Plastic mulches improve yield and reduce spotted-wing drosophila in primocane raspberry

Plastic mulches are increasingly used by growers producing perennial fruit crops to improve vegetative and fruit biomass, promote earlier yield, increase fruit quality, and enhance weed suppression. In this two-year study, we evaluated how black, white, and metallic plastic mulches impact primocane raspberry vegetative biomass, fruit yield and quality, and spotted-wing drosophila (Drosophila suzukii; SWD) infestation in a humid continental climate. All three plastic mulches increased vegetative biomass compared to the control with grass within the row. Marketable fruit yield was increased by 68-139%, 44-76%, and 33-110% in the black, white, and metallic plastic mulch plots, respectively, compared to the control. The black mulch extended fruit production by two weeks compared to the other treatments. Increases in vegetative and fruit biomass may be attributable to increased soil temperature under the black plastic mulch and increased reflection of photosynthetic active radiation (PAR) in the white and metallic mulches. None of the plastic mulches impacted the fruit quality parameters assessed, including soluble solids content, pH, titratable acidity, anthocyanin concentration, and total phenolics, compared to the control. All three plastic mulches reduced the proportion of unmarketable fruit, likely due to their 40-71% reduction in SWD larval infestation of fruit compared to the control. Overall, black, white, and metallic plastic mulches are an effective cultural practice for managing SWD while simultaneously increasing fruit and vegetative biomass.