Freeze Damage to North American Ginseng

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  • 1 Ontario Ministry of Agriculture and Food, Simcoe, Ontario, N3Y 4N5, Canada.
  • | 2 Department of Plant Agriculture, Division of Horticultural Science, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.

The Lake Erie counties of southern Ontario, Canada are the major producers of ginseng (Panax quinquefolius) in North America. In this area there is about 1740 ha (4299.5 acres) of ginseng and an annual production of 1455 t (1603.8 tons). Spring freeze damage to the crop is rare as the mean date of last freeze in spring is 12 May. On 21 May 2002, following three to six nights when air temperatures dropped below freezing, extensive damage to the crop was evident. A survey by the Ontario Ginseng Growers Association showed that 78% of growers had gardens showing freeze damage. The extent of the damage was variable across the growing area, and on individual farms. Most damage to plants occurred in low-lying areas where heavy cold air collected. Recently germinated seedlings that were exposed above the straw mulch were severely damaged, and many did not survive because they did not have leaves and no perennating bud was formed. Damage to 2-year-old plants was expressed as leaves wilting and turning black. In some cases stems froze and the plants toppled. In 3-year-old and older plants, damage was variable with some leaf collapse and stems broken, or damaged with corking-over taking place. Damage to inflorescences ranged from death and abscission, to distorted flowers and shriveled and split peduncles. Plant health was a concern following the freeze episode, and throughout the subsequent growing season. The fungicide fenhexamid received emergency registration to combat recurring problems in Botrytis control. The seed crop for 2002 was light. Damaged seedling gardens were replanted. Older gardens will undergo a period of adjustment. Root yield in 2002 was reduced by 30%, a 500 t (551.1 tons) loss. The full extent of the damage and associated financial implications are unknown and could impact the industry until 2005.

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