Efficacy of Mancozeb, Captan, Copper, and Pseudomonas chlororaphis for Control of Black Rot and Downy Mildew of Grape, 2025

Mancozeb, a broad-spectrum contact fungicide, is under regulatory pressure in the United States and elsewhere. In Georgia, mancozeb has been utilized extensively for early-season management of grape diseases. The removal of the Environmental Protection Agency (EPA) mancozeb tolerance for usage in grape production would necessitate the application of numerous low rates of captan and increased use of copper to provide broad-spectrum fungicides throughout as much of the season as possible. There are also biological materials with purported activity on many grape diseases. In a field trial, Captan 4L, Kocide 3000 (copper), and Howler Evo ( Pseudomonas chlororaphis) were reviewed for control of black rot and downy mildew. Mancozeb consistently provided lower disease levels than other treatments, but Captan 4L provided statistically equivalent control of both black rot and downy mildew. Kocide 3000, though providing efficacy against both pathogens, was not as efficacious as mancozeb. The biological product, Howler Evo, did not provide efficacy against either pathogen. Results from this trial will help growers determine which products are best to use for management strategies for these diseases in the future.