Good Fruit Grower

May 1

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N ematode management in the future will require a new approach, says a U.S. Department of Agriculture scientist. As soil fumigation becomes more restrictive, it will take new ways to control a growing problem in Washington State vineyards. Though most nematodes—microscopic roundworms that live in soil and water—are beneficial, plant-parasitic nematodes are not and cause economic damage by feeding on plant roots. Some nematode species can transmit viruses. "We keep losing nematode management tools," said Dr. Inga Zasada, U.S. Department of Agriculture research plant pathologist based in Corvallis, Oregon. "We don't have the nematode management tools that we had 40 years ago, and because of that, nematode management practices in the future will probably not be as effective as they were in the past." The U.S. Environmental Protection Agency initiated a first wave of new soil fumigant labels as part of its rereg- istration process. The new labels included such things as fumigation management plans and buffer zones. But the EPA is likely to impose more onerous restrictions when the agency completes its most recent review of soil fumigants, such as chloropicrin, dazomet, 1,3-dichloro- propene, methyl bromide, methyl isothiocyanate, and metam sodium/potassium. Zasada is working to develop sustainable plant-para- sitic nematode management systems for small fruits and grapes. Her research encompasses developing produc- tion systems that integrate a range of tools to promote root health and suppress nematodes, as well as providing information on management strategies. Zasada, who spoke during a session at the Washing- ton Association of Wine Grape Growers annual meeting, believes that a better understanding of nematode biol- ogy—knowing when they are most active, where they reside in the soil, and what host plants they like—will help growers improve management strategies, especially if soil fumigation becomes more restrictive in the future. Nematodes in Washington "We do have nematodes here," said Bill Riley, senior viticulturist for Ste. Michelle Wine Estates, Washing- ton's largest wine producer. Riley said, during a panel discussion, that soil samples taken from several of Ste. Michelle's older vineyards, like Cold Creek Vineyard, contained plant-parasitic nematodes. Chardonnay and Riesling vineyards had around 100 to 120 nematodes per sample, but one vineyard sample had 7,000 per sample. "We expect to see nematodes in old vineyards, espe- cially where vines are 30 to 35 years old," he said, add- ing that several Ste. Michelle vineyards are scheduled for replanting. "But we're concerned about going forward," he said, noting that some of the vineyards they will be replanting are certified under Salmon Safe and LIVE (Low Input Viticulture and Enology), both sustainable programs that prohibit soil fumigation. Todd Crosby, agronomist for Mercer Canyon Vine- yards, Prosser, agrees that nematodes in vineyards are a problem. "You can manage nematodes in existing 38 MAY 1, 2014 GOOD FRUIT GROWER Grapes New approach needed for nematodes Avoid white varieties if planting in a site with root knot nematodes. by Melissa Hansen PHOTO BY TJ MULLINAX Inga Zasada, USDA scientist, shares her latest research results during statewide grape talks. "We keep losing nematode management tools." —Dr. Inga Zasada

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