Field Crop Diseases
Information and Management for Illinois
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Gray Leaf Spot



  • Lesions first appear as small, necrotic spots with halos
  • The lesions become rectangular, 2-4 mm to1-6 mm in size and have a gray appearance
  • Mature lesions have distinct parallel edges and appear opaque when put up to the light

Pathogen Involved:

  • Cercospora zeae-maydis (a fungus)
  • Corn is the only known host of this pathogen
  • Overwinter in corn debris on the soil surface

Time of Occurrence:

  • This disease will occurs from silking to maturity

Conditions Favoring Disease:

  • Susceptible hybrids or inbreds
  • Corn on corn rotation
  • Moderate to warm temperatures
  • Extended periods of high humidity or wet weather
  • Minimum tillage

Disease Management:

  • Use resistant corn hybrids
  • Conventional tillage where appropriate
  • Crop rotation
  • Foliar fungicides if economically warranted. Typically only used with susceptible inbreds; or a combination of susceptible hybrids, high yield potential, prolonged humid conditions, and evidence of disease development.

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