Effect of adult experience on in-flight orientation to plant and plant-host complex volatiles in Aphidius ervi Haliday (Hymenoptera, Braconidae)

The effect of adult experience on in-flight orientation to plant-host complex volatiles by Aphidius ervi Haliday was studied in a wind tunnel bioassay, using Acyrthosiphon pisum (Harris), maintained on broad bean plants (Vicia faba) as host. A short oviposition experience (15 s) on the plant-host complex (PHC) was sufficient to induce a drastic decrease of flight propensity and stimulated a foraging behavior characterized by intense walking activity, However, flight activity resumed to normal levels 1 h after the oviposition experience on the PHC occurred. For parasitoids conditioned on the PHC for at least 1 min the recorded proportion making oriented flights to the PHC was significantly higher than that for naive females, In contrast, oviposition experience in the absence of plant material did not influence the A. ervi flight response, Oviposition attempts on aphid dummies without egg release did not reduce flight activity. When A. ervi females were exposed to glass beads coated with Ac. pisum cornicle secretion, a priming effect was observed, resulting, compared with naive females, in a significantly higher rate of oriented flights to the PHC. In contrast, oviposition attempts visually induced by colored aphid dummies did not influence flight behavior. A strong reaction to volatile cues from uninfested plants was induced by oviposition experience on newly infested broad bean plants, This appears to be a case of associative learning. In fact, uninfested broad bean plants are basically unattractive to naive A. ervi females. The results demonstrate that adult experience has a considerable influence on A. ervi behavior and may have important implications for biological control of natural pest aphid populations. (C) 1997 Academic Press.