Two relatively new variants of grape leafroll virus, known as V3 and V5, are alarming some winegrape growers in California's famed wine country, according to an article yesterday in the San Francisco Chronicle.

The virus is spread by grafting infected cuttings and by the feeding of vine mealybug. It won't kill the vineyard, but it will prevent normal sugar development and reduce yields.

The Chron article, written by Alice Feiring, said the late Ed Weber, Napa County's previous UC Cooperative Extension viticulture farm advisor, and Deborah Golino, director of