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.     

Comparison of the volatile emission profiles of ground almond and pistachio mummies: Part 1 – Addressing a gap in knowledge of current attractants for navel orangeworm

Over the years various tissues of almond and pistachio have been evaluated for their ability to attract the navel orangeworm moth, a major insect pest in California tree nut orchards. Almond meal, which typically consists of ground almond kernels, is a monitoring tool for navel orangeworm populations in almond and pistachio orchards. Recently, ground pistachio and almond mummies have been re-visited in field trapping studies for their potential to attract navel orangeworm moths. Surprisingly, the volatile profiles of these two systems have not been reported. The objective of this study was to survey and then compare and contrast the volatile profiles of both ground almond and pistachio mummies over the course of a week. Principal component analysis (PCA) of the headspace volatiles showed a distinct difference between ground almond and pistachio mummies. The volatile emission profile of the almond mummies remained consistent over the one-week period, albeit in low content and composition; whereas the profile of the pistachio mummies changed over time as shown by PCA. Seven compounds were identified as being common volatiles to both matrices. These data may help explain results from recent navel orangeworm field trapping studies using almond and pistachio mummies, as well as with the formulation of future synthetic blends.     

Differential electroantennogram response of females and males of two parasitoid species to host-related green leaf volatiles and inducible compounds

Parasitoids employ different types of host-related volatile signals for foraging and host-location. Host-related volatile signals can be plant-based, originate from the herbivore host or produced from an interaction between herbivores and their plant host. In order to investigate potential sex- and species-related differences in the antennal response of parasitoids to different host-related volatiles, we compared the electroantennogram (EAG) responses of both sexes of the specialist parasitoid, Microplitis croceipes (Cresson), and the generalist, Cotesia marginiventris (Cresson), to varying doses of selected plant-based host-related volatiles: two green leaf volatiles (cis-3-hexenol and hexanal) and three inducible compounds (cis-3-hexenyl acetate, linalool, and (E,E)-alpha-farnesene). Mating had no significant effect on EAG response. Females of both species showed significantly greater EAG responses than conspecific males to green leaf volatiles, which are released immediately after initiation of herbivore feeding damage. In contrast, males showed greater responses than conspecific females to inducible compounds released much later after initial damage. Cotesia marginiventris females and males showed greater EAG responses than counterpart M. croceipes to the tested compounds at various doses, suggesting that the generalist parasitoid shows greater antennal sensitivity than the specialist to the tested host-plant volatiles. These results are discussed in relation to the possible roles of green leaf volatiles and inducible compounds in the ecology of female and male parasitoids.     

Role of plant volatiles in host plant location of the leafminer, Liriomyza sativae (Diptera: Agromyzidae)

Abstract The role of plant volatiles in host plant location of the leafminer Liriomyza sativae Blanchard was studied. Four types of antennal sensilla were identified on the funiculus by scanning electron microscopy: trichoid, basiconic, clavate and grooved sensilla. An olfactory pit, containing groups of sensilla, was present on the ventral side of the funiculus. No sexual difference was detected in sensilla diversity and distribution. In behavioural assays, both males and females were attracted by the odour of the bean Phaseolus vulgaris L. They had distinct EAG responses to the bean odour. No significant sexual difference was found in behaviour or EAG responses.
Electroantennograms were recorded from female L. sativae to 14 plant volatile compounds. The most distinct EAG responses were obtained for: (1) the general green leaf volatiles 1-hexanol (E)-2-hexen-1-ol, (E)-3-hexen-1-ol and its isomers, (Z)-3-hexen-1-ol, the acetate (E)-3-hexenylacetate and the aldehyde hexanal; and (2) limonene, a compound associated with tomato, which is a key host plant of this insect. Other volatile compounds associated with host plants, such as α-pinene, myrcene, β-caryophyllene, and eugenol did not elicit responses. The ability of this insect to locate a host plant appears to be augmented by the perception of a combination of host-specific and general green leaf volatiles. A modification of the EAG recording method of Dipteran species was provided.     

