Grapevine red blotch associated virus (GRBaV) is a concern to grape growers throughout the state. The virus has been present in vines for many years- however, it was formally identified and a diagnostic assay developed in 2012. In late 2014, a group of growers, nursery operators, OWRI faculty, and ODA plant health scientists convened to share information, provide an overview of the grapevine virus situation in Oregon vineyards, and strategize future steps. Dr. Bob Martin, USDA-ARS plant pathologist, described his GRBaV survey results- GRBaV has been detected in the Willamette Valley, but is more widespread in vineyards in southern Oregon and recent sampling indicates that the virus moves very slowly from vine to vine, if at all. For example, of 100 vines tested in a Willamette Valley vineyard planted in the 1970’s, only one positive plant was identified in a block of Chardonnay adjacent to a small block of Pinot noir that was completely infected. Similarly, 30 samples each of Grüner veltliner and Pinot gris adjacent to an eight year old severely infected Syrah block were all negative. If funding is secured, Dr. Martin will continue to investigate the spread of red blotch and its effects on wine quality. Dr. Vaughn Walton, OSU entomologist, reported that vector identification studies are on-going in California, but very little is known about red blotch vectors or transmission. The focus of his research is to monitor location and spread of the disease. Studies are also being conducted in southern Oregon to assess the spread of the disease in that environment.
For more information regarding the research in southern Oregon, please click here to read a research report from Dr. Vinay Pagay and Dr. Bob Martin.
One question that may ease growers’ minds is that nurseries are now testing for red blotch. One nursery owner said that 3,000 tested vines in WV yielded no positive results but southern Oregon had positives in the cultivars Tempranillo, Mourvedre and Merlot. It is possible that red blotch has spread through planting stocks, either nursery materials or from top-working plants with wood from field sources. Education on how to stop the spread of the disease will be a key component of red blotch outreach efforts.
The movement of vines and the ODA plant quarantine system, which states that it is illegal to move known infected plant materials into or within the state is an important component in stopping the spread of infected vines. 95% of Oregon grapevine nursery stock comes from California, therefore potentially infected plants may have arrived prior to the testing for GRBaV. Nursery managers from Sunridge and Duarte noted that the new Grapevine Foundation Block at Russell Ranch (where all material has been tested using the 2010 protocol for grapevine disease testing) will become the primary source of wood for certified nurseries. All material at the Russell Ranch tested negative for GRBaV in 2013. This part of the discussion generated two practical recommendations to grape growers:
- Plant only certified grapevine materials. Vines from Russell Ranch and Clean Plant Center Northwest (Washington State University-Prosser, WA) are certified free of GRBaV, Grapevine leafroll associated viruses and viruses causing trunk diseases.
- Unless individual vines are tested for known viruses, do NOT propagate from any vines in your vineyard. The risk of spread of viruses, even from asymptomatic vines, is too great.
Geoff Hall, viticulturist from Ste. Michelle Wine Estates stated that WSU faculty and industry associations consistently reinforce the need to exercise caution and utilize proper practices when managing the spread of viruses in vineyards, which applies to Oregon growers as well.
Outcomes from this important meeting include:
- A letter has been drafted to Oregon Department of Agriculture Director Katy Coba requesting that grapevine red blotch associated viruses be added to Oregon’s plant quarantine list
- ODA plant pathologists together with the Oregon Wine Board will apply for an ODA specialty crop block grant to do a survey o