Y-tube Olfactometer Research Articles

Synergistic attraction of Western black-legged ticks, Ixodes pacificus, to CO2 and odorant emissions from deer-associated microbes.

Foraging ticks reportedly exploit diverse cues to locate their hosts. Here, we tested the hypothesis that host-seeking Western black-legged ticks, Ixodes pacificus, and black-legged ticks, I. scapularis, respond to microbes dwelling in sebaceous gland secretions of white-tailed deer, Odocoileus virginianus, the ticks' preferred host. Using sterile wet cotton swabs, microbes were collected from the pelage of a sedated deer near forehead, preorbital, tarsal, metatarsal and interdigital glands. Swabs were plated on agar, and isolated microbes were identified by 16S rRNA amplicon sequencing. Of 31 microbial isolates tested in still-air olfactometers, 10 microbes induced positive arrestment responses by ticks, whereas 10 others were deterrent. Of the 10 microbes prompting arrestment by ticks, four microbes-including Bacillus aryabhattai (isolates A4)-also attracted ticks in moving-air Y-tube olfactometers. All four of these microbes emitted carbon dioxide and ammonia as well as volatile blends with overlapping blend constituents. The headspace volatile extract (HVE) of B. aryabhattai (HVE-A4) synergistically enhanced the attraction of I. pacificus to CO2. A synthetic blend of HVE-A4 headspace volatiles in combination with CO2 synergistically attracted more ticks than CO2 alone. Future research should aim to develop a least complex host volatile blend that is attractive to diverse tick taxa.

Efficacy of the parasitic wasp, Dinarmus basalis Rondani (Hymenoptera: Pteromalidae), in reducing infestations by the cowpea beetle, Callosobruchus maculatus (L.) (Coleoptera: Chrysomelidae: Bruchinae)

BackgroundCowpea seed beetle, Callosobruchus maculatus (L.) (Coleoptera: Chrysomelidae: Bruchinae), is the most important pest of stored cowpea in tropical regions. This study was designed to determine the presence of parasitoids associated with C. maculatus, investigate the efficacy of the parasitic wasp, Dinarmus basalis Rondani (Hymenoptera: Pteromalidae), in controlling C. maculatus as influenced by time and number of applications and ascertain the use of olfactory cues by D. basalis in host searching. Three markets in Ibadan, Southwest Nigeria, namely: Bodija, Mapo and Ojoo, were purposively surveyed for parasitoids associated with C. maculatus. Two pairs of D. basalis were released at 3-day intervals into cowpea seeds previously infested with C. maculatus. Treatments included: four times of parasitoid applications (4-TPA), three applications (3-TPA), two applications (2-TPA), 1 application (1-TPA) and a control without parasitoid application (0-TPA). All treatments were replicated four times in a completely randomized design to determine F1 progeny of C. maculatus and seed damage. Olfactory bioassay was carried out with D. basalis adults placed in a Y-tube olfactometer; and their preference for infested or uninfested three cowpea varieties, namely: Ife Brown, Ife BPC (Branching Peduncle) and Oloyin, as well as infested cowpea grains or pure air was evaluated.ResultsAmong the previously known parasitoids associated with C. maculatus, only D. basalis was found in the sampled markets. F1 progeny of adult C. maculatus reduced from 4.75 individuals (0-TPA) to 1.25 (2-TPA), 0.25 (3-TPA) and 0 (4-TPA). Concurrently, the number of exit holes on cowpea seeds significantly (p < 0.05) ranged from 5.25 (0-TPA) > 3.21 (1-TPA) > 2.20 (2-TPA) > 2.18 (4-RAP) > 1.39 (3-TPA). Adults D. basalis were more attracted to infested grains of Ife Brown (χ2 = 4, df = 1, p = 0.0455) and infested grains of Ife BPC (χ2 = 4, df = 1, p = 0.0455) than clean air. Similarly, adults D. basalis were more attracted to infested Ife Brown than the uninfested (χ2 = 5, df = 1, p = 0.0254). The results further showed that there were non-significant differences between the infested and uninfested grains of Ife BPC (χ2 = 0.2, df = 1, p = 0.6547) and Oloyin (χ2 = 3.2, df = 1, p = 0.0736) varieties.ConclusionsAdult D. basalis reduced emergence of C maculatus and reduced damage in cowpea seeds. Olfactory cues played a necessary role in host-searching efforts of D. basalis.

