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Common smut on an ear. Note dark masses of teliospores in galls.

Photograph courtesy Mike Boehm
Dept Plant Pathology, The Ohio State University, 201 Kottman Hall
2021 Coffey Road, Columbus, OH 43210-1087

Host (Latin and common name): Corn (Zea mays)
Disease name: Common Smut of corn
Pathogen name: Ustilago maydis

Smuts occur worldwide on a variety of plant species.  Historically, however, smuts are of greatest concern and cause significant yield losses on cereal crops such as wheat, barley, rye and corn.  Many older varieties of Kentucky bluegrass are also extremely susceptible.  All smut fungi belong to the class of fungi referred to as the Basidiomycetes.  Rust and the wood decay fungi and most fleshy mushrooms are also classified as Basidiomycetes.  The smuts were so named because of the black or soot-colored masses of spores (called teliospores) that typically accompany the latter stages of disease development.  Although smut fungi may infect leaves, flowers, or stems, it is their ability to infect the ovaries or kernels of the grain that elicits the greatest concern as infection of the developing kernel directly affects grain quality and yield.  Common smut of corn is caused by the fungus Ustilago maydis and is a disease encountered by home gardeners and farmers alike.  Sweet corn is considered more susceptible to smut than field corn.  The disease may occur on leaves, stalks, tassels, or on ears.  The disease is easily recognized early in the season by the presence of silvery-white tumor-like growths called galls which as the season progresses, mature, rupture and release large masses of soot-colored smut spores similar to those shown above.  Interestingly, the galls are considered a prized food delicacy in certain parts of the world if harvested early enough in the season.  Corn smut is managed almost exclusively through the use of resistant varieties.  Sanitation or removal of galls may also be an effective means of managing this disease in small-scale or isolated plantings but is not practical for large acreage fields.

APS publication number:  IW00014

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