Y-tube Olfactometer Bioassays Research Articles

Identification on Key Volatiles Contributed to Oviposition Preference of Plodia interpunctella (Hübner, 1813) (Lepidoptera: Pyralidae) from High and Normal Oleic Varieties of Peanut

The Indian meal moth, Plodia interpunctella (Hübner, 1813) (Lepidoptera: Pyralidae), a primary stored peanut insect pest, exhibited a significant difference in oviposition preference among normal-oleic peanuts (NOPs) and high-oleic peanuts (HOPs). Identifying key volatile organic compounds (VOCs) that are attractive or repellent to P. interpunctella is of great significance for the ecological management of pests. The profiles and contents of VOCs among NOP and HOP varieties were measured and compared, and key bioactive VOCs were further confirmed via an electroantennogram (EAG) analysis, as well as behavioral responses in Y-tube olfactometer and wind tunnel bioassays. Females prefer to lay eggs on NOP varieties more than on HOP ones. Acetophenone, nonanal, decanal, dodecane, 2,5-dimethylbenzaldehyde, and 4-ethyl-benzaldehy derived from tested peanuts elicited stronger antennal EAG responses. The results of the Y-tube olfactometer and wind tunnel bioassay showed that the relative high levels of nonanal, dodecane, and unique VOC acetophenone in NOP varieties have a significant attraction to P. interpunctella. Conversely, 4-ethyl-benzaldehyde and the unique VOC 2,5-dimethyl-benzaldehyde commonly found in HOP varieties exhibit notable repellent effects on P. interpunctella. These VOCs could contribute to the development of attractants or repellents derived from special peanut varieties for pest management.

Electrophysiological and behavioral responses of Tamarixia radiata (Hymenoptera: Eulophidae) to volatiles of nymphal Diaphorina citri (Hemiptera: Liviidae)

Abstract Huanglongbing (HLB), a devastating citrus disease caused by Candidatus Liberibacter asiaticus, is efficiently vectored by the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). Tamarixia radiata (Waterston) plays a crucial role as an ectoparasitoid, preying on D. citri nymphs. By collecting and identifying headspace volatiles from fifth instar nymphs of D. citri using a gas chromatograph–mass spectrometer (GC–MS), we obtained a collection of 9 volatile compounds. These compounds were subsequently chosen to investigate the electrophysiological and behavioral responses of female T. radiata. At a concentration of 10 μg/μl, 9 compounds were compared with cis-3-hexen-1-ol (control), resulting in trans-2-nonenal inducing the highest relative electroantennogram (EAG) value, followed by hexanal, heptanal, n-heptadecane, tetradecanal, n-tetradecane, n-pentadecane, 1-tetradecanol, and 1-dodecanol. The top 5 EAG responses of female T. radiata to these compounds were further investigated through EAG dose–response experiments. The results showed positive dose–responses as concentrations increased from 0.01 to 10 μg/μl. In Y-tube olfactometer bioassays, female T. radiata exhibited a preference for specific compounds. They were significantly attracted to tetradecanal at a concentration of 10 µg/µl and trans-2-nonenal at 0.01 µg/µl, while no significant attraction was observed toward hexanal, heptanal, or n-heptadecane. Our report is the first to demonstrate that volatiles produced by D. citri nymphs attract T. radiata, which suggests that this parasitoid may utilize nymph volatiles to locate its host.

Behavioral responses of Rhyzopertha dominica (F.) to volatiles of different stored grains

