The risk of Botrytis is still high in ginseng gardens following frost damage. At this time of year the first symptom of the disease may be the grey fuzzy spores of the disease on damaged plant tissues (Figure 1). Affected leaves often turn tan and eventually glassy in appearance. The disease usually begins on damaged plant tissue and then spreads to healthy tissues through direct contact. Young tender tissues are especially susceptible to the disease. Gardens should also be monitored very closely for foliar Phytophthora because it usually develops around this time each year. Foliar Phytophthora often causes one or more leaflets to hang straight down with a water-soaked appearance. Phytophthora can infect healthy tissues and easily spread by wind. Once a plant is infected, spores can drop off of the plant into the soil and cause root disease.
Figure 1. Botrytis on a ginseng stem with frost damage.
Now is the time to monitor gardens for missing plants due to root disease and/or grubs. Grub damage will mainly appear in 2-year gardens and will likely be due to damage done in the seedling year. Conditions this winter were conducive to Rhizoctonia development. Look for expanding circles of missing plants. Progress of the disease can be slowed through a spot-spray of a registered Rhizoctonia product.
Slug damage has been seen on emerging ginseng plants (Figure 2), and control measures may be warranted. Growers should begin monitoring gardens for slug damage.
Figure 2. Slug damage on a newly emerged plant.