This is the time of year that ginseng leaves may show early senescence or discolouration due to root diseases. Red discolouration is usually a sign of advanced root rots like Cylindrocarpon or Phytophthora, whereas early purpling of the leaves can be a sign of less aggressive root issues like rusty root, nematode damage or insufficient watering. With the hot and dry conditions this summer, some ginseng tops are completely senescing when there are root issues that plants would normally survive. It is important to dig up affected roots and diagnose the issue so you know how best to control it, if control is possible.
When root rot symptoms appear, it is important to practice good sanitation practices to ensure the disease is not spread to unaffected areas of the garden. Ensure that any exposed soil is covered with straw, wood chips or gravel to reduce splashing of infested soil after rainfall and contamination of boots and farm machinery.
Despite recent rains in some areas, it is still very dry in most gardens. For proper seed set and to prevent berry abortion, it is critical to ensure adequate soil moisture in seed production gardens until berry harvest. Root development will also be significantly slowed by low soil moisture, especially in hot temperatures. Consider investing in soil moisture monitoring equipment to provide more accurate information on moisture availability in the soil. Click on the following links for more information:
This has been a busy summer of ginseng research with 20 different field trials on the go. Our latest ginseng replant research garden is showing the most aggressive replant disease to date, with unfumigated plots in one area nearly 100% destroyed 3 months after germination. Subtle differences in soil type appear to have a major effect on the severity of the disease. There will be a research plot tour at the end of the summer for growers. Look for more information from OGGA in mid-August.