The aim of this study was to explore the behavioral responses of the lesser grain borer, Rhyzopertha dominica (F.) to volatiles of different stored grains. The olfactory responses of R. dominica to the volatiles of five grains, i.e. wheat, rice, maize, sorghum, and soybean, were studied in Y-tube and six-arm olfactometer experiments. The volatile components of these grain were analyzed by gas chromatography-mass spectrometry (GC-MS). Y-tube olfactometer bioassays showed that both adults and larvae of R. dominica showed significant preferences for volatiles from the five grains, compared with clean air. In six-arm olfactometer bioassays, adults of R. dominica showed the strongest olfactory preference for wheat, followed by rice, maize, sorghum, and soybean, and larve showed similar preferences for the volatiles of these stored grains. The GC-MS analysis identified 31, 24, 17, 11, and 10 components in the volatile profiles of wheat, soybean, rice, maize, and sorghum, respectively. 1-hexanol was the most abundant component of the volatiles of wheat (27.43%) and soybean (48.28%), whereas nonanal was the most abundant component of the volatiles of rice (21.75%), maize (31.22%), and sorghum (40.78%). Therefore, the different olfactory responses of R. dominica are reasonably related to the differences in the types and contents of volatile components among these five grains. Noteworthy, the volatile components identified in grains may be useful as attractants in traps combined with insect phermones for monitoring or even control R. dominica.

Electrophysiological and behavioural responses of Plutella xylostella L. (Lepidoptera: Plutellidae) to thirteen non-host plant essential oils

The diamondback moth (DBM), Plutella xylostella (L.), is a cosmopolitan obligate pest of cruciferous crops. Currently, DBMs management is largely dependent on broad-spectrum synthetic pesticides, which has led to the adverse effects on the environment, human health, and nontargeted organisms. Thus, alternative control methods are needed. The essential oils (EOs) derived from bioactive species may be developed as effective alternatives for the management of DBMs that is safe and eco-sustainable than conventional pesticides. In this study, we investigated electrophysiological (EAG) and behavioral responses of DBM adults to the thirteen non-host EOs of Acorus calamus, Ageratum conyzoides, Artemisia argyi, Chenopodium ambrosioides, Cymbopogon citratus, Foeniculum vulgare, Ocimum basilicum, Pelargonium hortorum, Perilla frutescens, Pogostemon cablin, Polygonum hydropiper, Rosmarinus officinalis, and Ruta graveolens in order to contribute to the development of low environmental impact management alternatives. EAG recordings revealed all the tested EOs significantly elicited EAG responses of DBM females, and the males were sensitive to the eleven EOs except A. conyzoides and O. basilicum. Meanwhile, EAG recordings of DBMs exhibited dose-dependent responses to these tested EOs in most cases. In Y-tube olfactometer bioassays, the EOs of A. calamus, C. citratus, P. hortorum, P. hydropiper, and R. graveolen demonstrated prominent repellent effects on DBM females at concentrations of 10 μg/μL or higher. The results of oviposition bioassays found the number of eggs on the two plants with the five tested EOs were less than that on the two plants with paraffin oil. And the oviposition indexes of the plants that fixed with the EOs of P. hortorum, R. graveolen, A. calamus, P. hydropiper, C. citratus, and paraffin oil were –71.81%, –59.43%, –57.46%, –51.11%, –35.41%, and 0.09%, respectively. These findings indicate that the five EOs, especially P. hydropiper EO, provide active and safe tools for natural repellents to prevent and control DBMs infestations of cruciferous vegetables.

Epicuticular wax chemicals of Lablab purpureus subsp. bengalensis influence short-range attraction and oviposition responses in Aphis craccivora and Aphis gossypii.

Lablab purpureus subsp. bengalensis (Jacq.) Verdc. is an important legume of India and Africa. Both aphids, Aphis craccivora Koch and A. gossypii Glover (Hemiptera: Aphididae), are important herbivorous pests of this legume crop. These viviparous females lay nymphs on the leaf surface of this legume plant. Therefore, it is of considerable interest to study whether leaf surface wax chemicals (long-chain alkanes and free fatty acids) of this legume plant served as short-range attractants and oviposition stimulants in both females to lay nymphs. Twenty-one n-alkanes from n-C12 to n-C35 and 11 free fatty acids from C12:0 to C22:0 were identified in leaf surface waxes. Nonacosane and nonadecanoic acid were the most abundant among n-alkanes and free fatty acids, respectively. Both females were attracted towards one leaf equivalent surface wax against the control solvent (petroleum ether) in short Y-tube olfactometer bioassays. A synthetic blend of tetradecane, pentadecane, tetracosane, tridecanoic acid, tetradecanoic acid, and heneicosanoic acid comparable to one leaf equivalent surface wax served as short-range attractants and oviposition stimulants in A. craccivora; whereas a synthetic blend of tetradecane, hexadecane, docosane, nonadecanoic acid, and arachidic acid comparable to one leaf equivalent surface wax acted as short-range attractants and oviposition stimulants in A. gossypii. These results can provide the basis for efficient pest management strategies of A. craccivora and A. gossypii against L. purpureus subsp. bengalensis using host plant leaf surface wax compounds. Further, SEM studies of antennae and forelegs of both aphids were conducted to observe sensilla structures, which help in chemoreception.

