Erythritol combined with non-nutritive sucralose increases feeding by Drosophila suzukii, quickens mortality and reduces oviposition

Abstract

Drosophila suzukii, spotted-wing drosophila (SWD), is a fly pest of small fruits and cherries often managed by chemical insecticides, and finding a convenient, human-safe alternative is a challenge. Erythritol, a non-caloric sugar, is safe for humans and toxic to D. suzukii by causing an osmotic imbalance. Combining erythritol with sucrose as a phagostimulant can enhance fly mortality. However, sucrose is sticky when applied on plants and provides flies with nutritional carbohydrate if a non-lethal dose is ingested. Therefore, our objectives were to find a sucrose alternative, a non-caloric sugar that also has phagostimulative properties, where the formulation will enhance mortality, and reduce daily oviposition rates before females die. Through capillary no-choice and choice experiments, flies fed on 0.1 M sucralose (Sul) readily, and flies consumed more 1.5 M erythritol: 0.1 M sucralose (E:Sul) formulation than erythritol alone. In eleven different mortality assays, E:Sul induced mortality as did the 1.5 M erythritol: 0.5 M sucrose (E:S) formulation, while E:Sul was more successful than E:S when D. suzukii could also drink water to offset water loss. Sucralose (0.1 M) itself had modest insecticidal properties, but when combined with erythritol it increased the insecticidal effect. Both E:Sul and E:S formulations reduced oviposition when it was directly fed to D. suzukii in a cotton wick or applied on blueberry fruit. The latter suggests that the sugary coating on fruits has a deterrent effect. Given the potential of E:Sul, additional studies on the effect of sucralose on fly osmolar regulation, sugar metabolism, and field efficacy trials are underway to provide growers an efficacious tool.