Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2008
Publication Date: 9/15/2009
Citation: Yee, W.L. 2009. Reduction in Emergence of Rhagoletis indifferens (Diptera: Tephritidae) from Sweet Cherries with Different Egg and Larval Distributions Using Newer Insecticides. Journal of Entomological Science. 44(3):1-17.
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 the effects of insecticides on reducing emergence of larvae from cherries. It was found that several newer insecticides can reduce emergence, but that the numbers of eggs and larvae in cherries are important in determining their effectiveness. Insecticides were most effective when cherries had mostly eggs and much less effective when cherries had many larvae. Results are important because they suggest that for optimal fly control, sprays must be made as soon as possible after cherry harvest when eggs are likely to be the predominant stage in cherries.
Technical Abstract: Western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), is the major insect pest of sweet cherry, Prunus avium (L.) L., in the Pacific Northwest of the U.S. To reduce fly populations in unharvested fruit following the completion of commercial harvest, it is important to control immature stages in cherry fruit. In this study, the goals were to (1) identify the susceptibility of the eggs and larvae to neonicotinoid and other insecticides and to (2) determine the effects of these insecticides on larval emergence from sweet cherries with different egg and larval distributions (the relative percentages of different stages). Only 3.3% of eggs exposed for 15 s to thiacloprid hatched, whereas 25.0–41.0% of eggs exposed to water only, spinosad, and imidacloprid hatched. Larval mortalities in cherries 48–52 h after being treated with imidacloprid, thiacloprid and acetamiprid were 50.0–66.7%, significantly higher than the 24.0% mortality in untreated cherries. Imidacloprid, thiamethoxam, thiacloprid, acetamiprid, and clothianidin were equally effective in reducing larval emergence when sprayed on cherries in which eggs were 94.2% of the immature stages, but imidacloprid and acetamiprid appeared to be the most effective when sprayed on cherries in which eggs were only 19.7% and 53.8% of the immature stages. Results indicate neonicotinoids are toxic to eggs and larvae of R. indifferens, and that all are more effective in cherries against eggs than larvae. For fly control, the time interval between the last spray directed against adult flies and the first post-harvest spray of neonicotinoids should be no more than one week, in order to reduce chances eggs hatch and larvae develop. Key Words western cherry fruit fly, post harvest, spinosad, neonicotinoid insecticides