Male-Produced Aggregation Pheromone Compounds from the Eggplant Flea Beetle (Epitrix fuscula): Identification, Synthesis, and Field Biossays
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Volatiles from the eggplant flea beetle, Epitrix fuscula Crotch (Coleoptera: Chrysomelidae), feeding on host foliage, were investigated. Six male-specific compounds were detected and were identified through the use of mass spectrometry, nuclear magnetic resonance (NMR) spectrometry, chiral and achiral gas chromatography, high-performance liquid chromatography, electrophysiology (gas chromatography-electroantennography, GC–EAD), and microchemical tests. The two most abundant of the six compounds were (2E,4E,6Z)-2,4,6-nonatrienal (1) and (2E,4E,6E)-2,4,6-nonatrienal (2). The other four compounds, present in minor amounts, were identified as himachalene sesquiterpenes; two of these, 3 and 4, were hydrocarbons and two, 5 and 6, were alcohols. All four sesquiterpenes were previously encountered from male flea beetles of Aphthona spp. and Phyllotreta cruciferae. Synthetic 1 and 2 matched the natural products by GC retention times, mass spectra, and NMR spectra. Sesquiterpenes 3–6 similarly matched synthetic standards and natural samples from the previously studied species in all ways, including chirality. Both natural and synthetic 1 and 2 gave positive GC–EAD responses, as did sesquiterpenes 3, 5, and 6. Field trials were conducted with a mixture of 1 and 2, and the baited traps were significantly more attractive than control traps to both male and female E. fuscula. The E. fuscula pheromone has potential for monitoring or controlling these pests in eggplants.
Key wordsFlea beetles Epitrix fuscula Coleoptera Chrysomelidae aggregation pheromone (2E,4E,6Z)-2,4,6-nonatrienal (2E,4E,6E)-2,4,6-nonatrienal sesquiterpene himachalene field trials
We are grateful to Anne Patterson of Living Earth Farm for assistance and to Richard Stessman and Nathan Deppe for growing and tending eggplants at the NCAUR garden plots. David Weisleder and Karl Vermillion of NCAUR acquired the NMR spectra. Dr. Alexander S. Konstantinov (Chrysomelidae), Systematic Entomology Laboratory, Agriculture Research Service, US Department of Agriculture, provided insect identification.
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