Cultivar-specific responses of tomato essential oils to tomato red spider mite (Tetranychus evansi): Implications for pest management

Background: The tomato (Solanum lycopersicum L.) is a widely cultivated and nutritionally valuable plant species, known for its culinary and health benefits. However, tomato crops are susceptible to various pests, including the tomato red spider mite (Tetranychus evansi), which can cause substantial yield losses. Essential oils from plants have shown potential as natural alternatives for pest management. Methods: This study investigated the interaction between essential oils from seven different tomato accessions namely; 1 (money maker), 13 (marglobe), 51 (PI 134417), 162 (JKUAT 22/202183), 182 (JKUAT 19), 428 (LA 2185) and 460 (LO 3279) and T. evansi. The aim was to understand the role of essential oils in shaping mite behavior. Essential oils were extracted from these diverse tomato accessions using steam distillation. The response of spider mites to these essential oils was assessed using Y-tube olfactometer and glass slide bioassays. Gas chromatography/mass spectrometry was used to analyze the composition of volatile compounds released by the essential oils. Results: Spider mite responses to different concentrations of essential oils were not significantly different among accessions. However, specific accessions, such as 51 and 428, elicited negative responses across concentrations. Analysis of volatile compounds revealed qualitative and quantitative variations in essential oil composition among accessions. Compounds like 2-tridecanone, 2-undecanone, β-caryophyllene, and α-humulene exhibited distinct abundance patterns across accessions. Conclusions: The study provides insights into the complex interaction between tomato essential oils and spider mite behavior. While concentrations of essential oils did not strongly influence mite responses, the unique composition of essential oils in different accessions played a crucial role. These findings suggest the potential for selective breeding of tomato varieties with specific essential oil profiles to enhance resistance to spider mites. The research contributes to our understanding of natural pest management strategies and underscores the importance of phytochemical diversity in shaping arthropod behavior.

Semiochemicals from Trichosanthes anguina (Cucurbitaceae) plants influence behavior in Diaphania indica.

First to third instars of Diaphania indica (Saunders) (Lepidoptera: Crambidae) feed on the lower surface of leaves, while fourth and fifth instars gregariously consume leaves of Trichosanthes anguina L. After defoliating, the caterpillar also attacks flowers and fruits of the plant and finally, results in loss of crop yield. Therefore, behavioral responses of D. indica adults were investigated to volatiles from undamaged (UD), insect-damaged (ID, plants after feeding by D. indica larvae) and jasmonic acid (JA) treated T. anguina plants. Females showed attraction to volatiles of UD and ID plants of three T. anguina cultivars [MNSR-1 (MNS), Baruipur Long (BAR) and Polo No. 1 (POLO)] in Y-tube olfactometer bioassays. Females did not show significant negative responses from volatiles of JA treated plants. Females were more attracted to volatiles of ID plants than UD plants. Females showed attraction to volatiles of UD or ID plants compared to JA treated plants. Females were attracted to certain synthetic blends resembling volatiles of insect-damaged MNS, BAR and POLO plants in olfactometer bioassays. Females could not distinguish among these three certain synthetic blends in olfactometer bioassays. A synthetic blend of 3Z-hexen-1-ol, α-pinene, hexyl acetate, benzyl alcohol and 6Z-nonenal at mole ratios of 1.47:1.20:1:1.82:1.21 was prepared at 20 mg/mL dichloromethane and 100 μL when used as lure in funnel traps resulted in the capture of the highest number of D. indica adults in field trails. The earlier five-component chemical lure could be used in traps in an integrated pest management program of the insect pest, D. indica. © 2023 Society of Chemical Industry.

