Modifications of plant microclimate by plastic mulches reduces Drosophila suzukii infestation

Spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is one of the most detrimental pests of small fruit crops worldwide and its control relies heavily on pesticides, so there is a need to develop alternative management practices. Cultural practices that make the microclimate hotter, drier, and brighter than optimal conditions for the pest may be highly effective. In this two-year study, we evaluated how black, white, and metallic plastic mulches influence the raspberry plants’ microclimate to reduce D. suzukii larval infestation of fruit in the canopy and increase mortality of fallen larvae and pupae on the ground. All three plastic mulches reduced D. suzukii larval infestation of fruit by 40–72% and killed 80–100% of larvae and pupae placed on the mulch surface. The mechanisms at play are likely the compounded effects of increased ultraviolet (UV) light, hotter and drier conditions in the low canopy, and hot mulch surface temperature. UV light may be especially important since it reduced D. suzukii oviposition in the lab. Overall, plastic mulches can effectively modify the microclimate to make it less favorable for D. suzukii, reducing infestation in fruit and on the ground.