The hot and dry weather in early August has resulted in a number of issues in ginseng gardens. These issues include poor berry development, premature senescence, discolouring of leaves due to various root diseases and probably poor root growth. Recent rains and slightly cooler temperatures may have reduced the stress at least temporarily. However, the rains were relatively light in many ginseng production areas and would not have been enough to eliminate moisture stress if plants were not irrigated regularly.
At this stage of the year when the damage is already done, there is not much that can be done to reduce the damage other than to ensure plants are irrigated on a timely basis to reduce stress. For any signs of root disease, the diseases were probably there earlier in the year but affected plants only started to show symptoms under the very hot temperatures when the root system couldn’t keep up with the moisture needs of the plant.
The main culprits for causing tops to collapse at this time of year and under these dry conditions are Cylindrocarpon, severe rusty root or nematode damage, and/or less common diseases like Verticillium. Phytophthora has not been much of an issue this year due to the dry conditions, but any roots with minor Phytophthora root rot from earlier would also cause tops to discolour prematurely under hot and dry conditions.
The hot and dry weather can have a major impact on berry and seed development. Many berries have either not developed fully or have aborted and fallen off the cluster. Seed development in under-developed berries could also be affected. This could result in seeds that are more prone to disease, may be less viable, and may be smaller than usual. During berry harvest, consider not harvesting any berries on the cluster that are much smaller than usual or appear distorted. Large and evenly red berries will probably produce the best seed. It will be important to test seed viability and conduct float tests on seed harvested from affected fields for the next year to ensure they will still germinate at an acceptable rate. Sorting seed by size and discarding small, underdeveloped seed may reduce germination issues somewhat.