Synergism between aromatic compounds and green leaf volatiles derived from the host plant underlies female attraction in the oriental fruit moth

Blends of volatile compounds emitted by host plants are known to mediate the attraction of gravid female herbivores to oviposition sites, but the role of individual odor components is still little understood. We characterized the olfactory response of mated female Cydia (Grapholita) molesta (Busck) (Lepidoptera: Tortricidae) to synthetic mixtures of compounds emitted by peach shoot, a key host plant of this herbivore, and investigated the role of important constituents of bioactive mixtures in moth attraction. Relative ratios of constituents of the mixtures corresponded to the natural ratio of volatile compounds collected in the plant's headspace. A significant attractant effect was found for a comparatively complex 10‐compound mixture that included four green leaf volatiles [(Z)‐3‐hexen‐1‐ol, 1‐hexanol, (E)‐2‐hexenal, and (Z)‐3‐hexen‐1‐yl acetate], five aromatics (benzaldehyde, methyl salicylate, methyl benzoate, benzonitrile, and phenylacetonitrile), and a carboxylic acid (valeric acid). Using a subtraction approach, the number of compounds was progressively decreased, resulting in a bioactive 5‐compound mixture composed of two constituents, green leaf volatiles and aromatic compounds. Further evaluations revealed that benzaldehyde and benzonitrile must be present in association with three distinct green leaf volatiles to produce an attractant effect on the female moths. This 5‐compound mixture was as attractive as natural peach shoot volatiles, which are known to comprise over 20 compounds. Results are discussed in light of the documented synergistic effect between the three general green leaf volatiles and the two specific aromatic compounds.     

梨小食心虫化学通信中的信息物质

梨小食心虫Grapholitha molesta Busck是我国北方果区发生的重要害虫。当前对该虫的防治主要依赖化学农药, 但引起的害虫抗药性、 杀伤天敌和环境污染等问题非常严重。食心虫自身的信息素、 寄主/非寄主的他感化学物质对于调节其配偶选择和寄主定位起着至关重要的作用, 基于信息化学物质的害虫管理策略为果园食心虫的治理提供了新的途径。本文综述了国内外有关梨小食心虫化学信息物质研究进展, 包括雌蛾释放的性信息素组分及对雄、 雌两性的引诱, 雄蛾释放的信息素, 利用性信息素的迷向研究, 寄主植物挥发性引诱物质的鉴定和筛选, 以及梨小食心虫寄主转换机制等方面的研究现状和存在的问题。具体来说, 雌蛾的性信息素包括顺-8-十二碳烯醋酸酯、反-8-十二碳烯醋酸酯、顺-8-十二碳烯-1-醇和十二碳-1-醇, 各个组分的比例在地理种群间存在变异。在室内, 通过行为试验证实两种醋酸酯对雄蛾的引诱是必不可少的, 微量的顺-8-十二碳烯-1-醇对二元组分起到增效作用。在田间, 上述3种物质组成的诱芯具有较强的活性; 由此开发的性信息素迷向技术（人工迷向丝、 可喷施的微胶囊和蜡滴）被用于梨小食心虫交配干扰, 取得了很好的效果。梨小食心虫最主要的寄主植物桃梢挥发物包括22种化合物, 其中绿叶挥发物占到50%, 行为生测证实6~8个碳原子的物质是主要的活性化合物。顺-3-己烯丁酸酯、顺-3-己烯醇、反-2-己烯醛、苯甲醛和苯甲腈的五组分混合物, 其引诱力与天然桃梢挥发物相当。通过钙成像试验证实, 尽管苯甲腈在桃梢天然挥发物中仅占0.14%, 但雌蛾对含有该物质的混合物有显著趋性, 该物质对梨小食心虫成功识别寄主具有重要意义。最后对梨小食心虫信息化学物质下一步的研究和应用前景进行了探讨。     

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.     

