Electrophysiological, behavioral, and field responses of olive fruit fly to modified Brewer's spent yeast...

Olive fruit fly, Bactrocera oleae (Rossi), is the primary olive pest in the Mediterranean, where management increasingly seeks sustainable alternatives to synthetic insecticides. This study evaluates recycled Brewer's spent yeast (BSY) from Croatian breweries as a potential sustainable attractant. Two BSY types (ale and lager) were processed into modified formulations at concentrations of 5%, 10%, and 15% and tested through electroantennogram (EAG) analysis, laboratory multiple-choice assays, and field trials. Adult flies were categorized into 5 groups based on age and mating status. Normalized EAG analysis revealed a significant dose-response relationship in females, with sensitivity increasing with ale-type concentration (5% to 15%), especially in young flies (0 to 4 days). In contrast, female sensitivity to lager-type BSY showed a slight age-dependent decrease. Laboratory multiple-choice assays confirmed these findings: 10% modified lager-type BSY was most attractive to young adults, while older, mated females responded consistently to 15% lager and 10% ale formulations. In field trials across 2 orchards, the 5% lager-type bait was the most effective, capturing 1.46 flies per trap per day, while higher concentrations resulted in lower captures. The research shows that olive fruit fly attraction to BSY is physiologically modulated by age and mating status. The strong performance of these low-concentration, recycled yeast baits demonstrates their potential as cost-effective, sustainable attractants that may lead to promising approaches for Integrated Pest Management in olive cultivation.