Epidemiology
The fungus survives as thick-walled black teliospores, but unlike common smut, the teliospores produced by the head smut fungus are not contained within fleshy galls. And, in contrast to common smut, plants are systemically infected as seedlings, though infection is only obvious in flowering plants. Large amounts of teliospores are produced on the ear and sometimes the tassel of infected plants, both of which are usually sterile, and thus yield loss is directly related to the percent incidence of the disease. The fungus can also be seed borne, which is not considered to be an important source of infection, but can be a point source for introduction into a field.