|Klaus, Michael - Washington Department Of Agriculture|
Submitted to: Pan-Pacific Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2015
Publication Date: 12/1/2015
Citation: Yee, W.L., Klaus, M. 2015. Implications of Rhagoletis zephyria, 1894 (Diptera: Tephritidae), captures for apple maggot surveys and fly ecology in Washington state, U.S.A. Pan-Pacific Entomologist. 91(4):305-317.
Interpretive Summary: The apple maggot fly is a major quarantine pest of commercial apple in the Pacific Northwest of the U.S. Detecting the fly’s presence through trapping surveys is vital for preventing its spread into commercial apple orchards. However, a similar-looking fly, the snowberry maggot fly, is also caught during surveys, making identifications of flies more difficult. Personnel at the USDA-ARS Yakima Agricultural Research Laboratory in Wapato, WA, and the Washington State Department of Agriculture in Yakima, WA determined the numbers of snowberry maggot and apple maggot flies caught in surveys. Over nine years of surveys, many more snowberry maggot flies than apple maggot flies were caught on traps, increasing labor needed to accurately identify flies. Results imply that traps more specific for apple maggot flies should be useful for surveys and needs to be a primary focus for future research and development.
Technical Abstract: The apple maggot, Rhagoletis pomonella (Walsh), 1867 (Diptera: Tephritidae), is an introduced quarantine pest of apple (Malus domestica Borkhausen) (Rosaceae) in Washington state, U.S.A. A morphologically similar native fly, Rhagoletis zephyria Snow, 1894, infests snowberries (Symphoricarpos spp.) and is also present in Washington. Although it is not a pest of apples, R. zephyria is caught on sticky yellow rectangles baited with ammonia deployed for R. pomonella, which could have implications for apple maggot surveys and understanding differences in the ecology of the flies. Here, we report the relative abundance of R. zephyria and R. pomonella on traps placed in apple maggot host trees during surveys, including in the dry apple-growing regions of central and eastern Washington. Rhagoletis zephyria outnumbered apple maggot on traps by 3 to 1,102 times to one, increasing times required for accurate species identifications, implying that traps which are more specific for apple maggot would be useful. Despite the high numbers of R. zephyria caught, >94% of all female flies could be identified to species, implying that R. zephyria minimally compromised surveys. Detections of both fly species were lower in drier than wetter locations; however, mean annual precipitation was more positively correlated with R. pomonella than with R. zephyria. The greater relative abundance of native R. zephyria in drier counties implies that it is better adapted to central and eastern Washington than is the invasive R. pomonella or that habitat factors in these regions favor R. zephyria.