Exploring the influence of habitat, ground refugia and behavioral strategies on the overwintering success of Drosophila suzukii, Matsumura

BACKGROUND

The overwintering biology of Drosophila suzukii is poorly understood. While thermal tolerance studies suggest that winter morphotype females likely survive harsh winters given physiological changes that lead to cold-hardening, additional factors such as habitat selection are likely important but poorly understood. In the present study, we conducted a field study at three vineyard sites to investigate winter habitat selection, a semi-field study to measure survival outcomes depending on various ground refugia, and a laboratory study to evaluate vertical movement in response to simulated flood conditions often observed in winter.

RESULTS

Our results showed three things. First, Drosophila suzukii was most abundant in wooded areas of vineyards and near pomace piles. Few were captured in the vineyard itself and even fewer were captured in the winery facilities. Second, insulating ground cover such as straw was beneficial to improving survivability. Third, while insulating ground cover was beneficial during stable periods below freezing, during warm-up periods where snow melts and subsequently floods the ground, fly mobility and vertical movement was critical for survival.

CONCLUSION

Cold acclimated flies are active participants in their environment, even at freezing temperatures, navigating changing landscape features and adjusting their position in response to temperature and ground conditions. Our data showed for the first time that cold acclimated flies are capable of vertical movement even at freezing temperatures as water levels rise at the ground level during thaw events. Thus, the overwintering behavior and ecology of D. suzukii is more complex than previously thought, and there are likely several factors in addition to physiological cold hardening that contribute to overwintering success. © 2025 Society of Chemical Industry.