Rhagoletis pomonella (Walsh)--Tephritidae
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Native to eastern North America, apple maggot assumed pest status on apples in the 1800's. Native hosts of apple maggot are believed to include several species of hawthorn, Crateagus spp. (Dean & Chapman 1973, Bush 1966). Although quarantine restrictions had confined this pest to the eastern states for many years, it finally reached Portland, Oregon in 1979 (Croft & AliNiazee 1999), from which it has since invaded six additional western states (California, Oregon, Washington, Idaho, Utah and Colorado (AliNiazee & Brunner 1986).
Considerable research over the years on this fruitfly has revealed the activity of several important larval-pupal parasitoids (Monteith 1971, Dean & Chapman 1973, Cameron & Morrison 1977). Among the most important are Opius canaliculatus Gahan and Diachasma alloeum (Muesebeck) in eastern Canada (Rivard 1967); Biosteres melleus (Gahan), Opius canaliculatus and Diachasma alloeum in New York (Dean & Chapman 1973); and Biosteres melleus, Opius lectus Gahan, D. alloeum, Diachasma ferrugineum (Gahan), and Opius downesi Gahan from Connecticut (Maier 1981). Although these parasitoids are believed to exert a significant regulatory effect on the native hawthorn host plant, their impact on populations in apple is considered marginal (Croft & AliNiazee 1999). Such parasitoids as Psilus sp. and Aphaereta auripes (Prov.) and some undescribed eulophids, are considered unimportant in apple maggot regulation (Croft & AliNiazee 1999).
AliNiazee (1985) reported the activity of Opius lectoides Gahan and O. downesi from invaded areas in Oregon, which also attack closely related species such as the snowberry maggot, Rhagoletis zephyria Snow, but the attacks were mainly on hawthorn fruit. Parasitism of pupae reached 60% on the native host, but only 2% on apple. Both parasitoids have short ovipositors, which cannot reach host larvae in large fruit. In eastern North America, Diachosma alloeum has a longer ovipositor which allows it to successfully parasitize apple maggot larvae in apples, however.
Various predators have been reported feeding on apple maggot, which include carabids, spiders, birds and ants (Dean & Chapman 1973). Mature larvae and emerging adult flies are very vulnerable; nevertheless, predators are not thought to be very significant natural mortality factors. For this reason Croft & AliNiazee (1999) believe that parasitoids are deserving of primary attention.
Although apple maggot is native to North America, it might be possible to transfer parasitoids from closely related fruit flies in other hemispheres (Clausen 1978). In fact some of the more tropical parasitoids were imported against apple maggot in the 1950's, including Opius longicaudatus compensans (Silv.) and O. longicaudatus taiensis Full. These parasitoids were liberated in West Virginia in 1954, but were not established (Clausen 1978). Other exotic parasitoids that are currently considered for importation are those attacking European cherry fruit fly, Rhagoletis cerasi L. and the walnut husk fly, Rhagoletis completa Cresson (AliNiazee 1985, AliNiazee & Brunner 1986, Croft & AliNiazee 1999).
Croft and AliNiazee (1999) report that there has been no attempt to conserve or augment parasitoids of apple maggot, which is due in part to a remote chance for successful reductions to noneconomic levels. There is also very little known about the biology of the natural enemies. In New York and Oregon there appears to be a close synchrony between the parasitoids and their host (Dean & Chapman 1973, Croft & AliNiazee 1999), and it is suspected that current insecticidal spray practices may interfere with parasitoid control capacity.
REFERENCES: [ Additional references may be found at: MELVYL Library ]
AliNiazee, M. T. 1985. Opine parasitoids (Hymenoptera: Braconidae) of Rhagoletis pomonella and R. zephyria (Diptera:Tephritidae)intheWillametteValley,Oregon.Canad.Ent.117:166.
AliNiazee, M. T. & J. F. Brunner. 1986. Apple maggot in the western United States: A review of its establishment and current approaches to management. J. Ent. Soc. British Columbia 83: 49-53.
Bush, G. L. 1966. The taxonomy, cytology and evolution of the genus Rhagoletis in North America (Diptera: Tephritidae). Bull. Mus. Compl. Zool. Harvard University 134: 431-562.
Clausen, C. P. (ed.). 1978. Introduced Parasites and Predators of Arthropod Pests and Weeds: A World Review. U. S. Dept. Agric. 545 p.
Croft, B. A. & M. T. AliNiazee. 1999. Biological control in deciduous tree fruit crops. In: Bellows, T. S. & T. W. Fisher (eds.), Handbook of Biological Control: Principles and Applications. Academic Press, San Diego, New York. 1046 p
Cameron, P. J. & F. O. Morrison. 1977. Analysis of mortality in the apple maggot, Rhagoletis pomonella (Diptera: Tephritidae) in Quebec. Canad. Ent. 109: 769-88.
Dean, R. L. & P. J. Chapman. 1973. Bionomics of the apple maggot in eastern New York. Search Agric. 3: 1-64.
Maier, C. T. 1981. Parasitoids emerging from puparia of Rhagoletis pomonella (Diptera: Tephritidae) infesting hawthorn and apple in Connecticut. Canad. Ent. 113: 867-70.
Monteith, L. G. 1971. The status of parasites of the apple maggot, Rhagoletis pomonella (Diptera: Tephritidae) in Ontario. Canad. Ent. 103: 507-12.