Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/1997
Publication Date: N/A
Interpretive Summary: USDA-ARS scientists have found that pest fruit flies, including the Mediterranean, Mexican and Caribbean fruit flies, can be suppressed by releasing large numbers of parasitic wasps. These insects are harmless to humans, but search out and lay their eggs in immature flies. At present most of the wasps being released attack fruit fly larvae, a stage of the target insect that can be live deep inside large fruits and be sometimes difficult for the natural enemy to reach. Since fly larvae leave fruits to pupate in the soil, a parasite that can attack the pupal stage is undeterred by even the largest host fruits. However, many pupal parasitoids are not well suited to mass-rearing and release. They often develop in a broad range of insects, including species of flies that might beneficial to agriculture and other species of parasites. We have looked at how three pupal parasite species search for hosts and whether they can develop in two distantly related flies, the house fly and the Caribbean fruit fly. One of these species, recently discovered in Mexico, is attracted only to the fruit flies, will not lay eggs in house flies and does not attack fly pupae that already contain another species of parasite. This suggests it may be a useful addition to the arsenal of parasites used to biologically control fruit flies.
Technical Abstract: Because tephritid pupae are sometimes more vulnerable than larvae, pupal parasitoids are attractive candidates for augmented releases to control pest fruit flies. However, a number of such species have broad host ranges and act as hyperparasitoids of braconid primary parasitoids. Three pupal parasitoids were examined for: 1) host range (i.e., ability to develop in distantly related hosts; the house fly, Musca domestica, and the Caribbean fruit fly, Anastrepha suspensa); 2) whether host range is modifiable (i.e., would rearing in a particular host change adult response to that host) and 3) propensity to hyperparasitize a braconid parasitoid of Tephritidae, Diachasmimorpha longicaudata. The chalcid Dirhinus himalayanus was found to develop in both hosts, though it was more responsive to the pupae of house flies. Rearing in Caribbean fruit flies did not significantly affect this response. It avoided hyperparasitism to some extent (mortality of the primary parasitoid was approx. 2/3 that of the host fly). The pteromalid Spalangia gemina also preferred the pupae of house flies, but the response to house fly pupae was significantly less in insects reared on Caribbean fruit flies. S. gemina acted as a hyperparasitoid and did not appear to discriminate between parasitized and unparasitized pupae of Caribbean fruit flies. The diapriid Coptera sp. did not develop in the pupae of house flies and was responsive only to the pupae of Caribbean fruit flies. It did not act as a hyperparasitoid. Mass-rearing schemes using both larval parasitoids and pupal parasitoids that avoid hyperparasitizing are discussed.