Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/1994
Publication Date: N/A
Interpretive Summary: Several natural enemies are being investigated for their potential as biological control agents of the Russian wheat aphid, a new major pest of cereal crops. One such enemy is a tiny parasitic wasp, Diaeretiella rapae, that attacks a wide variety of aphids. This study addresses the aphid preference of this wasp. Since most predatory insects find their host or prey using airborne odors we examined the responses of wasps to the odor o two different aphid and plant species in a special chamber commonly used for testing odor responses of small insects. The tested wasps were attracted to the odor of the aphids and to the combination of the aphids and plants, but not to the plant odor alone. Also, D. rapae preferred the odor of the cabbage aphid over the odor of the Russian wheat aphid. Such a preferential odor response may result in this natural enemy being attracted to and attacking other aphids in the field besides the target pest, the Russian wheat aphid. Further work on host aphid preferences of the natural enemies of the Russian wheat aphid is needed to select the appropriate natural enemies and enhance their populations for control of the Russian wheat aphid.
Technical Abstract: Diaeretiella rapae (M'Intosh) (Hymenoptera: Aphidiidae) is a parasitoid of several aphid species, including the Russian wheat aphid (RWA), Diuraphis noxia Mordvilko, and the cabbage aphid, Brevicoryne brassicae (L.). The response of mated D. rapae females to odors from these two plants and plant-host complexes was investigated using a four-choice olfactometer. Parasitoids with ovipositional experience, but not inexperienced females, responded positively to odors of the wheat-RWA complex in a no-choise test. In choice tests, experienced parasitoids did not respond to odors of uninfested cabbage and wheat leaves, but did respond positively to aphid- infested plants and to aphids alone. The response of D. rapae to the cabbage aphid-plant complex and to cabbage aphids alone was significantly greater than to RWA-infested wheat and RWA alone, suggesting an innate odor preference for crucifer-feeding aphids.