Optimized trap lure for male Melolontha cockchafers

Abstract:  Melolontha cockchafer males search for mates using green leaf volatiles (GLV), released by host plants after female feeding. Thus, the feeding-induced plant volatiles act as sexual kairomones. Males of both Melontha hippocastani and Melontha melolontha are strongly attracted by the GLV ( Z )-3-hexen-1-ol ( Z -3-ol). Sex pheromones enhance the attractiveness of Z -3-ol and have been identified as toluquinone (TQ) in M. melolontha , and 1,4-benzoquinone (BQ) in M. hippocastani . Additionally, phenol acts as a male attractant in both species. From the perspective of potential application, we investigated by field experiments with volatile-baited traps the ways of enhancing the number of captured males by the use of specific binary or ternary blends of Z -3-ol with phenol, and TQ or BQ respectively. The data show that in both species binary lures containing Z -3-ol combined with TQ or BQ at a ratio of 10 : 1 are the most potent male attractants.     

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.     

Electrophysiological and behavioral responses of a parasitic wasp to plant volatiles induced by two leaf miner species

In the present study, Y-tube olfactometric assays demonstrated that headspace volatile extracts collected from leaf miner-damaged, or artificially damaged, bean plants were more attractive to naive females of the parasitoid insect Opius dissitus than those collected from healthy plants. Headspace extracts from both Liriomyza huidobrensis and Liriomyza sativae second-instar larvae-damaged beans were analyzed by coupled gas chromatography-electroantennographic detection (GC-EAD). Of nine EAD-active volatiles identified, (3E)-4,8-dimethyl-1,3,7-nonatriene, (3Z)-hexenyl acetate, (syn)-2-methylpropanal oxime, and (syn)-2-methylbutanal oxime were the most abundant compounds that evoked significant electroantennogram (EAG) responses. Compounds (3Z)-hexen-1-ol, (anti)-2-methylbutanal oxime, linalool, beta-caryophyllene, and (3E,7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene also elicited clear EAG responses but were present in smaller amounts. Choice experiments in a Y-tube olfactometer indicated that synthetic versions of (3Z)-hexen-1-ol, 2-methylpropanal oxime, 2-methylbutanal oxime, 3-methylbutanal oxime, linalool, (E,E)-alpha-farnesene, and (3E,7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene were attractive individually, while (3Z)-hexenyl acetate and (3E)-4,8-dimethyl-1,3,7-nonatriene were unattractive at concentrations similar to those obtained from the headspace collection. Moreover, a blend of nine EAD-active volatiles was significantly more attractive relative to hexane (solvent). A mixture of oximes, tereponids, and green leaf volatiles may facilitate host location by female O. dissitus.     

Nonhost angiosperm volatiles and verbenone disrupt response of western pine beetle, Dendroctonus brevicomis (Coleoptera: Scolytidae), to attractant-baited traps

Nonhost angiosperm volatiles and verbenone were tested for their ability to disrupt the response of western pine beetle, Dendroctonus brevicomis LeConte (Coleoptera: Scolytidae), to attractant-baited multiple funnel traps. Verbenone significantly reduced attraction; however, no difference was observed between 4 and 50 mg/24-h release rates. Combinations of six bark volatiles (benzyl alcohol, benzaldehyde, trans-conophthorin, guaiacol, nonanal, and salicylaldehyde), three green leaf volatiles [(E)-2-hexenal, (E)-2-hexen-1-ol, and (Z)-2-hexen-1-ol], and the nine compounds combined did not significantly reduce D. brevicomis response to attractant-baited traps. However, a significant effect was observed when the bark and green leaf volatiles were combined with verbenone. The nine nonhost angiosperm volatiles (NAVs) significantly augmented the effect of both release rates of verbenone, reducing trap catches to levels significantly below that of either release rate of verbenone alone. trans-Conophthorin, a compound reported to have behavioral activity in a number of other scolytids, was not critical to the efficacy of our NAV blend. Our results suggest that the addition of nonhost angiosperm volatiles to verbenone could be important for developing successful semiochemical-based management techniques for D. brevicomis.     

Representation of a mixture of pheromone and host plant odor by antennal lobe projection neurons of the silkmoth Bombyx mori

Pheromone-source orientation behavior can be modified by coexisting plant volatiles. Some host plant volatiles enhance the pheromonal responses of olfactory receptor neurons and increase the sensitivity of orientation behavior in the Lepidoptera species. Although many electrophysiological studies have focused on the pheromonal response of olfactory interneurons, the response to the mixture of pheromone and plant odor is not yet known. Using the silkmoth, Bombyx mori, we investigated the physiology of interneurons in the antennal lobe (AL), the primary olfactory center in the insect brain, in response to a mixture of the primary pheromone component bombykol and cis-3-hexen-1-ol, a mulberry leaf volatile. Application of the mixture enhanced the pheromonal responses of projection neurons innervating the macroglomerular complex in the AL. In contrast, the mixture of pheromone and cis-3-hexen-1-ol had little influence on the responses of projection neurons innervating the ordinary glomeruli whereas other plant odors dynamically modified the response. Together this suggests moths can process plant odor information under conditions of simultaneous exposure to sex pheromone.     

