Integrated Crop Management is published by the Department of Entomology , Iowa State University , Ames, Iowa. As soybeans start blooming, two foliar diseases start to appear in Iowa soybean fields. The diseases, bacterial blight and brown spot, are two of most commonly seen diseases. Already, we have received questions on these two diseases. Bacterial blight can be found in almost every soybean field in any year.
Bacterial blight is caused by Pseudomonas syringae glycinea .
This disease sometimes can be misidentified as bacterial pustule, a disease that occurs mainly in the South. The angular lesions enlarge in cool, rainy weather and merge to produce large, irregular lesions. The centers of old lesions often drop out, resulting in a ragged appearance of infected leaves. The bacteria also can infect stems, petioles, and pods. If pod infection occurs, bacterial blight can become seedborne.