It is difficult to distinguish healthy from diseased plants before heading out. Diseased plants are often overlooked at harvest because they are shorter than healthy plants and by this time they have lost their mass of spores. The spores of the loose smut fungus are spread mainly by wind. When spores land on a healthy head some germinate immediately, growing into the hulls or into the seed coats, while other spores that do not germinate immediately remain on the seed. When infected seed germinate, the fungus is activated and starts growing within the plant, keeping pace with the growing plant, and by heading time it has replaced the oat spikelets with masses of black spores.
Infection takes place between flowering and the time the grain is ready for harvest.
Loose smut can be controlled by seed treatments with systemic fungicides such as carboxin or triadimenol. Contact fungicides such as captan and thiram are ineffective against loose smut. The use of certified, disease-free seed and disease resistant varieties will also help prevent losses to loose smut. The hulls do not turn brown. Seedlings from infected seed are stunted, and many of them turn yellow and die.