Interruption of aggregation pheromone in Ips typographus (L.) (Col. Scolytidae) by non-host bark volatiles

Abstract 1 The antennally active nonhost bark volatiles (NHVs): trans‐conophthorin (tC), C₆‐alcohols (green leaf volatiles; GLVs) and C₈‐alcohols, were tested for their ability to reduce attraction of the spruce bark beetle Ips typographus (L) (Col. Scolytidae) to its pheromone sources in both laboratory walking bioassy and field trapping experiments. 2 In the walking bioassay with I. typographus females, individual NHVs such as tC, 3‐octanol and 1‐octen‐3‐ol, and the unsuitable host signal, verbenone (Vn), were inactive at the doses tested. However, the blend of C₆‐alcohols (3GLVs) and all the binary, ternary, or quarternary blends significantly reduced the female attraction to the pheromone sources. 3 In the field trapping experiments, individual NHV signals (tC, C6‐alcohols and C₈‐alcohols) all reduced catch of I. typographus in pheromone‐baited traps, with their inhibitory effects similar to that of the known inhibitor, Vn. The binary, ternary or quarternary combinations of these NHV signals or Vn, all caused significantly stronger reductions in trap catches than the individual signals. The blends showed similar levels of interruption, except the binary blend of C₈‐alcohols (2C8OH) and Vn. 4 Difference in trapping mechanism between pipe traps (attraction and landing) and Lindgren funnel traps (attraction) did not affect the pattern of inhibition of these active NHV signals and Vn. 5 These behaviourally active nonhost volatiles and Vn might be used effectively to protect spruce trees or stands against attacks by I. typographus.     

Identification of further sex pheromone synergists in the codling moth, Cydia pomonella

A number of angiosperm nonhost volatiles (NHVs) and green leaf volatiles (GLVs) were tested alone and as supplements to the antiaggregation pheromone, verbenone, for their ability to disrupt attack by the mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae), on lodgepole pine, Pinus contorta Dougl. ex Loud. var. latifolia Engel. Preliminary experiments led to a refined NHV blend [benzyl alcohol, guaiacol, benzaldehyde, nonanal, salicylaldehyde, and conophthorin] and a refined GLV blend [(Z)-3-hexen-1-ol and (E)-2-hexen-1-ol]. In a 20-replicate experiment, NHV and GLV groups both singly, and verbenone alone, significantly reduced MPB mass attack on pheromone-baited trees and on trees within 5 m of the pheromone-baited trees. Both blends in combination with verbenone reduced the number of mass attacked, baited trees to three out of 20 compared to 20 out of 20 of the baited controls. Each binary combination was also effective at reducing mass attack. In these experiments, all tested repellents were released from devices stapled to trees at the same point as the pheromone bait, suggesting that the repellency could have been to a point source, rather than to the whole tree. Therefore, in two further experiments bands of release devices were wrapped around the treated trees and the pheromone bait was removed from the treated trees. In one experiment, when the aggregation pheromone bait was suspended between pairs of trees treated with the NHV blend plus GLV blend plus verbenone, only three out of 25 treated pairs had mass attack on at least one member of the pair. In the other 60-replicate experiment, with no pheromone baits present, attack occurred on 13 untreated and 11 banded trees, all in the path of a large advancing infestation. However, the mean attack density on the banded trees was significantly reduced to a level below the 40 attacks m^–2 of bark surface required to kill a healthy lodgepole pine. As a result of these experiments, operational trials are recommended.     

Inhibition of Predator Attraction to Kairomones by Non-Host Plant Volatiles for Herbivores: A Bypass-Trophic Signal

Background

Insect predators and parasitoids exploit attractive chemical signals from lower trophic levels as kairomones to locate their herbivore prey and hosts. We hypothesized that specific chemical cues from prey non-hosts and non-habitats, which are not part of the trophic chain, are also recognized by predators and would inhibit attraction to the host/prey kairomone signals. To test our hypothesis, we studied the olfactory physiology and behavior of a predaceous beetle, Thanasimus formicarius (L.) (Coleoptera: Cleridae), in relation to specific angiosperm plant volatiles, which are non-host volatiles (NHV) for its conifer-feeding bark beetle prey.

