Plastic mulches reduce abundance of some arthropods but are not detrimental to pollinators in primocane raspberries

Abstract

Cultural practices modify agroecosystems to prevent or reduce pest outbreaks, but they may be detrimental to beneficial arthropods and non-target effects are not commonly evaluated. Plastic mulches are an effective management practice for spotted-wing drosophila (Drosophila suzukii Matsumura) since they increase UV radiance in the plant canopy to reduce larval infestation of fruit. In this 2-year study, we evaluated how black, white, and metallic plastic mulches impact populations of arthropods, including predators of D. suzukii and raspberry pollinators in Wisconsin. The three plastic mulches did not affect arthropod richness and did not affect the abundance of about 65% of arthropod groups identified. In the raspberry canopy, the black mulch decreased the abundance of Orthoptera and Thysanoptera and increased Orius spp.; the white mulch increased Diptera, Thysanoptera, and Orius spp.; and the metallic mulch decreased Coleoptera, micro-Hymenoptera, Orthoptera, and Thysanoptera. On the ground, all mulches decreased the abundance of Gryllidae, the black and metallic increased Formicidae, and the white increased Staphylinidae. We reported 10 insect groups visiting raspberry flowers. Bombus impatiens Cresson was the most common, accounting for 82% of flower visits. The plastic mulches did not reduce flower visitation, though the white plastic mulch increased the abundance of B. impatiens compared to the other mulch treatments. Plastic mulches can reduce populations of pests such as D. suzukii and overall have no severe non-target effects on other arthropods in Wisconsin raspberry.