Vacuum extraction: an effective larval sampling method for spotted-wing drosophila in small fruit crops

Detecting and sampling the pest for pest management, either through enumerating their life stages or by quantifying the crop damage, is the cornerstone in deploying integrated pest management. Currently, for spotted-wing drosophila, Drosophila suzukii Matsumura, larval extraction from the fruit samples involves immersing the fruits in hot water, salt, or sugar solution. We are introducing a novel, fast, and effective larval sampling technique where D. suzukii larvae can be extracted from infested fruits by subjecting the fruit samples to vacuum pressure. We optimized the vacuum pressure and vacuum duration for larval extraction from blueberries by testing a range of vacuum pressures and durations. A vacuum pressure of -98 kPa for 60 min resulted in the maximum larval recovery of the small, medium, and large larvae from blueberries. A 30-min incubation at -98 kPa also yielded similar results. Larval extraction at -98 kPa for 60 min on average recovered 61, 70, and 83% of larvae from 2, 4, and 6-day incubated fruit samples, respectively. The fruit sample size (37, 149, and 298 g) did not affect the larval extraction efficacy. Additionally, comparing larval extraction efficacy at -98 kPa with the salt and sugar extraction, incubated for 10, 30, and 60 min, suggests that vacuum extraction is comparable to or more efficient than the salt and sugar methods in extracting larvae from the infested blueberries. Overall, our results indicate that vacuum sampling is a promising method for detecting D. suzukii larval infestation in small fruit crops.