Searching behaviour of the aphid parasitoid Aphidius rhopalosiphi (Hymenoptera : Aphidiidae) in response to honeydew excreted by aphids on different host plants

Aphidius rhopalosiphi is a parasitoid, which parasitizes the aphid Rhopalosiphum padi on wheat and is a potential candidate in Biological Control Programmes. The effect of honeydew excreted by host aphids A. rhopalosiphi and Metapolophium dirhodum, and honeydew extracted by non-host aphids, Mizus percicae and Brevicoryne brassicae on searching and walking time of A. rhopalosiphi was tested. Water was used as the control. Walking time of A. rhopalosiphi on honeydew treated area was also investigated. When parasitoids were released, the time taken to reach the honeydew treated discs was significantly shorter than the time taken, to reach the control discs (P ≤ 0.05). The time taken by parasitoids to reach areas treated with honeydew of different aphid species did not differ significantly among the species (P ≥ 0.05). The time spent on different honeydew treated discs was significantly higher than controls (P ≤ 0.05). The time spent on non-host honeydew was significantly shorter than the time spent on the host honeydew (P ≤ 0.05). Speed of movements of A. rhopalosiphi on treated area was significantly higher than nontreated area (P ≤ 0.05). These results revealed that honeydew of both hosts and non -hosts act as an attractant. Distinct behaviour pattern suggests that host honeydew act as a stimulant as well.