Oviposition and electroantennogram responses of Dioryctria abietivorella (Lepidoptera: Pyralidae) elicited by monoterpenes and enantiomers from eastern white pine

Volatile emissions from twigs of eastern white pine, Pinus strobus L., stimulated oviposition by Dioryctria abietivorella (Grote) in laboratory bioassays. Chemical identification and percentage composition of monoterpenes emitted by twigs were determined by capillary GC and GC/MS analysis of headspace and of volatiles entrained on Porapak Q. Enantiomeric excess of optically active monoterpenes was determined by capillary GC analysis with a beta-cyclodextrin chiral column. Four of the six most abundant monoterpenes identified in twig volatiles elicited a significant oviposition response. Myrcene and car-3-ene [predominantly the (+)-enantiomer] were the most active compounds in both electroantennogram (EAG) and oviposition bioassays. In contrast, (-)-limonene elicited a significant oviposition response but was the least stimulating monoterpene in EAG tests. Female EAG responses to monoterpenes generally increased with age and mating and were larger than those from males of the same age.