Using landscape ecology to inform spotted wing drosophila management practices

Drosophila suzukii (SWD), an invasive vinegar fly native to Japan, made its first appearance in Oregon in the fall of 2009. Since then, SWD has been confirmed in 17 Oregon counties. The pest is known to attack an extensive range of small and stone fruits, resulting in 2009 crop losses as high as 80%. In addition to commercial crops, the host plant range of SWD also includes wild fruits and berries found in many areas of the Pacific Northwest. Development of sound, effective management practices therefore requires a thorough understanding of SWD behavior not only in cultivated crops but in adjacent trees and wildlands, as these areas may act as a refuge and alternative food source for the fly. In the present study, we examine the influence of environmental variables (light, temperature, wind) and habitat characteristics (canopy cover, plant species diversity and abundance) on SWD activity in cultivated crops and adjacent vegetation. To measure SWD abundance in these areas, baited traps were placed along several vertical and horizontal gradients. Ratings were assigned to quantify varying habitat characteristics at each region. SWD abundance in tree traps was positively correlated with trap height. Trap counts in regions adjacent to crops were highest in areas with greatest plant diversity. By taking into account the influence of the overall landscape on the seasonal abundance, behavior, and movement of SWD, studies of this type will open the door to development of more effective management tools for growers and crop consultants.