While the amount of rainfall has been highly variable across the ginseng growing area, all areas have received periodic showers this week that has resulted in long periods of leaf wetness. Foliar Phytophthora is still active in several farms and this wet weather will continue to allow for spread of the disease. Downpours will then result in new areas of root infection.
There are subtle difference in the foliar symptoms of a root infection and the symptoms of foliar Phytophthora. Root infection can lead to the top wilting straight down from the top of the stem, but the top will simply dry out with no darkening of the tissues. Foliar infection will lead to tops also collapsing straight down from the top of the stem, but with a blackened, water-soaked appearance. Microscopic examination of the tissues would reveal the sporangia of the pathogen (Figure 1.). When this infection is no longer active, it would retain the darkened appearance, but would be completely dried out.
If you have foliar Phytophthora in a garden, it is likely that you are not getting sufficient protection from fungicides, or you are not getting sufficient coverage with your sprays.
With the periodic rains, drip-line chlorosis is very obvious in many fields (Figure 2). Drip-line chlorosis is the yellowing of the ginseng leaves in strips through ginseng gardens where rainfall drips from the shade cloth. The larger the slope of the field, the more pronounced these lines are, since the water runs down the shade until it hits a wire. The chlorosis (yellowing) develops as a result of leaching of nutrients from the soils in these areas and perhaps other changes to soil nutrient and pH balance. These strips are often where diseases first develop not only because they are wetter but also because lower nutrition reduces the disease resistance of the plants. Supplemental fertilization can reduce the problem but it is important not to over fertilize and cause the unaffected plants to have excessive fertilization that can lead to higher root disease and poor seed development.
It has come to my attention that some growers are not aware of all of the resources OMAFRA provides to ginseng growers and all farmers. First there are the two ginseng-specific publications:
Publication 848 Guide to Ginseng Production. This guide provides an overview of ginseng production from start to finish including detailed information on pests. It is not updated regularly and costs $20 plus tax at the Simcoe Research Station or through Service Ontario.
Publication 847 Crop Protection Guide for Ginseng. This guide provides a listing of the pest control products currently registered on ginseng and their proper use and describes ginseng integrated pest management practices in detail. It is updated every year. Each member of the OGGA should have received a copy in the mail. Additional copies can be purchased for $5 plus tax at the same locations noted above.
OMAFRA also has a number of resources for both new and experienced farmer that help explain financial support programs, funding sources and general agricultural resources. A few of these are listed below:
Factsheet: Programs and Services for Ontario Farmers
Factsheet: Starting a Farm in Ontario – Business Information Bundle
Publication Series: Best Management Practices (Soil, Water, Pesticides etc.)
Website: OMAFRA Irrigation Information
Website: OMAFRA Soils Information
Website: OMAFRA Nutrient Management Information
Factsheets and Resources: Farm Succession Planning