NOTE: Ginseng Crop Updates will be issued biweekly for the remainder of the summer unless more urgent updates are required.
We have reached the point of the season when conditions in ginseng gardens generally remain stable unless extreme weather conditions occur. Throughout the summer consistent protection from Alternaria will be important. Thorough spray coverage is essential to protect plants against Alternaria, especially in gardens with frost damage. It will be important to maintain good soil moisture to prevent plant stress, which can lead to more severe Alternaria outbreaks.
Insect problems appear to be on the decline in ginseng gardens. However, leaf rollers are still being reported in some areas. In these areas, damage due to leaf rollers is beyond the small patches that are normally found.
In areas of gardens with a history of Phytophthora problems, root rot is currently spreading. Tops are beginning to senesce in these areas. To prevent further spread of the disease it is important to 1) ensure good straw coverage on beds and in trenches to prevent splashing of spores from exposed soil onto leaves and neighbouring beds, 2) avoid driving through infested areas, especially when leaves or soil are wet, 3) clean boots and machinery after moving through infested areas, and 4) consider applying more frequent spot-applications of protectant fungicides in these areas. It is not possible to control the disease on a plant once the root is infected.
With the hot and dry conditions forecast for the next week, heat stress and windburn symptoms may begin to show up. Heat stress symptoms normally occur first in the centre of gardens in elevated areas where the heat rises and builds up under the shade. Adding vents in the shade in these areas will reduce the build-up of heat. Windburn issues normally occur on the edges of gardens exposed to the prevailing winds. This can be prevented by adding wind-breaks and ensuring adequate soil moisture. However, adding wind-breaks can also contribute to a build-up of heat in the garden.
There are also reports of a few cases of Rhizopus in 2-yr gardens. Rhizopus causes isolated plants to become mushy or resemble toothpaste while the skin remains intact. The top quickly collapses in these cases. Rhizopus does not normally cause economic damage to a garden, and there are no products registered to control the disease.