Gary G. Grant

Behavioral and electrophysiological responses of the emerald ash borer, Agrilus planipennis, to induced volatiles of Manchurian ash, Fraxinus mandshurica

Summary.We investigated the volatile emissions of Manchurian ash seedlings, Fraxinus mandshurica, in response to feeding by the emerald ash borer, Agrilus planipennis, and to exogenous application of methyl jasmonate (MeJA). Feeding damage by adult A. planipennis and MeJA treatment increased volatile emissions compared to unexposed controls. Although the same compounds were emitted from plants damaged by beetles and treated with MeJA, quantitative differences were found in the amounts of emissions for individual compounds. Adult virgin female A. planipennis were similarly attracted to volatiles from plants damaged by beetles and those treated with MeJA in olfactometer bioassays; males did not respond significantly to the same volatiles. Coupled gas chromatographic-electroantennogram detection (GC-EAD) revealed at least 16 antennally-active compounds from F. mandshurica, including: hexanal, (E)-2-hexenal, (Z)-3-hexen-1-ol, 3-methyl-butylaldoxime, 2-methyl-butylaldoxime, (Z)-3-hexen-1-yl acetate, hexyl acetate, (E)-β-ocimene, linalool, 4,8-dimethyl-1,3,7-nonatriene, and E,E-α-farnesene. Electroantennogram (EAG) dose–response curves using synthetic compounds revealed that females had a stronger EAG response to linalool than males; and male responses were greater to: hexanal, (E)-2-hexenal, (Z)-3-hexen-1-ol, 3-methyl-butylaldoxime, 2-methyl-butylaldoxime, and hexyl acetate. These results suggest that females may use induced volatiles in long-range host finding, while their role for males is unclear. If attraction of females to these volatiles in an olfactometer is upheld by field experiments, host plant volatiles may find practical application in detection and monitoring of A. planipennis populations.

Electrophysiological Response and Attraction of Emerald Ash Borer to Green Leaf Volatiles (GLVs) Emitted by Host Foliage

Green leaf volatiles (GLVs) function as host attractants, pheromone synergists, or sexual kairomones for a number of coleopteran folivores. Hence, we focused on host GLVs to determine if they were attractive to adults of the emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae), which feeds on ash (Fraxinus) foliage. Eight GLVs were identified by chromatography-electroantennogram (GC) and GC-mass spectrometry in foliar headspace volatiles collected in traps containing Super-Q from white ash, Fraxinus americana, and green ash, Fraxinus pennsylvanica, trees. GLVs in the aeration extracts elicited antennal responses from both male and female adults in gas chromatography-electroantennogram detection bioassays. Male antennae were more responsive than female antennae and showed the strongest response to (Z)-3-hexenol. Six field experiments were conducted in Canada and the USA from 2004 to 2006 to evaluate the attractiveness of candidate GLVs, in various lure combinations and dosages. Field experiments demonstrated that lures containing (Z)-3-hexenol were the most effective in increasing trap catch when placed on purple traps in open areas or along the edges of woodlots containing ash. Lures with (Z)-3-hexenol were more attractive to males than females, and dosage may be a factor determining its effectiveness.

Evidence for a Volatile Pheromone in Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) that Increases Attraction to a Host Foliar Volatile