Methodology/Principal Findings

Olfactory detection in the clerid was confirmed by gas chromatography coupled to electroantennographic detection (GC-EAD) for a subset of NHV components. Among NHV, we identified two strongly antennally active molecules, 3-octanol and 1-octen-3-ol. We tested the potential inhibition of the combination of these two NHV on the walking and flight responses of the clerid to known kairomonal attractants such as synthetic mixtures of bark beetle (Ips spp.) aggregation pheromone components (cis-verbenol, ipsdienol, and E-myrcenol) combined with conifer (Picea and Pinus spp.) monoterpenes (α-pinene, terpinolene, and Δ³-carene). There was a strong inhibitory effect, both in the laboratory (effect size d = −3.2, walking bioassay) and in the field (d = −1.0, flight trapping). This is the first report of combining antennal detection (GC-EAD) and behavioral responses to identify semiochemical molecules that bypass the trophic system, signaling habitat information rather than food related information.

Conclusions/Significance

Our results, along with recent reports on hymenopteran parasitoids and coleopteran predators, suggest that some NHV chemicals for herbivores are part of specific behavioral signals for the higher trophic level and not part of a background noise. Such bypass-trophic signals could be of general importance for third trophic level players in avoiding unsuitable habitats with non-host plants of their prey.     

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).     

Effect of different semiochemicals blends on spruce bark beetle,Ips typographus (Coleoptera: Scolytidae)

The spruce bark beetle, Ips typographus, is a recent new introduction to the Qilian Mountains of China. An outbreak of these beetles has infested over 0.03 million hectares of spruce forests in this area. Although primary attraction to volatiles has been clearly demonstrated for I. typographus, the existence and role of attraction to insect‐produced pheromones have been widely debated. Currently, commercial lures for I. typographus include only the volatiles ipsdienol, cis‐verbenol, trans‐verbenol, 2‐methyl‐3‐buten‐2‐ol and 2‐phenylethanol in Europe. Several potential pheromone candidates have been identified for I. typographus. Our GC–MS and GC–FID analyses volatiles from hindgut extracts of I. typographus in different attack phases demonstrated that the 2‐methyl‐3‐buten‐2‐ol, ipsdienol, cis‐verbenol and trans‐verbenol as major hindgut components, and ipsenol, 2‐phenylethanol, trans‐ myrtenol and verbenone as minor components. We tested various combinations of semiochemical candidates, to determine an optimal blend. Our results suggest that addition of 2‐methyl‐3‐buten‐2‐ol to either ipsenol alone, or to blends of ipsenol and other semiochemical candidates, significantly enhanced attraction of I. typographus. Therefore, a simple lure consisting of ipsenol and 2‐methyl‐3‐buten‐2‐ol would be an optimal blend of I. typographus in the Qilian Mountains, China. We conclude that this optimal semiochemical blend may provide an effective biological pest control method for use in forest ecosystem against I. typographus.     

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.     

Ophiostomatoid fungi can emit the bark beetle pheromone verbenone and other semiochemicals in media amended with various pine chemicals and beetle-released compounds

Fungal volatile compounds can mediate fungal-insect interactions. Whether fungi can emit insect pheromones and how volatile chemicals change in response to chemicals the fungi naturally encounter is poorly understood. We analyzed volatiles emitted by Grosmannia clavigera (symbiont of the mountain pine beetle) and Ophiostoma ips (symbiont of the pine engraver beetle) growing in liquid media amended with compounds that the fungi naturally encounter: (−)-α-pinene, (+)-α-pinene, (−)-trans-verbenol, verbenone, or ipsdienol. Nine volatile compounds were identified among the fungal and amendment treatments. Volatiles qualitatively and quantitatively differed between fungal species and among amendment treatments. The bark beetle anti-aggregation pheromone (−)-verbenone was detected from both fungi growing in (−)-trans-verbenol-amended media. G. clavigera and O. ips can emit beetle pheromones and other beetle semiochemicals, suggesting that ophiostomatoid fungi could contribute to the chemical ecology of bark beetles. However, such contributions could be modulated by the presence of other environmental chemicals.     

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.     

