Development of an eco-friendly RNAi yeast attractive targeted sugar bait that silences the Shaker gene in spotted-wing drosophila, Drosophila suzukii

Background: Drosophila suzukii, or spotted-wing drosophila (SWD), (Diptera: Drosophilidae), are invasive vinegar flies of East Asian origin that have wreaked havoc on the small fruit and berry industry. In locations where SWD are well established, weekly chemical insecticide applications are necessary, resulting in increased economic costs, unwanted environmental impacts ensuing from loss of non-targeted organisms, and the eventual emergence of populations that are resistant to these insecticides. It is therefore critical that new classes of biorational pesticides and cost-effective technologies for controlling SWD are identified. Results: Here, we used the attractive properties of Saccharomyces cerevisiae, bakers yeast, which was designed to express an RNA interference (RNAi) pesticide that specically targets the SWD Shaker (Sh) gene, to lure and kill flies that feed on the yeast, which was delivered in a feeder as a component of an attractive targeted sugar bait (ATSB). The yeast, which was heat killed prior to preparation of the ATSB, silenced the Sh gene, resulting in severe neural defects and fly mortality in laboratory trials. The RNAi yeast was successfully fed to the flies in an easily assembled soda bottle feeder that continuously rewetted the yeast with soda, which lured and killed the flies in simulated field trials. Despite this toxicity observed in SWD, consumption of the yeast had no impact on the survival of other dipteran insects. Conclusion: This promising ATSB technology, which was prepared with a new class of RNAi yeast insecticides, could one day be an effective component in integrated SWD control programs.