Host Habitat Preference of Fopius arisanus (Hymenoptera: Braconidae), a Parasitoid of Tephritid Fruit Flies

ThebraconidparasitoidFopiusarisanus(Sonan)(Hymenoptera:Braconidae)isacandidate for augmentative biological control of tephritid fruit ßies. In the Puna district of Hawaii Island, F. arisanus parasitized 41Ð72% of oriental fruit ßies, Bactrocera dorsalis (Hendel), in wild common guava, Psidium guajava L.; strawberry guava, Psidium cattleianum Sabine; and tropical almond, Terminalia catappa L. In commercial papaya, Carica papaya L., in the same region, parasitism was only 22% in tree-collected fruit and 3% in ground-collected fruit. The low level of parasitism in papaya suggests that wild parasitoids may not track the host ßieswell in commercial fruit and that augmentative parasitoid releases could potentially increase parasitism and thus suppress host ßy populations in this habitat. The very low parasitism in ground-collected papaya suggests that F. arisanus may avoid foraging on ground fruit. Field cage experiments support this hypothesis. Numbers of females observed on tree fruit were two-fold higher than on ground fruit in small cages and 4Ð6-fold higher in large cages. In an experiment conducted in a papaya orchard, sentinel fruit was placed within the canopy, on the trunk, or on the ground. Parasitism was signiÞcantly higher in the canopy-placed fruit in only one of three trials. This variable response to ground fruit in theÞeld suggests that augmentativeparasitoid releasesmayhavea signiÞcant, albeit reduced, effect on host populations under conditions of poor sanitation.