It shows up as dark brown patches on leaves and edges of leaves curl. This fungi causing disease affects potatoes, peppers, eggplants, and particularly tomatoes. The disease first strikes the lower leaves and then may spread to the upper leaves. The infected leaves will wilt, yellow, and often die. Sometimes the problem will spread to the stems and fruit.
Crop rotation is important, as the disease can remain in the ground for about three years.
Use seed that has been hot water treated. Treat your own seed with Thiram. Control outbreaks of the disease with a fungicide, such as chlorothalonil or Maneb. An organic approach would be to simply remove and destroy infected plants to prevent spread of the disease. Also, avoid working the garden after watering to reduce the chance of spreading diseases.