(Phys) - 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," said Deborah Golino, a Cooperative Extension plant disease specialist and director of the UC Davis-based Foundation Plant Services. "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," Golino said. Golino encouraged vineyard owners and managers to evaluate their vineyards for red blotch disease as they would for any other viruses. Symptoms include blotches of pink or red veins on green leaves in the fall, when grape leaves would normally be turning a uniform gold color. Growers also might notice that their grapes are slow to develop sugar levels sufficient for winemaking, with some grapes never fully maturing.