ORIENTAL FRUIT FLY
Dacus dorsalis Hendel -- Diptera, Tephritidae
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Oriental fruit fly is presumed to be native to the Orient. It is thought to have invaded Hawaii in 1945 as a contaminant of military material returning from the western Pacific war zone. It increased rapidly to epizootic levels during 1946, attacking a variety of fruits. Larval infestations not only rendered most fruits worthless in Hawaii but also posed a serious potential threat to the warm fruit producing areas of mainland North America. Chemical control was difficult, expensive, hazardous to health and generally ineffective. Therefore, one of the most massive biological control efforts o modern times was launched (DeBach 1974).
The Hawaiian Territorial Board of Agriculture and Forestry initiated explorations for natural enemies in 1947-8 in the Philippines and Malaysia. Although it was impossible to ascertain the identity of the parasitoids being imported, it is apparent that the success obtained was due to the importations made at this time. Thus, in 1948-9 other interested organizations joined into a cooperative effort, including the USDA, the University of California, The Hawaiian Agricultural Experiment Station, the Hawaiian Sugar Planters Experiment Station and the Pineapple Research Institute. By 1951, fourteen explorers collected parasitoids from many fruit fly species in most of the tropical and subtropical areas of the world including especially the Philippines, Malaysia, Taiwan, Thailand, Borneo, India, Sri Lanka, Australia, New Caledonia, Fiji, South Africa, Kenya, Congo, Brazil and Mexico. Shipments were mostly of parasitized puparia sent by airmail or air freight and usually reached Hawaii in seven days or less from any given area. There were more than 4,246,000 fly puparia of over 60 species sent to Hawaii. About 1/3rd of these were Dacus dorsalis. About 80 species of parasitoids were obtained, of which at least 16 larval parasitoids of the genus Opius, six pupal parasitoids and one predator were cultured and released in the field. Recovery was made of 11 species initially, but one species became dominant.
DeBach (1974) relates that the story is somewhat confused because various of the imported species of Opius were very similar in appearance and some were misidentified initially. Therefore, the original material received from the Philippines in 1947 contained the three most important of all the parasitoids eventually imported, but only one of these, Opius longicaudatus (Ashmead) was correctly identified. The other two, Opius vandenboschi Fullaway and Opius oophilus Fullaway were thought to be one species. Opius persulcatus (Silvestri), which actually was never present. The same applied to the next group of shipments received from Malaysia in 1948. Parasitoids from these shipments became readily established. Opius longicaudatus increased rapidly in the field after its initial release on Oahu in 1948 but suddenly lost its dominant position during the latter half of 1948 to O. vandenboschi which had been released initially about the same time. Later O. vandenboschi was replaced by O. oophilus which had first been recognized to be established in 1949. In spite of the competition between these three species, each replacement of one by another was accompanied by a higher total parasitism and a greater reduction in the fruit fly infestation (DeBach 1974). Both O. longicaudatus and O. vandenboschi had virtually disappeared by 1951 and this status has since continued.
The final result has been a very substantial reduction in the Oriental fruit fly populations in all of the Islands estimated to be on the order of 95% as compared to the 1947-9 peak abundance. At that time practically 100% of most kinds of fruits were infested. The threat of movement to the mainland has been greatly reduced. Still, some preferred fruit such as guava and mangoes, which up to 1949 were 100% infested, are sometimes infested to ca. 50%, but with many fewer larvae per fruit. Yet on the average less than 10% of the mangoes are now infested, and many kinds of fruits that were once heavily infested are not practically free of attack (DeBach 1974).
DeBach (1974) stated that this project illustrates the basic importance of accurate knowledge of both taxonomy and biology to biological control. Opius oophilus was mistaken for some time as O. persulcatus. Had the latter been imported and established early with some degree of success, it is possible that further work, including the final discovery of the best parasitoid, O. oophilus, might have been dropped. Interestingly, O. oophilus has also turned out to be the best parasitoid of the Mediterranean fruit fly in Hawaii, having displaced O. tryoni (Cameron), which previously was well established and moderately effective. Had O. oophilus been recognized as a valid species and introduced from Malaysia in 1913-14 when importation of parasitoids of the Mediterranean fruit fly was being conducted, greater biological control would have occurred 40 years earlier.
