Sex pheromone of the alfalfa plant bug,Adelphocoris lineolatus

In northern China, due to the large‐scale adoption of transgenic Bacillus thuringiensis Berliner (Bt) cotton, the number of Adelphocoris lineolatus (Goeze) (Hemiptera: Miridae) has increased quickly, causing significant loss in cotton and alfalfa production. One of the environmentally safe strategies without use of pesticides is the application of insect pheromone for mating disruption. In our study, we aim to identify the active components in sexually mature virgin female A. lineolatus, and activity and optimal ratio of these components. By using gas chromatography–mass spectrometry (GC‐MS) and gas chromatography–electroantennographic detection (GC‐EAD), we identified three active compounds: hexyl butyrate (HB), (E)‐2‐hexenyl butyrate (E2HB), and (E)‐4‐oxo‐2‐hexenal (4‐OHE). We examined the release rate of septum and tube dispensers in a wind tunnel. In a field experiment, deletion of 4‐OHE or E2HB resulted in significant suppression of male trap catches, indicating that E2HB or 4‐OHE may be the active pheromone components. Traps baited with a blend of 4‐OHE and E2HB at 2:5, 3:4, and 4:3 caught significantly more males, suggesting that the optimal ratio of 4‐OHE and E2HB could be in the range of 1:1 to 1:2. The addition of a large amount of HB could strongly reduce the attractive activity of both virgin females and artificial lures. We also compared the attractiveness of septum lures and tube lures in field experiments. The septum lures attracted males in the first 3 days. The tube lures caught more males after 3 days and the attractive effects existed up to 5 weeks, suggesting them as a tool for long‐term monitoring and control of plant bugs.     

Physiological state influences the antennal response of Anastrepha obliqua to male and host volatiles

The sexual and host‐related behaviours of the fruit fly Anastrepha obliqua Macquart (Diptera: Tephritidae) are mediated by volatile compounds. However, whether the physiological state of this species affects its antennal and behavioural responses to semiochemicals is unknown. The effects of age, mating status, diet and the topical application of methoprene, a Juvenile hormone analogue (JHA), on the antennal sensitivity of this tephritid fruit fly species to selected male [(Z)‐3‐nonenol] and host fruit volatiles (ethyl benzoate, ethyl hexanoate, ethyl butyrate and trans‐β‐ocimene) are investigated using electroantennography (EAG). Overall, (Z)‐3‐nonenol and ethyl benzoate elicit the highest EAG responses in both sexes. Flies of both sexes aged 1, 5 and 10 days old show higher EAG responses to the tested compounds compared with flies aged 20 days old. Virgin females and males show higher EAG responses to volatile compounds than mated flies. Females and males fed with sugar plus protein show higher antennal responses to volatiles compared with flies fed sugar or protein alone. Flies of both sexes treated with methoprene show higher antennal responses than flies treated with acetone (control). These results suggest that the peripheral olfactory system in A. obliqua is modulated by the physiological state of the flies.     

Identification of female sex pheromone of a plant bug,Adelphocoris fasciaticollis Reuter (Hemiptera: Miridae)

The plant bug, Adelphocoris fasciaticollis, has begun to resurge and become a key pest for cotton and alfalfa in northern China, along with the widespread cultivation of Bt cotton. To control this plant bug without pesticides, we attempted to develop a new approach by utilizing sex pheromone. The sex pheromone components from the whole‐body extracts were analysed by GC‐MS and gas chromatography–electroantennogram detector analysis (GC‐EAD). (E)‐4‐Oxo‐2‐hexenal and hexyl butyrate, identified as the major components in the extracts of female bugs, elicited strong EAD responses. Field tests indicated that either (E)‐4‐oxo‐2‐hexenal or hexyl butyrate attracted few A. fasciaticollis males and was significantly less active than virgin females and the binary blend. Their ratio was optimized to be 1 : 11. Our results could expand acknowledge of the pheromone of mirids and provide novel approaches to monitor and control this plant bug without pesticides.     

