smut

is among the most prevalent barley diseases and can be found anywhere the grain is grown. The flowering heads of affected plants are covered by sporing structures of the fungi Ustilago nuda (loose smut) or Ustilago hordei (covered smut). These appear as either olive or dark brown spore masses, respectively, and are easily dispersed to spread the disease through the crop. Some smut spores are covered, that is, contained within a membrane. These are less likely to be dispersed until harvest time when mechanical agitation from the harvesting machinery may release them into the air. Dispersed spores can infect the developing seeds of adjacent plants by penetrating the seed embryos during their development. Smut is a very pernicious disease, and early infections tend to spread systemically through the entire plant, penetrating most of its parts during the growth cycle. Infected plants may appear normal until the seed head emerges. In the seed head smut destroys the embryo and leaves only a small amount of plant tissue intact. The result is a catastrophic effect on yield. A variety of fungicides are effective against the disease, but proper crop rotation and the sowing of uninfected seeds can break the cycle from one harvest to the next.

Smut is a fungal disease that can have a catastrophic effect on barley yields. damian herde/shutterstock

See also barley diseases.