Evaluation of Conventional and Alternative Products for Management of Grapevine Powdery Mildew in San Diego County, California

Powdery mildew, caused by Erysiphe necator , is one of the most economically important diseases of grapevine worldwide, reducing both fruit yield and quality. This study evaluated the efficacy of experimental, biological, and conventional treatments for managing grape powdery mildew. A field trial was conducted during 2025 in an established commercial Vitis vinifera ‘Picpoul Blanc’ vineyard located in the San Pasqual Valley agricultural region of San Diego County, California. Treatments were assessed for their ability to reduce powdery mildew incidence and severity on grape clusters. The results provide information on the relative performance of registered and experimental products and will support the development of effective powdery mildew management programs for grape growers in coastal California.