Loose Smut of Barley and Wheat

Ustilago segetum var. tritici

Ustilago tritici

Description:

A dark brown to blackish mass of powdery spores replaces the Barley or Wheat head. The spore mass is initially covered by a thin membrane that ruptures soon after the cereal head emerges. Spores are released to infect flowering crops. By harvest only the bare stem of the Barley or Wheat head may remain. Newly infected grain appears normal.

Species Affected:

The Barley strain only affects Barely and the Wheat strain only affects Wheat and Triticale.

Biology:

Spores carried by wind.
Moist conditions during flowering with temperatures between 16 and 220C favour infection.
Seed from infested crops will probably produce heavy infestations in subsequent crops.

Life Cycle:

Spores released as infected heads emerge are released and carried by the wind to infect cereal florets. The fungus grows into the developing cereal seed and the seed looks normal at harvest. After the planting the fungus grows through the plant to form spore masses in the cereal heads.

Origin and History:

Distribution:

Prevalent in areas with an average rainfall of more than 450 mm

Significance:

Yield loss is proportional to the number of heads infected.
Grain containing Loose Smut will not be accepted for malting.
There have been several serious outbreaks in Barley in WA.

Management and Control:

Use seed from uninfected areas.
Do not use seed from areas where more than 5% of heads are infected.
Treat seed with a fungicide. Seed dressing usually don't provide complete control of severely infested seed.
Varieties differ in their tolerance to Loose Smut. If persistent problems are occurring then consider changing varieties.

Thresholds:

5 infected heads per hundred heads produces levels of seed infection that may not be adequately controlled by seed dressings. Don't use this seed for planting a crop. Collect plants at heading to determine the levels of disease.

Related and Similar Species:

Bunt of Wheat (Ustilago tritici)
Covered Smut of Barley (Ustilago segetum var. hordei)

References:

1293

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.HerbiGuide.com.au for more information.