Electroantennogram responses of the carrot fly, Psila rosae, to volatile plant components

ABSTRACT. Electroantennogram (EAG) responses of male and female carrot flies, Psila rosae F. (Diptera: Psilidae), were recorded to thirty-six volatile plant constituents. The most distinct EAG responses were obtained to: (1) the general green leaf volatiles 1-hexanol, trans-2-hexen-1-ol and cis-3-hexen-1-ol, their isomers cis-2-hexen-1-ol and trans-3-hexen-1-ol, the alcohol 1-heptanol, the ester cis-3-hexenyl acetate and the leaf aldehydes hexanal and trans-2-hexenal, and (2) from four compounds associated with the umbelliferous host plants of this insect, namely trans-methyl-iso-eugenol, β-caryophyllene, linalool and trans-2-nonenal. Higher responses were elicited by the leaf aldehydes than by the corresponding alcohols. Although the absolute amplitude of the female response was over twice that of the male, there were no differences between the relative responses to the compounds tested in both sexes, with the exception of a much higher response to the leaf aldehydes in the male. The shape of the EAG evoked by the various compounds was consistently different, with the slowest recovery being recorded for trans-methyl-iso-eugenol. While the antennal olfactory receptors of the carrot fly are sensitive to the closely related general green leaf volatiles, they are most specifically tuned to the aldehyde component of this green odour complex. In addition, the ability of this insect to discriminate between different plants may be augmented by the perception of a group of more host specific volatiles. The conformity of the responses of males and females to the compounds tested may indicate that host plant volatiles plays an additional role as an aggregation cue for both sexes.     

Host plant volatiles induce oriented flight behaviour in male European grapevine moths, Lobesia botrana

The European grapevine moth Lobesia botrana relies on a female produced sex pheromone for long-distance mate finding. Grapevine moth males compete heavily during limited time windows for females. The aim of this study was to investigate the perception of host plant volatiles by grapevine moth males and whether such compounds elicit upwind oriented flights. We compared five host plant headspace extracts by means of gas chromatography linked electroantennogram (EAG) recording. We identified 12 common host plant volatiles (aliphatic esters, aldehydes, and alcohols, aromatic compounds and terpenes) that elicit EAG responses from grapevine moth males and that occur in at least three of the host plant volatile headspace extracts tested. Subsequently the behavioural response of grapevine moth males to four these compounds presented singly and in mixtures (1-hexanol, 1-octen-3-ol, (Z)-3-hexenyl acetate and (E)-β-caryophyllene) was recorded in a wind tunnel. Grapevine moth males engaged in upwind flights to all of four compounds when released singly at 10,000 pg/min and to all, except 1-octen-3-ol, when released at 100 pg/min. A blend of the four host plant volatiles released at 10,000 pg/min and mixed at a ratio based on the analysis of Vitis vinifera cv. Solaris volatile emissions attracted significantly more males than any single compound. Grapevine moth males perceive and respond to host plant volatiles at biologically relevant levels indicating that host plant volatiles figure as olfactory cues and that L. botrana males can discern places where the likelihood of encountering females is higher.     

OLFACTORY RESPONSES OF COTTON BOLLWORM,HELICOVERPA ARMIGERA TO SEX PHEROMONE AND PLANT VOLATILE COMPONENTS*

Abstract Electroantennograms (EAGs) were recorded from unmated, laboratory-reared male and female Helicover pa armigera (Lepidoptera:Noctuidae) adults to two sex pheromone components and a range of plant volatile components, some of which are known volatiles from leaves and fruits. The female-produced sex pheromone was not detected by other female moths. The sex pheromone components to which male moths responded previously show to possess biological activity. As for plant volatile components, a large degree of EAG response uniformity between male and female moth was observed. The greatest EAG responses of all plant volatiles tested were elicited by monoenic C-6 alcohol and aldehyde. They are constituents of the “general green-leaf odor” that emanates from most plants. The potential adaptive benefit of selective perception to sex pheromone and green-leaf volatile components is discussed.     

棉铃虫Helicverpa armigera对性外激素和植物气味物质的嗅觉反应(英文)

本文用EAG技术研究棉铃虫对性外激素和植物气味物质的嗅觉反应。供试的气味物质有棉铃虫性外激素的二种主要组分和36种与棉铃虫寄主植物有关的植物气味物质。试验结果表明：1）只有棉铃虫雄蛾对性外激素组分产生反应,二种性外激素的组分中,Z-11-16：AL能引起较强的EAG反应。2）对植物气味物质,雌雄棉铃虫之间的嗅觉反应没有明显的差异。棉铃虫对性外激素和植物气味组分的嗅觉感受过程是一个有选择性的感受过程：不同种类的气味物质能引起不同的EAG反应。只有棉铃虫雄蛾才对性外激素组分起反应,在二种性外激素组分中：主要组分：Z-11-16：AL引起的EAG反应最高,高于大多数植物气味物质。次要组分Z-9-16：AL引起的EAG反应很弱。雌、雄棉铃虫对植物气味组分的嗅觉反应的选择性表现出一致的规律：对苯甲醛和绿叶气味物质的反应最高。单萜类中的萜烯衍生物（萜类醇、醛、酯等）的触角电位反应次之。棉铃虫对大多数的供试化合物的EAG反应都很小。最后,作者讨论了性外激素和植物气味物质对棉铃虫行为的作用。     

Electroantennogram (EAG) responses of Microplitis croceipes and Cotesia marginiventris and their lepidopteran hosts to a wide array of odor stimuli: Correlation between EAG response and degree of host specificity?

