Evaluation of Biopesticides and Novel Chemicals for Grape Ripe Rot and Sour Rot Disease Management in Virginia

Two endemic late-season grape rot diseases, ripe rot and sour rot continue to pose a significant challenge to grape growers in Virginia and similar climates. Managing these diseases in the vineyard is challenging due to concerns over the increased risk of resistance against traditional single-site mode of action pesticides. This study evaluated the efficacy of different biopesticides and novel chemical options with a series of field trials across four vineyards in northern Virginia in 2021 and 2022. Among the tested products, a potassium-based nutrient formulation resulted in consistent ripe rot suppression in two of the three trials, showing around 46% and 83% less mean disease severity at the AHS AREC trial in 2022 and 2021, respectively, and 63% and 19% less mean disease incidence at the South Loudoun trial in 2021 and AHS AREC trial in 2022. For sour rot, zeta-cypermethrin with cyprodinil + fludioxonil or hydrogen peroxide + peroxyacetic acid resulted in effective control in two of the five trials, with a high of 71% and 73% less mean disease incidence compared to the untreated check in the Frederick trial in 2021 and 2022, respectively. In general, treatments with spinosad were less effective and resulted in lower disease control compared to those with zeta-cypermethrin and its fungicides/antimicrobials counterpart. The results suggest that integrating these biopesticides and novel chemicals into a spray program could offer a more sustainable solution for sour rot and ripe rot disease management without compromising the level of disease control.