Evaluation of high tunnels for management of Drosophila suzukii in fall-bearing red raspberries: Potential for reducing insecticide use

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is an invasive pest of soft-skinned fruit causing significant damage on a variety of fruit crops in North America, Europe, and Asia. In North America, fall-bearing fruit, such as primocane raspberries, ripen when D. suzukii populations peak and thus are vulnerable to high levels of infestation. In recent years, growers in northern climates have increased raspberry production under protected culture (high tunnels), resulting in season extension, increased yield, and improved fruit quality. High tunnels may be used as a pest management tool by physically excluding insect pests. This study investigated whether D. suzukii can be excluded from fall-bearing raspberries cultivated under tunnels covered with plastic or fine mesh netting, and whether this production technique can improve fruit marketability and serve as an alternative to insecticide application. We found that berries in plastic-covered tunnels had low season-long levels of infestation by D. suzukii (mean = 2 %), compared to netted tunnels (35 %), insecticide-treated open plots (60 %) and untreated open plots (81 %). Our microclimate data show that temperature and humidity levels inside the plastic-covered tunnels were often outside the previously published optimal temperature range for development, mating, and/or oviposition for D. suzukii , and may have therefore limited overall population growth. We conclude that exclusion and modification of microclimate may be effective and complementary pest management strategies for fall-fruiting raspberry and serve as an alternative to insecticide applications, particularly for small-acreage and organic production systems.