Covered kernel smut, caused by the fungus Sporisorium sorghi (synonym Sphacelotheca sorghi) attacks all groups of sorghums, including johnsongrass. Covered kernel smut is the most common disease of sorghum in Illinois and other states where farmers plant untreated seed. Usually, all of the kernels in a smutted head are destroyed and replaced by dark brown, powdery masses of smut spores (teliospores or chlamydospores) covered with a tough, grayish white or brown membrane (Figure 1). The membrane usually ruptures at harvest time. The infected kernels (smut sori) break, and the microscopic spores adhere to the surface of healthy seeds where they overwinter. Only seeedborne spores cause infection. Smut sori are generally smooth; oval, conical or cylindrical; and vary in size from those small enough to be concealed by the glumes to those over one cm long. They may be white, gray, or brown.