Pheromone‐binding proteins in the Asian gypsy moth females,Lymantria dispar,recognizing the sex pheromone and plant volatiles

Lepidopterans are known to have different pheromone‐binding proteins with differential expression patterns that facilitate specific signal transduction of semiochemicals. Two PBPs of the Asian gypsy moth, Lymantria dispar, were reported to express in both females and males, but their physiological functions were unknown. Results showed that LdisPBP1 and LdisPBP2 were expressed in the sensilla trichodea of males and the s. trichodea and s. basiconica of females. When LdisPBP1 gene was targeted by RNA interference (RNAi) in males, the expression of LdisPBP1 and LdisPBP2 decreased by 69 and 76%, respectively, and when LdisPBP2 gene was targeted by RNAi, they decreased by 60 and 42%, respectively. In females, after treatment with LdisPBP1 dsRNA, LdisPBP1 and LdisPBP2 levels were reduced by 26 and 69%, respectively, and LdisPBP2 dsRNA reduced the relative expression of them by 4 and 62%, respectively. The expression of LdisPBP1 and LdisPBP2 was interdependent. Electroantennogram (EAG) recordings showed that LdisPBPs participate in the recognition of the sex pheromone in males, and the sex pheromone and plant volatiles in females. The function of LdisPBPs represents the sex‐specific roles.     

Electroantennogram response and attraction of Anastrepha suspensa to volatiles of various sugar sources and aged sugar solutions

With the aim of finding new, sugar‐based volatile attractants for economically important tephritid fruit fly species, we used electroantennography (EAG) to quantitate olfactory responses of female Caribbean fruit fly, Anastrepha suspensa (Loew) (Diptera: Tephritidae), to volatiles of six sugar sources (refined white and brown cane sugar, coconut sugar, date sugar, date jaggery, and cane panela). Laboratory‐strain and wild flies, both sexually immature and mature, were tested for EAG responses to the volatiles of dry crystallized sugar sources and 10% (wt/vol) aqueous solutions that had aged in the laboratory for 0–7 days. In general, wild flies exhibited higher EAG responses than laboratory flies, and immature females responded more strongly than mature females. With the exception of date jaggery and cane panela, volatiles of dry sugar sources and 0‐ and 1‐day‐old solutions elicited lower EAG responses than any of the aged solutions. Most solution volatiles elicited the strongest EAG response after 2 days of aging. Of the treatments evaluated, volatiles of the 5‐day‐old date jaggery solution elicited the highest‐amplitude EAG responses (39%) in A. suspensa females. On the basis of the latter, we tested the attraction response of mature and immature females to date‐jaggery solutions aged over 2 and 4 days in two‐choice flight tunnel bioassays. With both mature and immature females, the 2‐day‐old solution was more attractive than the 4‐day‐old jaggery solution, but significantly more mature females (70% of captures) were attracted to 2‐day‐old jaggery solution. We discuss our results with respect to the improvement of fruit fly lures and attractants by incorporating elements from aged date‐jaggery sugar.     

豆野螟成虫触角对植物挥发性和性信息素化合物的触角电位反应

以顺3-己烯乙酸酯为标准化合物,研究了豆野螟雌、雄成虫触角对不同浓度的植物挥发性和性信息素化合物组分的触角电位（EAG）反应.结果表明：豆野螟雌、雄成虫触角对植物挥发性气味具有强烈的EAG反应,但在大部分浓度下,雌、雄虫的反应没有显著差异.在测试的9种植物挥发性化合物中,雌、雄虫对高浓度反-2-己烯醛刺激的相对EAG反应的最大值分别达到250%和260%,且雌、雄虫触角对这种化合物的EAG反应的形状也有很大差异;但对豇豆花气味中的柏木烯和柏木脑没有明显的EAG反应.雌、雄蛾对性信息素都有明显反应,且雌、雄虫的反应存在显著差异,雄虫触角对性信息素化合物主要组分（反10,反12）-十六碳二烯醛的EAG反应的最大值达到250%,远超过雌虫反应的最大值(53%).雌、雄成虫这种神经感觉反应的差异反映了它们在感器结构、功能和行为上的差异.     

