This disease is most common after soil temperature increases and high rainfall results in soils waterlogged for long periods. It is especially prevalent in low-lying areas of the field. 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. Varieties possessing high levels of resistance should be used in fields where Phytophthora Rot is identified as a problem. Pythium Root Rot Various species of Pythium cause root rots of soybean. Symptoms caused by Pythium spp. The determination of which fungus is the causal organism must generally be done in the laboratory.