Blueberries infected with the fungal pathogen Colletotrichum fioriniae release odors that repel Drosophila suzukii

BACKGROUND: Spotted-wing drosophila, Drosophila suzukii, is a serious pest of thin-skinned fruits. Alternative methods to control this pest are needed to reduce insecticide use, including new repellents. Previous research demonstrated that D. suzukii adults use odor cues to avoid blueberries infected with the fungal pathogen Colletotrichum fioriniae, which causes the disease anthracnose. To identify novel D. suzukii repellents, we investigated the volatile emission from experimentally infected fruit, which were inoculated with C. fioriniae isolates in the laboratory, and from field-collected fruit, which were naturally infected and harvested from a field. We then tested the pathogen-induced volatiles on D. suzukii adult behavior.

RESULTS: Volatile emission was similar between all five C. fioriniae strains, with good agreement between experimentally-infected and field-collected berries. In total, 14 volatiles were found to be more abundant in infected versus uninfected fruit headspace. In multiple-choice bioassays, nine of the 14 volatiles elicited repellency responses fromadult D. suzukii. These nine volatiles were further evaluated in dual choice assays, where all nine reduced fly capture by 43–96% compared to the control. The most repellent compounds tested were the esters ethyl butanoate and ethyl (E)-but-2-enoate, which weremore or equally repellent to the known D. suzukii repellents 1-octen-3-ol, geosmin, and 2-pentylfuran. Dose–response assays identified concentration-dependent effects on D. suzukii repellency and oviposition when applied individually and consistent aversion observed across doses of a 1:1 blend.

CONCLUSION: We report two repellents from C. fioriniae-infected blueberries that could be useful semiochemicals for the behavioral manipulation of D. suzukii in the field.