Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2015
Publication Date: 12/1/2015
Citation: Yee, W.L. 2015. Temperature-mediated kill and oviposition of Western Cherry Fruit Fly (Diptera: Tephritidae) in the presence of Spinosad. Journal of Economic Entomology. 109:132-142.
Interpretive Summary: Western cherry fruit fly is a quarantine pest of sweet cherry in the Pacific Northwest of the U.S. that is managed using insecticides, including spinosad, an organic compound that can be applied in low volume sprays. Identifying factors that can increase the efficacy of spinosad can be useful for improving fly control. Personnel at the USDA-ARS Yakima Agricultural Research Laboratory in Wapato, WA, determined if temperature can mediate kill and oviposition by the fly in the presence of low spinosad coverage in the laboratory. More flies were killed at 23.9 and 29.4 °C than at 18.3 °C. However, despite more flies being killed at the two higher temperatures, flies laid more eggs at these temperatures than at 18.3 °C. Results suggest that spinosad rates in sprays used against cherry fruit flies should take into account ambient temperature.
Technical Abstract: Western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), is a quarantine pest of sweet cherry (Prunus avium (L.) L.) that is managed using insecticides, including spinosad, an organic compound that can be applied in low spray volumes. Identifying factors that can increase the efficacy of spinosad can be useful for improving fly control. Here, the major objective was to determine if temperature mediates kill and oviposition by R. indifferens in the presence of low spinosad coverage in the laboratory. Experiments were conducted by placing flies in cages with cherries and with a Petri dish containing three to 12 small spots of dry spinosad at 18.3, 23.9, and 29.4 °C. Effects of spinosad rates were also determined. More flies were killed at 23.9 and 29.4 °C than at 18.3 °C by 1–7 days post exposure. More flies were killed at 29.4 than 23.9 °C by 1 day post exposure. However, flies laid more eggs at these temperatures than at 18.3 °C. Higher spinosad rates increased kill and decreased oviposition, but even within the highest rate, oviposition was greater at 29.4 than 18.3 °C. More flies walked over 5-min observation periods at 29.4 and 23.9 °C than 18.3 °C, suggesting higher temperatures up to 29.4 °C increase kill by increasing fly contact with spinosad as well as increase oviposition rate. Results imply that spinosad rates in low spray volumes used against R. indifferens should take into account ambient temperature.