Behavioral responses, rate of mortality, and oviposition of western cherry fruit fly exposed to malathion, zeta-cypermethrin, and spinetoram

Western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), is a pest of sweet and tart cherry, Prunus avium L. (L.) and P. cerasus L., respectively, in western North America. This fly is commonly controlled with spinosad bait sprays. Spotted wing drosophila, Drosophila suzukii Matsumura, is potentially a new pest of cherries in this region that could be a threat to orchards at the same time as R. indifferens. Drosophila suzukii apparently is not controlled using spinosad bait sprays, but may potentially be controlled using malathion, zeta-cypermethrin, and spinetoram. However, how well these last three materials protect fruit against reproductively mature R. indifferens is not known. In laboratory observations, R. indifferens spent the least amount of time on cherries treated with zeta-cypermethrin, possibly because of its toxicity and irritant effects. In laboratory experiments, zeta-cypermethrin killed flies more quickly than malathion and spinetoram, causing up to 100% mortality 2 h after exposure. Zeta-cypermethrin prevented all oviposition when flies walked on dried residues for 20-25 min or were directly sprayed, and then exposed to cherries with dried residues, simulating exposure of mature female flies in a treated orchard. Malathion and spinetoram reduced oviposition compared with controls, but did not prevent it, when flies contacted residues or were directly sprayed at a high volume. Results suggest zeta-cypermethrin is the most effective of the three materials at protecting cherries against mature R. indifferens and could be used in an integrated control program for it and D. suzukii.