First Paragraph: What is red blotch? Grapevine red blotch-associated virus (GRBaV), is the latest addition to the list of more than 75 graft-transmissible agents that have been identified in grapevines. This recently reported virus is associated with the emerging red blotch disease that was described for the first time on Cabernet Sauvignon in Napa Valley in 2008. There is a very good correlation between the presence of GRBaV and red blotch symptoms, but this correlation does not prove causality.
