Grapevine Red Blotch Disease
Grapevine red blotch virus
2 host plants
Last updated
This profile contains verified disease data from extension databases. Regional field notes and expert review are in progress.
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.
Quick Reference
Management
Initial infection occurs when three-cornered alfalfa treehoppers acquire virus from infected grapevines and transmit to healthy vines during feeding. Foliar symptoms appear mid-summer (June-July in northern hemisphere) and progress throughout the growing season. Fruit symptoms develop concurrently with foliar symptoms, reducing berry quality for that vintage and subsequent years. Once infected, grapevines remain infected for life. Young vineyards post-planting are vulnerable to infection from nearby infected vines via treehopper vectors. Source: UC Davis research
Symptom expression becomes visible mid-summer after several months of systemic infection. Red varieties show characteristic red blotches while white varieties show pale green or yellow blotches. Berry development quality is impacted throughout ripening season. Treehopper vector presence and feeding activity influence virus spread and initial infection. Vine vigor, irrigation stress, and nutritional status may influence symptom severity. Source: UC Davis research, Wikipedia