Functional investigation of monoterpenes for improved understanding of the relationship between hosts and bark beetles

Spruce bark beetle (Ips typographus L.) is the most destructive insect pest of spruce forests in Eurasia. However, contact toxicity, in vivo metabolism, and ecological functions of host monoterpenes are poorly understood at the spruce tree–bark beetle–predator tritrophic level. Spruce monoterpenes including S-(–)-α-pinene, R-(+)-α-pinene, and myrcene showed contact toxicity to I. typographus, with LD₅₀ values ranging from 22–32 μg/mg. When topically treated with S-(–)-α-pinene or R-(+)-α-pinene, the amounts of volatile metabolites, including 4S-(–)-cis-verbenol, 4S-(+)-/4R-(–)-trans-verbenol, R-(+)-/S-(–)-verbenone and 1R-(–)-/1S-(+)-myrtenol, in the hindgut extracts of I. typographus varied significantly between sexes, and their quality (enantiomeric composition) varied significantly with the chirality of α-pinene. More importantly, S-(–)-α-pinene induced male adults to produce large amounts of 4S-(–)-cis-verbenol and S-(–)-verbenone. When topically treated with myrcene, the expected semiochemicals such as E-myrcenol, ipsenol and ipsdienol were not detected in the beetle hindguts, indicating that the pheromone biosynthetic system of I. typographus does not participate in the metabolism of host myrcene. In trap tests, S-(–)-α-pinene and R-(+)-α-pinene increased the catches of I. typographus and its predator Thanasimus substriatus in pheromone-baited traps, whereas myrcene exhibited a strong repellent (or inhibitory) effect on I. typographus but not on its predator. I. typographus seems to adopt different ecological strategies (e.g. avoidance to myrcene and preference for α-pinene) to adapt to and tolerate different host monoterpenes. Extensive investigation of these monoterpenes will help us understand their roles in manipulating the arms race between host trees and bark beetles, and potentially improve the efficacy of controlling I. typographus via the push-pull strategy using host kairomones.     

Olfactory recognition and behavioural avoidance of angiosperm nonhost volatiles by conifer-inhabiting bark beetles

Abstract 1 When searching for suitable hosts in flight, especially in mixed forests, conifer‐inhabiting bark beetles will encounter not only suitable host trees and their odours, but also unsuitable hosts and nonhost trees. Rejection of these trees could be based on an imbalance of certain host characteristics and/or a negative response to some nonhost stimuli, such as nonhost volatiles (NHV). 2 Recent electrophysiological and behavioural studies clearly indicate that conifer‐inhabiting bark beetles are not only able to recognize, but also to avoid, nonhost habitats or trees by olfactory means. Green leaf volatiles (GLV), especially C₆‐alcohols, from the leaves (and partly from bark) of nonhost angiosperm trees, may represent nonhost odour signals at the habitat level. Specific bark volatiles such as trans‐conophthorin, C₈‐alcohols, and some aromatic compounds, may indicate nonhosts at the tree species level. Flying bark beetles are also capable of determining whether a possible host is unsuitable by reacting to signals from conspecifics or sympatric heterospecifics that indicate old or colonized host tree individuals. 3 Combined NHV signals in blends showed both redundancy and synergism in their inhibitory effects. The coexistence of redundancy and synergism in negative NHV signals may indicate different functional levels (nonhost habitats, species, and unsuitable hosts) in the host selection process. Combinations of NHV and verbenone significantly reduced the number of mass attacked host trees or logs on several economically important species (e.g. Dendroctonus ponderosae, Ips typographus, and I. sexdentatus). 4 We suggest a semiochemical‐diversity hypothesis, based on the inhibition by NHV of bark beetle host‐location, which might partly explain the lower outbreak rates of forest insects in mixed forests. This ‘semiochemical‐diversity hypothesis’ would provide new support to the general ‘stability‐diversity hypothesis’. 5 Natural selection appears to have caused conifer‐inhabiting bark beetles to evolve several olfactory mechanisms for finding their hosts and avoiding unsuitable hosts and nonhost species. NHV and unsuitable host signals have potential for use in protecting trees from attack. The use of these signals may be facilitated by the fact that their combination has an active inhibition radius of several metres in trap test, and by the observation of area effects for several trees near inhibitor soruces in tree protection experiments. Furthermore, incorporation of negative signals (such as NHV and verbenone) and pheromone‐based mass‐trapping in a ‘push–pull’ fashion may significantly increase the options for control against outbreaks of conifer‐inhabiting bark beetles, especially in high risk areas.     

