First Report of Grapevine Red Blotch Associated Virus (GRBaV) on Norton

Written by

Phil Brannen

June 26, 2017

We recently had a Norton (aka Cynthiana) vine submitted to our clinic by Clark McAllister (county agent in Lumpkin County), and the vine(s) were showing odd symptoms for Norton. Leaves were somewhat chlorotic, but the major concerning symptom was a ring spot on the leaves, along with spots on the shoots which are similar to those of Phomopsis (see attached). The plant was eventually diagnosed with grapevine red blotch associated virus (GRBaV). We have previously identified this virus on vinifera grapes, but this might be the first report of this virus on Norton (aestivalis). Without regard, it is a first report for Georgia. If you see Norton with similar symptoms, this could be the cause. The symptoms observed on Norton are generally different from previously observed symptoms in vinifera, and I am not sure how consistent these will be. See attached for a fact sheet on GRBaV for vinifera, as symptoms are very similar in many cases to those of leaf roll virus. If the results of viral infection are consistent, we can expect infected Norton plants to show reduced photosynthesis, less pruning weight (growth), lower sugars, uneven ripening, and possible decline over time. However, all of this is speculative at this point, and impact may be minimal. If you do observe odd symptoms on Norton, please report this to your county agent. Nutrient issues or mites (yellowing) could also be at play, but the ring spot is unique.

Norton Grapevine Red Blotch Associated Virus Symptoms

Grapevine red blotch associated virus

Posted in: Bunch Grapes, Pest management Guidelines

Phil Brannen

Phil Brannen is a Professor in the Plant Pathology Department at the University of Georgia. He attended the University of Georgia for his undergraduate degree in Plant Protection and Pest Management, where he also received an M.S. in Plant Pathology, followed by a Ph.D. in Plant Pathology from Auburn University. He has extensive experience with disease management programs in numerous cropping systems. He serves as the extension fruit pathologist for Georgia – conducting research and technology transfer for multiple fruit commodities. His efforts are directed towards developing IPM practices to solve disease issues and technology transfer of disease-management methods to commercial fruit producers. He also teaches the graduate level Field Pathology Course, the History of Plant Diseases and their Impact on Human Societies Course, team-teaches the IPM Course, coordinates the Viticulture and Enology in the Mediterranean Region Course (Cortona, Italy), and guest lectures in numerous other courses throughout the year.