Ustilago maydis

Nature of damage

• The fungus attacks ears, stalks, leaves, and tassels.
• The disease is most severe in young, actively growing plants and may stunt or kill them.

Signs

• Conspicuous closed white galls replace individual kernels. In time the galls break down and release black masses of spores that will infect maize plants the following season.
• Common smut is easily distinguished from head smut by the lack of host vascular bundles that appear as fibers in smut-infected ears.

Factors favoring development

• Plant injury (caused by factors including strong winds, hail, insect damage, or blowing soil) tends to increase disease severity.
• Nitrogen fertilizer may also increase disease severity.

Geographical distribution

• Common smut occurs throughout most maize growing regions, but can be more severe in humid, temperate environments than in hot, humid, tropical lowlands.

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