Loose smut

Loose smut is a seed-borne disease which affects winter and spring barley. A crop will appear normal up to head emergence. Once the heads have emerged, the heads will be covered in black spores. Affected plants tend to be shorter at this stage, and when the spores have dispersed, it will be apparent that no grains will be produced from the head.

Loose smut is caused by the fungus Ustilago nuda. It is a seed-borne fungus which is deep-seated within the grain. This is the reason why systemic seed treatments are required to control it. Crops can become infected at flowering from spores which are wind dispersed from plants showing the typical loose smut symptoms. Grains will develop normally, but the fungus will grow inside the grain. After sowing, plants will germinate and develop normally. The fungus will, however, be growing within the plant. Symptoms will only become obvious at heading time when the grain sites will be taken over by the black spores.