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Common smut  (Ustilago maydis) is generally a minor problem, but it can cause serious damage if injury occurs to actively growing (young) plant tissue. Mechanical injury (machinery, hail) and insect feeding can increase the likelihood of infection. Although all plant parts may be affected, symptoms are seen most often on ears and tassels. On ears, galls first appear as greenish or white enlargements. As the galls mature, their contents darken and evolve into masses of spores that can be seen when the galls rupture; they will serve as the overwintering stage of the causal agent.

Common smut on ear

(Photo: Paul Vincelli, University of Kentucky)

Management: 

• Removal of infected material prior to maturation of galls, insect control, minimizing injury to plants, crop rotation, and resistant varieties.

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