Loose Smut of Wheat: Cause and Management

Loose smut of wheat is caused by the fungus Ustilago tritici. Unlike common bunt, the fungus grows inside the developing seed embryo, replacing it with a mass of black spores. Infected seeds look normal externally.

Key Facts

• Seed-borne: fungus survives inside the seed.
• Yield loss typically <1% annually in the Great Plains.
• Grain quality for milling/feed is largely unaffected.
• Do not plant infected seed without systemic fungicide treatment.

Control

• Use certified smut-free seed.
• Treat seed with systemic fungicide (e.g., difenoconazole, tebuconazole, carboxin) before planting.
• Resistant varieties available.

Corn does not get loose smut—it gets common smut (Ustilago maydis) and head smut (Sporisorium reilianum), different diseases with different biology.