ABSTRACT Analysis by gas chromatography/mass spectrometry (GC/MS) of volatiles from virgin female emerald ash borer, Agrilus planipennis Fairmaire confirmed the emission of (3Z)-lactone [(3Z)-dodecen-12-olide] but not its geometric isomer, (3E)-lactone [(3E)-dodecen-12-olide]. Gas chromatographic/electroantennographic (GC/EAD) analysis of synthetic (3Z)-lactone, which contained 10% (3E) -lactone, showed a strong response of male and female antennae to both isomers. EAG analysis with 0.01 - to100-µg dosages showed a positive dose response, with females giving significantly higher responses than males. In field experiments with sticky purple prism traps, neither lactone isomer affected catches when combined with ash foliar or cortical volatiles (green leaf volatiles or Phoebe oil, respectively). However, on green prism traps, the (3Z)-lactone significantly increased capture of male A. planipennis when traps were deployed in the canopy. Captures of males on traps with both (3E)-lactone and (3Z)-hexenol or with (3Z)-lactone and (3Z)-hexenol were increased by 45–100%, respectively, compared with traps baited with just (3Z)-hexenol. In olfactometer bioassays, males were significantly attracted to (3E) -lactone, but not the (3Z) -lactone or a 60:40 (3E): (3Z) blend. The combination of either (3E)- or (3Z)-lactone with Phoebe oil was not significantly attractive to males. Males were highly attracted to (3Z)-hexenol and the (3Z)-lactone + (3Z)-hexenol combination, providing support for the field trapping results. These data are the first to demonstrate increased attraction with a combination of a pheromone and a green leaf volatile in a Buprestid species.

(3Z,6Z,9Z,12Z,15Z)-Pentacosapentaene, a Key Pheromone Component of the Fir Coneworm Moth, Dioryctria abietivorella

The sex pheromone of the fir coneworm moth consists of a blend of (3Z,6Z,9Z,12Z,15Z)-pentacosapentaene and (9Z,11E)-tetradecadienyl acetate. Analogous blends of polyunsaturated, long-chain hydrocarbons with much shorter chain aldehydes or alcohols recently have been discovered in three other moth species in the superfamily Pyraloidea. These combinations of components from two distinct structural classes may represent an important and widespread new pheromone blend motif within the Lepidoptera.

Comparison of Male and Female Emerald Ash Borer (Coleoptera: Buprestidae) Responses to Phoebe Oil and (Z)-3-Hexenol Lures in Light Green Prism Traps

ABSTRACT We conducted trapping experiments for the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) in Michigan, USA, and Ontario, Canada, to compare unbaited light green sticky prism traps with traps baited with phoebe oil, (Z)-3-hexenol (Z3-6:OH), or blends of other green leaf volatiles (GLVs) with Z3-6:OH. Traps were placed in the lower canopy of ash trees (Fraxinus spp.). Catches with Z3-6:OH—baited traps showed a significant male bias and these traps caught significantly more males than the unbaited controls at both sites. They were also superior to phoebe oil-baited traps and those baited with GLV blends. Catches with phoebe oil showed a significant female bias but there was no difference in the number of females captured between traps baited with phoebe oil or Z3-6:OH lures. Catches were analyzed at regular time intervals to examine the response of A. planipennis to the lures over the course of the flight season. Z3-6:OH—baited traps consistently caught more males than the controls at each interval throughout the flight season. Catches of females with Z3-6:OH and phoebe oil were significantly better than the controls early in the flight season but declined to control levels by midseason. Our results suggest that Z3-6:OH—baited green traps placed in the ash canopy would be a superior lure for detecting and monitoring A. planipennis throughout the flight season.

(Z)6, (E)8-Heneicosadien-11-One: Synergistic Sex Pheromone Component of Douglas-Fir Tussock Moth, Orgyia pseudotsugata (McDunnough) (Lepidoptera: Lymantriidae)

Three candidate sex pheromone components, (Z)6,(Z)9-, (Z)6,(E)8-, and (Z)6,(E)9-heneicosadien-11-one (Z6Z9, Z6E8, and Z6E9) were identified in pheromone gland extracts of female Douglas-fir tussock moths (DFTM), Orgyia pseudotsugata (McDunnough). Their occurrence in subnanogram quantities in extracts and structural conversion during analytical procedures and bioassays complicated chemical identifications. Complete identification required comparative analyses of stereoselectively synthesized and female-produced dienones by coupled gas chromatographic–electroantennographic detection (GC-EAD), high-performance liquid chromatography (HPLC) and coupled GC–mass spectrometry (MS). Determination of the pheromone component was contingent upon an experimental design that minimized structural rearrangement of dienones before and during the field test. In a 40-min field experiment, acetonitrile solutions of each of the above dienones were carried on Dry Ice to traps and were syringed onto cotton release devices below trap lids. In combination with the previously known sex pheromone component of DFTM, (Z)6-heneicosen-11-one (Z6), Z6E8 was the only synergistic dienone and the mixture was highly attractive. Because Z6 by itself attracts seven species of tussock moths (two sympatric with DFTM), a blend of Z6 and Z6E8 may impart specificity to DFTM pheromone communication. In commercial lures, this binary blend may facilitate species-specific, sensitive monitoring and efficacious control by mating disruption of this important forest defoliator.

