Red Leaf Virus Update

UC Davis researchers suspect that red blotch disease is widespread wherever grapes are grown. (UC Agriculture and Natural Resources/photo)

Author/ Editor David Eddy, of American/Western Fruit Grower wrote on the recent seminar seminar on the UC-Davis campus titled: “An In-Depth Look At Red Leaf Viruses” on

Winegrape growers in California, as well as other scattered locations across the country, are seeing red in their normally green foliage, and they want to know why. Many assume their problem is the latest disease to be identified, red blotch.

But they shouldn’t jump to conclusions, warns Andy Walker of the University of California-Davis Department of Viticulture and Enology. Walker addressed an audience of growers, Extension advisors, and other industry players at a mid-May seminar on the UC-Davis campus titled: “An In-Depth Look At Red Leaf Viruses.”

Walker said there’s an awful lot unknown about what causes leaves to turn red, followed by plunging yields and Brix levels.

“We don’t even know if they are viruses or not,” he said.

Diagnosing such maladies is incredibly complicated, noted just about every speaker. Maher Al Rwahnih, a scientist at Foundation Plant Services at UC-Davis, noted that so far, 63 viruses have been found in grapevines.

“Fortunately not all of them cause problems,” he added.

For more great information from leaders in the field, see the complete article, The Red Leaf Virus Update. Additional background can be found at the University of California Integrated Viticulture web site.

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