Buckwheat Flower Volatiles Attract Peristenus spretus and Enhance Its Field-Level Parasitism of Apolygus lucorum.

Volatile compounds play indispensable roles in the interactions among host plants, herbivores and natural enemies. Previous studies showed that the addition of buckwheat strips in cotton fields could attract Peristenus spretus, the dominant parasitoid of Apolygus lucorum, and enhance its parasitic activity. Through the combined analysis of Y-tube olfactometer, solid-phase microextraction (SPME), gas chromatography-mass spectrometer (GC-MS) and electroantennography (EAG), we found that male and female P. spretus responded to compounds present in buckwheat flowers. The five major components of buckwheat flowers, cis-3-hexenyl acetate (Z3HA), 4-methylanisole, 4-oxoisophorone, p-methylphenol and 2-ethylhexyl salicylate, all had a significant attraction to P. spretus adults and led to positive electroantennogram responses, especially for 10 mg/mL 4-oxoisophorone, indicating the components played a key role in the selection behavior of P. spretus to buckwheat flowers. Additionally, field trials showed that the five volatiles could significantly increase the parasitism by P. spretus. Our study screened the key active components of buckwheat flower volatiles that have an attractive effect on P. spretus, revealing its behavioral selection mechanism and emphasizing the important role of plant volatiles on host selection and parasitism of parasitic wasps, providing a theoretical basis for the development of attractants for P. spretus and the reduction of pesticides in the field to promote conservation biological control (CBC) of A. lucorum.

Comparison of Preference for Chemicals Associated with Fruit Fermentation between Drosophila melanogaster and Drosophila suzukii and between Virgin and Mated D. melanogaster.

Two taxonomically similar Drosophila species, Drosophila melanogaster and Drosophila suzukii, are known to have distinct habitats: D. melanogaster is mostly found near overripe and fermented fruits, whereas D. suzukii is attracted to fresh fruits. Since chemical concentrations are typically higher in overripe and fermented fruits than in fresh fruits, D. melanogaster is hypothesized to be attracted to higher concentrations of volatiles than D. suzukii. Therefore, the chemical preferences of the two flies were compared via Y-tube olfactometer assays and electroantennogram (EAG) experiments using various concentrations of 2-phenylethanol, ethanol, and acetic acid. D. melanogaster exhibited a higher preference for high concentrations of all the chemicals than that of D. suzukii. In particular, since acetic acid is mostly produced at the late stage of fruit fermentation, the EAG signal distance to acetic acid between the two flies was higher than those to 2-phenylethanol and ethanol. This supports the hypothesis that D. melanogaster prefers fermented fruits compared to D. suzukii. When comparing virgin and mated female D. melanogaster, mated females showed a higher preference for high concentrations of chemicals than that of virgin females. In conclusion, high concentrations of volatiles are important attraction factors for mated females seeking appropriate sites for oviposition.

The response of the egg parasitoid, Trissolcus semistriatus (Nees) (Hymenoptera: Scelionidae) to metathoracic scent gland extract from Eurygaster maura (L.) (Hemiptera: Scutelleridae)

ABSTRACT This study was conducted in 2013–2014 in order to determine the response of the egg parasitoid, Trissolcus semistriatus (Nees) (Hymenoptera: Scelionidae) to metathoracic scent gland (MSG) extract from Eurygaster maura (L.) (Hemiptera: Scutelleridae) in laboratory conditions. For this purpose, the MSG extracts obtained separately from males and females were diluted with hexane and six different concentrations were prepared. Naïve, mated parasitoids (2-3 days old) were used in the experiments. Hexane and distilled water were used as control treatments. In a Y-tube olfactometer, low concentrations of MSG extract from both sexes attracted the T. semistriatus but the preference for MSG extract was reduced with the increase in extract concentration and parasitoids oriented towards clean air. In order to determine the effect of MSG extract of E. maura on parasitisation and emergence rates of T. semistriatus, a single parasitoid was presented with two egg masses on blotting paper treated with MSG extract and two on blotting paper treated with hexane 4 cm apart in a Petri dish. The parasitoid was allowed 24 h for parasitisation. Parasitisation rates were higher than control at low concentrations of MSG extract of both sexes. There was no effect of MSG extracts on the emergence rates of parasitoids from eggs. According to the present results, the performance of the egg parasitoid, T. semistriatus in the control of the sunn pest, E. maura, can be enhanced by MSG extracts of the pest.