In order to test whether the electroantennogram (EAG) response spectrum of an insect correlates to its degree of host specificity, we recorded EAG responses of two parasitoid species with different degrees of host specificity, Microplitis croceipes (specialist) and Cotesia marginiventris (generalist), to a wide array of odor stimuli including compounds representing green leaf volatiles (GLVs), herbivore-induced plant volatiles (HIPV), ecologically irrelevant (not used by the parasitoid species and their hosts for host location) plant volatiles, and host-specific odor stimuli (host sex pheromones, and extracts of host caterpillar body and frass). We also tested the EAG responses of female moths of the caterpillar hosts of the parasitoids, Heliothis virescens and Spodoptera exigua, to some of the odor stimuli. We hypothesized that the specialist parasitoid will have a narrower EAG response spectrum than the generalist, and that the two lepidopteran species, which are similar in their host plant use, will show similar EAG response spectra to plant volatiles. As predicted, the specialist parasitoid showed greater EAG responses than the generalist to host-specific odor and one HIPV (cis-3-hexenyl butyrate), whereas the generalist showed relatively greater EAG responses to the GLVs and unrelated plant volatiles. We detected no differences in the EAG responses of H. virescens and S. exigua to any of the tested odor.     

Electroantennogram and flight orientation response of Cotesia plutellae to hexane extract of cruciferous host plants and larvae of Plutella xylostella

The braconid wasp Cotesia plutellae is an important larval parasitoid of the diamondback moth (DBM) Plutella xylostella, which a major pest of crucifers in the tropics and subtropics. The peripheral olfactory responses of antennal chemoreceptors of C. plutellae to various cruciferous host plants of DBM and host larval body (cuticle) extracts were examined by electroantennogram (EAG) detection and the behavioral response to a concentration of 1% was analyzed in a Y‐tube olfactometer. Females of C. plutellae exhibited dose‐dependant EAG response for all the extracts tested. Antennal stimulation with 0.1 and 1% concentrations elicited stronger EAG responses than lower concentrations for all the extracts. Host plant extracts were more stimulatory to virgin females, while gravid females exhibited increased antennal sensitivity to host larval body extract odors. In the flight orientation studies, virgin females exhibited increased orientation toward host plant extracts, while gravid females oriented more toward host larval body odors. The EAG response profile and the corresponding orientation behavior revealed a differential preference by the parasitoid wasp to host plant and host‐related cues. Mustard and cauliflower extracts were more attractive to females than other extracts. The possible behavioral manipulation of this specialist parasitoid using these extracts for effective biological control of diamondback moth is discussed.     

Antennal responses of Cydia pomonella (L.) exposed to surfaces treated with methoxyfenozide

Electroantennogram (EAG) measurements were recorded from the antennae of male and female codling moth, Cydia pomonella L., to determine whether adult moths exposed to surfaces treated with the ecdysteroid agonist methoxyfenozide experience a decline in their antennal reception and thus olfactory sensitivity. Such a phenomenon would offer a possible mechanism for the previously reported decreased responsiveness from moths treated with methoxyfenozide to pheromone‐ and plant volatile‐based monitoring lures. Mean EAG data revealed that the antennae from methoxyfenozide‐treated male moths appear to be just as sensitive to various doses of synthetic codlemone as the antennae from the control and surfactant‐treated moths, but they appeared to be less sensitive to the pheromone component 12OH (collected from female effluvia) than the control male antennae. Mean male EAG responses to the pheromone components E8,E10‐12Al and codlemone collected from methoxyfenozide‐treated females were significantly less than the responses towards those two pheromone components collected from the control and surfactant‐treated females. Female moth exposure to methoxyfenozide did not negatively impact the sensitivity of female antennae to the plant volatile pear ester, but it did towards the apple volatile butyl hexanoate. Data from this study show that adult C. pomonella exposure to methoxyfenozide‐treated surfaces does appear to negatively impact, in a minor way, the (i) olfactory sensitivity (or detection) of male antennae towards some components of the female sex pheromone, (ii) the female antennal sensitivity towards a key apple volatile and (iii) the attractiveness of female pheromone effluvia.     

