Covered smut

Ustilago segetum var. hordei

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Covered smut in barley is very similar to bunt in wheat, except the infection is clearly visible in the crop as a greyish-black head. Smutted heads appear stunted and the awns shrivel soon after flowering. Each smutted head contains many thousands of black spores, which contaminate the normal grain during harvest.

Infected heads can emerge later than healthy heads but may also fail to emerge altogether. Infected plants are often shorter than healthy plants. Detection of this disease is difficult, except in severe cases.

Life cycle

Covered smut spores are carried on the outside of the seed and can remain viable for up to three years. When infected seed begins to germinate, the spores also germinate and penetrate the shoot of the seedling just before emergence.

The fungus then grows in between the plant cells just behind the growing point of the plant. Plants become resistant to covered smut infection after emergence and therefore, if an uninfected plant has emerged, it cannot become infected. The fungus enters the tissues of the head, once formed, and black spore masses are produced in the head instead of normal grain.

Covered smut infection is spread during harvest and other seed handling operations, when infected grains are mechanically broken and spread amongst healthy grain.