They run parallel with the veins and may run the entire length of the leaf. When plants are older at the time of infection, the streaks are much smaller and are more numerous. The lower leaves are usually affected the worse. Leaves may wilt. Tassels may grow slowly, and reach maturity late, be bleached in appearance, or may die.
Cavities form in the center of the stalks near the soil line.
The flea beetle is most important because the bacteria spend the winter in flea beetles. Small droplets of yellowish bacterial ooze may appear at the cut surface. Touch a knife blade flat to the cut surface and slowly pull it away. Damage may also look like Northern Corn Leaf Blight, caused by a fungus. In Stewart's Wilt, flea beetles are usually present, the streaks are of a similar shape to one another and are separate from one another.