Characteristics
Although it can infect any part of the plant, it usually enters the ovaries and replaces the normal kernels of the cobs with large, distorted tumors analogous to mushrooms. These tumors, or "galls", are made up of much-enlarged cells of the infected plant, fungal threads, and blue-black spores. The spores give the cob a burned, scorched appearance. The generic name Ustilago comes from the Latin word ustilare (to burn).
Huitlacoche grows best during times of drought in a 78 to 93 °F (26 to 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.
Read more about this topic: Corn Smut