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.

Features of floral odor and nectar in the distylous Luculia pinceana (Rubiaceae) promote compatible pollination by hawkmoths.

It is hypothesized that in heterostylous plant species, standardization of signals of floral attraction between different morphs is advantageous, encouraging flower visitors to switch between morphs. It remains unclear whether signals of floral attraction (floral odor and properties of nectar) are similar between morphs in distylous species pollinated by hawkmoths, and how these relate to hawkmoth behavior. We observed the behavior of visitors to distylous Luculia pinceana (Rubiaceae), collected and analyzed floral odor, and examined properties of nectar (volume, sugar concentration, and composition) of long-styled and short-styled morphs during the day and night. Pollinator responses to the floral scent were tested with a Y-tube olfactometer. We conducted diurnal and nocturnal pollination treatments and six other pollination treatments to test the importance of nocturnal pollinators and to examine the self-incompatibility system. A species of hawkmoth, Cechenena lineosa, was the effective pollinator. The floral odor was rich in methyl benzoate, and sucrose was dominant in the nectar. There were no significant differences between the two morphs in the methyl benzoate content or the properties of nectar. Flowers released more methyl benzoate and secreted larger volumes of nectar with lower sugar concentration at night than during the day. The hawkmoth had a significant preference for methyl benzoate. Luculia pinceana was partially self-incompatible and relied on nocturnal pollinators for reproductive success. This study verifies that floral attraction signals are consistent between different morphs in this distylous species, promoting compatible pollination, and the features and the diel pattern of these signals between day and night are adapted to hawkmoth behavior.

Green Leaf Volatile Function in Both the Natural Defense System of Rumex confertus and Associated Insects’ Behavior

Rumex confertus is a rhizomatous, invasive, and difficult to control plant. Nevertheless, for sustainable agriculture, studies to biologically control R. confertus continue. Towards this, considerable attention has been devoted to investigating the emission of a wide array of volatile organic compounds (VOCs) from herbivore-damaged plants, which are known to induce protection measures in neighboring, undamaged plants. The goals of this study are to (1) determine if the profile of green leaf volatiles (GLVs), which are organic compounds naturally produced by undamaged plants, is similar to that provoked by the chemical stimulants Z-jasmone (ZJA) and dihydrojasmone (DJA), (2) establish if the Apion miniatum beetle’s reproductive choices are influenced by their sex and mating status, and (3) assess if chemically stimulated GLV emissions can be used as signals to attract pests to R. confertus for biological control purposes. Synthetic forms of naturally produced Z-jasmone (ZJA) and dihydrojasmone (DJA), which can act as either an attractant or a repellent of various species of insects, were used to treat R. confertus. In olfactory analysis, the behavioral responses of individual insects to mated and unmated insects and to two GLV blends were evaluated. It was found that unmated male insects were fairly equally divided between going for food (Y-tube olfactometer arm with a GLV blend) and opportunities for reproduction (Y-tube olfactometer arm with unmated females). However, an increase in the GLV blend concentration attracted the insects. Meanwhile, unmated females were definitely indifferent to food and, independent of the GLV blend dose, were more interested in reproduction. Mated males, even with weak feed stimuli, increased their reproduction activity, in opposition to mated females. We provide evidence that synthetic GLV blends can be used to attract predators, making their use an effective means to biologically control R. confertus. The idea of applying synthetic GLVs as a biological control is based on the insects’ mutual relationships, which work as follows: (i) mated males fully invade the weed, (ii) reproduction-driven females follow the mated males to R. confertus, and (iii) the unmated males follow the females with the purpose to reproduce. Therefore, all insect groups (mated and unmated males and females) can be induced to invade the weed. Upon feeding, the insects will damage the generative organs of R. confertus. We propose that the use of chemical stimulants to increase GLV emissions can be effectively used for weed (here R. confertus) control by attracting a plant pest (here A. miniatum).

