Department of Plant Pathology

Powdery mildew is a pervasive disease of cultivated grape. We conducted six field trials in a mature Chardonnay vineyard in Sacramento County to determine the efficacy of selected chemical and ‘soft chemistry’ fungicides (including new experimental materials) to control powdery mildew. Overall disease pressure at the site was low during much of the 2007 field season, but reached moderate levels by the time of veraison. Treatments exhibited a range of efficacy, with synthetic materials usually providing better control than copper-based products, biological fungicides, or other soft chemistry materials.