Seasonal distributions of the western cherry fruit fly (Diptera: Tephritidae) among host and nonhost fruit trees.

Seasonal distributions of the western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), in sweet cherry (Prunus avium (L.) L.) (major host), black hawthorn (occasional developmental host) (Crataegus douglasii Lindley), and other trees were determined in a ponderosa pine ecosystem in Washington state, USA. The hypothesis that most fly dispersal from cherry trees occurs after fruit senesce or drop was tested, with emphasis on movement to black hawthorn trees. Sweet cherry fruit developed earlier than black hawthorn, bitter cherry (common host), choke cherry, and apple fruit. Flies were usually captured first in sweet cherry trees but were caught in bitter cherry and other trees throughout the season. Peak fly capture periods in sweet cherry began around the same time or slightly earlier than in other trees. However, peak fly capture periods in black hawthorn and other nonsweet cherry trees continued after peak periods in sweet cherry ended, or relative fly numbers within sweet cherry declined more quickly than those within other trees. Larvae were reared from sweet and bitter cherry but not black hawthorn fruit. Results provide partial support for the hypothesis in that although R. indifferens commonly disperses from sweet cherry trees with fruit, it could disperse more, or more flies are retained in nonsweet cherry trees after than before sweet cherries drop. This could allow opportunities for the flies to use other fruit for larval development. Although R. indifferens infestation in black hawthorn was not detected, early season fly dispersal to this and other trees and fly presence in bitter cherry could make fly management in sweet cherry difficult.