Male-Produced Aggregation Pheromone Compounds from the Eggplant Flea Beetle ( Epitrix fuscula ): Identification, Synthesis, and Field Biossays

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 (2 E ,4 E ,6 Z )-2,4,6-nonatrienal ( 1 ) and (2 E ,4 E ,6 E )-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.