Grapevine Red Blotch Disease

California grape cultivars show red discoloration of leaves and veins in late growing season. This emerging viral disease affects grape production. Current management relies on using disease-free planting stock. The virus spreads slowly in vineyards, and commercial significance remains under investigation in western regions.

Leaf spot and blotch diseases are primarily cosmetic on established plants, though repeated years of heavy infection can weaken them. Rake up and remove fallen leaves to reduce the spore load going into the next season. Avoid overhead watering that splashes spores from the ground onto lower leaves. If the problem is severe, protective fungicide sprays during spring leaf emergence can help, but sanitation does more than chemistry for most leaf spots.