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.     

Electroantennogram responses of the potato tuber moth, <Emphasis Type="Italic">Phthorimaea operculella</Emphasis> (Lepidoptera; Gelichiidae) to plant volatiles

Electroantennograms (EAGs)were recorded from males and females of the potato tuber moth,Phthorimaea operculella in response to a broad range of plant volatile compounds belonging to diverse chemical classes.The responses to 27 compounds were evaluated,which indicated significant differences in EAGs between chemicals as well as between sexes.The fatty acid derivatives comprising essentially green leaf volatile components elicited significantly greater responses in females.The response profile of males was,in general,lower than that of females.EAG responses to the oxygenated and hydrocarbon monoterpenes were lower in both males and females.Dose -response studies indicate differences in response between the sexes and concentrations,suggesting the existence of sexual dimorphism. Compounds belonging to the fatty acid derivatives class appear to be important for an oligophagous pest such as the potato tuber moth and the findings are discussed in relation to host plant selection in this species.     

松毛虫狭颊寄蝇对被害马尾松针叶挥发物的触角电位反应

松毛虫狭颊寄蝇Carcelia matsukarehaeShima是我国松毛虫Dendrolimus punctatus(Walke)的重要天敌。通过对被害马尾松(Pinus massonianaLamb.)针叶挥发性物质的提取、鉴定以及对松毛虫狭颊寄蝇的电生理测定,结果表明,大多数的挥发性物质,包括绿叶性挥发物以及松针特有的单萜、氧化单萜和倍半萜,对雌蝇均有明显的电生理活性,其中以顺-3-己烯-1-醇最高,长叶烯最低。雌蝇对4大类挥发性物质的平均相对触角电位反应值,以绿叶性挥发物为最高,其余依次为单萜、氧化单萜和倍半萜。     

Comparison of the olfactory sensitivity of two sympatric steppe grasshopper species (Orthoptera: Acrididae) to plant volatile compounds

Two Oedipodinae grasshopper species Oedaleus decorus asiaticus B.-Bienko and Angaracris baraben-sis Pall. (Orthoptera: Acrididae) are important pests on the natural grasslands in Inner Mongolia and often require insecticide treatment during outbreaks[1]. They both prefer overgrazed steppes and xerophytous habi-tats, and have thus been suggested as indicator species for steppe deterioration in typical steppe zones of In-ner Mongolia[2]. The two species have a sympatric distribution and sync…     

Identification and Characterization of an Antennae-Specific Aldehyde Oxidase from the Navel Orangeworm

Antennae-specific odorant-degrading enzymes (ODEs) are postulated to inactivate odorant molecules after they convey their signal. Different classes of insect ODEs are specific to esters, alcohols, and aldehydes – the major functional groups of female-produced, hydrophobic sex pheromones from moth species. Esterases that rapidly inactive acetate and other esters have been well-studied, but less is known about aldehyde oxidases (AOXs). Here we report cloning of an aldehyde oxidase, AtraAOX2, from the antennae of the navel orangeworm (NOW), Amyelois transitella, and the first activity characterization of a recombinant insect AOX. AtraAOX2 gene spans 3,813 bp and encodes a protein with 1,270 amino acid residues. AtraAOX2 cDNA was expressed in baculovirus-infected insect Sf21 cells as a ≈280 kDa homodimer with 140 kDa subunits. Recombinant AtraAOX2 degraded Z11Z13–16Ald and plant volatile aldehydes as substrates. However, as expected for aldehyde oxidases, recombinant AtraAOX2 did not show specificity for Z11Z13–16Ald, the main constituent of the sex pheromone, but showed high activity for plant volatile aldehydes. Our data suggest AtraAOX2 might be involved in degradation of a diversity of aldehydes including sex pheromones, plant-derived semiochemicals, and chemical cues for oviposition sites. Additionally, AtraAOX2 could protect the insect''s olfactory system from xenobiotics, including pesticides that might reach the sensillar lymph surrounding the olfactory receptor neurons.     

