DEVELOPING YEAST-BASED INTERFERING RNA BIOPESTICIDES AGAINST SPOTTED-WING DROSOPHILA

In the proposed research, the Wilson Tree Fruit Entomology laboratory at Michigan State University (MSU), with expertise in applied, on-farm research and Extension related to Drosophila suzukii in tart cherry orchards, will collaborate with the Scheel laboratory at Indiana University (IU), which recently developed cost-effective, scalable, stakeholder-accepted, user-friendly, species-specific yeast ribonucleic acid (RNA) pesticides that target mosquitoes (Duman-Scheel, 2019) and who has now identified double-stranded RNA (dsRNA) targets specific to D. suzukii. This interdisciplinary collaboration synergizes the strength of MSU's D. suzukii applied chemical ecology and behavioral science expertise with that of IU's insect genetics expertise, to develop interfering RNA (RNAi) attractive targeted sugar bait (ATSB) technology against D. suzukii. We propose to exploit the attractive properties of yeast to lure these economically destructive agricultural pests to feed on ATSBs containing yeast that has been designed to express biorational RNA insecticides that target D. suzukii-specific neural genes required for fly survival. It is hypothesized that this strategy can be used for species-specific D. suzukii control, and this hypothesis will be tested through pursuit of the following objectives.Objective 1. Scaled production of D. suzukii-specific heat-killed yeast RNAi insecticides (IU). We have identified a yeast strain expressing short hairpin RNA (shRNA) corresponding to the D. suzukii Shaker gene. Preliminary data show that this yeast will kill D. suzukii but is not toxic to non-target insects. Using established methodology, we will pursue scaled production of the insecticidal yeast for further assessment of this hypothesis in laboratory and field trials.Objective 2. Evaluation of yeast-based RNAi ATSBs for competitive efficacy, longevity, and non-target effects to relevant biological control agents (MSU). We hypothesize that yeast RNAi pesticides 1) can be designed to outcompete other attractants including ovipositional substrates, 2) will maintain their attractiveness for the duration of a growing season, and 3) will not affect parasitoids of D. suzukii.Objective 3: Evaluation of yeast-based RNAi ATSBs to prevent fruit infestation by D. suzukii (MSU). We hypothesize that RNAi baits will be able to prevent fruit infestation below detectible levels and that the best deployment strategy will be to use ATSBs along orchard margins adjacent to habitat out of which D. suzukii are expected to emigrate. Objective 4. Extension of project results to stakeholders. We hypothesize that when presented with the results of this study, 1) growers of susceptible fruit crops will be receptive to the idea of using RNAi technology to manage D. suzukii on their farms, and 2) pesticide manufacturers will be convinced of this technology as being valuable and marketable.