Spots may also occur on veins and petioles, and leaf margins may be turned under. Infected rachis, stems and petioles have dark brown to black streaks or blotches. Cluster stems may become brittle and break. Infected fruit become dark brown and brittle. Proper pruning is essential for the control of this disease.
Early sprays are particularly important.
Powdery Mildew Powdery mildew can infect all green parts of vines. Symptoms are a white powdery growth on infected parts. Berries infected before they are fully grown split and either dry up or rot. Infection of fully grown fruit results in a blotchy appearance or a netlike pattern of scar tissue. Infected fruit may cause off flavors in wine.