Loose Smut


Symptoms

Loose Smut on wheat

Loose Smut

Erik Stromberg, VPI&SU, Bugwood.org

Loose smut can easily be recognized in the field. Symptoms of this disease will be most obvious just after heading. The floral parts of infected plants are transformed into a mass of black, powdery spores. Diseased tillers usually head out in advance of healthy tillers. The disease name "loose" smut comes from the fact that spores covering the heads can be spread by wind and can be washed away by rain.

Cause

The causal fungus for loose smut is Ustilago tritice. This fungus is unique in that it can be incorporated into developing kernels and remain dormant until the infected seed kernels germinate.

Loose smut is spread when spores produced by diseased heads blow to and infect healthy heads during rainy weather. Infected heads then give rise to infected grain. The infected grain develops normally, but harbors the loose smut fungus which remains dormant until the seed is planted and germinates. Infected plants appear normal, but develop smutted heads.

Wheat is the primary host for loose smut. However, rye and triticale can also carry this disease.

IPM Techniques

  • Plant certified or high-quality, disease-free seed.

References and Additional Information

  • IPM-4 Kentucky IPM Manual for Small Grains
  • PPA-6 Fungicide Seed Treatments for Control of Small Grain Diseases
  • PPA -10c Kentucky Plan Disease Management Guide for Small Grains by D.E. Hershman and Paul Vincelli
  • Compendium of Wheat Diseases, M.V. Wiese (The American Phytopathological Society Press, 1987)
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