Leaf spots caused by several fungi genera are usually not serious. Infected leaves can be collected and destroyed.
Various genera of powdery mildew cause a white coating on the leaves. Severe infections kill the leaves. Use sprays of benomyl or sulfur.
Crown gall caused by Agrobacterium tumefaciens causes formation of warty-looking galls on the vine trunks. There is no satisfactory control. Avoid planting in soil where the disease has been a problem.