Seasonal changes in odour preferences of spotted wing Drosophila (SWD) and their implications for monitoring

The Asiatic vinegar fly Drosophila suzukii (spotted wing Drosophila, SWD) has recently invaded Europe, and immediately became a key pest of grapes, stone and soft fruits. Unlike other fruit flies that typically infest only overripe and rotten fruit, SWD females oviposit in ripening fruit, leading to considerable economic damage in a broad range of soft-skinned fruits. Here we present recent outcomes from applied research revealing important insights into SWD population dynamics and seasonal changes in odour preferences. Firstly, we demonstrated that the currently widely applied monitoring programs, with traps and liquid attractant based on apple cider vinegar (ACV), provide a distorted picture of the actual SWD population dynamics profile. Use of alternative attractants clearly showed that there is an underestimation of the SWD population development during the main soft and stone fruit production periods (late spring-summer). Secondly, we attempted to unravel the seasonal shifts in preference of the SWD population between fermentation cues (like ACV) and fruit odour. Differences in seasonal odour preferences between winter and summer morphs of SWD were observed in a two-year field experiment. A lab experiment only partially confirmed these findings.