Volatiles induced by the larvae of the Asian corn borer (Ostrinia furnacalis) in maize plants affect behavior of conspecific larvae and female adults

Abstract  Effects of maize ( Zea mays L.) volatiles induced by larvae of the Asian corn borer, Ostrinia furnacalis (Guenée), on the orientation behaviors of Asian corn borer larvae and oviposition of the females were investigated. Nineteen volatile chemicals, with terpenes being the major components, were identified from maize plants attacked by third instar Asian corn borer larvae. Coupled gas chromatographic-electroantennographic detection (GC-EAD) analyses revealed some electroantennographic differences between female and male Asian corn borer antennae in response to larvae-induced maize volatiles; female responded to ( E )-2-hexenal, nonanal, ( Z )-3-hexen-1-ol and three unknown compounds while the male only responded to ( E )-2-hexenal, nonanal and one unknown compound. In laboratory orientation bioassays, Asian corn borer neonate larvae were attracted to extracts collected from Asian corn borer-damaged plants as well as to synthetic farnesene, but were repelled by ( Z )-3-hexen-1-ol. In laboratory oviposition bioassays, gravid females laid fewer eggs on plants damaged by larvae than on mechanically damaged plants or undamaged plants. Adult Asian corn borer females deposited fewer eggs on wax paper treated with ( E )-2-hexenal or ( Z )-3-hexen-1-ol than on wax paper treated with hexane (control). The results suggest that Asian corn borer can affect the behaviors of conspecific larvae and adults by changing host plant volatiles.     

OLFACTORY RESPONSE OF THE GRASSHOPPER MELANOPLUS SANGUINIPES TO PLANT ODOURS AND VOLATILE COMPOUNDS

Abstract Electroantennograms (EAGs1 were recorded from male adults of Melanoplus sanguinipes to foliage odours from 5 plant species and 9 volatile compounds as well as their blends. Higher EAG responses were recorded for Louisianna sage and Alfalfa foliages, compared to other three gramineous plants. Among green odour chelricals, 6-carbon alcohols (e. g. E-2-hexen-1–01 and E-3-hexen-1–01] resulted in the highest EAG responszs. No significant differences among the pentenol, 3-pentanone and blank control were observed. In ternary and quaternary mixture tests of volatile compounds, the combinations with pentenol did not elicit greater amplitudes; thus pentenol and 3-pentanone were proved to be unimportant to the response of this generalist grasshopper. The EAG data are discussed with regard to the role of host plant volatiles in host plant orientation and selection by the grasshopper.     

无翅茶蚜对茶树挥发物的触角电生理和行为反应

分别使用昆虫触角电位仪(EAG)和四臂嗅觉仪,测定了无翅茶蚜Toxopteraaurantii Boyer对14种茶树挥发性化合物、14种挥发物中"绿叶气味"组成的混合物(GLV)、14种挥发物的混合物(ACB)、以及新鲜嫩叶、芽、嫩茎、成叶和茶蚜为害嫩叶(ADYL)的EAG反应和行为反应。ACB引出最大的EAG反应值,茶树挥发物主要组分Z-3-己烯-1-醇、E-2-己烯醛、n-己醇、水杨酸甲酯和苯甲醇也引起较大的EAG反应值。4种正常茶梢的器官也引出较大的EAG反应,以嫩叶最强、依次为芽、嫩茎和成叶。有趣的是ADYL引出弱的负的EAG值。用嗅觉仪进行的生物测定表明,嫩叶以及主要的茶梢挥发性成分乙酸-Z-3-己烯酯、水杨酸甲酯、E-2-己烯-1-醇和Z-3-己烯-1-醇等也具有较强引诱活性。研究显示无翅茶蚜可能利用茶梢挥发物作为利它素而寻觅适宜的取食场所,如茶树嫩梢。     

