Field Crop Diseases
Information and Management for Illinois
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Southern Corn Leaf Blight



  • Common lesions are elongated, tan lesions between veins on leaves
  • Different isolates of this pathogen will cause lesions of different sizes
  • Race O causes long, tan, lesions that have brown borders on leaves.
  • Lesions will develop differently on various inbreds and hybrids

Pathogen Involved:

  • Cochliobolus heterostrophus (=Bipolaris maydis) (a fungus)
  • Overwinters in corn residue
  • Especially prevalent in areas with a warm, humid climate
  • Three races known of this pathogen: race O, race T, and race C
  • Race T and race C are known to be specifically virulent to corn with cytoplasm male-sterile T and cytoplasm male-sterile C, respectively. Since the switch from cytoplasm male sterile T to normal cytoplasm corn, race T is not considered to be a threat.

Time of Occurrence:

  • When corn has reached mid-whorl up to maturity

Conditions Favoring Disease:

  • Warm, temperatures (70 - 90° F) and wet conditions
  • Monoculture
  • Reduced tillage

Disease Management:

  • Use of resistant hybrids
  • Crop rotation
  • Tillage may be helpful

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