Submitted to: Journal of Applied Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2008
Publication Date: 6/1/2009
Citation: Yee, W.L. 2009. Insecticide, Sugar and Diet Effects on Feeding and Mortality in Rhagoletis indifferens (Dipt., Tephritidae). Journal of Applied Entomology 133:297-306.
Interpretive Summary: Western cherry fruit fly is an important quarantine pest of sweet cherries in the Pacific Northwest. Personnel at the Yakima Agricultural Research Laboratory in Wapato, WA are determining feeding responses and mortality of cherry fruit flies caused by newer and safer insecticides mixed with sugar. We found that flies fed more on insecticides with than without sugar and mortality was correspondingly higher in flies exposed to insecticides with sugar. Flies exposed to thiamethoxam and spinosad suffered similar mortalities. Flies that had fed on sugar only suffered higher mortalities than flies that had fed on a sugar and yeast extract diet. Results are important because they suggest that thiamethoxam is comparable to spinosad in its effects on mortality, and that using it with sugar in bait to control cherry fruit fly may give results similar to spinosad, but that food abundance in the environment may affect whether flies will feed on them.
Technical Abstract: The effects of spinosad bait and various insecticides, the presence of sugar in insecticides, and diet on feeding responses and mortality in western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), were determined. Diet was defined as feeding on sugar only or yeast extract + sugar before insecticide exposure and feeding responses were percent feeding, number of feeding events, and feeding duration. Feeding durations on the neonicotinoid acetamiprid with or without sugar was shorter than on sugar water and spinosad bait. Numbers of feeding events on insecticides with sugar were greater than on insecticides alone, but there was no effect of diet on feeding responses to insecticides with sugar. At 48 h after exposure, flies that fed on sugar only suffered higher mortalities when exposed to spinosad, thiamethoxam, and azinphos-methyl than to imidacloprid, acetamiprid, and indoxacarb, and mortality in between these two groups of treatments when exposed to spinosad bait. Mortalities were greater when sugar was added to insecticides, and were higher in sugar only than yeast extract + sugar diet flies. Flies that fed once on thiamethoxam were killed more quickly than those that fed once on spinosad bait and spinosad. Results suggest that thiamethoxam is comparable to spinosad in its effects on mortality, and that using it with sugar in bait may also have similar results as using spinosad bait or spinosad. One benefit of using thiamethoxam with sugar may be that it kills flies more quickly, before they can oviposit, than spinosad bait, although whether a fly will feed on it may depend on how much sugar or nitrogenous food it has eaten.