How to Manage Pests
Pests in Gardens and Landscapes
Common smut of corn—Ustilago maydis
Common smut is easily recognized by the tumorlike galls that form on any aboveground plant part. Galls
at first are a glistening, greenish white to silvery white. Galls on ears and stems expand and fill with
masses of powdery, dark olive brown to black spores. Galls on leaves and tassels remain small and become
hard and dry. Ear and stem galls rupture, and wind, rain, or irrigation water spread them through the
Head smut may be confused with common smut. However, the vascular bundles within the galls of head smut readily differentiate head smut from common smut. In head smut, leaflike proliferations often occur in tassels and partially smutted ears.
Spores overwinter in the soil. Under favorable conditions they form secondary spores that are carried by air currents or splashed by water to young, developing corn tissues. Development of common smut is favored by dry conditions and temperatures between 78 and 93°F. The incidence of smut is higher in soils high in nitrogen or after heavy applications of manure. Injury to the plant tissue of any kind increases the potential for smut infection.
Remove and destroy tumorlike growths as soon as noticed; keep the black powder in galls from getting
into the soil. Plant early as common smut becomes more prevalent in later harvests. All corn varieties
are susceptible to common smut to some degree. Try to plant varieties that are the least susceptible to
the disease. Rotating out of corn for as long as possible can help reduce overwintering spores in the
smut of corn