The attractive host volatiles can enhance oviposition of Anoplophora glabripennis on a non-host tree.

The Asian longhorned beetle (ALB), Anoplophora glabripennis, is a serious wood borer of hardwood trees. Populus deltoides 'Shalinyang' (PdS) is attractive to ALB adults for oviposition but highly resistant to their offspring. Investigation of the chemicals regulating ALB oviposition is scarce in previous studies until now. To determine which chemicals emitted by PdS were attractive and induced oviposition behavior by ALB on non-host poplar tree species, we first: collected and identified the bio-active volatiles produced by PdS using coupled gas chromatography-mass spectrometry (GC-MS) and coupled gas chromatography-electroantennographic detector (GC-EAD); then evaluated which chemicals were attractive in a Y-tube olfactometer bioassay; and finally screened key compounds affecting ALB oviposition using a 'chemical-stimulated oviposition on non-host tree' bioassay. (E)-2-Hexenal, hexyl acetate, (Z)-3-hexenol acetate, 1-hexanol, (Z)-3-hexenol, β-caryophyllene, and salicylaldehyde emitted from PdS were attractive to ALB. When (E)-2-hexenal, 1-hexanol, (Z)-3-hexenol acetate, and (Z)-3-hexenol were applied to the non-host tree Populus tomentosa, oviposition by ALB females was significantly increased. Furthermore, the mean number of oviposition pits increased as the (Z)-3-hexenol concentrations increased. Further tests on synergy between pairs of chemicals showed that (Z)-3-hexenol stimulated production of the most oviposition pits, but that the percentage of effective oviposition pits (those containing an egg and larva and not empty) decreased. (Z)-3-Hexenol is the main chemical component inducing ALB oviposition. These results increase understanding about the oviposition behavior of ALB and could help improve management strategies that regulate ALB behavior by planting mixed-species forests resistant to ALB. © 2023 Society of Chemical Industry.

Kairomone-induced changes in foraging activity of the larval ectoparasitoid Holepyris sylvanidis are linked with an increased number of male parasitoid offspring

Interactions between stored product pest insects and their parasitoids are well known to be mediated by infochemicals. However, little knowledge is available about the extent to which parasitoid responses to host kairomones improve host search and parasitization success. Here, we tested whether the release of host-specific kairomones of the confused flour beetle, Tribolium confusum, improves host finding of the larval ectoparasitoid Holepyris sylvanidis. Previous studies revealed that volatiles from host larval feces [i.e., (E)-2-nonenal and 1-pentadecene] attract the parasitoid. To determine the most attractive concentration of these two key components, we conduced Y-tube olfactometer bioassays. Most female parasitoids were attracted to a mixture of (E)-2-nonenal and 1-pentadecene at the lowest concentration, while the highest concentration was repellent. Volatiles from host adults (methyl-p-benzoquinone and 4,8-dimethyldecanal) did not attract the parasitoid females at any of the concentrations tested. In flight cage experiments, we analyzed the host finding success of H. sylvanidis by offering host larvae in a Petri dish for 3 days (i) with additionally applied host larval kairomones in the most attractive concentration (test) or (ii) without additional kairomones (control). In test cages, the parasitoids removed a significantly higher number of paralyzed host larvae from the initial population within 48 h than in control cages. After 72 h, significantly more host larvae were parasitized in test cages than in the control. The offspring of parasitoids in test cages differed from the one in control cages by total numbers and especially the number of males. Significantly more parasitoids emerged from the parasitized host larvae in test cages, with enhanced male offspring. Our study demonstrates that the parasitoid’s response to host-associated volatiles can improve parasitization success but also affects the number of males in the parasitoids’ progeny.

Dog hair volatiles attract Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) females.

