Potential of Muscadine Grapes as a Viable Host of Drosophila suzukii (Diptera: Drosophilidae) in Blueberry-Producing Regions of the Southeastern United States

Spotted wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), is an economically important invasive pest of many soft- and thin-skinned fruits in the United States. This pest has recently threatened blueberry production, a multimillion dollar industry in the southeastern United States. Muscadine grapes are often planted in mixed-crop production systems with blueberries. Although D. suzukii can oviposit in intact soft-skinned grapes, it has yet to be investigated whether muscadine grapes, having thicker-skinned berries, can be a viable host. The goal of this study was to assess the potential of muscadine grapes as a viable host of D. suzukii. Choice and no-choice assays were conducted with two muscadine grape varieties to determine the effect of ripeness and wounding of berries on their susceptibility to D. suzukii infestation. Results from the ripeness assays indicate that D. suzukii was unable to complete development to adulthood in unripe muscadine grapes. D. suzukii was able to complete their development in ripe and overripe grapes, although their success rate was significantly lower than in ripe blueberries. In both choice and no-choice wounding assays, wounded grapes had significantly more oviposition and subsequent development to adulthood than intact grapes. Moreover, wounded muscadines were similar to intact blueberries in D. suzukii oviposition, pupation, and adult eclosion. These data suggest that ripe and overripe muscadine grapes, especially when split and wounded by other pests such as birds, can support D. suzukii development and possibly sustain their populations around berry orchards for a longer period of time after blueberry harvest.