What to Do About Red Blotch

(Wines&Vines) - Among many useful sessions at the Unified Wine & Grape Symposium, one of the most valuable was the workshop on red blotch virus for winemakers organized by Alison Crowe of Garnet Vineyards, part of the Silverado Premium Properties family.

Crowe was joined by Peter Opatz of Silverado Winegrowers, Chik Brenneman of the University of California, Davis, Lise Asimont of Francis Ford Coppola Presents in Geyserville and Charles Thomas, winemaker for Huneeus Vintners including Quintessa Vineyards.

Opatz began by describing a “nightmare” in a 40-acre vineyard he manages in Alexander Valley: “It was a great site, and it wasn’t until the third leaf that we found a problem with red blotch. The symptoms we noted could almost be attributed to deficiencies with phosphorus or potassium at first.”

The vines had many red and pink leaves, and the grapes stopped accumulating sugar at 19º Brix. Commercial labs couldn’t identify the problem at the time, so Opatz turned to Jim Wolpert at U.C. Davis, who confirmed the virus. “About 75% of the vines in the vineyard were infected,” Opatz said.

Fortunately, a winery bought the grapes anyway, and the grower paid for Mega Purple and concentrate to make them usable.

Another infected vineyard Opatz managed contained Ruby Cabernet—and in this case, they could only sell the grapes for distilling. Opatz said the red blotch problem became so serious that Silverado stopped planting last year, though it has started again after much testing of vines.