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Access Practical Winery & Vineyard article archive online: practicalwinerylibrary.com TECHNICAL RESOURCE FOR GROWERS & WINERIES 55 Cold stability of wine part two—Evaluating cellar/laboratory methods By Patricia Howe 64 Berry ripening and wine aroma By Alain Deloire 68 Leaf spots not caused by insects or disease By Fritz Westover and Jim Wolpert 72 GCoP improves viticulture outreach education By Eric Stafne 75 Smart Viticulture—An extraordinary book By Richard Smart grapegrowing GRAPEVINE RED BLOTCH PhotoS: Marc Fuchs, Cornell University, Geneva, N.Y. New technology identifies virus BY PWV Staff N ew DNA sequencing technology has been used to discover the grapevine red blotch-associated virus (GRBaV) in grapevines affected by "red blotch," a disease that discolors grape leaves in early fall and reduces sugar levels in grapes. Nursery managers received the new information during an annual industry update at the University of California, Davis, Feb. 20, 2013. The virus is of particular concern to wine grape growers, whose grapes must reach a certain sugar content level before they are suitable for winemaking. "The most urgent research need now is to determine how the virus spreads," says Deborah Golino, director of the University of California, Davis-based Foundation Plant Services and a cooperative extension plant disease specialist. "Due to the distribution of the virus in many parts of the United States and evidence that it can be transmitted by grafting, we suspect that red blotch disease is widespread wherever grapes are grown. "Red blotch disease has been identified among red and white vinifera culti- Red blotch in Cabernet franc. vars both young (first leaf) and mature (5- to 20-years-old), grape vineyards in California, New York, Virginia, Maryland, Pennsylvania, Texas and Washington. A virus almost genetically identical to red blotch also was found in Canada." GRBaV has been detected in nine red cultivars: Cabernet franc, Cabernet Sauvignon, Malbec, Merlot, Mourvédre, Petite Sirah, Petit Verdot, Pinot Noir and Zinfandel." Detection in Chardonnay and Riesling vines occurred during harvest 2012, and the description of the symptoms will be available after harvest 2013. Red blotch disease was first recognized Leafroll in Cabernet franc. in 2008 in a Napa Valley vineyard by Jim Wolpert, a UC Davis-based cooperative extension viticulturist, and Mike Anderson, a viticulture researcher and manager of UC Davis' Oakville Experiment Station. Investigations into what appeared to be a new disease began in 2009. GRBaV was reported in independent studies in California and New York in 2012. There is a very good correlation between the presence of GRBaV and red blotch symptoms. Two virologists—Mysore Sudarshana, a USDA-ARS researcher at UC Davis and Maher Al Rwahnih, a researcher at Foundation Plant Services (UC Davis)— pr actica l win ery & vin eya rd APRIL 20 13 51