Rhipicephalus sanguineus sensu lato (s.l.) (Latreille) feeds on domestic dogs worldwide. This tick species uses dog volatiles during host-seeking behavior. In this study, we identified volatile compounds from dog hairs involved in the host location of R. sanguineus s.l. The R. sanguineus s.l. females, but not males, were attracted to hair samples and Super Q extracts from Schnauzer dogs in Y-tube olfactometer bioassays. A total of 54 compounds from dog hair extracts were identified by gas chromatography coupled to mass spectrometry, including hydrocarbons, aldehydes, alcohols, ketones, and carboxylic acids. Screening the identified compounds by the single sensillum recording technique showed that isovaleric acid, hexanal, heptanal, and sucaltone (6-methyl-5-hepten-2-one) significantly stimulated the olfactory receptor neurons of the basiconic, chaeticum, and trichodeum sensilla of female ticks. When synthetic compounds were evaluated alone, or in binary, tertiary, or quaternary mixtures, female ticks were only attracted to isovaleric acid and 1 tertiary mixture (hexanal, heptanal, and isovaleric acid). We conclude that isovaleric acid functions as an attractant for R. sanguineus s.l. These findings contribute to the understanding of the chemical ecology of ticks during host location.

Conserved Odorant Receptor, EcorOR4, Mediates Attraction of Mated Female Eupeodes corollae to 1-Octen-3-ol

Odorant receptors (ORs) in insects are crucial for the detection of chemical signals. However, the functions of the conserved OR genes among insect species are rarely studied. In this study, we analyzed a well-conserved OR clade in Diptera insects and cloned a gene from this clade, EcorOR4, in the hoverfly Eupeodes corollae. Real-time quantitative PCR showed that EcorOR4 was highly expressed in the antennae and upregulated in the mated females, and in vitro functional characterization showed that EcorOR4 was narrowly tuned to 1-octen-3-ol. Electroantennogram assays revealed that the antennal response of mated females to 1-octen-3-ol was significantly higher than that of mated males, but no significant differences were observed between male and female virgins. Finally, a Y-tube olfactometer bioassay showed that 1-octen-3-ol is an attractant for only mated female E. corollae adults. These results demonstrate that EcorOR4 is involved in the detection of 1-octen-3-ol and that this compound may affect the host-finding and oviposition behavior in female E. corollae.

Location of olfactory organs and architecture of gustatory organs in the poultry red mite, Dermanyssus gallinae (Acari: Dermanyssidae)

Dermanyssus gallinae is a hematophagous ectoparasitic mite in the poultry industry worldwide. Its current control mainly relies on spraying acaricides with many deficiencies. It's urgently needed to develop novel control approaches, such as pheromones. The pheromones are detected by chemoreceptors, which are not well investigated in D. gallinae. In the current study, Y-tube olfactometer bioassays revealed that extracts of feces of mites could attract D. gallinae, indicating aggregation pheromones existed in feces. After varnishing the tips of the foreleg tarsi, the female mites' response to feces extracts disappeared in Y-tube olfactometer bioassays. Still, their response to guanine (a non-volatile compound acting as a potential arrestment pheromone) remained in filter paper contact bioassays. These results suggested that the sensilla at tips of the foreleg tarsi had olfactory function, and the sensilla at the tips of the pedipalpal tarsi could have gustatory function and the gustatory organs were located in other body parts of female mites. Through scanning electron microscopy (SEM), it was found that adults and nymphs possess a cluster of 8 peg-like sensilla as well as 2 blunt, peg-like sensilla at the tip of each pedipalpal tarsus. Nevertheless, the larvae had only a cluster of 5 blunt peg-type sensilla. Each sensillum has a terminal pore or depression, suggesting it functions as gustatory organ. The present study confirmed the location and explored the architecture of gustatory organs of D. gallinae, which would facilitate the development of novel control method based on pheromones.

Ecological function of key volatiles in Vitex negundo infested by Aphis gossypii.