Bioactive volatile compounds from Penicillium digitatum-infected apples: Oviposition attractants for yellow peach moth Conogethes punctiferalis (Lepidoptera: Crambidae)

IntroductionPlant-associated microbes critically shape the dynamics of plant-and insect-associated communities. In previous studies, we reported that the yellow peach moth Conogethes punctiferalis (YPM) preferred to Penicillium digitatum-infected apples (PDA) for oviposition. However, the underlying mechanisms remains unclear.MethodsIn the present study, the behavioral and physiological experiments were conducted to determine how P. digitatum affects the oviposition selection of mated YPM females via altering host plant volatile organic compounds (VOCs).ResultsMated YPM females were attracted to and laid more eggs on PDA than on non-infected apples (NIA), mechanically damaged apples (MDA), and P. digitatum in potato dextrose agar medium (PPD) in the oviposition selection experiments. Four-arm olfactometer assays further confirmed that odors in PDA were responsible for the attractiveness of mated YPM females. Further analyses showed that 38 VOCs were collected and identified from all treatments by GC-MS, with five specific VOCs (methyl 2-methylbutyrate, styrene, methyl caproate, butyl caprylate, and n-tetradecane) emitting from PDA. A principal component analysis (PCA) based on the absolute contents of 38 VOCs revealed a clear separation of PDA from NIA, MDA, and PPD. Moreover, when P. digitatum-induced specific VOCs were added to apples in individual or synthetic blends, there was a significantly higher percentage of mated YPM females to apples with individual or synthetic blends consisting of methyl 2-methylbutyrate, butyl caprylate, or n-tetradecane in Y-tube olfactometer experiments, suggesting that these three specific VOCs acted as predominant olfactory signals for mated YPM females to PDA.DiscussionTaken together, the microbe P. digitatum was an important driver of the interactions between YPMs and host plants by altering plant volatiles. These findings may form the basis for developing attractant baits for field trapping YPMs in the future.

Spatial repellency effects of Taiwanese plant oils on the biting midge, Forcipomyia taiwana

The biting midge, Forcipomyia taiwana (Shiraki) (Diptera: Ceratopogonidae), can cause severe allergic reactions. It can pass through typical mosquito netting, so repellents are an important control measure against it. This project sought to identify spatial repellents from plants traditionally used by Taiwanese Aboriginal peoples as insect repellents. Fresh plant leaves were collected, frozen, and powdered, and essential oils extracted using hexane then ethyl acetate as solvents. Some commercial oils were also used. The extracts were tested against lab-reared F. taiwana using a Y-tube olfactometer. The composition of the extracts was identified using gas-chromatography mass-spectrometry (GC-MS). Commercial citronella, lavender, and Formosan cypress oils were effective repellents, as were lab-made capillary wormwood and camphor oils. Knockdown was detected in commercial clove leaf, rosemary, common wormwood, and cajuput oils. The oil composition data is the first for many of the Taiwanese plants, many of which contained repellent compounds like caryophyllene, α-pinene, and germacrene D. The results agreed with previous studies on the effects of some plants but differed on others, possibly due differences in plant chemotype, extraction method, and oil concentrations. Key Policy Highlights Botanical oils may have some effect as personal repellents against Forcipomyia taiwana. Commercially available oils show the most promise. Certain endangered trees show promise as sources of repellents, so their conservation should be prioritized.

Repellent efficacy of 20 essential oils on Aedes aegypti mosquitoes and Ixodes scapularis ticks in contact-repellency assays

Cases of mosquito- and tick-borne diseases are rising worldwide. Repellent products can protect individual users from being infected by such diseases. In a previous study, we identified five essential oils that display long-distance mosquito repellency using a Y-tube olfactometer assay. In the current study, the contact repellent efficacy of 20 active ingredients from the Environmental Protection Agency’s (EPA) Minimum Risk Pesticides list were tested using Aedes aegypti and Ixodes scapularis. We utilized an arm-in-cage assay to measure complete protection time from mosquito bites for these active ingredients. To measure tick repellency, we used an EPA-recommended procedure to measure the complete protection time from tick crossings. We found that of the 20 ingredients tested, 10% v/v lotion emulsions with clove oil or cinnamon oil provided the longest protection from both mosquito bites and tick crossings. We conclude that in a 10% v/v emulsion, specific active ingredients from the EPA Minimum Risk Pesticides list can provide complete protection from mosquito bites and tick crossings for longer than one hour.

