There have been several reports of scattered ginseng plants collapsing in 2-yr gardens. Random plants scattered throughout the garden turn red and suddenly collapse. The roots usually are very soft and have a toothpaste consistency with the skin intact at first and eventually rotting away. After a short time the root is completely gone, similar to disappearing root rot, but without the initial scaly/crumbly and dark Cylindrocarpon symptoms. This exact issue occurred in 2008 in 2-yr gardens around the same time of year. Figure 1 shows the symptoms as they occurred on July 17, 2008. Given another week to develop, the symptoms this year will be virtually identical to those of the same date in 2008.
Figure 1. Scattered collapsed plants in a 2-year old garden on July 17, 2008.
The conclusion in 2008 was that the disease was seed-borne, given the scattered and even nature of the symptoms in the garden. Cylindrocarpon was thought to be a potential cause, but a secondary rot organism like Rhizopus may have taken over in wet conditions and rapidly rotted the root. This year, samples have been sent to a laboratory for diagnosis.
Growers may recall that 2007 was a very dry year in the ginseng growing area, and this was followed by a very wet year in 2008. The conditions this year are virtually identical, with a very wet year following a very dry year. It is possible that seed-borne pathogens that normally cause damping-off of seedlings do not kill off the plant entirely in the seedling year when conditions are dry. These pathogens could then remain on the plant, waiting for ideal conditions before rotting the rest of the root. When isolated seedlings collapse and die from damping-off, they can often go unnoticed, but the same cannot be said for a 2-yr old plant. However, other factors may be involved in the development of this disease.
In 2008, the disease did not spread from the initial plants to neighbouring plants. It is unknown if spread would occur under different weather conditions. Growers should monitor healthy plants next to diseased plants to determine if the disease is spreading. Results of laboratory diagnosis will be reported in a subsequent crop update, and may help to identify potential solutions.