The frost on Wednesday night has caused damage to ginseng in some areas. The damage has appeared on all ages of plants. The extent of the damage will not be known for a few days. The first symptoms of damage will be kinking and softening along the stem. Seedlings will not recover from kinked stems (Figure 1). Older plants can survive stem kinking but will likely be stunted and deformed (Figure 2). The developing flower head may appear green after a frost (Figure 3), but will likely senesce over the next few days if the stem is kinked or split. As a result of this damage, growers should delay de-budding until the extent of the damage is known. Growers may need to retain a larger area for seed production to compensate for the loss of some seed heads. With warmer and more humid weather forecast over the weekend, the risk of Botrytis will remain high on damaged tissues. Dry and warm conditions will also increase the risk of Alternaria.
Figure 1. A kinked seedling stem on May 17. Seedlings rarely survive this type of damage.
Figure 2. Kinked stems in a 3-year garden on May 17. The top of these plants may continue to expand but will remain stunted and deformed.
Figure 3. The developing flower head may appear healthy just after a frost, but will often senesce within a few days if the stem is damaged.
Despite the dry conditions this spring, slug populations are high in ginseng gardens. The wet conditions last fall and mild temperatures over the winter may have increased slug populations. Continue to monitor gardens for slug damage even if the weather is not conducive to their development, and apply appropriate controls.
Growers should monitor soil moisture levels in gardens closely this year. Last July, the sudden onset of hot and dry conditions resulted in yield losses and affected berry production. Soil moisture levels this spring are much lower than last year at this time and an extended period of dry and warm conditions could result in moisture stress. By the time visual symptoms of moisture stress appear, yield potential may have been lost. Irrigate proactively to prevent yield loss and ensure good seed production. Maintaining good soil moisture may also reduce the effects of hot temperatures on ginseng. Growers with overhead irrigation should avoid extending the leaf wetness period as much as possible by irrigating early in the morning when leaves are already wet. This will reduce the development of foliar diseases.