We have some new information. Premature dying has been found in soybeans infected by the SDS pathogen. This symptom has not been described previously. Plants with premature dying lack the typical drastic defoliation symptom of SDS, but diseased plants yellow and die gradually. By closely examining diseased plants, you can find symptoms typical of SDS plants.
Leaves exhibit chlorotic spots and necrosis between green veins.
The roots of these plants have deteriorated. The simplest method of identifying SDS is to look for bluish fungal colonies on the taproot in severely affected plants. If you find the bluish fungal colonies, SDS is present. However, plants with SDS do not always have bluish colonies, particularly when the soil is too wet or too dry, or the plant sample is not fresh. In recent years, the incidence of Cercospora has been increasing and we have seen Cercospora leaf spot in Iowa this year.