Soil Scientists Dig into the Mystery of Replant Disease
Concord grape growers have had a problem for years: when they plant a young vine in a gap where another grape plant was removed, the new vine frequently dies in the first year.
Some suspect nematodes, others blame bacteria but, in fact, no one knows for sure why Concord grape vines tend to suffer from what is generally called replant disease. With other species, particularly apple, the problem is better understood. Soil pests and pathogens (such as worm-like nematodes and fungal root diseases) build up in the soil over a number of years. Populations of these pests and pathogens don’t affect mature plants, which are robust enough to tolerate them. But when the same land is replanted with young plants that have small and fragile root systems, they may be encountering a well-established population of pests and diseases that cripple them and prevent them from becoming established.
In the case of Concord grapes, though, all this is mere speculation. That’s why Washington State University soil scientist Joan Davenport and her graduate student Enrique Proano are digging into the problem. For added expertise in plant pathogens and nematodes, the pair is collaborating with Michelle Moyer, WSU Extension viticulturist, and USDA plant pathologist Inga Zazada.
“What we do know is that Concord is an economically important crop,” said Davenport from her base at the WSU Irrigated Agriculture Research and Extension Center (IAREC) in Prosser. Washington state is the nation’s largest producer of Concords, the main ingredient in grape juice and that beloved dietary mainstay, the PB&J sandwich. “We also know that there is limited land area that can be used for agriculture and that can be irrigated,” she added.
A frequent response to the replant issue – which is observed in apple, cherry, pear, rose, citrus, and other economically important crops – is to establish new plantings on ground that has not been planted with the same species for a decade or so. While this fact leads many scientists to strongly suspect a soil-borne biological cause, Davenport and Proano are leaving nothing to chance.
“The first phase of this study is to eliminate possible causes,” said Proano. “We’re trying to narrow things down – is this problem caused by something in the soil or is it something related to vineyard management?”
Proano has 140 young Concord grape plants growing in pots in a WSU greenhouse in Prosser. “We’re growing the plants in 14 types of soil,” he said, “including virgin soil from land that has never been farmed.”
The scientists are using virgin soils as controls, along with soils from apple and cherry orchards as well as from two Concord vineyards, one of which has been replanted, the other which has not.
“All these soils are of the Warden silt-loam series,” Davenport said, meaning that the soil type is not a variable in the experiment.
The plants went into the greenhouse in March, Proano said, so it’ll take a while before they start to see the die-off expected when vines suffer from replant issues. “We typically see this take place over the course of a growing season,” Proano said.
In addition, the pair plans to test the soil for the presence of nematodes and potentially pathogenic micro-organisms, as well as perform standard soil chemistry analysis for the presence of macro- and micro-nutrients, pH, organic matter, and other factors.
A couple times each week, Proano measures the plants for key growth indicators in order to detect correlations between soil type and plant development. He is also closely monitoring soil moisture and temperature, in order to keep those variables in check and in line with strong experimental design. At the end of the growing season, they will harvest the plants and do further analysis in order to measure any potential difference between soil types.
In the 2014 growing season, they’ll take the project to the next level. “If we find soils with problems, we’ll sterilize that soil and plant again to see if that prevents replant issues,” Proano said. With other plant species, soil sterilization does eliminate replant problems.
In the meantime, Proano patiently and methodically collects data. His research project is funded by a grant from the Washington State Concord Grape Research Council, along with additional funding from the WSU Department of Crop and Soil Sciences, the WSU Agricultural Research Center, and the WSU IAREC.
Learn more about the research at WSU IAREC at bit.ly/13T5zOU.
Native Plants in the Vineyard: Enhancing Ecosystems
Robin Dobson and Kathleen Perillo know they will have succeeded in designing a resilient farming system when the Western Meadowlark returns to nest under their grapevines. At Klickitat Canyon and Columbia Gorge Winery and Meadowlark Vineyard in the Columbia River Gorge near Lyle, Washington, restoring native habitat is front and center.
On a warm, sunny Earth Day among blooming meadows, ancient oak woodlands, and stunning views of Mt. Hood, participants on a farm walk sponsored by the WSU Small Farms Program and Tilth Producers of Washington were treated to an insider’s look at what Dobson and Perillo call ecodynamic farming.
“Native plants growing within a cropping area enhance ecosystem services; for example, the natural functions provided by native beneficial insects. We call this ecodynamic agriculture to distinguish it from other types of landscaping. The concept here is to add natives within the cropping area. It’s a form of restorative agriculture,” Dobson said.
