DECEMBER 2018
CELEBRATING 139 YEARS AS CANADA’S PREMIER HORTICULTURAL PUBLICATION
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TEAM GINSENG
Searching for the root of ginseng’s replant disease
Ontario’s ginseng crop earns a surprising $250 million in farmgate receipts. At this time of year, the sand-plains growers are receiving bids from Hong Kong buyers who are assessing volume and quality. One of those growers is Carl Atkinson, chair of the research committee of the Ontario Ginseng Growers’ Association. He’s looking forward to solving the soil health issue of replant disease that may temper the long-term future. Photos by Glenn Lowson.
KAREN DAVIDSON Down below, underneath the mat of ginseng plants, is a whodunit mystery that’s slowly being unearthed. For all the success of the medicinal root, there is something in the soil that results in crop failure when ginseng is replanted in the same garden. In ginseng circles, it’s simply called replant disease. For Ontario’s 160 ginseng growers on the sand plains of Lake Erie, replant disease is a serious issue that threatens the long-term future of a $250 million industry. Since the 1960s, the soil-borne disease has baffled ginseng growers. Basic research shows that several fungi in the soil may be involved. Now that 8,000 acres are planted to ginseng, 2,500 of
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which are in mature production, the industry has pledged to manage its destiny. “It’s been a rallying cry,” says Carl Atkinson, chair, Ontario Ginseng Growers’ Association (OGGA) research committee. “We’re closer to solving the replant issue with government funding of $420,000 over the last five years. But the fact remains that sandy soils are finite in this area and we compete with vegetable crops. We can’t own every piece of land.” So fierce is the competition for land that $800 per acre leasing costs are considered the norm. Ginseng is harvested once, after a three or four-year growth period under shading that replicates its natural forest habitat. Then new planting ground must be sought.
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“Replant disease lasts at least 30 years,” explains Dr. Sean Westerveld, ginseng and herbs specialist, Ontario Ministry of Agriculture, Food and Rural Affairs, while pointing out that the disease does not affect any other subsequent crop. “We don’t know why the disease is so severe in the second planting. This is not the normal pattern of a disease.” Speculation is that the exudates of the ginseng root, the very medicinal components that are so healthy for humans, are actually contributing to disease in the second crop. “There are a whole range of them,” says Westerveld. These exudates are called ginsenosides. About 70 per cent of Westerveld’s time is spent in the ginseng industry,
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coordinating and monitoring a 25-person working group. Thanks to Agriculture and Agri-Food Canada (AAFC) funding in the last five years, there is a multipronged approach to understanding the disease. Many university, government and industry experts have joined growers on a methodical approach. Soil testing has been the natural place to start a baseline of knowledge. A fungus called Ilyonectria mors-panacis is thought to be the main culprit. Dr. Mary Ruth McDonald, professor in the Department of Plant Agriculture for the University of Guelph, is working on improving soil diagnostics for the fungus. Other researchers are working on next-generation sequencing to scan all fungi in the soil. Continued on page 3
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