Impact
Loose smut is a fungus disease common wherever small grains are grown. The fungus Ustilago is the causal agent. Individual species and/or strains infect each type of small grain. Yield loss is directly related to the percentage of infected heads. Losses can range from the typical I percent to an entire field.
Loose smut occurs throughout the San Luis Valley but typically has a limited impact. Severe cases can occur within individual fields. Disease severity depends on the infection level of the planted seed.

Description and Symptoms

Loose smut symptoms are not present until heading.

Infected heads emerge from the boot slightly earlier than normal and are darker than healthy heads. The darkening i~ due to spore masses, which replace the kernels.

Spore masses are covered by a thin membrane that ruptures easily after head emergence, permitting the spores to be dispersed by wind or water. After a short time, only the naked rachis remains.

Loose smut is a seedborne disease. The fungus infects the developing embryo (germ) at the time of flowering. Infected seed can germinate without showing symptoms.

Integrated Management

Plant disease-free certified seed from fields inspected for loose smut. Use resistant cultivars when available.

Use only systemic fungicidal seed treatments specific for treatment of loose smut. Seed-surface active fungicides are not effective. Control cannot be achieved after seed germination.