This disease is caused by the soilborne fungus Phytophthora sojae . This fungus is widely distributed in North Carolina, but is most serious in heavy, poorly drained soils. Therefore, symptoms may vary in their severity, depending on the relative susceptibility of the variety planted. Symptoms on older plants are root rot, wilting, and death of plants. The stem of highly susceptible cultivars is usually dark brown, and this discoloration may extend from the base of the plant to more than 10 inches above the soil line.
Leaves remain attached to wilted plants.
The disease may appear to be restricted to low-lying areas of the field, portions of the field with heavier soils, or the entire field may be affected if poorly drained. Soybean varieties resistant or tolerant to this disease are available. Resistant varieties should be used when disease pressure is very high. In most instances, however, varieties with field tolerance to this disease are adequate for conditions in North Carolina. Some stunting and loss of stand may occur with a tolerant variety, but this is usually not at levels that are economicaly damaging.