Good Fruit Grower

March 15

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L eafhoppers in grapes are receiving new attention since being implicated as a vector of the emerging red blotch wine grape disease. Economic thresh- olds for the insect may become a thing of the past if the virus moves into Washington State vine- yards and growers must shift from control to eradication. The pest landscape for wine grapes could be chang- ing as more is learned about a serious new disease called grapevine redleaf (or red blotch) associated virus. The disease was first described on Cabernet Sauvignon grapes in California's Napa Valley in 2008 and has since infected many vineyards in Napa and Sonoma counties. The disease, confirmed in both red and white variet- ies, has been detected in the major wine grape-producing regions of Washington, New York, other East Coast and southern states, and Canada. Symptoms in red varieties include reddening regions within leaf blades. In white cultivars, symptoms can range from subtle to obvious chlorotic regions within leaf blades. The disease is feared because it causes inconsistent ripening and delayed matu- rity, and significantly reduces grape yield and quality. Scientists are quickly getting up to speed on the new disease. Preliminary research at Washington State University has shown that the Virginia creeper leafhopper, under greenhouse conditions, can spread the disease to uninfected plants. Redleaf disease is in the geminivirus family, of which leafhoppers and whiteflies are known vectors. Washington State has two species of leafhoppers that inhabit vineyards, according to Dr. Doug Walsh, WSU entomologist and statewide integrated pest management spe- cialist. The grape leafhopper and Virginia creeper leafhopper are found in Washington vineyards but have not been major pests for grape growers in the past. "But with the pending concern regarding leafhoppers and red blotch disease, this is particularly disconcerting," Walsh said during talks of the Washington State Grape Soci- ety. Wine and juice grape growers in the state usually have few pest problems, thanks in 36 MARCH 15, 2014 GOOD FRUIT GROWER Grapes Craft Distilling Training Sign up now for Training Workshops . . . Workshops to be held in Gig Harbor, WA June 23-27 September 15-19 November 10-14 Your First Big Step to the next Big Thing! To learn more about the workshops and to enroll online, go to For more information call 509-989-2683 This new market niche in the alcohol beverage industry is growing fast all over the country. Join us and those attendees from around the world to learn about this business and how to create your position in it. rDistillation Arts & Sciences r Licensing and Compliance r Business planning and Marketing r Hands On Distillation Participation Demos This comprehensive training will include: Special room and board rates for attendees at the Inn at Gig Harbor. Control leafhoppers to AVOID VIRUS The risk of grapevine redleaf virus makes controlling leafhoppers all the more important. by Melissa Hansen Virginia creeper leafhopper. The adult is shown at top and the nymph below. PHOTO BY LARRY WRIGHT, WSU PHOTO BY LORRAINE SEYMOUR, WSU "It may be that we only need to be concerned about one of the two species." —Dr. Doug Walsh

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