Development and optimisation of a sex pheromone lure for monitoring populations of saddle gall midge,Haplodiplosis marginata

Saddle gall midge, Haplodiplosis marginata (von Roser) (Diptera: Cecidomyiidae), is a sporadic pest of cereals in Northern and Central Europe and is of increasing importance in the UK. Recently, the major component of the sex pheromone produced by adult female H. marginata was reported to be 2‐nonyl butyrate. The importance of absolute configuration on attractiveness, the effects on trap catches of the addition of minor pheromone components, dispenser type, and pheromone loading are described in the development of an optimised pheromone lure with which to trap H. marginata males. In analyses of volatiles collected from virgin female H. marginata by gas chromatography (GC) coupled with electroantennographic recording (EAG) from the antenna of a male H. marginata, two EAG responses were observed. Analyses by coupled GC‐mass spectrometry (MS) indicated these were due to 2‐nonyl butyrate and a trace amount (1%) of 2‐heptyl butyrate. A similar trace amount of 2‐nonanol was detected in GC‐MS analyses but this compound did not elicit an EAG response when the synthetic compound was tested, whereas the other two compounds did. These three compounds were not observed in collections of volatiles made from male H. marginata. The 2‐nonyl butyrate was shown to be the (R)‐enantiomer. In field trapping tests (R)‐2‐nonyl butyrate was at least 10× more attractive to male H. marginata than the racemic compound, and the (S)‐enantiomer was unattractive. Addition of the potential minor components individually or together at the naturally occurring ratios did not increase or reduce the attractiveness of the lure. Polyethylene vials and rubber septa were equally effective as pheromone dispensers, lasting for at least 5 weeks in the field in the UK, although laboratory tests indicated release from the former was more uniform and more likely to last longer in the field. Increasing loading of pheromone in the dispenser increased attractiveness. Traps baited with polyethylene vials containing 0.5 mg of (R)‐2‐nonyl butyrate are recommended for monitoring H. marginata and these are far more sensitive than water or sticky traps currently used for monitoring this pest.     

Volatiles released from foliar extract of host plant enhance landing rates of gravid Polygonia c‐album females,but do not stimulate oviposition

The role of olfactory cues for host search is much less investigated in day‐active butterflies than in their relatives, the nocturnal moths. The goal of this study was to investigate whether host‐plant volatiles from foliar extracts of hop, Humulus lupulus L. (Cannabaceae), evoke electroantennographic (EAG) responses, increase landing rates, and stimulate egg‐laying behavior of gravid Polygonia c‐album L. (Lepidoptera: Nymphalidae) females. Eighty‐nine volatile compounds were detected in a non‐concentrated methanol extract of hop by gas chromatography–mass spectrometry, 11 of which elicited an EAG response. Concentration of the crude extract significantly reduced landing rates on artificial leaves treated with the sample due to loss of volatile compounds, but after landing the oviposition response of gravid females was not affected. A mixture of eight commercially available EAG‐active volatiles increased the landing rate of gravid females to their source but did not act as oviposition stimulants. Dividing the volatile compounds into two groups – consisting of (1) hexanal, (E)‐2‐hexenal, octanal, nonanal, and decanal, and (2) sulcatone, humulene, and benzyl alcohol – obliterated effectiveness, revealing synergism between compounds. Although volatiles did not stimulate oviposition, they significantly contributed to the distribution of eggs by increasing the landing rates on treated artificial leaves.     

Three physical barriers with obvious effects on Carposina sasakii selection behavior to two dominant jujube tree volatiles

The peach fruit moth (PFM), Carposina sasakii Matsumura (Lepidoptera: Carposinidae), a severe pest of Ziziphus jujuba Miller fruit trees (jujube, Rhamnaceae) mainly grown in China, has increasingly hindered the development of the jujube industry in recent years. In order to provide a theoretical basis for a physical obstruction method, we evaluated the effect of three commonly sold physical barriers on PFM host‐searching behavior. Two principal volatiles generated by the jujube tree, α‐farnesene and cis‐3‐hexenyl acetate (leaf acetate), were used as references to detect electroantennography (EAG) response values of 2‐, 4‐, and 6‐day‐old PFM adults. The results indicated different EAG responses toward α‐farnesene and leaf acetate between different ages of PFM, and males responded differently than females. The EAG responses were stronger in 4‐day‐old males to leaf acetate and in 2‐day‐old females to α‐farnesene. The two‐choice behavioral Y‐tube olfactometer assay confirmed that PFM was strongly attracted to α‐farnesene and leaf acetate. We determined the EAG and behavioral responses of PFM after spraying three kinds of physical barriers: Liquid Film Fruit Bag, High Lipid Film, and Jujube Protection No. 1. We obtained strong inhibitory effects on PFM attraction to both volatile lures using these barriers, including negative taxis by both females and males to Liquid Film Fruit Bag and Jujube Protection No. 1. We can infer that Liquid Film Fruit Bag is the most promising potential physical barrier for PFM control, with Jujube Protection No. 1 ranking as second‐best.     

