Diagnosing smut in oats

Loose smut (Ustilago avenae) and covered smut (Ustilago hordei) of oats are both externally seed- borne diseases with similar symptoms which are difficult to distinguish in the field. Both diseases are managed in the same way.

At head emergence, each grain is replaced by brown to black powdery spores

What to look for

    Paddock

  • Smaller plants with smutted heads that are scattered throughout the paddock.
  • Infected plants may be hard to see.

    Plant

  • At head emergence, each grain is replaced by brown to black powdery spores.
  • Spores disperse leaving the bare stem.

Where did it come from?

  • Air-borne spores lodge in healthy glumes, where they remain dormant until seeding or else they grow into the hulls and seed coats and remain inactive until seeding.
  • Smut infection is favoured by moist conditions during flowering with temperatures of 15-20° C. Early seeding into warm seedbeds is also associated with smut outbreaks.
  • After infection, the fungus invades the developing seedling and grows within the plant.
  • As the plant matures the fungus reaches the developing flowers replacing the grain with spores.

Management strategies

  • Replace contaminated seed with new seed from a clean source.
  • Seed treatments control the disease if used regularly.

Where to go for expert help

+61 (0)8 9956 8504
DDLS Seed Testing and Certification
+61 (0)8 9368 3721
Page last updated: Tuesday, 25 July 2017 - 8:21am