By Tim Martinson
Grapevine red blotch is a disease that has emerged in several locations on the West Coast and in the East. It is associated with a newly identified virus called grapevine red blotch-associated virus (GRBaV). The virus was jointly identified by USDA-ARS virologist Mysore Sudarshana and his colleagues at UC-Davis and Cornell virologists Keith Perry and Marc Fuchs, who published its DNA sequence last summer.
Red blotch disease presents symptoms somewhat similar to grapevine leafroll virus on red varieties. Leaves turn red, but in contrast to leafroll, smaller veins turn red, and leaves do not curl as with grapevine leafroll virus. The major impact identified to date is that grapevines with red blotch stop accumulating soluble solids and end the season at four to six degrees brix lower than uninfected vines. Vegetative vine growth does not seem to be affected.
Grapevine red blotch disease has been identified in several varieties and in vineyards in California, New York, Virginia, Maryland, Pennsylvania, Texas and Washington. It was first identified in 2008 in experimental vineyards in Napa Valley and Lansing, New York. Thanks are due to Justine Vanden Heuvel for bringing the disease to Marc Fuchs' attention early on. Field studies of its distribution, spread, and effect on vine health are ongoing, and more research will be needed to identify its impact, symptoms on different varieties, and best management options.
The National Clean Plants Network released a factsheet on February 15.
A National Clean Plants Network webinar (announcement here) on Grapevine Red Blotch and GRBaV will be held on March 27, from 3:30 to 5:00 Eastern Daylight Savings Time. Preregistration is required.
Tim Martinson is senior extension associate with the department of horticulture, based at the New York State Agricultural Experiment Station in Geneva, NY.