Gray leaf spot


Also known as Cercospora leaf spot
Cercospora zeae-maydis, C. sorghi varmaydis

Nature of damage

  • Can result in severe leaf senescence following flowering and in poor grain fill.
  • Loss of photosynthetic leaf area results in reduced yield.
  • Yield losses up to 70% due to gray leaf spot have been reported.

Signs

  • Lesions begin as small, regular, elongated brown-gray necrotic spots growing parallel to the veins.
  • Occasionally, lesions may reach 3.0 x 0.3 cm.
  • Lesions usually develop on the lower leaves, gradually spreading upwards on the plant during the season.

Factors favoring development

  • Minimum tillage practices have been associated with an increased incidence of GLS.
  • Development is favored by extended periods of leaf wetness and cloudy conditions

Geographic distribution

  • May occur in subtropical and temperate, humid areas.
  • The disease is of concern in South America and eastern and southern Africa.

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