SPRING MIGRATION OF DAMSON-HOP APHID, PHORODON-HUMULI (HOMOPTERA, APHIDIDAE), AND SUMMER HOST PLANT-DERIVED SEMIOCHEMICALS RELEASED ON FEEDING

Behavioral studies using an olfactometer demonstrated that spring migrants of the damson-hop aphid, Phorodon humuli, respond to semiochemicals released by spring migrants feeding on hop leaves. Samples of the total volatiles released on feeding were analyzed by coupled gas chromatography-single cell recording techniques and showed the presence of several active components. Three compounds were identified, using coupled gas chromatography-mass spectrometry, as methyl salicylate, (E)-2-hexenal and beta-caryophyllene. These three compounds elicited responses from separate olfactory receptors on the antenna. In the olfactometer, both (E)-2-hexenal and beta-caryophyllene gave positive responses from spring migrants, and a mixture of the two compounds in the natural ratio was more attractive than (E)-2-hexenal alone. Addition of methyl salicylate eliminated the response to the active binary mixture.