OLFACTORY RESPONSES OF THE PARASITOID DIAERETIELLA-RAPAE (HYMENOPTERA, APHIDIIDAE) TO ODOR OF PLANTS, APHIDS, AND PLANT-APHID COMPLEXES

Diaeretiella rapae (M'Intosh) (Hymenoptera: Aphidiidae) is a parasitoi d of several aphid species, including the Russian wheat aphid (RWA), D iuraphis noxia (Mordvilko), and the cabbage aphid (CA), Brevicoryne br asicae (L.). The response of mated D. rapae females to odors from whea t, cabbage, and plant-host complexes was investigated using a four-cho ice olfactometer. Experienced parasitoids, but not inexperienced femal es, responded positively to odors of the wheat-RWA complex in a no-cho ice test. In choice tests, experienced parasitoids did not respond to odors of uninfested cabbage and wheat leaves, but did respond positive ly to aphid-infested plants and to aphids alone. The response of D. ra pae to the cabbage-CA complex and to CA alone was significantly greate r than to the wheat-RWA complex and RWA alone, suggesting an innate od or preference for crucifer-feeding aphids.