Earlier activity of Drosophila suzukii in high woodland landscapes but relative abundance is unaffected.
Natural habitats can affect the population dynamics of mobile insects, and the spatial and temporal effects on agricultural pest species may be especially relevant for tailoring management strategies to the farm context. Drosophila suzukii Matsumura (Diptera: Drosophilidae) is suspected to utilize woodland habitat for wild hosts and overwintering with possible adverse effects of woods on adjacent fruit crops. A two-year study in the Upper Midwest, USA examined if the amount of woodland in the landscape affects early season activity and relative abundance of D. suzukii in raspberry fields. Thirty-five farms were selected to span a gradient of low-to-high woodland area at the 1.5 km scale. The first capture of D. suzukii occurred earlier at farms in high woodland landscapes. However, woodland area was not correlated with metrics of D. suzukii abundance in raspberry (growth rate, peak, fall, or total fly catch) suggesting similar crop infestation risk across landscapes. However, woodland area was negatively correlated with fall fly catch in the adjacent woods and significantly more flies were captured in the woods than raspberry. This study suggests woodland landscapes affect early season crop risk and the high numbers of D. suzukii in the woods have implications for understanding overwintering.