Specialization of the olfactory receptor cells in the bark beetleIps typographus and its predatorThanasimus formicarius to bark beetle pheromones and host tree volatiles

Summary Olfactory receptor cells of the spruce bark beetle,Ips typographus, and its predator, the clerid beetleThanasimus formicarius, were studied using electrophysiological techniques. Recordings were made of nerve impulses from single cells and of the summated receptor potential (electroantennogram).Information from bark beetle pheromones and host volatiles is detected by separate olfactory receptor cells inI. typographus. Those which detected bark beetle pheromones responded to only one key substance. Some receptor cells which responded to spruce bark volatiles were strongly activated by one of the synthetic host compounds tested. However, too few host compounds were tested to reach definite conclusions about the specialization of host odour cells. T. formicarius has evolved olfactory receptor cells for bark beetle pheromones. These have similar specificities (specialist types) to those of the bark beetles. Furthermore, the predator has olfactory receptor cells for many bark beetle pheromones. This indicates thatT. formicarius is able to detect and discriminate between many bark beetle species. No significant differences were found between prey and predator cells which responded to host volatiles.     

Development of lady beetle attractants from floral volatiles and other semiochemicals for the biological control of aphids

Aphids are among the most destructive phytophagous pests of host plants, because of their rapid reproduction, parthenogenesis, extensive crop damage, and the transmission of many plant viruses. Since lady beetles are important predatory natural enemies of aphids, developing lady beetle attractants to increase their field abundance is vital for aphid control. Floral volatiles and other semiochemicals are reportedly attractive to lady beetles. In this research, a total of 58 floral volatiles were tested by Y-tube olfactometer assays, among which 29 were highly attractive to both Harmonia axyridis (Coleoptera: Coccinellidae) and Coccinella septempunctata (Coleoptera: Coccinellidae). Meanwhile, the results of wind tunnel trials showed that only isoamyl acetate, α-humulene, trans-3-hexen-1-ol, methyl salicylate, and β-pinene lure these two species. Thereafter, 15 semiochemicals from pests, natural enemies, and pest-infested crops were mixed with the selected floral volatiles, to determine optimum formulations for attracting lady beetles through wind tunnels and further field trials. Eventually, formulas (1) α-humulene: β-pinene: methyl salicylate: trans-3-hexen-1-ol = 1:3:3:10; (5) α-humulene: β-pinene: methyl salicylate:1-nonanal = 1:3:3:10; (8) α-humulene: β-pinene: methyl salicylate: indole = 1:3:3:10 (1, 5, and 8 are labels used for the various formulations in field trials) were successfully verified to be attractive to lady beetles in both pumpkin and wheat fields. These formulations will be of great significance in developing integrated pest management strategies for aphid control.     

Electroantennogram responses of the Colorado beetle, Leptinotarsa decemlineata, to plant volatiles

Electroantennogram responses of Colorado beetles were recorded to 53 plant volatiles including isomers. The system of antennal olfactory receptors is selective, even at high doses several compounds cause fairly small responses. Diminishing the concentration to a moderate stimulus strength reduces the number of perceptible chemicals. Distinct electroantennogram responses are obtained to a group of closely related components, namely the general green leaf volatiles trans-2-hexen-1-ol, cis-3-hexen-1-ol, hexanol-1, trans-2-hexenal, hexanal and cis-3-hexenyl-acetate, and to isomers such as trans-3-hexen-1-ol and cis-2-hexen-1-ol. The threshold concentration of the most effective compound, trans-2-hexen-1-ol is 1.2×10⁸ molecules per ml of air. The antennal olfactory receptors of the Colorado beetle are sensitively tuned to the perception of these general green leaf volatiles. As olfactory receptors of a number of phytophagous insects have been reported to respond to these components, this volatile complex probably plays a part in the host selection behaviour of various phytophagous insects.

