The fungus is dispersed by wind-blown rain. Wet, windy weather, which favors spore dispersal, increases the severity of this disease. Dry periods not only prevent infections, but also halt lesion and pycnidial development. At first, diseased heads are blackened and clearly visible among newly emerged green, healthy heads. Infected heads emerge slightly earlier than normal and their spikelets, except for a delicate membrane, transform into a dry, olive black spore mass.
Infected seed appear normal.
The fungus, found inside the embryo of the seed, grows when the seeds are planted and begin to germinate. Smutted grain is seen only after seed heads emerge from plants that came from infected seed. Therefore, infection that takes place in one year is not seen until plants from these infected seed mature in the succeeding year. Poor Plant Color Cold, wet soils, typical of North Carolina winters, often cause plants to become yellow, or in the case of oats, yellow and red. Older leaves sometimes die and plants look unthrifty.