|Alston, Diane - Utah State University|
Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2015
Publication Date: 4/1/2016
Citation: Yee, W.L., Alston, D.G. 2016. Sucrose mixed with spinosad enhances kill and reduces oviposition of Rhagoletis indifferens (Diptera: Tephritidae) under low-food conditions. Journal of Entomological Science. 51(2):101-112.
Interpretive Summary: Western cherry fruit fly is a quarantine pest of sweet cherry in the Pacific Northwest of the U.S. that can be managed using the organic insecticide spinosad. Identifying factors that can increase the efficacy of spinosad can further improve fly control. Personnel at the USDA-ARS Yakima Agricultural Research Laboratory in Wapato, WA and at Utah State University, Logan, UT determined whether sucrose mixed with spinosad can increase kill of adult flies and reduce egg laying by flies in the laboratory. It was found that adding sucrose to spinosad increased fly kill and reduce damage to cherries when flies had little food. Results suggest adding sucrose to spinosad could help growers reduce the threat of flies causing economic losses in orchards that have low food abundance.
Technical Abstract: Whether sugar mixed with insecticides enhances kill of western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), may depend on insecticide rate and food availability. Here, the hypothesis that sucrose mixed with the insecticide spinosad (in the Entrust® SC formulation) enhances kill of adults and reduces oviposition when food is scarce was tested. Three- to five-day-old flies were exposed to a low or high rate of dried spinosad or spinosad mixed with sucrose in the presence of (1) supplemental food in the form of yeast extract + sucrose (YE + S) and sweet cherries (Prunus avium [L.]) or (2) only sweet cherries. Cherries were a food source and an oviposition substrate. At the low spinosad rate, sucrose enhanced fly kill over spinosad alone under both food conditions the first four or during all seven days of experiments. At the high spinosad rate, sucrose enhanced kill only when supplemental food was absent. Sucrose-enhanced-spinosad did not reduce oviposition versus spinosad alone at either spinosad rate when supplemental food was present, but it did at both spinosad rates when only cherries were present. Results suggest that sucrose mixed with the formulation of spinosad tested here in low volume sprays could be useful for managing R. indifferens in low food environments, but offers no benefit in preventing oviposition when applied in food-rich environments.