Phenol--another cockchafer attractant shared by Melolontha hippocastani Fabr. and M. melolontha L

The response of the two most abundant cockchafer species in central Europe, Melolontha hippocastani and M. melolontha, towards phenol, mixtures of phenol with the leaf alcohol (Z)-3-hexen-1-ol and the known cockchafer pheromones, 1,4-benzoquinone (M. hippocastani) and toluquinone (M. melolontha), was investigated in the field. During the swarming period at dusk, phenol attracted males of both species, and enhanced the known attraction of cockchafer males towards (Z)-3-hexen-1-ol. A mixture of phenol plus (Z)-3-hexen-1-ol was less attractive for M. hippocastani males than a mixture of (Z)-3-hexen-1-ol plus 1,4-benzoquinone, whereas phenol plus (Z)-3-hexen-1-ol attracted as many M. melolontha males as a mixture of (Z)-3-hexen-1-ol plus toluquinone. In both species three component mixtures containing phenol, (Z)-3-hexen-1-ol, and the respective benzoquinone did not capture more males than two component mixtures consisting of only (Z)-3-hexen-1-ol and the benzoquinone. A possible role of phenol as another cockchafer sex pheromone component is discussed.     

假眼小绿叶蝉对茶梢挥发物的行为反应

【目的】研究假眼小绿叶蝉Empoasca vitis G?the对健康茶梢和蝉害茶梢挥发物的行为反应,筛选出可引诱假眼小绿叶蝉的茶梢挥发物。【方法】以动态吸附法收集健康茶梢和蝉害茶梢挥发物,用气相色谱–质谱联用仪(GC-MS)进行定性定量分析,借助于Y形嗅觉仪检测多种挥发物引诱假眼小绿叶蝉成虫的活性。【结果】从健康茶梢和蝉害茶梢中共鉴定出30种挥发物组分,其中烯烃类含量较大。健康茶梢和蝉害茶梢挥发物中共有组分有13种,蝉害之后其含量皆上升,其中Z-b-罗勒烯和乙酸叶醇酯的含量分别是健康茶梢中的142.27倍、12.90倍。蝉害茶梢中新出现的组分有12种,其中紫苏烯含量较高。在10-2、10~(-4)、10-6 g/mL浓度下,乙酸叶醇酯表现出极显著的引诱水平(P<0.01);紫苏烯在10~(-2)和10~(-4) g/mL浓度下表现出极显著引诱水平(P<0.01);10~(-4) g/mL浓度下,Z-b-罗勒烯和D-柠檬烯极显著引诱假眼小绿叶蝉(P<0.01);10~(-4) g/mL芳樟醇、10~(-6) g/mL乙酸正丁酯和10~(-6) g/mL D-柠檬烯呈现出显著引诱水平(P<0.05);混合物组分Blend1和Blend2分别表现出极显著和显著引诱水平;而10~(-6) g/mLa-法尼烯显著排斥假眼小绿叶蝉(P<0.05)。【结论】假眼小绿叶蝉成虫对健康茶梢和蝉害茶梢挥发物多种组分具有不同的行为反应,引诱效果较强的单组分或混合组分的选定可为田间引诱效果试验提供参考。     

Methyl salicylate, identified as primary odorant of a specific receptor neuron type, inhibits oviposition by the moth Mamestra brassicae L. (Lepidoptera, noctuidae)

The cabbage moth, Mamestra brassicae L. (Lepidoptera, Noctuidae), is a polyphagous species that is often choosing plants of Brassica as hosts for oviposition. In the search for biologically relevant odorants used by these moths, gas chromatography linked to electrophysiological recordings from single receptor neurons (RNs) has been employed, resulting in classification of distinct types of neurons. This study presents specific olfactory RNs responding to methyl salicylate (MeS) as primary odorant and showing a weak response to methyl benzoate, the 2 aromatic compounds occurring together in several plant species. In 2 cases, the neuron was colocated with another RN type responding to 6 green leaf volatiles: 1-hexanol, (3Z)-hexen-1-ol, (2E)-hexen-1-ol, (3Z)-hexenyl acetate, (2Z)-hexen-1-ol, and an unidentified compound. Whereas the specific RNs detected the minor amounts of MeS in some plants, the compound was not found by gas chromatography linked to mass spectrometry in intact plants, but it was found after herbivore attack. The behavioral effect of MeS was studied in outdoor test arenas with Brassica napus and artificial plants. These experiments indicated that mated M. brassicae females avoid plants with dispensers emitting MeS. As it is induced by caterpillar feeding, this compound may mediate a message to mated M. brassicae females that the plant is already occupied.     

