Evaluation of Fungicide Programs for the Management of Powdery Mildew on Table Grapes in California, 2024

Grape powdery mildew, caused by Erysiphe necator, is one of the most economically important grape diseases worldwide, significantly reducing crop yield and quality. All green tissues of the vine are susceptible to infection; therefore, intensive fungicide applications are implemented throughout the growing season. Symptoms first appear as chlorotic spots on the upper surface of leaves accompanied by white to grey mycelium with a filamentous aspect on the lower surface. On fruit and rachises, infections produce white, powdery masses that can cover the entire cluster surface, reducing photosynthesis and causing berry cracking. This report evaluates the efficacy of fungicide programs for the management of powdery mildew in table grapes in Kern County, CA. The trial was conducted in 2024 in a 6-year-old Vitis vinifera ‘Flame Seedless’ vineyard. Results from this trial provide valuable insights for U.S. grape growers in optimizing fungicide application timing and coordination to enhance disease management.