Galls are usually formed on ears, but may also form on leaves, stems, and tassels. This disease is more severe on young, actively growing plants. As they mature, they become darker gray and spongier. When the are fully mature, they break open easily. Inside the mature galls are millions of black dusty spores.
Galls can be up to several inches in diameter.
Galls on leaves usually remain small and hard, and do not break open to release spores. Unmistakable due to appearance of galls. A 6 to 8-year crop rotation may help prevent the disease, but the spores are carried long distances by wind. Avoid excess nitrogen levels. Avoid injuring plants.