The utilization of parasites of oriental fruit fly (Dacus dorsalis) against Queensland fruit fly (Strumeta tryoni)

In 1950, a programme was initiated to utilize against the Queensland fruit fly (Strumeta tryoni) parasites which were introduced during 1948–1950 into Hawaii, where they produced a considerable reduction in the incidence of oriental fruit fly (Dacus dorsalis). The present paper describes the work carried out under this programme up to October 1959. During 1951–1957 the emphasis was on rearing, at Sydney, on Queensland fruit fly, stocks of Opius longicaudatus and O. oophilus from small stocks imported from Hawaii. It was found that O. oophilus, O. vandenboschi, and O. longicaudatus could parasitize Queensland fruit fly in the laboratory, and that O. longicaudatus could parasitize the Solanum fruit fly, Strumeta cacuminata, which occurs widely in the distribution area of the Queensland fruit fly and hence might act as a valuable alternative host for the parasites. Liberations were made at Coffs Harbour and Sydney in New South Wales in 1956–1957 of 21 000 O. longicaudatus and 1 700 O. oophilus, but establishment was apparently not achieved. The programme was changed in 1957 to provide for larger releases over n much wider area. In view of production difficulties at Sydney, a field station was set up in Hawaii to rear parasites, which were shipped to Australia by air, checked in quarantine at Sydney, and despatched to various parts of Australia for liberation. Between March 1958 and October 1959 the following numbers of foreign parasites were liberated: O. oophilus, 229 200; O. vandenboschi, 28 100; O. longicaudatus and closely related species, 198 700; O. incisi, 27 100; Dirhinus giffardii, 2 500; Tetrastichus giffardianus, 2 500; and Syntomosphyrum indicum, 3 200. The liberations in 1958–1959 were made at 25 locations in New South Wales, 59 in Queensland, 12 in Western Australia, and 6 on Lord Howe Island. The liberations were made in the presence of populations of Queensland fruit fly in New South Wales, Queensland, and on Lord Howe Island, and of Mediterranean fruit fly (Ceratitis capitata) in Western Australia. Data from a total of 185 fruit samples taken between January and August 1959 in New South Wales and Queensland indicate that O. oophilus was possibly established in five localities in New South Wales and two in Queensland, and that some field breeding had occurred of O. vandenboschi and O. longicaudatus in New South Wales. There were no recoveries indicating field breeding of the three species in central or north Queensland. The indications of establishment of O. oophilus are tentative because the relevant samples were taken before the parasite populations had been subjected to winter conditions. There were no recoveries of O. incisi, S. indicum, or T. giffardianus.