The Role of Chemical Cues in Host and Mate Location in the Pear Psylla Cacopsylla bidens (Homoptera: Psyllidae)

Chemical communication was shown to play a role in the pear psylla, Cacopsylla bidens. Electrophysiological (EAG) and behavioral responses were investigated in males and females pear psylla . Males were found to be attracted to females, and especially to those on host plants, but not to males, uninfested host plants, or plants infested with conspecific larvae. On the other hand, females were not attracted to males or females but displayed some attraction to host plants. Furthermore, females showed a preference for uninfested pear versus plants infested with conspecific larvae. The antennae of males gave highest electroantenographic response to volatiles from pears infested with females but not males, while females, responded also toward the volatiles of pear alone. These results indicate that females of C. bidens emit sex pheromones that are attractive to the males and suggest that, host volatiles may play a role in host selection by pear psylla females.     

Attractiveness of synthetic volatile blends of flowering rice panicles to Trigonotylus caelestialium (Kirkaldy) (Heteroptera: Miridae)

The attractiveness of 22 synthetic volatile blends or seven individual chemicals emitted from flowering rice panicles to a rice leaf bug, Trigonotylus caelestialium (Kirkaldy), were investigated with an olfactometer to identify the active compounds responsible for the invasion of the bugs into paddy fields. n‐Decanal attracted only male bugs, whereas β‐caryophyllene attracted only females. β‐Elemene repelled males and methyl benzoate marginally repelled females. The other chemicals did not attract or repel male and female bugs at all. Two‐, 3‐, 4‐ and 5‐component blends of β‐caryophyllene, n‐decanal, n‐tridecene, methyl salicylate and geranyl acetone were attractive to neither females nor males. Two‐component blends comprised of β‐caryophyllene and methyl salicylate, or n‐decanal and methyl salicylate, marginally repelled females. The three‐component blend comprised of β‐caryophyllene, n‐decanal and geranyl acetone marginally repelled females. The five‐component blend comprised of β‐caryophyllene, n‐decanal, n‐tridecene, methyl salicylate and geranyl acetone repelled males. The seven‐component blend comprised of β‐caryophyllene, n‐decanal, n‐tridecene, methyl salicylate, geranyl acetone, methyl benzoate and β‐elemene attracted female bugs and marginally attracted male bugs. Six‐component blends without any one of these seven components were not attractive to the bugs although the six‐component blend without n‐decanal was marginally attractive to females. The six‐component blend without n‐tridecene repelled males. These findings suggest that mixtures of these seven compounds play an important role in the attractiveness of flowering rice panicles to both sexes of the bugs, although the attractiveness of individual compounds differs between sexes.     

Disruption of sexual communication in the mirid bug Lygocoris pabulinus by hexyl butanoate

1 The metathoracic scent gland in Lygocoris pabulinus contains mostly hexyl butanoate. As secretions of this gland in Heteroptera may serve as an alarm pheromone, we determined whether hexyl butanoate is released by disturbed bugs, and whether this compound disrupts sexual attraction of L. pabulinus males towards females. 2 Undisturbed males and females, and disturbed males released less than 100 ng/h hexyl butanoate, whereas disturbed females released a highly variable amount, ranging from 25 ng/h to more than 1 μg/h. 3 In the field, traps with virgin females and rubber septa containing 20 mg hexyl butanoate, caught a total of one male in a month. In control traps without hexyl butanoate, 36 males were caught in the same period. 4 In Y‐track olfactometer tests, males were not attracted to virgin females when a dispenser with 20 mg hexyl butanoate was placed in the bottle with females. Males were attracted to females when the dispenser was placed downwind from the females, but upwind from the point of male release. 5 These results suggest that males are not repelled by hexyl butanoate, but that this compound inhibits sex pheromone release in females. Application possibilities for pest management are discussed.     