Electroantennogram responses of Apanteles obliquae (Hym., Braconidae) to various infochemicals

Abstract:   The electroantennogram recording technique (EAG) was used to study the olfactory sensitivity of Apanteles obliquae (Hym., Braconidae), a gregarious larval endoparasitoid of Spilosoma obliqua (Walker) (Lep., Arctiidae), to 25 general plant volatiles belonging to alcohol, aldehyde and terpenoid groups and also to volatiles from the host and plant–host complex. The EAG data indicated different olfactory sensitivity between the sexes, not only to individual plant volatiles but also to the volatiles from host and plant–host complex. Females were found to be more responsive than males. However the synthetic sex pheromone blend of the host insect elicited similar EAG responses in both sexes. The EAG data of the present study is correlated with the reported behaviour observed in other parasitoids.     

An improved aphid electroantennogram

Excised antennae have been used to record aphid electroantennograms (EAGs) but these preparations have small, rapidly declining responses and a short usable life. An improved EAG technique is described and evaluated using alate virginoparae of the black bean aphid, Aphis fabae, and a series of plant volatiles. EAG recording with fine-tip glass electrodes inserted into the surface of the intact antenna of a whole insect preparation gave stable EAG peaks of a few mV and EAG peak amplitude decreased by only 22% over an 8 hour recording period. The EAG responses showed typical dose-dependent characteristics. There was variation in EAGs from different preparations, so normalisation of the EAG responses against a standard stimulus is still necessary. The thirty compounds tested elicited an EAG response profile largely similar to that reported previously from excised antennae. EAG responses recorded with the electrode at three different positions, between the 5th-6th (A), 4th-5th (B), and 3rd-4th (C) antennal segments, were smaller when recorded closer to the head. Position B produced larger EAG responses than those at C although there was no olfactory receptor between position B and C.     

Electroantennogram responses of the three migratory forms of the damson-hop aphid, Phorodon humuli, to aphid pheromones and plant volatiles

Electroantennogram (EAG) responses were recorded from alate fundatrigeniae (spring migrants), gynoparae (the winged female form that produces sexual females) and males, the three migratory forms of the damson-hop aphid, Phorodon humuli (Schrank). EAG responses of gynoparae and males showed typical dose response characteristics to (E)-2-hexenal, (-)-R-carvone, hexanenitrile and (1RS,4aR,7S,7aS)-nepetalactol, the sex pheromone of this species. The 34 plant volatiles elicited broadly similar EAG response profiles in the three migratory forms. Green leaf volatiles produced large responses in all forms; however, the relative order of responsiveness varied. EAG responses to isomers of the monoterpene carvone differed between forms, with males being most, and spring migrants least, responsive. The hop-plant volatile and aphid alarm pheromone, (E)-beta-farnesene, evoked similar EAG responses in all forms. By contrast, males were most responsive to the three sex pheromone components, (-)-(4aS,7S,7aR)-nepetalactol, (+)-(4aS,7S,7aR)-nepetalactone and (1RS,4aR,7S,7aS)-nepetalactol. Males were no more responsive to their own sex pheromone, (1RS,4aR,7S,7aS)-nepetalactol, than to the other aphid sex pheromone components tested. Spring migrants and gynoparae also responded to the three sex pheromone components. This study indicates that migratory forms of P. humuli detect a wide range of volatile compounds, and that they are equally well-adapted for the detection of volatiles associated with host and non-host plants and with other species of aphid.     

棉铃虫齿唇姬蜂对植物挥发物和寄主性信息素腺体化合物的EAG反应

测试了棉铃虫齿唇姬蜂Campoletis chlorideae Uchida对58种植物挥发物和5种寄主性信息素腺体化合物的EAG反应。在100 μg的刺激剂量下,棉铃虫齿唇姬蜂对C₅～C₇脂肪醇的EAG反应最强,碳链延长或缩短都将导致反应的降低;对脂肪醛、酮、酸和酯都有一定的反应。棉铃虫齿唇姬蜂对萜烯的EAG反应很低,对氧化萜的反应普遍升高。3种芳香化合物均可激起棉铃虫齿唇姬蜂较强的EAG反应。剂量反应曲线表明,具有EAG活性的化合物激起的反应强度与化合物的剂量呈正相关,而2种萜烯——α-蒎烯和反式石竹烯,在测定的剂量范围内EAG活性都很低。棉铃虫齿唇姬蜂对寄主性信息素腺体化合物也有EAG反应,用100 μg和1 000 μg的寄主性信息素刺激,雄蜂的反应可比雌蜂的反应高出1倍。对植物挥发物在棉铃虫齿唇姬蜂寻找寄主中的作用进行了讨论。