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APPLE MAGGOT Rhagoletis pomonella (Walsh)--Diptera,
Tephritidae (Contacts)
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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. |