Host Location of Hyssopus pallidus, a Larval Parasitoid of the Codling Moth, Cydia pomonella

Abstract

Abstract The effectiveness of parasitoids as biological control agents depends largely on their host location behavior. In this study we describe the host-searching behavior of Hyssopus pallidus (Askew), a larval parasitoid of the codling moth Cydia pomonella L. We observed parasitoid behavior on mature apples (a potential host patch) and elucidated some of the stimuli which determine host location. Female wasps showed more complex and intensive searching on infested apples than on mechanically damaged or noninfested apples. Wasps were able to enter infested apples through the calyx or the tunnel made by the host larvae and parasitize them. Area-restricted searching was observed on infested apples, in particular on areas contaminated with host frass. In a further bioassay, we confirmed that host frass contains a host location kairomone. The kairomone appears to be produced by the host independently from its diet, even though frass produced by hosts fed on an apple are more attractive than frass produced by hosts fed on a fruit-devoid artificial diet. The capability of H. pallidus to locate its host inside apples makes the foraging strategy of this species potentially useful as a biological control agent.