Induced volatiles in soybean and pigeon pea plants artificially infested with the neotropical brown stink bug, Euschistus heros, and their effect on the egg parasitoid, Telenomus podisi

Herbivory is known to increase the emission of volatiles, which attract natural enemies to herbivore‐damaged plants in laboratory and agricultural systems. We report on signalling through volatiles induced by Euschistus heros (F.) (Heteroptera: Pentatomidae) in two legumes that influence the attraction and retention of the egg parasitoid Telenomus podisi (Ashmead) (Hymenoptera: Scelionidae). Air‐borne extracts obtained from two host plants of E. heros, soybean, Glycine max, and pigeon pea, Cajanus cajan (Leguminosae), produce a different blend of emitted volatiles when attacked by adult males or females and nymphs of the pest species, compared with the undamaged plants. The same results were obtained when the plants were treated with extracted saliva of E. heros which had been mechanically introduced into the plants. This indicates that some substance in the saliva contributed to the release of the volatiles. Bioassays in a Y‐tube olfactometer with female T. podisi and treated plants confirmed the significant preference of the egg parasitoid for plants attacked by either males, females, or fourth instar nymphs of the pest species. On the other hand, volatile extracts obtained from soybean subjected to the velvetbean caterpillar, Anticarsia gemmatalis, a non‐host species for T. podisi, showed a different blend of volatiles compared to those obtained from plants subjected to E. heros. Additionally, the volatiles obtained from this plant–host complex were not attractive to T. podisi. These results indicate that E. heros causes an increase in the emission of specific plant volatiles, and that the induction is possibly caused by an elicitor present in the pest saliva. The possibility that these plant volatiles play an important role in the attraction and retention of the egg parasitoid T. podisi is discussed.     

Olfactory antennal responses to plant volatiles in apterous virginoparae of the vetch aphidMegoura viciae

Electroantennogram (EAG) responses were recorded from apterous virginoparae of the vetch aphidMegoura viciae Buckton (Homoptera, Aphididae) to more than eighty volatile compounds in order to investigate its sensory ability to perceive plant odours. The response profile ofM. viciae reveals a differential sensitivity for the array of plant volatiles tested. The whole group of general green leaf volatiles is very stimulatory. In addition to (E)-2-hexenal, the following compounds of this group elicit large EAG responses: (E)-2-heptenal, 1-octenol-3, hexyl acetate, (Z)-3-hexenyl acetate, hexanol-1, hexanal, 2-heptanone and 3-octanone. Relatively large EAGs are also produced by 4-methoxybenzaldehyde (p-anisaldehyde), hexanonitrile, heptanonitrile, 1,6-hexanedithiol, butyl isothiocyanate, 4-pentenyl isothiocyanate, (−)-(1S)-β-pinene, (+)-(S)-carvone, (−)-(R)-carvone, α-terpineol, linalool and citronellal. The nitriles are the most effective of all plant volatiles tested. Structure-activity relationships occur in various groups of chemicals and members of the green leaf volatiles, benzaldehydes, isothiocyanates and monoterpenes are ranked accordingly. In the group of green leaf volatiles, aliphatic aldehydes are more stimulating than the corresponding alcohols. EAG responses to series of saturated aliphatic alcohols and aldehydes reveal that C₆ and C₇ compounds are the most stimulatory. Dose-response curves show that the rank order of EAG response amplitudes hardly changes at lower dosages. It is concluded thatM. viciae perceives general plant volatiles as well as more-specific components, such as nitriles and isothiocyanates, associated with the odour blends of non-host plant species.     

