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.
What to look for
- Smaller plants with smutted heads that are scattered throughout the paddock.
- Infected plants may be hard to see.
Paddock
- At head emergence, each grain is replaced by brown to black powdery spores.
- Spores disperse leaving the bare stem.
Plant
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.
See also
Where to go for expert help
Page last updated: Tuesday, 25 July 2017 - 8:21am