In 2017, Foundation Plant Services (FPS) detected grapevine red blotch disease, caused by grapevine red blotch virus (GRBV), in the Russell Ranch Vineyard (RRV) and Classic Foundation Vineyard. This occurrence of red blotch resulted in additional precautions to prevent the spread of the disease. FPS implemented more frequent inspections for disease symptoms and signs of vector activity, annual testing of all foundation vines for GRBV, and a comprehensive program to control the vector. In addition, we conducted a study on the seasonal variation and distribution of GRBV within vines to minimize the risk of false negatives.
This year, we tested every vine in both foundation vineyards for GRBV and grapevine leafroll associated virus-3 (GLRaV-3); 21 vines tested positive for GRBV (see table 1) and no vines tested positive for GLRaV-3. All affected vines were removed and destroyed. In all cases, positive vines were negative in our previous annual maintenance testing, indicating that material was likely GRBV-free at the time of distribution (see table 2). All customers who received material from these vines have been offered additional material and testing services by FPS. For current orders, selections are being tested individually prior to distribution. FPS continues its commitment to clean plant health, maintaining the highest testing standard for our foundation vineyards, and keeping the community informed as new information becomes available.