(Z,Z)-6,9-Heneicosadien-11-One, Labile Sex Pheromone of the Whitemarked Tussock Moth, Orgyia leucostigma

The whitemarked tussock moth (WMTM), Orgyia leucostigma (J. E. Smith), is a major pest of coniferous and deciduous trees in eastern Canada. Chemical identification of its sex pheromone depended primarily on GC-EAD and HPLC analysis, with confirmation of behavioral activity by wind tunnel and field tests. We identified (Z,Z)-6,9-heneicosadien-11-one (Z,Z-6,9-ket) at 4–5 ng/female as the only essential sex pheromone component. Also detected in female extracts were (Z)-6-heneicosen-11-one (Z6-ket) at 2.5 ng/female, (Z,E)-6,8-heneicosadien-11-one (Z,E-6,8-ket) at about 0.5 ng/female, and a trace amount of (Z,E)-6,9-heneicosadien-11-one. Traps containing as little as 1 μg of Z,Z-6,9-ket attracted males at low population levels, indicating it is a potent sex attractant. Traps baited with Z6-ket attracted few males, and in wind-tunnel bioassays it was at least 100-fold less attractive to males than Z,Z-6,9-ket. No improvement in trap catch occurred with the addition of Z6-ket in various binary mixtures with Z,Z-6,9-ket, including the female ratio, and a ternary mixture of Z,Z-6,9-ket, Z6-ket, and Z,E-6,8-ket in the 9:5:1 ratio detected in females was no better than Z,Z-6,9-ket alone. We attribute the presence of Z,E-6,8-ket and Z,E-6,9-ket in female extracts to the spontaneous and rapid stereospecific isomerization of Z,Z-6,9-ket at room temperature. Male flight began at sunset but peaked during the second half of the night.

Oviposition response of spruce budworm (Lepidoptera: Tortricidae) to host terpenes and green-leaf volatiles

A dual-choice behavioral bioassay and gas chromatography – electroantennogram detection (GC–EAD) were used to determine the effect of host terpenes and nonhost green-leaf volatiles (GLVs) on the oviposition preference of the spruce budworm, Choristoneura fumiferana (Clemens). Some emphasis was placed on assessing the ability of females to distinguish between enantiomers of chiral monoterpenes because (+)-α-pinene but not (–)-α-pinene or (±)-α-pinene had been shown previously to promote oviposition. Headspace volatiles from white spruce, Picea glauca (Moench) Voss (Pinaceae), and balsam fir, Abies balsamea (L.) Mill. (Pinaceae), were sampled using solid-phase microextraction and identified by gas chromatography – mass spectrometry with the aid of a chiral column. Females deposited significantly more egg masses on filter paper substrate treated with host monoterpenes than on controls. Contrary to expectation, substrates treated with several GLVs were also preferred over the controls. None of the GLVs or terpenes was deterrent. Females showed no significant ability in either the behavioral or the GC– EAD bioassays to distinguish between enantiomers of selected chiral monoterpenes, including αpinene, in contrast to earlier findings. We conclude that host terpenes serve as general rather than host-specific oviposition stimuli for spruce budworm. Résumé—Un bioessai comportemental à deux choix et une technique GC–EAD (chromatographie en phase gazeuse et détection électro-antenno-graphique) nous ont servi à déterminer les effets des terpènes de l’hôte et des substances volatiles des feuilles vertes (GLV) ne provenant pas de l’hôte sur les préférences de ponte de la tordeuse des bourgeons de l’épinette, Choristoneura fumiferana (Clemens). Nous avons, de façon particulière, déterminé la capacité des femelles à distinguer entre les énantiomères des monoterpènes chiraux, puisqu’on a démontré antérieurement que la (+)-α-pinène favorise la ponte, ce qui n’est pas le cas de la (–)-α-pinène, ni de la (±)-α-pinène. Nous avons échantillonné à l’aide de SPME (micro-extraction en phase solide) et identifié par chromatographie en phase gazeuse et par spectrométrie de masse à l’aide d’une colonne chirale les substances volatiles dans l’espace supérieur immédiat émises par l’épinette blanche, Picea glauca (Moench) Voss (Pinaceae) et le sapin baumier, Abies balsamea (L.) Mill. (Pinaceae). Les femelles pondent significativement plus de masses d’oeufs sur un substrat de papier filtre traité avec les monoterpènes de l’hôte que sur les témoins. Contrairement à notre prévision, les substrats traités avec différents GLV sont aussi préférés aux témoins. Aucun des GLV et des terpènes n’est inhibiteur. Contrairement à des résultats antérieurs, les femelles ne montrent aucune aptitude significative, tant dans les tests comportementaux que dans les tests GC–EAD, à distinguer entre les énantiomères des monoterpènes chiraux sélectionnés, y compris de la α-pinène. Nous concluons que les terpènes de l’hôte servent de stimulus généraux de la ponte chez la tordeuse de bourgeons de l’épinette, plutôt que de stimulus spécifiques à l’hôte. [Traduit par la Rédaction]

