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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Vegetable > Sweet corn > Spots or streaks on leaves

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Sweet corn > Leaves > Spots or streaks on leaves

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Common Rust
Puccinia sorghi

  • Elongated rusty orange brown streaks on leaves
  • Powdery orange spores rub off on hands and tools
  • Leaves may turn yellow and become easily tattered in strong winds
  • At the end of the season leaf streaks turn black
  • More information on Common Rust
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Anthracnose Leaf Blight
Colletotrichum graminicola

  • Leaf spots start as tan ovals with a brown margin (1/4 – ½ inch long) often surrounded by yellow
  • Leaf spots can grow into 5-6 inches long streaks
  • Entire leaves may be blighted by leaf spots that have grown together
  • Black raised spots with tiny black spines can be seen with a handlens in the center of dead leaf spots
  • Infection often starts on the lower leaves early in the growing season and moves progressively up the plant
  • More information on Anthracnose Leaf Blight
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Northern Corn Leaf Blight
Exserohilum turcicum (syn. Helminthosporium turcicum)

  • 1-6 inch elliptical or cigar-shaped spots on leaves that are first gray-green then turn tan
  • A distinct margin is present between the infected and healthy tissue
  • Lesions may appear "dirty" because of fungal sporulation
  • Disease starts on the lower leaves first than moves up the plant
  • Disease spreads rapidly in warm (64-80F) wet weather
  • More information on Northern Corn Leaf Blight
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Gray Leaf Spot
Cercospora zeae-maydis

  • Leaves have rectangular lesions which become tan and then gray in color, about 1/8" wide by up to 2"- 3"long
  • Lesions have very distinct parallel edges
  • More information on Gray Leaf Spot
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Eye Spot
Aureobasidium zeae

  • Leaf spots are small (1/16" – 1/8") and round
  • Leaf spots start as a dark spot with a yellow halo then turn tan with a dark brown or purple margin
  • Spots can grow together into larger tan areas
  • Common in fields where corn has been grown several years in a row
  • More information on Eye Spot
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Dwarf mosaic and maize chlorotic dwarf

  • Leaves have light and dark green mottling or streaks
  • Infected plants are stunted and may produce many tillers
  • Plants may not produce an ear, or ear is poorly developed
  • More information on Virus
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Stewart's Wilt
Pantoea stewartii

  • Plants infected early in the season wilt, remain stunted, and may die
  • Plants infected late season have pale-green to yellow streaks with wavy edges run parallel to the leaf veins
  • Older leaves may have scorched brown edges
  • Cut stalks exude a yellow sticky bacterial slime
  • Occurs rarely in Minnesota
  • More information on Stewart's Wilt

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