Stewart's disease of corn
Stewart's disease is caused by the bacteria Pantoea stewartii. The bacteria is vectored by the corn flea beetle. Stewart's disease lesions spread from flea beetle feeding scars (a tiny scratch on the leaf) and are initially pale green to yellow streaks, later becoming brown as tissue dies. The margins of the streaks are usually wavy but generally follow leaf veins. If stalk infection occurs, the entire plant will wilt. When cut, infected stalks may ooze droplets of pale yellow bacteria.
Most hybrids are resistant enough that no further management is required. Cultural practices and fungicides are not effective against this disease. Systemic insecticides applied to the soil or seed can be used to manage corn flea beetles and, consequently, Stewart's disease. Water soaked, wavy margins of Stewart's disease lesions. Image: A. Robertson
Stewart's disease leaf lesions. Image: A. Robertson