Herbivore induced plant volatiles (HIPVs) are key components of plant-herbivorous-natural enemies communications. Indeed, plants respond to herbivores feeding by releasing HIPVs to attract natural enemies. The present study analyses the effect of HIPVs of Vitex negundo (Lamiaceae), an indigenous plant species in northern China, on the predatory ladybug species Harmonia axyridis. Y-tube olfactometer bioassay showed that H. axyridis adults were significantly attracted by V. negundo infested by the aphid Aphis gossypii. We analyzed and compared volatile profiles between healthy and A. gossypii infested V. negundo, screened out the candidate active HIPVs mediated by A. gossypii which could attract H. axyridis, and tested the olfactory behavior of the candidate active compounds on H. axyridis. The gas chromatography-mass spectrometry analysis showed that five volatile compounds were significantly up-regulated after V. negundo infestation by A. gossypii, and five substances were significantly down-regulated in the terpenoid biosynthesis pathway. The olfactory behavior response showed that H. axyridis has significant preference for sclareol, eucalyptol, nonanal and α-terpineol, indicating that this chemical compounds are the important volatiles released by V. negundo to attract H. axyridis. This study preliminarily clarified that V. negundo release HIPVs to attract natural enemies when infected by herbivorous insects. The description of the volatile emission profile enriches the theoretical system of insect-induced volatile-mediated plant defense function of woody plants. Applications in crop protection would lie in designing original strategies to naturally control aphids in orchards.

The Role of Honey Bee Derived Aliphatic Esters in the Host-Finding Behavior of Varroa destructor

Varroa destructor is an obligate ectoparasite of honey bees and shifted from its original host Apis cerana to the new host Apis mellifera in the first half of the twentieth century. The host shift has resulted in a great threat to the health and survival of A. mellifera colonies worldwide. Chemical signals play a crucial role in all aspects of the Varroa life cycle, including host finding. However, the chemical cues that affect the host finding behavior of Varroa mites are still not fully understood. In this study, we systematically profiled the headspace volatiles of both worker and drone larvae of the two honey bee species by using solid phase micro-extraction coupled to gas chromatography-mass spectrometry (SPME-GC-MS), and then used electrophysiological recording and Y-tube olfactometer bioassay to study the potential roles of the selected compounds. The chemical profiling showed that there were four aliphatic esters, ethyl myristate (EM), methyl palmitate (MP), ethyl palmitate (EP), and ethyl oleate (EO) commonly detected from all four types of larval hosts. Among them, EM was a new substance identified from honey bee headspace volatiles. Results from electrophysiological recordings indicated that all the aliphatic esters could elicit significant responses of Varroa pit organs on its forelegs. Moreover, behavioral analyses revealed that EM could significantly attract V. destructor at a medium dosage (10 µg), while MP had no observable effect on the mites and both EP and EO were able to repel the parasites. Our findings suggest an important role of host-derived aliphatic esters in Varroa host finding, and provide new chemicals for Varroa monitoring and control.

Attraction of Myzus persicae (Hemiptera: Aphididae) to Volatiles Emitted From the Entomopathogenic Fungus Beauveria bassiana.

Beauveria bassiana (Balsamo) Vuillemin infects a wide variety of insects, including the green peach aphid, Myzus persicae (Sulzer). Volatiles emitted from B. bassiana can act as semiochemical attractants or repellents, with most responses reported to date resulting in insects avoiding B. bassiana. Since insects can detect 'enemy-specific volatile compounds', we hypothesized the preference behavior of M. persicae would be influenced by volatile emissions from B. bassiana. We conducted Petri dish and Y-tube olfactometer bioassays to characterize the preference of M. persicae to B. bassiana strain GHA. During Petri dish bioassays, more apterous and alate M. persicae were recorded in the vicinity of agar colonized by B. bassiana compared to agar, or Fusarium proliferatum (Matsushima) Nirenberg and Ambrosiella grosmanniae Mayers, McNew, & Harrington as representatives of nonentomopathogenic fungi. Petri dish bioassays also determined that apterous and alate M. persicae preferred filter paper saturated with 1 × 107, 1 × 106, and 1 × 105B. bassiana conidia/ml compared to Tween 80. Y-tube bioassays documented that more apterous and alate M. persicae oriented upwind to volatiles from B. bassiana mycelia compared to agar. Apterous and alate Myzus persicae were also preferentially attracted to 1 × 107 and 1 × 106B. bassiana conidia/ml compared to Tween-80 during Y-tube bioassays. These results complement a previous finding that the mosquito Anopheles stephensi (Diptera: Culicidae) Liston is attracted to volatiles from B. bassiana. Future studies aimed at characterizing the olfactory mechanism leading to the attraction of M. persicae to B. bassiana could aid in optimizing lure-and-kill strategies.

