Comparative Responses of Rhagoletis zephyria and Rhagoletis pomonella (Diptera: Tephritidae) to Commercial and Experimental Sticky Traps and Odors in Washington State.

Abstract

Rhagoletis zephyria Snow and Rhagoletis 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 United States, increasing labor needed to process catches. Comparing responses of the two species with 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, United States, we found that R. zephyria responded most to yellow rectangles and more to white than red spheres (RSs) baited with ammonium carbonate (AC), whereas R. pomonella responded most to RSs with AC. Yellow plastic rectangles with AC were more effective in capturing R. zephyria than cardboard rectangles, as has been found for R. pomonella. R. zephyria did not respond to apple fruit volatiles associated with RSs 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 RSs are better than yellow rectangles for surveying R. pomonella when snowberries are abundant. However, if discrimination from R. zephyria is paramount, RSs 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.