Predator–prey interactions: olfactory adaptations of generalist and specialist predators

1 Olfactory responses of the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), a generalist predator, Podisus maculiventris (Say) (Hemiptera, Heteroptera: Pentatomidae) (Pm), and a specialist predator, Perillus bioculatus (F.) (Hemiptera, Heteroptera: Pentatomidae) (Pb) were investigated. Volatiles tested included 20 compounds emitted by undamaged potato plants (Solanum tuberosum), plants that had been artificially damaged, or plants damaged by feeding by CPB larvae. 2 Coupled gas chromatography/electroantennogram detector (GC/EAD) recordings revealed five compounds for which reliable responses were recorded from CPB antennae: (E)-2-hexen-1-ol, (Z)-3-hexen-1-ol, (±)-linalool, nonanal, methyl salicylate, and indole. Both Pm and Pb responded selectively to the same compounds as the CPB with exceptions: (1) (Z)-3-hexenyl butyrate elicited reliable responses for both Pm and Pb, and (2) (E)-2-hexen-1-ol and (Z)-3-hexen-1-ol were inactive for Pm and Pb under these conditions. Dose–response curves showed that CPB was at least 100 times more sensitive to (E)-2-hexen-1-ol than were the predators. Both predators were more sensitive to each of the other compounds than were CPB. Both CPB and Pm were attracted to a five component blend comprising (E)-2-hexen-1-ol, (Z)-3-hexen-1-ol, (±)-linalool, nonanal and methyl salicylate. However, attraction of CPB to the blend occurred only with lower doses of (E)-2-hexen-1-ol and (Z)-3-hexen-1-ol. 3 These results show that the herbivore (CPB) has olfactory receptors which are more sensitive to constitutive host plant volatiles, e.g. green leaf volatiles, while both generalist (Pm) and specialist (Pb) predators are more sensitive to systemic volatiles produced in response to prey feeding. Keywords Colorado potato beetle, constitutive compounds, host plant, induced compounds, olfaction, Perillus bioculatus, Podisus maculiventris, predator, prey, tritrophic.     

Pine shoot beetle, Tomicus piniperda (Col., Scolytidae), responses to common green leaf volatiles

We tested the hypothesis that green leaf volatiles (GLVs) disrupt the response of overwintered pine shoot beetles, Tomicus piniperda (L.) to multiple-funnel traps baited with the attractive host volatile α-pinene. A combination of four GLV alcohols, 1-hexanol ( E )-2-hexen-1-ol ( Z )-2-hexen-1-ol, and ( Z )-3-hexen-1-ol, caused 54 and 36% reduction in the number of pine shoot beetles captured in two separate trapping experiments. Similarly, a combination of the four alcohols plus two GLV aldehydes, hexanal and ( E )-2-hexenal, caused 38% reduction in the number of pine shoot beetles captured compared with α-pinene alone. A blend of the two GLV aldehydes was not disruptive. None of the four GLV alcohols nor the two GLV aldehydes were disruptive when tested individually. The finding that the blend of four GLV alcohols reduced attraction of T. piniperda supports the general hypothesis that GLVs common to nonhost angiosperms are disruptive to conifer-attacking bark beetles (Scolytidae).     

Responses of Dendroctonus brevicomis (Coleoptera: Curculionidae) in behavioral assays: implications to development of a semiochemical-based tool for tree protection

