Prior to the discovery of the soybean aphid, researchers at the University of WisconsinMadison have been researching the cause of several abnormal symptoms of unknown cause common to soybean in most regions of Wisconsin. Major symptoms are changes in leaf and pod appearance that frequently are confused with symptoms caused by post-emergence herbicides. Plants with abnormal leaf phenotypes are commonly stunted, produce fewer pods, and have stems that remain green while other plants in the field mature normally. Frequently, seed from symptomatic plants have mottled seed coats resulting from hilum pigments “bleeding” into the seed coat. Viruses were suspected as a cause of these symptoms, but research was needed to prove this theory.