Sex Pheromones and Reproductive Isolation in Five Mirid Species

Mate location in many mirid bugs (Heteroptera: Miridae) is mediated by female-released sex pheromones. To elucidate the potential role of the pheromones in prezygotic reproductive isolation between sympatric species, we investigated differences in the pheromone systems of five mirid species, Apolygus lucorum, Apolygus spinolae, Orthops campestris, Stenotus rubrovittatus and Taylorilygus apicalis. GC/MS analyses of metathoracic scent gland extracts of virgin females showed that all five species produced mixtures of hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal, but in quite different ratios. (E)-2-hexenyl butyrate was the major component of A. spinolae, while hexyl butyrate was the most abundant component in the pheromone blends of the other four species. In addition to the three compounds, a fourth component, (E)-2-octenyl butyrate, was present in the gland extracts of A. lucorum and T. apicalis females. Field tests suggest that the ternary blends of hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal as found in the extracts of the females of each species do not inhibit attraction of conspecific males but ensure species-specificity of attraction between A. lucorum, O. campestris and T. apicalis. Furthermore, (E)-2-octenyl butyrate was essential for attraction of A. lucorum and T. apicalis males, but strongly inhibited attraction of male A. spinolae, O. campestris and S. rubrovittatus. The combined results from this study and previous studies suggest that the minor component and pheromone dose in addition to the relative ratio of the major components play an important role in reproductive isolation between mirid species.     

Efficiency of volatile baited sticky traps for the Tarnished Plant Bug (Lygus lineolaris) in strawberry fields

Insecticides have adverse effects on human health and the environment. Thus, the development of non-chemical replacement to manage insect pests is urgent. An alternative is to bait sticky traps with attractive insect sex pheromones or plant volatiles. In Quebec, the tarnished plant bug (Lygus lineolaris) is a major insect pest. We tested the efficiency of sex pheromones (mixture of hexyl butyrate (HB), (E)-2-hexenyl butyrate (E2HB) and (E)-4-oxo-2-hexenal (KA)) and sunflower (Helianthus annuus) volatiles (pinene, sabinene and phenylacetaldehyde) as sticky trap baits for the tarnished plant bug in strawberry fields of the Laurentians in Southern Québec, Canada. The pheromones decreased the number of tarnished plant bug caught in the traps compared to a control. The sunflower volatile did not have any effect on the number of individuals caught in the traps. Different Lygus species use HB, E2HB and KA in different ratios for sexual signals and alarm signals and for species recognition. GC-MS analysis of the sex pheromone bait revealed that the ratios between the three main compounds did not match the intended ratio for the L. lineolaris species. This mismatch probably explains our results. Individuals were not attracted to sunflower volatiles. Our results point to the difficulty of manufacturing and using sex pheromones as baits. Future work should assess the effect of several pheromone ratios.     

Identification and functional analysis of two P450 enzymes of Gossypium hirsutum involved in DMNT and TMTT biosynthesis

The homoterpenes (3E)‐4,8‐dimethyl‐1,3,7‐nonatriene (DMNT) and (E,E)‐4,8,12‐trimethyl‐1,3,7,11‐tridecatetraene (TMTT) are major herbivore‐induced plant volatiles that can attract predatory or parasitic arthropods to protect injured plants from herbivore attack. In this study, DMNT and TMTT were confirmed to be emitted from cotton (Gossypium hirsutum) plants infested with chewing caterpillars or sucking bugs. Two CYP genes (GhCYP82L1 and GhCYP82L2) involved in homoterpene biosynthesis in G. hirsutum were newly identified and characterized. Yeast recombinant expression and enzyme assays indicated that the two GhCYP82Ls are both responsible for the conversion of (E)‐nerolidol to DMNT and (E,E)‐geranyllinalool to TMTT. The two heterologously expressed proteins without cytochrome P450 reductase fail to convert the substrates to homoterpenes. Quantitative real‐time PCR (qPCR) analysis suggested that the two GhCYP82L genes were significantly up‐regulated in leaves and stems of G. hirsutum after herbivore attack. Subsequently, electroantennogram recordings showed that electroantennal responses of Microplitis mediator and Peristenus spretus to DMNT and TMTT were both dose dependent. Laboratory behavioural bioassays showed that females of both wasp species responded positively to DMNT and males and females of M. mediator could be attracted by TMTT. The results provide a better understanding of homoterpene biosynthesis in G. hirsutum and of the potential influence of homoterpenes on the behaviour of natural enemies, which lay a foundation to study genetically modified homoterpene biosynthesis and its possible application in agricultural pest control.     

