Abundances, ecologies, and distributions of Rhagoletis Loew, 1862 (Diptera: Tephritidae) flies in central Washington State, U.S.A. inferred from fly trapping surveys

Authors: Yee, Wee; MILNES, JOSHUA - WASHINGTON DEPARTMENT OF AGRICULTURE; BUSH, MICHAEL - WASHINGTON DEPARTMENT OF AGRICULTURE

Submitted to: Pan Pacific Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2023
Publication Date: 12/30/2023
Citation: Yee, W.L., Milnes, J.M., James, T., Bush, M.R. 2023. Abundances, ecologies, and distributions of Rhagoletis flies (Diptera: Tephritidae) in central Washington State, U.S.A. inferred from fly trapping surveys. Pan Pacific Entomology. 99(4):226-245. https://doi.org/10.3956/2023-99.4.226.
DOI: https://doi.org/10.3956/2023-99.4.226

Interpretive Summary: Pest and non-pest fruit flies trapped in surveys can provide new information on fly abundances, in a region. Personnel at the USDA-ARS Temperate Tree Fruit & Vegetable Research Unit in Wapato, WA and the Washington State Department of Agriculture in Yakima, WA analyzed data from surveys for pest cherry fruit flies and apple maggot flies in central WA to determine relative abundances of fly species on traps and factors related to their abundances. We found that cherry fruit flies were common, but that apple maggot flies were very rare in central Washington. The most abundant fly was walnut husk fly. We infer from abundance data that apple maggot is less tolerant of arid central WA summers than other fruit flies and that relative fly abundances depend on site, tree type, and seasonal period. Results are important in that they identify possible factors responsible for abundances and distributions of fruit flies in central WA, which could be useful for managing the pest species.

Technical Abstract: Target and non-target Rhagoletis flies (Diptera: Tephritidae) trapped in surveys can provide new information on fly abundances, ecologies, and distributions. Here, data from surveys for native Rhagoletis indifferens Curran, 1932, in non-commercial sweet cherry trees in 2018 and non-native Rhagoletis pomonella (Walsh), 1867, in non-commercial apple, crabapple, and hawthorn trees in 2019–2022 in central Washington State, U.S.A. were analyzed. We determined relative abundances of target and non-target Rhagoletis on traps and hypothesized that abundances are site, tree type, and seasonal period dependent. Rhagoletis indifferens was the most abundant Rhagoletis in cherry trees. Non-native Rhagoletis completa Cresson, 1929, was the most abundant Rhagoletis in R. pomonella host trees, with overall results suggesting it is the most numerous or dispersive Rhagoletis in central Washington. With support from the literature, we infer that R. pomonella is less tolerant of arid central Washington summers than R. completa, R. zephyria Snow, 1894, R. indifferens, and native R. basiola (Osten Sacken), 1877; Rhagoletis species diversity is lower in urban than rural habitats due to different predominant host plants present in them; all species disperse annually at similar relative abundances, resulting in geographic range expansions over a few generations; peak seasonal dispersal of flies to non-natal tree species coincides with natal host fruit development, resulting in colonization of new fruiting host patches. Differential fly tolerances of arid summer climates due to adaptation or preadaptation, habitat type, and annual and seasonal dispersal patterns could explain abundances and distributions of native and non-native Rhagoletis species in central Washington.