Opius oophilus attacks eggs and O. longicaudatus and O. vandenboschi attack host larvae. The former lays its eggs in an egg of the host, then completes development in the host larva. Had this habit been known in 1935-6 when F. C. Hadden probably imported O. oophilus along with other Opius species from Malaysia and India for control of the Mediterranean fruit fly, it probably could have been cultured and established. But insectary propagation did not occur, probably because its habit of ovipositing only in host eggs was not then known and also only host larvae were provided during culture attempts. If the biology had been understood so that the parasitoid had become established on the Mediterranean fruit fly at that time, it not only would have provided better biological control of that fruit fly from 1936 to 1950 (when O. oophilus finally was established), but it would have been present to attack the Oriental fruit fly when it first reached Hawaii in 195 and might have made the later massive and expensive project unnecessary (Bess & Haramoto 1958, Clausen et al. 1965, DeBach 1974).
For additional details of biological control effort and biologies of host and natural enemies, please also refer to the following (Silvestri 1914, Noble 1942, van den Bosch & Haramoto, 1951, 1953; van den Bosch et al. 1951, Clancy et al. 1952, Dresner 1953, Fullaway 1953, Hagen 1953, Peterson 1957, Christenson & Foote 1960, Bess & Haramoto 1961, Bess et al. 1961, 1963).
REFERENCES: [Additional references may be found at: MELVYL Library ]
Bess, H. A. & F. H. Haramoto. 1958. Biological control of the oriental fruit fly in Hawaii. Proc. 10th Intern. Cong. Ent. (1956)4: 835-40.
Bess, H. A. & F. H. Haramoto. 1961. Contributions to the biology and ecology of the Oriental fruit fly, Dacus dorsalis Hendel (Diptera: Tephritidae) in Hawaii. Hawaii Agric. Expt. Sta. Tech. Bull. 44: 30 p.
Bess, H. A., R. van den Bosch & F. H. Haramoto. 1961. Fruit fly parasites and their activities in Hawaii. Hawaii. Ent. Soc. Proc. 17: 367-68.
Bess, H. A., F. H. Haramoto & A. D. Hinckley. 1963. Population studies of the Oriental fruit fly, Dacus dorsalis Hendel (Diptera: Tephritidae). Ecology 44: 197-201.
Christenson, L. D. & R. H. Foote. 1960. Biology of fruit flies. Ann. Rev. Ent. 5: 171-92.
Clancy, D. W., P. E. Marucci & H. Dresner. 1952. Importation of natural enemies to control the Oriental fruit fly in Hawaii. J. Econ. Ent. 45: 85-90.
Clausen, C. P., D. W. Clancy & Q. C. Chock. 1965. Biological control of the oriental fly (Dacus dorsalis Hendel) and other fruit flies in Hawaii. U. S. Dept. Agric. Tech. Bull. 1322. 102 p.
DeBach, P. 1974. Biological Control by Natural Enemies. Cambridge University Press, London & New York. 323 p.
Dresner, E. 1953. Observations on the biology and habits of pupal parasites of the Oriental fruit fly. Hawaii. Ent. Soc. Proc. 15: 299-310.
Fullaway, D. T. 1953. The Oriental fruit fly (Dacus dorsalis Hendel) in Hawaii. 7th Pacific Sci. Cong. Proc. 4: 148-63.
Hagen, K. S. 1953. A premating period in certain species of the genus Opius (Hymenoptera: Braconidae). Hawaii. Ent. Soc. Proc. 15: 115-16.
Newell, I. M. & F. H. Haramoto. 1968. Biotic factors influencing populations of Dacus dorsalis in Hawaii. Proc. Hawaiian Entomol. Soc. 20: 81-139.
Noble, N. S. 1942. Melittobia (Syntomosphyrum indicum) (Silv.) (Hymenoptera, Chalcidoidea), a parasite of the Queensland fruit fly, Strumeta tryoni (Frogg.). Linn. Soc. New South Wales, Proc. 67: 269-76.
Peterson, G. D., Jr. 1957. An annotated check list of parasites and predators introduced into Guam during the years 1950-1955. Hawaii. Ent. Soc. Proc. 16: 199-202.
Silvestri, F. 1914. Report of an expedition to Africa in search of the natural enemies of fruit flies (Trypaneidae). Hawaii Bd. Agric. Forestry, Div. Ent. Bull. 3. 176 p.
van den Bosch, R & F. H. Haramoto. 1951. Opius oophilis Fullaway, an egg-larval parasite of the Oriental fruit fly discovered in Hawaii. Hawaiian Ent. Soc. Proc. 14: 251-55.
van den Bosch, R, H. A. Bess & F. H. Haramoto. 1951. Status of Oriental fruit fly parasites in Hawaii. J. Econ. Ent. 44: 753-59.