By MATTHEW WEAVER
Researchers are working to determine why some Concord grape vines do not grow back after replanting.
Michelle Moyer, extension specialist and assistant professor in viticulture at Washington State University's Irrigated Agriculture Research and Extension Center in Prosser, Wash., and Joan Davenport, WSU soil scientist, are examining "replant disorder." It occurs when growers replant an orchard or vineyard but have trouble getting vines to re-establish.
With the disorder, vines tend to collapse or don't establish at all.
"Sometimes they're referred to as diseases, but we're referring to it as a 'disorder' since we don't know what causes it yet," Moyer said. "The basis behind replant disorders is the general unknown of what tends to build up in the soil on a particular site after repeated cropping."
Replant issues could be due to nematodes that build up over time, especially when old vineyards are replanted after 30 or 40 years. Soil chemistry and nutrition could also play a part, with pH built up or a lack of potassium or phosphorus.
Moyer is working to examine nematodes and other potential soil-borne pathogens, while Davenport will look at soil chemistry and nutrient issues.
Apple replant disorder is well-studied at WSU, Moyer said. Different rootstocks and fumigation strategies are used to counteract it. The researchers are modeling their work on apple research already conducted.
Washington wine grapes haven't had as many replanting issues yet because they are a little younger compared to Concord grape vineyards, Moyer said. The Concord research could provide starting points for wine research if replanting becomes an issue.
Replanting is necessary because after a while, the plant reaches a point where it's necessary to start over, Moyer said. Grapes reach the peak of productivity at 10-25 years in Washington's climate.
"It's not a problem until people try (replanting)," Moyer said. "It's very frustrating because they don't know it's an issue until they plant and three years in they should be harvesting at least a partial first-year crop and nothing's happening."
There are roughly 25,000-30,000 acres of juice grapes in the state.
A graduate student just began working with Moyer and Davenport this summer.
If Concord grape producers are noticing replant issues or thinking about replanting a Concord grape vineyard with more Concord grapes, Moyer and Davenport would like to know about it.