Considered a pest in most of the United States, smut feeds off the corn plant and decreases the yield. Usually smut-infected crops are destroyed. Some farmers may also choose to prepare corn silage out of the smutted corn. However, in Mexico corn smut is called huitlacoche (wit͡ɬakot͡ɕe, sometimes spelled cuitlacoche), a Nahuatl word reportedly meaning raven's excrement. It is considered a delicacy, even being preserved and sold for a higher price than corn. For culinary use, the galls are harvested while still immature — fully mature galls are dry and almost entirely spore-filled. The immature galls, gathered two to three weeks after an ear of corn is infected, still retain moisture and, when cooked, have a flavor described as mushroom-like, sweet, savory, woody, and earthy. Flavor compounds include sotolon and vanillin, as well as the sugar glucose.
The fungus has had difficulty entering into the American and European diets as most farmers see it as blight, despite attempts by government and high profile chefs. In the mid-1990s and due to demand created by high-end restaurants, Pennsylvania and Florida farms were allowed by the United States Department of Agriculture (USDA) to intentionally infect corn with huitlacoche. Most observers consider the program to have had little impact, although the initiative is still in progress. Regardless, the cursory show of interest is significant because the USDA has spent a considerable amount of time and money trying to eradicate huitlacoche in the United States. Moreover, in 1989 the James Beard Foundation held a high-profile huitlacoche dinner. This dinner famously tried to get Americans to eat more of it by renaming it the Mexican truffle.
Huitlacoche grows best during times of drought in a 78°F to 93°F (25°C–34°C) temperature range. Aztecs purposely inoculated corn with the spores by scratching their corn plants at the soil level with a knife—thereby allowing the water-borne spores easy entrance into the plant.
Mature spores are released from the tumors and spread by rain and wind. Under appropriate conditions a probasidium is formed in which meiosis occurs. Resulting haploid nuclei migrate into elongated single cells. These cells detach from the probasidium; these are the sporidia, completing the life cycle.
Native Americans of the American Southwest, including the Zuni tribe, have used corn smut to induce labor. It has similar medicinal effects to ergot, but weaker, due to the presence of the chemical ustilagine.
Ustilago maydis is not only used to study plant disease. It has also been used to study recombination, DNA repair and the role of the cytoskeleton in polarized growth as well. It is largely due to work with Ustilago maydis that the function of the breast-cancer gene BRCA2 is now known.