Comparative responses of Rhagoletis zephyria and R. pomonella (Diptera: Tephritidae) to commercial and experimental sticky traps and odors in Washington State

Authors: Yee, Wee; GOUGHNOUR, R - Washington State University; FEDER, J - University Of Notre Dame; LINN, C - Cornell University; Cha, Dong

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2017
Publication Date: 9/23/2017
Citation: Yee, W.L., Goughnour, R.B., Feder, J.L., Linn, C.E., Cha, D.H. 2017. Comparative responses of Rhagoletis zephyria and R. pomonella (Diptera: Tephritidae) to commercial and experimental sticky traps and odors in Washington State. Environmental Entomology. 46(6):1351-1358. https://doi.org/10.1093/ee/nvx130.
DOI: https://doi.org/10.1093/ee/nvx130

Interpretive Summary: The apple maggot fly (Rhagoletis pomonella) is a threat to the commercial apple industry in the western U.S., requiring trapping surveys to detect its presence. A similar non-pest fly species, the snowberry maggot fly (Rhagoletis zephyria), is also caught on survey traps, increasing labor needed to process fly catches. Personnel at the USDA Yakima Agricultural Research Laboratory, Wapato, WA, Washington State University, Vancouver, WA, University of Notre Dame, IN, and Cornell University, NY compared responses of the two flies to various traps and odors to identify best practices for reducing snowberry maggot fly captures in surveys. We found that snowberry maggot flies responded more to sticky yellow rectangle than sticky red sphere traps, while the reverse was true for apple maggot flies. Snowberry maggot flies did not respond to apple odors attractive to apple maggot flies, but rather to snowberry fruit doors, while both speices were attracted to ammonia odor. Our results are important in that they suggest red spheres with apple or ammonia odor are better to use than yellow rectangles in apple maggot fly trapping surveys where snowberries are abundant.

Technical Abstract: Rhagoletis zephyria Snow and R. pomonella (Walsh) (Diptera: Tephritidae) are morphologically similar flies that attack white-colored snowberry fruit (Symphoricarpos spp.) and yellow/red or dark-colored apple/hawthorn fruit (Malus/Crataegus spp.), respectively. The two flies are caught together on traps in R. pomonella surveys in the western U.S.A., increasing labor needed to process catches. Comparing responses of the two species to different traps could help identify best practices for reducing R. zephyria captures in these surveys and could contribute to understanding population divergence in Rhagoletis flies. In Washington state, U.S.A., we found that R. zephyria responded most to yellow rectangles and more to white than red spheres baited with ammonium carbonate (AC), whereas R. pomonella responded most to red spheres with AC. Yellow plastic rectangles with AC were more effective in capturing R. zephyria than cardboard rectangles, as has been found for R. pomonella. Rhagoletis zephyria did not respond to apple fruit volatiles associated with red spheres that were attractive to R. pomonella. In contrast, R. zephyria responded more to yellow rectangles with snowberry than apple volatiles. Both species responded to AC. Our results suggest that red spheres are better than yellow rectangles for surveying R. pomonella when snowberries are abundant. However, if discrimination from R. zephyria is paramount, red spheres with apple volatiles should be used. Differences in the species’ responses to traps appear related to odor/color cues of the flies’ host fruit, while commonalties appear related to visual/olfactory stimuli associated with protein feeding, for which AC is a general attractant.