silk kairomone

Choice experiments were performed to investigate details of femaleApanteles melanoscelus (Ratzeburg) behavior when exposed to gypsy moth silk kairomone [Lymantria dispar (L.)] and to host larvae when kairomone is present. Female parasites only responded to the kairomone when it had been placed on thin strands such as cotton fibers. Both gypsy moth silk and silk glands contain the same or similar kairomones. Silk gland extracts were more active than head, alimentary canal, or hemolymph extracts of host larvae. Female responses decreased when low concentrations of silk gland extract or small numbers of treated fibers were presented to them. Silk gland extract was stable when frozen for 2 weeks, heated to 100 °C for 0.5 hr, freeze dried, or treated with 95% ethanol. The active component was nondialyzable. Silk deposited on the substrate increased host contacts and oviposition attempts, more so if wider areas were covered with silk, and even if the areas having silk were separated from the host. A theory of host selection inA. melanoscelus is proposed.Hymenoptera, Braconidae. Lymantria dispar L. (Lepidoptera: Lymantriidae).     

Effects of Peruvian Maize Extracts on Growth, Development, and Fecundity of the European Corn Borer

Twelve Peruvian maize, Zea mays, accessions were selected because of their relatively high level of field resistance to first-generation European corn borer (ECB), Ostrinia nubilalis, larval leaf-feeding. Water extracts of freeze-dried, powdered, leaf tissue were incorporated into a standard ECB diet, fed to larvae, and the effects on larval growth, development, and fecundity were measured. Larval and pupal weights were monitored as were the time elapsed in the larval, pupal, and adult stages. Adult fecundity and egg fertility were recorded. The experiment was a randomized block design (larvae and pupae) or a completely randomized design (adults) and analyzed with ANOVA ( = 0.05). Pairwise comparisons were made between groups of insects grown on diets containing extracts from the Peruvian lines, a standard diet, or diets containing extracts of a known susceptible inbred, and a known resistant inbred line. Survival was analyzed with a chi-squared test ( = 0.05). Two Peruvian accessions significantly reduced female larval and pupal weights, extended pupal and adult development time, and decreased survival of pupae and adults. Water extracts also had a pronounced impact on males; two accessions significantly reduced pupal weight and extended the time required to pupate, and one reduced male survival to adults. The results indicate that water-soluble factors from resistant Peruvian accessions inhibit the growth, developmental time, and survival of ECB. These resistance factors could be useful in the development of maize germplasm with insect-resistant traits.     

Phenolic compounds on the pod-surface of pigeonpea,Cajanus cajan,mediate feeding behavior of Helicoverpa armigera larvae

A methanol extract of the pod surfaces of Cajanus cajan, a feeding stimulant for fifth-instar Helicoverpa armigera, was shown to contain four main phenolic compounds. Three of these were identified as isoquercitrin, quercetin, and quercetin-3-methyl ether, by comparing UV spectra and HPLC retention times with authentic standards. The fourth compound was isolated by semipreparative HPLC and determined to be 3-hydroxy-4-prenyl-5- methoxystilbene-2-carboxylic acid (stilbene) by NMR spectroscopy and mass spectrometry. Quercetin, isoquercitrin, and quercetin-3-methyl did not affect the selection-behavior of fifth-instar H. armigera. However, larvae were deterred from feeding on glass-fiber disks impregnated with the stilbene. Furthermore, larvae exposed to quercetin-3-methyl ether consumed significant amounts of both disks. In a binary-choice bioassay, a combination of quercetin-3-methyl ether and the stilbene on one disk and pure quercetin-3-methyl ether on the other disk resulted in increased consumption of both glass-fiber disks by larvae. In contrast, consumption was reduced if the combination was presented to larvae on one disk with purified stilbene on the other disk. Cajanus cajan cultivars that varied in their susceptibility to H. armigera were surveyed for the presence of the four phenolic compounds. An absence of quercetin and higher concentrations of isoquercitrin than the cultivated variety characterized pod surface extracts of pod-borer-resistant cultivars. In addition, the ratio of the stilbene to quercetin-3-methyl ether was greater in the pod-borer-resistant cultivars. These findings are discussed in relation to the identification of chemical characters that can be used for crop improvement.     

