Cause The causal fungus for loose smut is Ustilago tritice . This fungus is unique in that it can be incorporated into developing kernels and remain dormant until the infected seed kernels germinate. Loose smut is spread when spores produced by diseased heads blow to and infect healthy heads during rainy weather. Infected heads then give rise to infected grain. The infected grain develops normally, but harbors the loose smut fungus which remains dormant until the seed is planted and germinates.
Infected plants appear normal, but develop smutted heads.
Wheat is the primary host for loose smut. However, rye and triticale can also carry this disease.