Dobson, who has a Ph.D. in plant pathology from Washington State University, has been restoring native plants and woodlands on the property since he acquired the land to establish a vineyard in 1992. Together, Dobson and Perillo have established the Center for Eco-dynamic Agriculture, a non-profit organization on a mission to teach and promote sustainable farming techniques.
All 35 of their acres, including the vineyard, are stocked with plants native to the Columbia Gorge, including blue bunchgrass, arrowleaf balsamroot, lupine, and groves of Garry oak. Native ground cover from the surrounding woodlands grows seamlessly around neat rows of grapevines that are carefully pruned to produce high quality grapes.
Asked how he does it, Dobson’s reply is: “Patience. It takes eight years for balsamroot to bloom after planting, yet, once established, it is extraordinarily drought-tolerant and resistant to trampling, and it lives for decades.”
Plant diversity breeds system diversity
David James, an entomologist based at WSU’s Research and Extension Center in Prosser, has been monitoring beneficial insects and pests in this habitat-enhanced farming system and comparing it with a conventional vineyard in the same region. “Natural insect enemies available [to do] biological control here far outnumber those in the conventional system and corresponding insect pest populations are much lower,” James said.
James also found nine butterfly species compared with only one in the conventional vineyard. Next, he plans to figure out exactly which plants are attracting which beneficial insects so that recommendations for specific plantings can be shared with other producers. James has been awarded a BIOAg Grant from the Center for Sustaining Agriculture and Natural Resources to further his research on this topic.
James believes that a farm like this provides unique research conditions that could benefit the entire Washington wine industry. He explained that what Dobson and Perillo have done allows him to carry out research trials that would have been impossible under the standard three-year grant funding timeframe.
“The types of native plants that flourish at Meadowlark Vineyard could not have been established in such a short time,” Dobson said.
Unfettered terroir, unbridled customer loyalty
Dobson claims that the carefully cultivated native vegetation in his vineyard can be tasted in the grapes that go into his handmade, organic estate wines. Dobson uses no additives to ferment or flavor his wine, simply allowing sufficient time for the natural yeasts found on the grapes to do their work.
The payoff for such an approach is found in the marketplace. A unique terroir, combined with meticulous organic growing and processing techniques brings a premium for Dobson’s wines and cultivates loyal customers. Klickitat Canyon Winery sells all the wine as they can make through an on-site tasting room as well as one in the nearby town of Stevenson. While some of their wines are composed solely of grapes from this vineyard, others incorporate grapes from neighboring small, organic vineyards, thereby creating an outlet for products from like-minded farmers following similar practices.
This farm walk, just one of many offered each growing season, demonstrated how information needed for sustainable farming is discovered and shared among producers and scientists. Farmers’ local knowledge, with outcomes carefully documented by WSU researchers, was shared through dialogue and demonstration. The information was hungrily absorbed by an audience of aspiring and established farmers, as well as by agricultural professionals.
For more information about the WSU Small Farms Team farm walk education serieshttp://smallfarms.wsu.edu/farmwalks/index.html.
New Hands-On Educational Tool Available
Anyone interested in growing grapes for juice or wine will want to get a copy of the newly released Field Guide for Integrated Pest Management in Pacific Northwest Vineyards (PNW644). The guide features over 240 full-color photographs of the region’s most common pests, diseases, weeds, and abiotic stresses, along with detailed descriptions of recommended monitoring and management methods for vineyards.
This vineyard management manual is the result of collaboration among experts in fields ranging from entomology and plant pathology to viticulture, and has been written by 24 specialists from Washington, Oregon, and Idaho’s leading universities, related industries, and the USDA. More than just a book for trouble-shooting problems, PNW644 presents information about general vineyard management for a systems-wide integrated pest management (IPM) approach.
Production of the IPM field guide was made possible by funding from the Western Integrated Pest Management Center and Washington Wine Industry Foundation. A limited number of free copies will be available for participants at various WSU Viticulture Extension events throughout the year; next on the schedule is the August 16 Washington State Viticulture Field Day in Prosser, organized by the Irrigated Agriculture Research and Extension Center. Copies also may be purchased ($30) from the WSU Extension Online Store.
For additional information on grape production and upcoming Viticulture & Enology events, visit http://wine.wsu.edu/research-extension.
Immerse Yourself in Washington Wine!
August 15 through 17 will be three fun and wine-derful days of events including wine tastings, winemakers’ dinners and a gala wine auction, in support of the WSU Viticulture and Enology program and the Seattle Children’s Hospital. More than 90 of Washington’s premier wineries will participate, pouring and discussing their vintages, and individual wineries will host special events with family-friendly activities. For more information, visit http://www.auctionofwashingtonwines.org/.