Effects of two plant secondary metabolites,cineole and gallic acid,on nightly feeding patterns of the common brushtail possum

We investigated effects of two plant secondary metabolites (PSMs), cineole and gallic acid, on the nightly feeding behavior of the common brushtail possum (Trichosurus vulpecula), a generalist folivore. We tested whether possums altered their feeding behavior in response to increasing levels of cineole, a dietary terpene. Possums were fed artificial diets containing three levels of cineole; zero (basal diet), medium (6.8% of total dry matter, DM), and high (15.3% DM). In another experiment, we introduced gallic acid, a dietary phenolic, into the diets. Possums were offered a Choice PSM diet (cineole and gallic acid diets simultaneously) or a No-Choice PSM diet (containing either cineole or gallic acid). Detoxification products of cineole and gallic acid were examined in urine to determine that different detoxification pathways were utilized in the elimination of each compound. With increasing cineole levels, possums ate less, had smaller feeding bouts, and had a lower rate of intake, but did not extend their total nightly feeding time. Possums offered the Choice PSM diet, compared with the No-Choice diets, ate more, had larger feeding bouts, and tended to increase their rate of intake. Results from the urinary analysis indicated that gallic acid and cineole were not involved in competing detoxification pathways in brushtail possums. There was also a significant sex effect: females ate more overall, ate more per feeding bout, and ate at a higher rate than males. These results indicate that PSMs not only constrain overall intake, but that possums alter their feeding behavior in response to them. Altered feeding patterns may reduce the negative influence of PSMs on intake.     

Induction of Plant Volatiles by Herbivores with Different Feeding Habits and the Effects of Induced Defenses on Host-Plant Selection by Thrips

Induced plant responses to attack by chewing insects have been intensively studied, but little is known about plant responses to nonchewing insects or to attack by multiple herbivores with different feeding habits. We examined volatile emissions by tobacco, Nicotiana tabacum, in response to feeding by the piercing–sucking insect western flower thrips (WFT), Frankliniella occidentalis, the chewing herbivore Heliothis virescens, and both herbivores simultaneously. In addition, we examined the effects of herbivore-induced plant defenses on host-plant selection by WFT. Plants responded to thrips feeding by consistently releasing five compounds. Simultaneous feeding by WFT and H. virescens elicited the same 11 compounds emitted in response to caterpillar feeding alone; however, two compounds, α-humulene and caryophyllene oxide, were produced in greater amounts in response to simultaneous herbivory. In choice tests, thrips consistently preferred uninduced plants over all other treatments and preferred plants damaged by caterpillars and those treated with caterpillar saliva over those treated with caterpillar regurgitant. The results are consistent with a previous finding that caterpillar regurgitant induces the release of significantly more volatile nicotine than plants damaged by caterpillars or plants treated with caterpillar saliva. A repellent effect of nicotine on WFT was confirmed by encircling unwounded plants with septa releasing volatile nicotine. Our results provide the first direct evidence that thrips feeding induces volatile responses and indicates that simultaneous herbivory by insects with different feeding habits can alter volatile emissions. In addition, the findings demonstrate that induced plant responses influence host-plant selection by WFT and suggest that the induction of volatile nicotine may play a role in this process.     

Effects of dodecyl acetate andZ-10-tridecenyl acetate on attraction ofEupoecilia ambiguella males to the main sex pheromone component,Z-9-Dodecenyl acetate

Attraction ofE. ambiguella males toZ-9-dodecenyl acetate (Z9-12Ac), alone and in combination with dodecyl acetate (12Ac) orZ-10-tridecenyl acetate (Z10-13Ac) was tested in both wind-tunnel and field experiments. In the laboratory, response toZ9-12Ac reached a distinct dosage optimum at which attraction was nearly as good as to live females. Addition of 12Ac, a minor component of female glands and effluvia, had no effect at low doses ofZ9-12Ac and only marginally improved attraction at the optimum. However, inclusion of 12Ac with an overdose ofZ9-12 Ac fully restored activity. In the field,Z9-12Ac alone was not very attractive at any dose; catches markedly increased by adding 12Ac and climbed with increasing dose of each compound up to 10 mg. Optimum ratio ofZ9-12Ac to 12Ac was 11 to 15. Another compound,Z10-13Ac, had the same effect as 12Ac in the laboratory and the field but was effective at a lower dose. In the field, inclusion of the synergist permits use of high cap loads to attract more males, perhaps from greater distances.