False loose smut
(Ustilago nigra)

Overview

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False loose smut is a fungal disease of barley caused by the plant pathogen Ustilago nigra. The causal pathogen is very similar to that of U. nuda, the cause of true loose smut, both of which fungi belonging to Basidiomycotina.

Main description

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Smutted head emerges through the sheath below the boot leaf. At head emergence, infected heads are covered by a delicate greyish membrane, under which is hidden a dark brown or black powdery mass of spores. Spores are blown or washed away, leaving an inconspicuous bare rachis. This disease over-winters on the seed’s surface. Under favorable conditions, seed-borne spores may germinate and produce mycelium under kernel hulls. Both mycelium and spores remain dormant until germination, when the fungus grows and penetrates the seedlings. Growth continues undetected until heads develop. By head emergence, heads contain smut spores instead of seed and chaff.

Scouting

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Look for abnormal head emergence through the sheath below the boot leaf. Scout at heading for delicate membranes over emerging heads. After heading, look for unusual, tightly-compacted heads and deformed awns or only a remaining rachis, as the disease may have affected the development and maturity of the grains.