The smut diseases of small grains involve pathogens in the genera Ustilago and Tilletia , which belong to the order Ustilaginales . Smuts can be grown in culture, but do not grow saprophytically in the field. Infected host tissue is eventually completely converted to smut mycelium and then to telisopores. Overwintering is by telisopores on contaminated seed, plant debris, or in soil. In the case of some smuts, mycelium overwinters within seed or within plants.
Control is primarily through seed treatments, seed testing, and resistant varieties.
The first practical control of a plant disease based on scientific principles was with smuts. Since the plant was infected systemically as a seed, usually all the kernels on a head become infected and transformed completely to teliospores. This leaves behind an empty rachis. Pericarp stay intact Teliospores dispersed during harvest and contaminate seed andsoil. Historically, covered smuts or bunts have been the most significant small grain pathogen after rusts.