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Common
Corn Smut, caused by the fungus Ustilago zeae or Ustilago maydis,
is a well-known disease that usually does not cause economic damage. Smut can
infect any part of the plant, especially actively growing meristematic tissue.
Infections of the stalk, ear, or tassels result in smut galls, which are
distorted growths that have a shiny, silvery-white surface. These galls
eventually rupture to release millions of powdery black teliospores. Stalk
infections often cause stunting or death of the top of the plant, frequently
followed by lodging. Leaf infections cause wart-like growths that are yellow and
then turn brown. These infections can sometimes be confused with other leaf
diseases. The leaf infections do not usually produce spores. When young plants
are infected, the disease can destroy the growing point, killing the plant. The
base of these plants may be swollen and the leaves in the whorl transformed into
a smut gall. The spores released by the smut galls usually do not infect plants
during the same season, but fall into the soil where they can survive many
years. If the spores fall onto susceptible plants parts, such as silks,
infection may occur in the same season. Silk infection results in ear infection.
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