The disease is common smut caused by the fungus Ustilago maydis. Smut galls may occur on all aboveground plant parts but are most common on corn ears, tassels, and stalks - any tissue that is actively growing. Infections occur through injuries made to the plant by hail, cultivation, or insects. IThe disease is spread from plant to plant by wind and water.

Remove and destroy galls from infected plants in the garden before they rupture. Unopened galls are white and may be covered with a white, greasy, or powdery substance. Corn ears infected with smut are not usable, and plants attacked early in the season may yield less as a result. Remove and destroy infected crop debris after harvest. Plant adapted sweet corn varieties. Larger, later-maturing varieties are usually more tolerant of smut than early, small varieties. There are no chemical controls available.

Interestingly, young smut galls are used in some ethnic cuisines.