The Role of Green Gram Plant Volatile Blends in the Behavior of Arctiid Moth, Spilosoma obliqua.

This study investigated effects of volatile blends released from undamaged (UD), insect-damaged [ID, plants fed by larvae of Spilosoma obliqua Walker (Lepidoptera: Arctiidae)] and mechanically-damaged (MD) plants of three green gram cultivars [PDM 54, Pusa Baisakhi and Samrat] including synthetic blends on the behavior of conspecific adult moths in Y-tube olfactometer bioassays. Females showed attraction towards volatile blends of UD, ID and MD plants of these green gram cultivars against the control solvent (CH2Cl2). The components of volatile blends in UD plants of three green gram cultivars are not similar, but no any difference was found among three cultivars in term of the attractive effect on the insect moths when volatile blends from UD plants of these three cultivars were tested against one another. Females were more attracted towards volatile blends of ID plants of a particular cultivar compared to UD plants of the same cultivar. Total amount of volatiles was higher in ID plants than UD plants. Some herbivore-induced plant volatiles - (Z)-3-hexenal, 1-hexanol, (Z)-3-hexenyl acetate, 2-octanol and ocimene were attractive to the insect moths. Females were attracted towards three synthetic blends resembling amounts present in natural volatile blends of ID plants of these three cultivars in Y-tube olfactometer and wind tunnel bioassays, suggesting that involvement of host-specific chemical cues in long-range host location by S. obliqua females. If attraction of adult S. obliqua to these synthetic volatile blends is upheld by field trials then these blends may find practical application in detection and monitoring of S. obliqua populations.

Effect of Trichosanthes anguina L. flower surface wax chemicals as short-range attractants and oviposition stimulants in Diaphania indica (Saunders) (Lepidoptera: Crambidae)

Larvae of Diaphania indica (Saunders) (Lepidoptera: Crambidae) feed on flowers of Trichosanthes anguina L., and reduce crop production. Therefore, we have tried to find whether flower surface wax chemicals (alkanes and free fatty acids) of three T. anguina cultivars [MNSR-1 (MNS), Baruipur Long (BAR), and Polo No. 1 (POLO)] could act as short-range attractants and oviposition stimulants in females of D. indica. One mg flower surface wax of these cultivars acted as attractants in short Y-tube olfactometer bioassays and stimulated oviposition in females. A synthetic blend of nonadecane, pentacosane, and palmitoleic acid, a synthetic blend of pentacosane and palmitoleic acid, and a synthetic blend of pentacosane and oleic acid in amounts comparable to those present in 1 mg flower surface wax of MNS, BAR, and POLO cultivars, respectively, served as short-range attractants and oviposition stimulants in D. indica. Females exhibited equal egg-laying behavior towards these three synthetic blends when these blends were tested against one another, and hence, these blends could be used as lures in developing baits for traps in pest management strategies.

Attractive host kairomones for the cigarette beetle, Lasioderma serricorne (Coleoptera: Anobiidae)

