Host-associated volatile cues drive foraging behavior of Trichopria drosophilae toward Drosophila suzukii- infested fruits

The spotted-wing drosophila ( Drosophila suzukii ), a globally invasive pest, induces distinct shifts in the volatile organic compound (VOC) profiles of infested cherry fruits, enhancing their attractiveness to the pupal parasitoid Trichopria drosophilae . Comparative VOC analysis revealed significant differences among D. suzukii -infested, mechanically damaged, and healthy fruits. Infested cherries emitted elevated levels of key attractants, including esters (ethyl acetate: 0.36 ng/µL; isoamyl acetate: 0.48 ng/µL) and aromatic aldehydes (4-ethylbenzaldehyde: 0.86 ng/µL), which were absent or minimal in controls. Non-metric multidimensional scaling (NMDS) confirmed distinct VOC clustering, with infested fruits chemically diverging from healthy or mechanically damaged samples. Electrophysiological (EAG) assays identified ethyl acetate as the most potent stimulant, while behavioral assays showed concentration-dependent responses: 10 µg/µL isoamyl acetate elicited strong attraction (72% response rate), whereas 3-methylbutanoic acid acted as a repellent (34% response rate). Cage experiments demonstrated that benzyl alcohol, ethyl acetate, and isoamyl acetate significantly increased parasitism rates in D. suzukii pupae compared to controls, with isoamyl acetate showing the strongest effect. These results reveal specific semiochemicals mediating tritrophic interactions and underscore their potential for optimizing T. drosophilae -based biocontrol strategies against D. suzukii .