Identification of biorational insecticides for managing spotted wing drosophila in organic blueberry production

Drosophila suzukii (Matsumura) is an invasive pest of thin-skinned fruits, including strawberry, blueberry, and blackberry, and a serious threat to Florida's small fruit industry. The female fly uses her serrated ovipositor to puncture the skin of ripening fruits and lay an egg beneath the surface. Larvae-infested fruit are unacceptable for the fresh market and have caused severe economic losses for the industry. Organic growers have a limited number of effective compounds available for use against D. suzukii. This encourages the overuse of effective insecticides and increases the potential for the development of insecticide resistance. The objective of this study was to evaluate the effectiveness of biorational insecticides that are labelled for organic use for management of D. suzukii in field-grown southern highbush blueberries (Vaccinium corymbosum L. × V. darrowi Camp). Treatments were applied using the manufacturer's recommended rates and applications were made at 7-d intervals using an airblast sprayer. Adult D. suzukii flies were sampled weekly using clear plastic cup traps baited with a yeast-sugar-water mixture. Ten berries were randomly selected each week to evaluate berry infestation. Natural enemies were sampled using yellow sticky cards. Burkholderia spp. and spinosad were not different than the control in terms of adult flies or berry infestation and were greater than all other treatments evaluated. Among the beneficial insects, two families of parasitoids, Aphelinidae and Pteromalidae varied among treatments. Our results indicate that three biorational insecticides, Chromobacterium subtsugae, sabadilla, and pyrethrins+azadirachtin, can be used to control adult D. suzukii and reduce fruit infestation with minimal effects on natural enemies. Furthermore, the effectiveness of spinosad on D. suzukii was reduced compared with previous studies.