This disease is very common early in the season but seldom persists until maturity, and yield losses are small. It is seed-borne or survives in crop residue. The disease can spread rapidly through a field by the blowing and splashing of spores. Angular brown spots form on leaves. Later, the leaves turn yellow and drop, giving the lower plant a barren appearance. The disease is most common in humid areas where rotation is not practiced. Crop rotation, removal of debris, and planting disease-free seed are recommended management practices.
Taken from Kansas State University Agricultural Experiment Station and Cooperative Extension Service Publication #C-449. Soybean Diseases, Dr. Douglas J. Jardine, Extension State Leader, Plant Pathology Program.