Smut (Ustilago maydis) is a fungal disease of corn that may infect leaves, stems, tassels or ears though infections on ears are the most obvious. Immature galls are white and spongy but become brown with dark powdery spores with maturity. Leaf galls remain small but those on the ears or stems can become rather large and will release large numbers of spores when they rupture. This disease is likely to be most severe on plants injured by hail, cultivation or insects and tends to be worse on soils that have had heavy applications of nitrogen fertilizer or manure.
Also anything that slows growth such as hot, dry weather or cool, wet weather when the plants are young can result in more infections.
Immature smut galls are considered an edible delicacy known as cuitlacoche in Mexico. They are a high value crop for some growers in the northeast U.S. who sell them to Mexican restaurants. There is no chemical control for this disease. Crop rotation and a balanced fertilizer program can help minimize this disease. Remove and destroy galls from infected plants before they
rupture. (Ward Upham)
