Submitted to: Annals of the Entomological Society of America
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/3/2007
Publication Date: 7/1/2007
Citation: Eitam, A., Vargas, R.I. 2007. Host habitat preference of Fopius arisanus (Hymenoptera: Braconidae), a parasitoid of tephritid fruit flies. Annals of the Entomological Society of America. 100(4):603-608. Interpretive Summary: The parasitic wasp Fopius arisanus is the dominant natural enemy of the oriental fruit fly in the Puna district of Hawaii Island. Its numbers are lower in commercial papaya than in wild fruits. Field surveys and field cage studies showed that females prefer to forage on fruits on trees than on fruits on the ground. Thus, leaving ripe fruits on the ground may reduce the efficiency of the wasp to control populations of the fruit fly.
Technical Abstract: The braconid parasitoid Fopius arisanus is a candidate for augmentative biological control of tephritid fruit flies. In the Puna district of Hawaii Island, F. arisanus parasitized 41-72% of oriental fruit flies in wild common guava, strawberry guava and tropical almond. In commercial papaya in the same region, parasitism was only 22% in tree-collected fruits and 3% in ground-collected fruits. The low level of parasitism in papaya suggests that wild parasitoids may not track the host flies well in commercial fruits, and that augmentative parasitoid releases could potentially increase parasitism and thus suppress host fly populations in this habitat. The extremely low parasitism in ground-collected papaya suggests that F. arisanus may avoid foraging on ground fruits. Field cage experiments confirmed this hypothesis: numbers of females observed on tree fruits were 2-fold higher than on ground fruits in small cages, and 4-6-fold higher in large cages. Given this avoidance of ground fruits, the impact of wild parasitoids on host populations is significantly reduced, and augmentative releases may not have a significant effect, when poor sanitation is practiced in papaya orchards. Field testing is needed to evaluate the full impact of augmentative releases under different sanitation regimes.