PD/GWSS Board Evaluates Red Blotch Disease for Possible Study
The California Department of Food and Agriculture’s (CDFA) Pierce’s Disease/Glassy-Winged Sharpshooter (PD/GWSS) Board held a lengthy discussion at its April 29 meeting in Sacramento regarding the designation of red blotch disease as a new disease for the Board to target for research and funding, but decided to defer a vote on the designation until its next meeting, scheduled for June 21 in Sacramento.
Board member Steve McIntyre of Monterey Pacific Vineyards, who chairs the Board’s “Other Pest or Disease Designation Committee,” that held two meetings to discuss red blotch, said, “There is a ton of interest in this and we’ve gotten a lot of calls. There is a lot we don’t know about this disease.”
With input from red blotch researchers Mysore Sudarshana, Adib Rowhani, and Maher Al Rwahnih of UC Davis (UCD), and Marc Fuchs of Cornell University, the committee went through the CDFA checklist for recommendation to declare a designation, and McIntyre said, “It scored higher than any other pest or disease we’ve evaluated to designate,” receiving 11 out of 13 points.
The PD/GWSS Board received authorization following 2009 legislation and the 2010 grower referendum to use assessment funds for research and outreach on other serious pests and diseases of winegrapes, as long as such funding does not interfere with PD/GWSS control and research efforts. To date, only the European Grapevine Moth has received designation by the Board and received funding for outreach.
Three grapevine nursery representatives attended this week’s meeting, citing industry concerns and business problems since red blotch was officially announced as a new grapevine disease in October 2012. Although he acknowledged red blotch has probably been around a long time, and the number of affected acres identified to date is small, Sunridge Nurseries field representative Michael Monette said, “It’s a major fire in our house right now, because of the unknown for growers who want to plant or replant, and because of vines being rejected because growers don’t want to take the risk.”
Red blotch disease, caused by grapevine red blotch-associated virus, shows symptoms similar to leafroll disease with discolored grape leaves in fall and reductions in grape sugar levels up to 5 degrees Brix. The virus can be graft transmissible, and it appears it can spread from neighboring vineyards to uninfected vineyards. It is believed that a vector could cause spread, but possible vectors have not yet been identified. Monette said research to identify a vector is a high priority.
Designation is supported by the California Association of Winegrape Growers (CAWG) according to president John Aguirre who said CAWG’s executive committee met last week and concluded there is sufficient concern about the problem to support research and funding. Aguirre said CAWG has also requested the U.S. Department of Agriculture allocate funds to study red blotch.
UCD Foundation Plant Services director Deborah Golino informed the Board that the American Vineyard Foundation (AVF) would likely announce funding for red blotch research within the next couple weeks as part of its annual funding cycle of project proposals that were recently evaluated. The California table grape industry has already contributed to AVF to specifically fund red blotch research. Some PD/GWSS Board members suggested the Board wait to vote on the issue after it has more specific information about what AVF has funded, and has more information on other sources of support for research and control efforts.
Board member Jim Ledbetter of Lodi-based Vino Farms acknowledged the disease is a serious issue, noting that his company had rejected two million vines out of 4 million ordered, but he advocated the Board wait to vote until it had more information. Board member Greg Coleman, VP of grower relations for E & J Gallo noted that red blotch is found in at least eight other states, and suggested it may be an issue for larger and more cooperative efforts. “My concern is whether this is the right venue. This is a bigger issue, and there may be other organizations that can take this on better than we can,” Coleman said.