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Résumé Les électroantennogrammes de Leptinotarsa decemlineata en présence de 53 substances volatiles (y compris des isomères) ont été enregistrés. Le système des récepteurs olfactifs antennaires est sélectif, même à des doses élevées plusieurs composés ne provoquent que d'assez faibles réponses. La diminution de la concentration jusqu'à une puissance stimulante modérée réduit le nombre de substances perçues. Des électroantennogrammes différents ont été obtenus pour un groupe de composés très voisins, à savoir les substances volatiles de feuilles vertes: trans-2-hexen-1-ol, cis-3-hexen-1-ol, hexanol-1, trans-2-hexenal et cis-3-hexenyl-acetate, et aux isomères tels que trans-3-hexen-1-ol et cis-2-hexen-l-ol. La concentration seuil du composé le plus efficace, trans-2-hexen-1-ol, est de 1,2×10⁸ molécules par ml d'air. Les récepteurs olfactifs antennaires du Doryphore sont sensoriellement ajustés à la perception de ces substances volatiles générales des feuilles vertes. Comme les récepteurs olfactifs de nombreux insectes phytophages ont été signalés comme répondant à ces composés, ce complexe volatile joue probablement un rôle dans le comportement de sélection de l'hôte par différents insectes phytophages.

     

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.     

Fungal,host and non-host volatiles modify attraction of the walnut twig beetle,Pityophthorus juglandis,to pheromone lures

1. Thousand Cankers Disease (TCD) of walnut trees is caused by the pathogenic fungus Geosmithia morbida vectored by the walnut twig beetle (WTB) Pityophthorus juglandis. Monitoring efforts for WTB rely on pheromone-baited traps, but lures are likely effective at attracting beetles only over short distances. Fungal-derived kairomones may increase the efficacy of current lures, while additional volatiles may repel beetles from valuable trees.
2. The objective of this study was to determine the extent to which fungal, host and non-host volatiles modify the attraction of WTB to pheromone-baited traps. A trapping study that combined fungal, host-associated and non-host compounds with WTB-pheromone lures was conducted over three years in black walnut plantations experiencing a TCD outbreak in Walla Walla, WA.
3. Traps baited with pheromone and G. morbida volatiles (i.e., isoamyl and isobutyl alcohol) consistently attracted more WTB, while other fungal volatiles inconsistently increased attraction compared to those baited with pheromone lure alone. This is the first field study that demonstrates fungal volatiles can increase the attraction of a bark beetle to its pheromone in a hardwood system.
4. One fungal (benzyl alcohol) and two additional volatiles (limonene, piperitone) repelled WTB from pheromone-baited traps. Although limonene is known to repel WTB, this is the first demonstration that benzyl alcohol and piperitone repel a bark beetle.
5. Fungal volatiles may increase the efficacy of monitoring efforts and may play an important role in management tactics for WTB, especially in detecting the introduction and establishment of nascent populations and protecting trees from colonizing beetles.

     

Volatile Flavor Components of Kumazasa (Sasa albo-marginata)

The volatile flavor components of Kumazasa (Sasa albo-marginata) were studied by headspace and steam distillation analyses. Thirty nine and 90 components were identified in the headspace and steam distillation concentrate respectively by GC and GC-MS. The identified components include 7 hydrocarbons, 23 alcohols, 14 aldehydes, 8 ketones, 17 phenols and 14 acids.

The components which are believed to contribute to the characteristic flavor of Kumazasa are deduced to be: 1-penten-3-ol, trans-2-hexenal, 1-hexanol, cis-3-hexen-1-ol, cyclohexanol, α-ter-pineol, 4-octanolide and β-ionone.     

