Which fungus causes corn smut, forming edible galls called huitlacoche?

The fungus commonly identified as causing corn smut and producing edible galls called huitlacoche is Ustilago maydis.

The fungus infects maize and teosinte, forming swollen tumors or galls on above-ground plant tissues, especially ears and kernels. As the galls mature, they fill with dark spores, giving the disease its characteristic blackened appearance. In modern taxonomy, the species is also treated under the name Mycosarcoma maydis, but Ustilago maydis remains the familiar and widely used name in agriculture, food writing, and biology.

The immature galls are harvested as huitlacoche, a valued ingredient in Mexico. They are used in quesadillas, soups, tacos, and other dishes, where cooking produces a savory, earthy flavor. Fully mature galls become dry and heavily filled with spores, so culinary use generally focuses on younger infections.

Corn smut is therefore both a crop disease and a food resource. Farmers may try to prevent it because it reduces corn yield, while others deliberately encourage infection to produce huitlacoche. The alternate genus name is a taxonomic update, not a different fungus.