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Cucumber > Leaves > Discolored leaves

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  • Image: Powdery Mildew 1
    Credit: M. Grabowski, University of Minnesota
  • Image: Powdery Mildew 2

    Credit: T.A. Zitter, Cornell University

  • Image: Powdery Mildew 3

    Credit: M. Grabowski, University of Minnesota

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green arrowPowdery Mildew
Podosphaera xanthii

  • Initially pale yellow spots develop on the oldest leaves
  • White to gray powdery felt in spots, blotches or complete covering of leaves
  • Lesions develop on underside of leaves, or on shaded leaves first
  • Older leaves infected first
  • Severe infection can cause leaves and vines to wither and die
  • Fruit may be blotchy or have sunscald
  • More information on Powdery Mildew...
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  • Image: Cold Temperature 1
    Credit: E.C. Burkness, University of Minnesota
  • Image: Cold Temperature 2

    Credit: Sue Morris

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green arrowCold Temperature

  • Weather has been cold (below 50°F) and wet
  • Soil is cold (below 62°F) and damp to the touch
  • Leaf edges turn olive green to brown
  • In severe cases entire leaves, young shoots or the entire plant may be completely discolored and wilted
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  • Image: Squash Bug 1
    Credit: J. Hahn, University of Minnesota
  • Image: Squash Bug 2

    Credit: E. C. Burkness, University of Minnesota

  • Image: Squash Bug 3

    Credit: E. C. Burkness, University of Minnesota

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green arrowSquash Bug
Anasa tristis

  • Feeding can cause yellowing and wilting
  • More common on squash and pumpkins than cucumber
  • Adults are 5/8 inch long, somewhat flattened, and gray to dark brown with alternating orange and brown stripes on the edges of their abdomen
  • Nymphs are 1/10 to 1/2 inch and are a light to dark gray color
  • Active from May through September
  • More information on Squash Bug...
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  • Image: Virus 1
    Credit: M. Grabowski, University of Minnesota
  • Image: Virus 2

    Credit: M. Grabowski, University of Minnesota

  • Image: Virus 3

    Credit: M. Grabowski, University of Minnesota

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green arrowVirus
Squash mosaic, cucumber mosaic, watermelon mosaic

  • Irregular, blotchy to wavy patterns of yellows and greens on leaves
  • Leaves may be distorted (sometimes fern-like), wrinkled, and curled
  • Plants may be stunted
  • Fruit may have unusual color patterns, blotches or rings but are not rotten
  • Fruit are often deformed and distorted
  • More information on Virus...
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  • Image: Bacterial Wilt 1
    Credit: H. Schwartz, CSU, Bugwood.org
  • Image: Bacterial Wilt 2

    Credit: Charles Averre, North Carolina State University, Bugwood.org

  • Image: Bacterial Wilt 3

    Credit: Charles Averre, North Carolina State University, Bugwood.org

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green arrowBacterial Wilt
Erwinia tracheiphila

  • Leaves first appear dull green, wilt during the day, and recover at night
  • Eventually wilted leaves die
  • Wilt progresses down the vine until entire vine is wilted or killed
  • Striped or spotted cucumber beetles will be present in the garden
  • Cucumbers and muskmelon most commonly affected (pumpkins & squash less affected)
  • More information on Bacterial Wilt...
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  • Image: Spider Mites 1
    Credit: Whitney Cranshaw, Colorado State University, Bugwood.org
  • Image: Spider Mites 2

    Credit: M. Ellis, Ohio State University

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green arrowSpider Mites
Tetranychus urticae

  • Feeding on the underside of leaves causes leaves to appear pale and stippled
  • Webbing can be found on underside of leaves when heavy infestations are present
  • Adult spider mites are very small (approximately 1/50 inch in length), and are yellow to dark crimson, with dark spots
  • Mites usually appear in late June and August, and are more prevalent in hot, dry weather
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  • Image: Downy Mildew 1
    Credit: David B. Langston, University of Georgia, Bugwood.org
  • Image: Downy Mildew 2

    Credit: P. Bachi, UKY, Bugwood.org

  • Image: Downy Mildew 3

    Credit: G. Holmes, NCSU Bugwood.org

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green arrowDowny Mildew
Pseudoperonospora cubensis

  • Pale green to yellow spots on upper surface of leaves, later turn brown
  • Angular spots bounded by leaf veins
  • Dark purplish grey fuzz on underside of leaf when high humidity
  • In wet or very humid conditions disease progresses rapidly, leaves turn brown and look like they were killed by frost
  • On watermelons, an exaggerated upward leaf curling is common
  • Cucumber and muskmelon most susceptible
  • More information on Downy Mildew...
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  • Image: Aphids 1
    Credit: M. Grabowski, University of Minnesota
  • Image: Aphids 2

    Credit: M. Grabowski, University of Minnesota

  • Image: Aphids 3

    Credit: Whitney Cranshaw, Colorado State University, Bugwood.org

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green arrowAphids
Aphis gossypii, Myzus persicae

  • Aphids feed on leaves, resulting in yellowing
  • Leaves may wilt
  • Small (1/6” – 1/8”) soft bodied insects
  • Aphids can transmit viruses
  • Active from April through October
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  • Image: Squash Vine Borer 1
    Credit: E.C. Burkness, University of Minnesota
  • Image: Squash Vine Borer 2

    Credit: J. Hahn, University of Minnesota

  • Image: Squash Vine Borer 3

    Credit: J. Hahn, University of Minnesota

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green arrowSquash Vine Borer
Melittia cucurbitae

  • Feeding by larvae causes yellowing of leaves and wilting
  • Holes filled with green to orange excrement near the base of the plant may be present
  • Less common on cucumbers
  • Adult borer resembles a wasp, is active mid-June through July
  • More information on Squash Vine Borer...

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