Analyses of pooled headspace volatiles from three commercial chili pepper, Capsicum spp., products by coupled gas chromatographic-electroantennographic detection (GC-EAD) and coupled GC-mass spectrometry (MS) revealed 10 compounds (β-pinene, γ-terpinene, linalool, 2-phenylethanol, cumin aldehyde, 1,3-menthadienal, eugenol, trans-β-caryophyllene, caryophyllene oxide, and an unknown compound which co-eluted with 2-phenylethanol) that elicited responses from the antennae of cigarette beetles, Lasioderma serricorne. The unknown compound was separated by silica fractionation and identified by MS and NMR spectroscopy as 2-hydroxy-2,6,6-trimethyl-cyclohexanone. In Y-tube olfactometer bioassays, beetles were attracted to the 10-component synthetic blend and to many six- and four-component blends, demonstrating widespread redundancy in bioactivity among the components. Eugenol was discounted as an attractant, whereas β-caryophyllene and linalool had previously been identified as kairomones for L. serricorne. The remaining seven compounds are novel host kairomones for L. serricorne, bringing the total of known host kairomones for this species to 18. The redundancy among host kairomones may enable L. serricorne to find and infest many highly variable stored products, any one of which may emit only a few of the known kairomones.

Floral and Bird Excreta Semiochemicals Attract Western Carpenter Ants

Ant colonies have vast and diverse nutritional needs but forager ants have limited mobility to meet these needs. Forager ants would accrue significant energy savings if they were able to sense and orient toward odor plumes of both carbohydrate and protein food sources. Moreover, if worker ants, like other flightless insects, had reduced olfactory acuity, they would not recognize the specific odor signatures of diverse carbohydrate and protein sources, but they may be able to orient toward those odorants that are shared between (macronutrient) food sources. Using the Western carpenter ant, Camponotus modoc, as a model species, we tested the hypotheses that (1) food sources rich in carbohydrates (aphid honeydew, floral nectar) and rich in proteins (bird excreta, house mouse carrion, cow liver infested or not with fly maggots) all prompt long-distance, anemotactic attraction of worker ants, and (2) attraction of ants to plant inflorescences (fireweed, Chamaenerion angustifolium; thimbleberry, Rubus parviflorus; and hardhack, Spiraea douglasii) is mediated by shared floral odorants. In moving-air Y-tube olfactometer bioassays, ants were attracted to two of four carbohydrate sources (thimbleberry and fireweed), and one of four protein sources (bird excreta). Headspace volatiles of these three attractive sources were analyzed by gas chromatography-mass spectrometry, and synthetic odor blends of thimbleberry (7 components), fireweed (23 components), and bird excreta (38 components) were prepared. In Y-tube olfactometer bioassays, synthetic blends of thimbleberry and fireweed but not of bird excreta attracted ants, indicating that only the two floral blends contained all essential attractants. A blend of components shared between thimbleberry and fireweed was not attractive to ants. Our data support the conclusion that C. modoc worker ants can sense and orient toward both carbohydrate and protein food sources. As ants were selective in their responses to carbohydrate and protein resources, it seems that they can discern between specific food odor profiles and that they have good, rather than poor, olfactory acuity.

Evaluation and optimization of blends for attracting Trichogramma dendrolimi based on semiochemicals mediating tritrophic interactions in the orchard habitat

Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) is one of the most important parasitic natural enemies of Grapholita molesta (Busck) (Lepidoptera: Tortricidae) in peach and pear orchards. The artificial rearing T. dendrolimi have been widely used in biological control programs in recent years. However, its actual parasitic effect on the pest in the field is less, so it is important to develop attractants to increase the parasitic efficiency of the parasitoids. T. dendrolimi can be easily attracted by semiochemicals derived from flowers, intact plants, herbivore-attacked plants, and insects in its orchard habitats. In this paper, 73 semiochemicals were evaluated as potential attractants at three concentrations (0.1 mg/mL, 1 mg/mL, and 10 mg/mL) to T. dendrolimi by Y-tube olfactometer bioassays and Electroantennogram (EAG) technology, and then the mixtures of active individual compounds were further tested and evaluated in the field. As a result, 17 individual compounds showed attractive bioactivity to T. dendrolimi. Interestingly, when methyl salicylate and benzaldehyde mixed with linalool oxide or cis-3-hexenyl caproate in a volume ratio of 10:3:3 respectively showed excellent attractant bioactivity for T. dendrolimi in the orchard field. Thus, introducing such parasitoid attractants in orchard habitat may improve the biological control effect to pests.