DIFFERENCES IN VOLATILITY AMONG TEST COMPOUNDS INFLUENCEELECTROANTENNOGRAM RESPONSES OF DIORYCTRIA ABIETIVORELLA (LEPIDOPTERA:PYRALIDAE).

Eckehard G. Brockerhoff¹ and G.G. Grant^2
1Faculty of Forestry, University of Toronto, 33 WillcocksSt., Toronto, ON, M5S 3B3
²Canadian Forest Service, P.O. Box 490, Sault Ste. Marie,ON, P6A 5M7

Olfactory stimuli for EAG bioassays are commonly evaporated from testsolutions applied to a filter paper substrate. Because the volatility oftest compounds can vary widely, the actual amounts of stimuli deliveredto the antennae may differ and potentially lead to false conclusions aboutantennal sensitivity. To examine the impact of this bias, we evaluatedthe EAG responses of female fir coneworm, Dioryctria abietivorella,to green leaf volatiles, monoterpenes, and a sesquiterpene. Stimuli weregenerated either from equimolar (‘uncorrected’) solutions or from ‘corrected’solutions that were adjusted to yield similar concentrations in the airpuffed over antennae. We describe a GC method used to determine the appropriateconcentrations in the air. When uncorrected solutions were tested, thetwo most volatile compounds, (E)-2-hexenal and (E)-3-hexenyl acetate, elicitedsignificantly larger EAG responses than the terpenes. The ranking of theseresponses changed when corrected concentrations were tested: (E)-2-hexenalelicited significantly smaller EAGs than (-)-?-pinene, (-)-limonene,and (E)-3-hexenyl acetate. On the other hand, the correction of concentrationshad no effect on the ranking of responses to the monoterpenes and the sesquiterpene,(-)-trans-caryophyllene, relative to each other.