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.

Plantas de cobertura com potencial de reduzir a população do ácaro-rajado na soja

Abstract The objective of this work was to evaluate the potential of cover plants in reducing the population of the two-spotted spider mite, Te t r a n y c h u s urticae, in soybean. Seven host plants – cotton (Gossypium hirsutum), Urochloa ruziziensis, crotalaria (Crotalaria juncea), corn (Zea mays), radish (Raphanus sativus), soybean (Glycine max), and sorghum (Sorghum bicolor) – were evaluated for their effect on T. urticae biological parameters (oviposition, development stages, and survival) and preference for volatile odors (using a Y-tube olfactometer). Tetranychus urticae preferred cotton and showed a higher population growth rate on this host plant. The survival and oviposition of T. urticae was prolonged in radish and crotalaria plants, whereas juveniles did not complete their immature development on U. ruziziensis leaves. No preference was observed between the volatile odors of U. ruziziensis, radish, and crotalaria. Urochloa ruziziensis can reduce T. urticae populations in soybean plants.

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.

Exogenous Calcium Suppresses the Oviposition Choices of Frankliniella occidentalis (Thysanoptera: Thripidae) and Promotes the Attraction of Orius similis (Hemiptera: Anthocoridae) by Altering Volatile Blend Emissions in Kidney Bean Plants.

Frankliniella occidentalis is a destructive pest of horticultural plants, while Orius similis is a natural enemy of thrips. It has been demonstrated that exogenous calcium could induce plant defenses against herbivore attack. We examined whether CaCl2 supplementation altered the volatile emissions of kidney bean plants, which influence the oviposition preference of F. occidentalis. We also assessed the influence of volatile cues on O. similis. Using Y-tube olfactometer tests, we found that exogenous CaCl2 treatment inhibited the selectivity of F. occidentalis but attracted O. similis. In addition, CaCl2 treatment reduced the oviposition preference of F. occidentalis. Gas chromatography-mass spectrometry analyses revealed that CaCl2 treatment altered the number and relative abundance of the volatile compounds in kidney bean plants and that (E)-2-hexen-1-ol, 1-octen-3-ol, β-lonone, and (E,E)-2,4-hexadienal might be potential olfactory cues. Furthermore, the results of the six-arm olfactometer test indicated that 1-octen-3-ol (10-2 μL/μL), β-lonone (10-2 μL/μL), and (E,E)-2,4-hexadienal (10-3 μL/μL) repelled F. occidentalis but attracted O. similis. Overall, our results suggested that exogenous CaCl2 treatment induced defense responses in kidney bean plants, suggesting that CaCl2 supplementation may be a promising strategy to enhance the biological control of F. occidentalis.

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.

Electrophysiological and Behavioral Responses of Apis mellifera and Bombusterrestris to Melon Flower Volatiles.

As important pollinators, honeybees and bumblebees present a pollination behavior that is influenced by flower volatiles through the olfactory system. In this study, volatile compounds from melon flowers were isolated and identified by headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS), and their effects on Apis mellifera and Bombus terrestris were investigated by electroantennogram (EAG) and behavior tests (Y-tube olfactometer). The results showed that 77 volatile compounds were detected in melon flowers, among which the relative content of aldehydes was the highest (61.34%; 82.09%). A. mellifera showed a strong EAG response to e-2-hexenal, e-2-octenal, and 1-nonanal. B. terrestris showed a strong EAG response to e-2-hexenal, e-2-octenal, 2,5-dimethyl-benzaldehyde, benzaldehyde and benzenepropanal. In behavior tests, the volatiles with the highest attractive rate to A. mellifera were e-2-hexenal (200 μg/μL, 33.33%) and e-2-octenal (300 μg/μL, 33.33%), and those to B. terrestris were e-2-hexenal (10 μg/μL, 53.33%) and 2,5-dimethyl-benzaldehyde (100 μg/μL, 43.33%). E-2-hexenal and e-2-octenal were more attractive to A. mellifera than B. terrestris, respectively (10 μg/μL, 10 μg/μL, 200 μg/μL). In conclusion, the volatiles of melon flowers in facilities have certain effects on the electrophysiology and behavior of bees, which is expected to provide theoretical and technical support for the pollination of A. mellifera and B. terrestris in facilities.