Figure 10. Loose and covered smuts of oats
Loose smut and covered smut, caused by Ustilago avenae and U. segetum, respectively, occur in Ohio. When disease outbreaks are severe, both yield and grain quality can be significantly reduced. However, fungicide seed treatments effectively control both diseases.
Symptoms of these diseases are very similar. Smutted oat panicles emerge from sheaths as olive-brown to black fungal spore masses. Smutted panicles remain more compact than healthy ones, and usually all spikelets on a diseased plant are affected. Smutted plants are often stunted and easily detected in a recently headed field of oats.
The thin membrane enclosing the spore masses of U. avenae usually rupture and disintegrate after panicle emergence as opposed to those of U. segetum, which can persist longer.
Figure 10. Loose and covered smuts of oats