THE ROLE OF THE PLANT IN HOST ACCEPTANCE BY THE PARASITOID APHIDIUS-RHOPALOSIPHI (HYMEOPTERA, BRACONIDAE)

Female Aphidius rhopalosiphi De Stefani Perez reared on Rhopalosiphum padi (Linnaeus) made equal numbers of encounters with another suitable host aphid (Sitobion avenae (Fabricius (both Homoptera: Aphididae))) in arenas where the aphids were on either pieces of wheat leaf or mois t filter paper. However, the number of oviposition stabs made in arena s with wheat was far higher than with filter paper, demonstrating the importance of host-plant cues in the acceptance of the aphids by the p arasitoid. Diet reared aphids (even if subsequently fed on wheat) appe ared to be accepted more readily than totally wheat reared individuals . In another arena experiment, there were more encounters with and mor e stabs made into both S. avenae and a non-host aphid (Myzus persicae (Sulzer) on wheat than on Brussels sprouts (a host plant of M. persica e), again showing the over-riding importance of host-plant cues.