Root and stem rot of soybean
Phytophthora can attack soybean plants at any stage of development. Symptoms in young plants include rapid yellowing and wilting accompanied by a soft rot and collapse of the root. More mature plants generally show reduced vigor and may be gradually killed as the growing season progresses. Foliar symptoms on older plants occur as general yellowing of the lower leaves that progresses upward on the plant, followed by wilting and death. The root system is usually severely affected such that lateral and branch roots are almost completely discolored. Tap roots show a brown discoloration on the surface and, if split, the inner tissues show a tan to brown discoloration. Perhaps the best diagnostic symptom of the disease on susceptible varieties is a lower stem discoloration that may extend several nodes up the stem.