Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2010
Publication Date: 9/1/2010
Citation: Yee, W.L. 2010. Yeast Extract: Sucrose Ratio Effects on Egg Load, Survival, and Mortality Caused by GF-120 in Western Cherry Fruit Fly. Florida Entomologist 93(3):422-431.
Interpretive Summary: Cherry fruit fly is a serious quarantine pest of commercial cherries in the Pacific Northwest. The fly is currently controlled using protein bait sprays mixed with insecticides, but flies are not consistently attracted to protein baits. Personnel at the USDA-ARS Yakima Agricultural Research Laboratory in Wapato, WA are determining the effects of bait nitrogen concentrations on feeding and attraction to protein baits by cherry fruit fly. It was found that as nitrogen concentrations in diets increased, feeding intake also increased, and that more eggs developed. More importantly for fly control, as nitrogen concentrations increased, numbers of flies attracted to protein bait decreased. Results are important because they suggest that more attractive baits that also stimulate feeding by flies may be needed to achieve more rapid fly control in highly infested trees.
Technical Abstract: Extrinsic sources of nitrogen are needed by tephritid fruit flies for optimal nutrition. In this study, relationships between yeast extract diets containing 0, 0.109, 0.545, 1.09, 2.18, 3.27, and 5.45% nitrogen (N) and diet intake, survival, egg production, and responses to spinosad bait in western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), are determined. Diet intake by males and females increases as nitrogen concentrations increase. Survival of virgin females to 10 d is highest when they are fed 1.09% N diet, and that of mated females is highest and lowest when they are fed 0–0.545% and 5.45% N diets, respectively. Egg production in virgin flies is higher when they are fed 2.18 than 0.109–1.09% N diets and in mated flies it is highest when they are fed 1.09–5.45% N diets. In one experiment where N was present during exposure to dried spinosad bait, responses to it are highest in flies fed 0 and 0.109% N diets and numerically the lowest in flies fed 2.18 and 3.27% N diets. In another experiment where N was absent during exposure to dried bait, responses in flies fed 0 and 0.545% N diets to it are higher than in flies fed 2.18% N diet. Results show that intake of high N concentration diets maximizes egg production but can compromise survival, and suggest that intake of higher N concentrations that result in maximal egg production also maximize the suppression of responses to spinosad bait when there is no competing N source. More attractive baits that stimulate feeding by flies of all nutritional states, including those that have fed on large amounts of N, may be needed to achieve more rapid fly control in highly infested trees. Key words: Tephritidae, nitrogen concentration diets, physiological responses, behavioural responses