Head smut

Sphacelotheca reiliana

Nature of damage

  • The infection is systemic: the fungus penetrates the seedlings and grows inside the plant without showing symptoms, until the tasseling and silking stages.
  • Infection of the tassel also leads to reduced pollen production.

Signs

  • Abnormal development of the tassels, which become malformed and overgrown
  • Black masses of spores that develop inside individual male florets
  • Masses of black spores in place of the normal ear, leaving the vascular bundles exposed and shredded

Factors favoring development

  • Dry and cool weather at the start of the season favors the disease as maize seedling growth is slow.
  • Later in the season dry and warm conditions (21-30°C) favor disease severity.
  • Soil moisture content of 15-25% W/w is optimal for seedling infection.
  • Head smut has been recorded as being more severe under nitrogen deficiency.

Geographic distribution

  • Worldwide distribution

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