Electrophysiological Responses of the Beech Leaf-Mining Weevil,Orchestes fagi, to Seasonally-Variant Volatile Organic Compounds Emitted by American Beech,Fagus grandifolia

The beech leaf-mining weevil,Orchestes fagi, is a common pest of European beech,Fagus sylvatica, and has recently become established in Nova Scotia, Canada where it similarly infests American beech,F. grandifolia. We collected volatile organic compounds (VOCs) emitted byF. grandifolialeaves at five developmental stages over one growing season and simultaneously analyzed them for volatile emissions andO. fagiantennal response using gas chromatography-electroantennographic detection (GC-EAD). Volatile profiles changed significantly throughout the growing season, shifting from primarily beta-caryophyllene, methyl jasmonate, and simple monoterpene emissions to dominance of the bicyclic monoterpene sabinene during maturity. Two VOCs dominant during bud burst, (R)-(+)-limonene and geranyl-p-cymene, may be of biological relevance due to the highly specific oviposition period ofO. fagiat this stage though antennal responses were inconclusive. Senescence showed a decrease in blend complexity with an increase in (Z)-3-hexenyl acetate and (Z)-3-hexen-1-ol as well as a resurgence of alpha-terpinene and geranyl-p-cymene. We present a novel electroantennal preparation forO. fagi. Antennae of both male and femaleO. fagiresponded to the majority of detectable peaks for host volatiles presented via GC-EAD. Females displayed greater overall sensitivities and less specificity to host volatiles and it is hypothesized that this translates to more generalist olfaction than males. It is clear that olfactory cues are important physiologically though their implications on behaviour are still unknown. The results presented in this study provide a baseline and tools on which to connect the complex and highly time-specific phenology of bothF. grandifoliaand the destructive pestO. fagithrough which olfactory-based lures can be investigated for monitoring systems.