Plastic mulches reduce adult and larval populations of Drosophila suzukii in fall-bearing raspberry

The invasive spotted-wing drosophila, Drosophila suzukii, is a major pest of fruit crops world-wide. Management of D. suzukii relies heavily on chemical control in both organic and conventional systems, and there is a need to develop more sustainable management practices. We evaluated the efficacy of three colors of plastic mulches at reducing populations of D. suzukii in fall-bearing raspberry and assessed the mulches impacts on canopy microclimate factors relevant to D. suzukii. Black, white, and metallic plastic mulches reduced adult D. suzukii populations by 42-51% and larval populations by 52-72% compared to the grower standard. The mulches did not change canopy temperature or relative humidity, but metallic mulches increased canopy light intensity compared to the black mulch. Radiance in the visible spectrum (401-680 nm) was higher for the white and metallic mulch plots, but the black mulch plots did not differ from the control. In the UV spectrum (380-400 nm), all three plastic mulches had higher radiance than the control plots. Future studies will determine whether changes in radiance are associated with the observed reduction in D. suzukii populations. Plastic mulches are a promising cultural practice for managing D. suzukii since they can reduce adult and larval populations and could be incorporated into an integrated pest management program in both organic and conventional systems.