Enhanced attraction of Plutella xylostella (Lepidoptera: Plutellidae) to pheromone-baited traps with the addition of green leaf volatiles

Diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is one of the most serious pests of Brassicaceae crops worldwide. Electrophysiological and behavioral responses of P. xylostella to green leaf volatiles (GLVs) alone or together with its female sex pheromone were investigated in laboratory and field. GLVs 1-hexanol and (Z)-3-hexen-1-ol elicited strong electroantennographic responses from unmated male and female P. xylostella, whereas (Z)-3-hexenyl acetate only produced a relatively weak response. The behavioral responses of unmated moths to GLVs were further tested in Y-tube olfactometer experiments. (E)-2-Hexenal, (Z)-3-hexen-1-ol, and (Z)-3-hexenyl acetate induced attraction of males, reaching up to 50%, significantly higher than the response to the unbaited control arm. In field experiments conducted in 2008 and 2009, significantly more moths were captured in traps baited with synthetic sex pheromone with either (Z)-3-hexenyl acetate alone or a blend of (Z)-3-hexenyl acetate, (Z)-3-hexen-1-ol, and (E)-2-hexenal compared with sex pheromone alone and other blend mixtures. These results demonstrated that GLVs could be used to enhance the attraction of P. xylostella males to sex pheromone-baited traps.     

Discovery and characterization of chemical signals for citrus root weevil, Diaprepes abbreviatus

The tropical root weevil Diaprepes abbreviatus (L. 1758) (Coleoptera: Curculionidae) is a polyphagous insect from the Caribbean Islands and an invasive insect in the southern part of the United States where it is pest of citrus crops and ornamental trees. Adults feed upon foliage where aggregation, mating and oviposition take place. Here, the headspace volatiles from Citrus macrophylla Wester (Rutaceae), D. abbreviatus adults feeding on this plant, adults alone and adult feces, were collected by aeration and solid-phase microextraction (SPME) for analysis by gas chromatography-linked mass spectrometry (GC-MS). Electrophysiological responses of weevil antennal receptors to volatile headspace extracts and synthetic analogues were recorded by gas chromatography-linked electroantennographic detection (GC-EAD) and electroantennograms (EAGs). Antennal responses were recorded to the monoterpenes (R)-(−)-linalool, citronellal, nerol, citral, and geraniol; all present in the headspace of C. macrophylla. Antennal responses were also recorded to carvacrol, present in the headspace of adults and adult feces. The green leaf volatiles cis-3-hexen-1-ol and trans-2-hexen-1-ol, produced by other host plants, elicited reliable responses on the D. abbreviatus antenna. When comparing EAGs between (±)-linalool and (R)-(−)-linalool, no significant difference was found; responses to (R)-(+)-citronellal were larger than for (S)-(−)-citronellal. Among the individual compounds and blends tested using an open T-track dual choice olfactometer, only the blend of (±)-linalool, cis-3-hexen-1-ol and carvacrol (source dose 25:25:2.5 μg) elicited significant attraction of females, the same blend was repellent for males. The biologically active compounds found here likely play a role in host finding by D. abbreviatus and other interactions of the insect with its hostplant. Handling editor: Sam Cook     

Oriented responses of grapevine moth larvae Lobesia botrana to volatiles from host plants and an artificial diet on a locomotion compensator

Larvae of the grapevine moth Lobesia botrana (Lepidoptera: Tortricidae) are a major pest of vine, Vitis vinifera. As larvae have limited energy reserves and are in danger of desiccation and predation an efficient response to plant volatiles that would guide them to food and shelter could be expected. The responses of starved 2nd or 3rd instar larvae to volatile emissions from their artificial diet and to single host plant volatiles were recorded on a locomotion compensator. Test products were added to an air stream passing over the 30 cm diameter servosphere. The larvae showed non-directed walks of low rectitude in the air stream alone but changed to goal-oriented upwind displacement characterised by relatively straight tracks when the odour of the artificial diet and vapours of methyl salicylate, 1-hexanol, (Z)-3-hexen-1-ol, terpinen-4-ol, 1-octen-3-ol, (E)-4,8-dimethyl-1,3,7-nonatriene and (Z)-3-hexenyl acetate were added to the air stream. This chemoanemotactic targeted displacement illustrates appetence for certain volatile cues from food by starved Lobesia larvae. Analysis of the larval behaviour indicates dose dependent responses to some of the host plant volatiles tested with a response to methyl salicylate already visible at 1 ng, the lowest source dose tested. These behavioural responses show that Lobesia larvae can efficiently locate mixtures of volatile products released by food sources as well as single volatile constituents of their host plants. Such goal-oriented responses with shorter travel time and reduced energy loss are probably of importance for larval survival as it decreases the time they are exposed to biotic and abiotic hazards.