Currently, techniques for managing western pine beetle, Dendroctonus brevicomis LeConte (Coleoptera: Curculionidae, Scolytinae), infestations are limited to tree removals (thinning) that reduce stand density and presumably host susceptibility, and/or the use of insecticides to protect individual trees. There continues to be significant interest in developing an effective semiochemical-based tool for protecting trees from D. brevicomis attack, largely as an alternative to conventional insecticides. The responses of D. brevicomis to tree volatiles and verbenone were documented in eight experiments (trapping assays) conducted over a 4-yr period in which 88,942 individuals were collected. Geraniol, a tree volatile unique to Pinus ponderosa that elicits female-specific antennal responses in D. brevicomis, did not affect D. brevicomis behavior. Blends of two green leaf alcohols [hexanol + (Z)-3-hexen-1-ol] tested at two release rates (5.0 and 100.0 mg/d) had no effect on the response of D. brevicomis to attractant-baited traps. A nine-component blend [benzaldehyde, benzyl alcohol, guaiacol, nonanal, salicylaldehyde, (E)-2-hexenal, (E)-2-hexen-1-ol, (Z)-2-hexen-1-ol, and (-) -verbenone; NAVV] and subsequent revisions of this blend disrupted the response of D. brevicomis to attractant-baited traps in all experiments. The inhibitory effect of a revised five-component blend [nonanal, (E)-2-hexenal, (E)-2-hexen-1-ol, (Z)-2-hexen-1-ol, and (-)-verbenone; NAVV5] on the response of mountain pine beetle, D. ponderosae Hopkins, to attractant-baited traps was also documented. Acetophenone significantly reduced D. brevicomis attraction, but was not as effective as verbenone alone. Acetophenone increased the effectiveness of NAVV5 in one of two experiments. Furthermore, by adding acetophenone to NAVV5 we were able to remove the aldehydes from NAVV5 without compromising effectiveness, resulting in a novel four-component blend [acetophenone, (E)-2-hexen-1-ol + (Z)-2-hexen-1-ol, and (-)-verbenone; Verbenone Plus]. We discuss the implications of these and other results to development of Verbenone Plus as a semiochemical-based tool for management of D. brevicomis and D. ponderosae infestations.     

Attractiveness of host volatiles combined with background visual cues to the tea leafhopper,Empoasca vitis

The tea green leafhopper, Empoasca vitis (Göthe) (Hemiptera: Cicadellidae), is a serious pest of tea plants. We examined the behavioral responses of E. vitis adults to odors from the shoots of three host plants in a Y‐tube olfactometer with background visual cues. The host plants were tea [Camellia sinensis (L.) Kuntze (Theaceae)], peach [Prunus persica (L.) Siebold & Zucc. (Rosaceae)], and grapevine [Vitis vinifera L. (Vitaceae)]. Volatiles from the shoots were analyzed. Both yellow‐green and gold backgrounds enhanced the olfactory responses of E. vitis adults to tea plant odors, and this enhancement was stronger under a high light intensity. On the yellow‐green background, E. vitis adults significantly preferred the odors from shoots of the three host plants compared with clean air. Moreover, E. vitis adults preferred grapevine odor over the tea plant odor. The volatile blends of the three plant species were distinctly different. Peach plant shoots emitted the greatest amount of volatiles, whereas grapevine shoots released the greatest diversity of compounds. These results provide evidence that background visual cues could enhance the response of E. vitis adults to host‐plant volatiles. The leafhoppers can discern different host odors, suggesting the possibility of using peach plant and grapevine odors to monitor and manage this pest in tea plantations.     

EAG and behavioral responses of the wingless tea aphid Toxoptera aurantii (Homoptera: Aphididae) to tea plant volatiles

Electrophysiological and behavioral responses of the wingless tea aphid, Toxoptera aurantii (Boyer), to 14 synthetic volatiles identified from tea shoots, their partial (GLV mixture) and full (ACB mixture) blends, and fresh young tea leaves, buds, tender stems, adult tea leaves and tea aphid-damaged young leaves (ADYL) were studied by using an electroantennography (EAG) and a four-arm olfactometer. ACB elicited the largest EAG responses. Major volatile components, Z-3-hexen-1-ol, E-2-hexenal, n-hexanol, methyl salicylate and benzylalcohol, from the tea shoots were strongly EAG active. All the 4 tested tea shoot tissues also elicited significant EAG responses, with the young tea leaves being the strongest, followed by buds, tender stems and adult tea leaves. Surprisingly, ADYL elicited a weakly negative EAG response. In the olfactory assays, the fresh and tender tea leaves, as well as the individual major volatile components, e.g. Z-3-hexenyl acetate, methyl salicylate, E-2-hexen-1-ol and Z-3-hexen-1-ol, from the tender shoots (EAG-active) were all attractive. This result might indicate that the wingless tea aphids may use tea shoot volatiles as kairomone to find their optimal feeding sites, e.g. fresh tender tea shoots.