(3Z,6Z,9Z,12Z,15Z)-Pentacosapentaene and (Z)-11-Hexadecenyl Acetate: Sex Attractant Blend for Dioryctria amatella (Lepidoptera: Pyralidae)

ABSTRACT In 2006–2008, we tested (3Z,6Z,9Z,12Z,15Z)-pentacosapentaene (pentaene) with the pheromone components (Z)-11-hexadecenyl acetate (Z11–16:Ac) and (Z)-9-tetradecenyl acetate (Z9–14:Ac), as sex attractants for four sympatric species of coneworms, Dioryctria Zeller (Lepidoptera: Pyralidae) in slash (Pinus elliottii Engelm.) and loblolly pine (Pinus taeda L.) seed orchards in Georgia and Louisiana, respectively. The addition of pentaene increased catches of male southern pine coneworm, Dioryctria amatella (Hulst), in wing traps baited with Z11–16:Ac, whereas catches of Dioryctria disclusa Heinrich in traps baited with Z9–14:Ac were unaffected by the addition of pentaene, The effect of pentaene on male Dioryctria merkeli Mutuura & Munroe was inconsistent. In 2006, pentaene seemed to inhibit attraction of D. merkeli to traps baited with Z9–14:Ac, whereas in a subsequent trial in 2008, moths were equally attracted to Z9–14:Ac with or without the pentaene. We caught too few Dioryctria clarioralis (Walker) in any experiment for meaningful analyses. Our field results with pentaene and the unresolved complexity of the taxonomy, ecology, and management of southern coneworms support the need for a comprehensive examination of the chemical ecology of Dioryctria spp.

(3Z,6Z,9Z,12Z,15Z)-Pentacosapentane and (9Z, 11E)-Tetradecadienyl Acetate: Attractant Lure Blend for Dioryctria ebeli (Lepidopterea: Pyralidae)

Feeding damage by larval coneworms (Lepidoptera: Pyralidae) on flowers and cones of pines can cause significant economic losses in pine seed orchards in the southern USA (Ebel et al. 1980, USDA Forest Service GTR SE-8, Asheville, NC). The south coastal coneworm, Dioryctria ebeli Mutuura & Monroe, is a common pest in seed orchards of slash pine (Pinus elliottii L.) in the coastal region of southeastern USA, particularly Florida (Ebel et al. 1980). With multiple generations per year, infestations of D. ebeli can be severe, especially in seed orchards infected by the southern pine cone rust, Cronartium strobilinum Hedgc. & Hahn (Merkel 1958, J. Forestry 56:651 ).