Two volatiles from anthracnose-infected blueberries trigger electrophysiological and aversive behavioral responses in Drosophila suzukii (Diptera: Drosophilidae)

Native to Southeast Asia, the spotted-wing drosophila (Drosophila suzukii Matsumura) is an economically important invasive pest of thin-skinned fruits such as raspberries, blueberries, and strawberries worldwide. To reduce the reliance on insecticides for managing this pest, alternative strategies like behavioral manipulation are needed. Previous studies have shown that D. suzukii adults avoid blueberry fruits infected with the fungal pathogen Colletotrichum fioriniae Marcelino & Gouli, which causes anthracnose fruit rot, leading to the identification of 9 potential repellent compounds. In this study, we further investigated the two most potent of these compounds-ethyl butanoate and ethyl (E)-but-2-enoate-to assess their repellent properties on the antennal and behavioral responses of D. suzukii. Electroantennogram (EAG) assays revealed that both esters elicited similar dose-dependent responses in male and female D. suzukii, which were often stronger than those triggered by 2-pentylfuran, a known repellent of this species. Additionally, we examined the behavioral responses of adult D. suzukii to these 3 repellent compounds under semi-field and field conditions using outdoor cages containing potted and planted blueberry bushes, respectively. Results from the cage studies showed that all 3 tested compounds can significantly reduce D. suzukii oviposition and adult emergence from blueberry fruits, with ethyl (E)-but-2-enoate sometimes outperforming the other compounds. Our findings indicate that the esters ethyl butanoate and ethyl (E)-but-2-enoate, which are induced from C. fioriniae-infected blueberries, elicit dose-dependent effects on D. suzukii antennae and act as effective oviposition deterrents. This supports their potential as promising tools for managing this pest through behavioral strategies.