Effects of pear fruit-derived volatiles and their concentrations on the responses of oriental fruit moths

Grapholita molesta (Busck) is an important pest of pear trees. Numerous esters accumulate consistently in mature pear fruits. However, little is known about the effects of single esters from pear fruits at different concentrations on the responses of male and female G. molesta. In this study, the responses of virgin males, virgin females, and gravid females to five esters (3-methylbutyl acetate, ethyl hexanoate, ethyl butanoate, butyl acetate, and hexyl acetate) of pear fruits at three dosage levels (1, 5 and 10 μg/μL) were investigated using electroantennography (EAG), wind tunnel experiments, and field tests. Our results showed that ethyl butanoate (5 μg/μL) elicited higher EAG responses in virgin females and males than a mixture of all five volatiles, and elicited an equal EAG response to that for the mixture in gravid females, with all responses to ethyl butanoate and the mixture being higher than the response to hexane alone. For upwind flight, ethyl butanoate (5 μg/μL) excited equal moth flight–location behavior in virgin and gravid females to that for the mixture, which were both higher than the response to hexane. For close flight, ethyl hexanoate (5 μg/μL) and 3-methylbutyl acetate (10 μg/μL) appeared to be the activating compounds, eliciting equal responses from virgin females to that of the mixture, and higher responses of gravid females to that of the mixture, both of which were higher than the responses to hexane. Upwind and close flight responses of virgin males were lower than those of virgin and gravid females. In field trials, we verified that traps baited with ethyl butanoate (5 μg/μL) captured more moths than the other esters. Therefore, from the esters and concentrations tested, we recommend ethyl butanoate (5 μg/μL) for potential use as an attractant for G. molesta in orchards.     

Behavioural and chemical evidence of a male‐produced aggregation pheromone in the flower thrips Frankliniella intonsa

The response of adult flower thrips Frankliniella intonsa (Trybom) (Thysanoptera: Thripidae) to conspecifics is investigated in Y‐tube olfactometer bioassays. The results show that both males and females are attracted to the odours of adult males, which indicates a male‐produced aggregation pheromone in this species. Gas chromatography‐mass spectroscopy analyses of headspace volatiles collected on solid‐phase microextraction fibres show that two major components and six minor components are present in volatiles from males but not in females. Further gas chromatography‐mass spectroscopy analyses reveal that the two major components in head‐space volatiles produced by F. intonsa males are the same compounds that are reported in volatiles of Frankliniella occidentalis males: (R)‐lavandulyl acetate and neryl (S)‐2‐methylbutanoate. However, the quantity of these two compounds in the volatiles differs between the species.     

Electroantennogram responses of Plutella xylostella (L.), to sex pheromone components and host plant volatile semiochemicals

The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a notorious insect pest of cruciferous crops worldwide. Attract-and-kill strategies to manage the DBM based on insect pheromone and plant volatile semiochemicals have been explored and partially applied in the field. However, little is known about whether the attractant effects of insect pheromone and host plant volatile semiochemicals on insects are affected by insect age or volatile concentrations. Therefore, we examined the electroantennogram (EAG) responses of both DBM males and females varying in age and body size to a range of concentrations of seven host plant volatiles and two main female sex pheromone components. Our results showed that DBM age had no influence on EAG responses to trans-2-Hexenal, trans-2-Hexenol, Heptanal, cis-3-Hexen-1-ol and Z11-16:Ald and significantly influenced the EAG responses to Z11-16:Ac and three isothiocyanates. Age and sex had interaction effects on EAG responses of DBMs to some tested semiochemicals. DBM females had significantly stronger responses than males to all tested plant volatiles, and values were enhanced with increasing concentrations. Moreover, the degree of enhancement of EAG responses in females was larger than that in males for trans-2-Hexenal, trans-2-Hexenol, cis-3-Hexen-1-ol, 2-Phenylethyl isothiocyanate and Methyl isothiocyanate treatments. Body size seemed to have no influence on EAG responses. Our results might provide a theoretical basis for optimizing attract-and-kill strategies for insect pests.