In 1999, there was a resurgence of stem canker in Illinois and neighboring states. It is not known if it was the northern or southern variety. Symptoms of northern and southern stem canker include leaf and stem discoloration. The first symptoms occur during the early reproductive stage as small, reddish-brown lesions, usually near a lower leaf node. As the season progresses, the lesions expand longitudinally to form cankers on the plant.
Infections leading to cankers occur during early vegetative growth.
But the symptoms appear much later during reproductive growth. The fungi survive the winter in debris. Some have suggested that infection of the seed may spread the fungi. But Hartman says the role of seed infection remains unclear. Click here .