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Zinnia > Leaves > Leaves discolored white, yellow or pale green

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  • Powdery mildew 1
    Credit: Michelle Grabowski, University of Minnesota Extension
  • Powdery mildew 2

    Credit: Michelle Grabowski, University of Minnesota Extension

  • Powdery mildew 3

    Credit: Michelle Grabowski, University of Minnesota Extension

  • - CLICK PHOTOS TO ENLARGE -

green arrowPowdery Mildew
Golovinomyces (syn. Erysiphe) cichoracearum

  • Powdery, fluffy white spots and blotches on leaves, stems, and flower parts
  • Tiny black round spheres may be visible within white spots late in the season
  • Spots typically start on lower leaves but can spread to cover the entire plant
  • Severely infected leaves may be completely covered in white or grayish white fungi
  • In some cases, leaves become curled or twisted or turn yellow due to the infection
  • More information on Powdery Mildew
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  • Spider mite damage 1
    Credit: Whitney Cranshaw, Colorado State University, Bugwood.org
  • Spider mites 2

    Credit: David Cappaert, Michigan State University, Bugwood.org

  • Spider mites 3

    Credit: David Cappaert, Michigan State University, Bugwood.org

  • - CLICK PHOTOS TO ENLARGE -

green arrowSpider Mites
Tetranychus urticae

  • Active during summer, particularly abundant during hot, dry weather
  • Pale stippling appears on the upper leaf surface
  • Leaves are discolored off-green to whitish, yellowish, or bronze
  • Premature leaf drop can occur
  • Visible webbing occurs on infected leaves when populations are high
  • Adults are tiny (1/50th inch long) and oval, greenish or yellowish with a dark spot on either side of the body
  • More information on Spider Mites (86 K PDF)
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  • Zinnia aster yellows 1
    Credit: Michelle Grabowski, University of Minnesota Extension
  • Zinnia aster yellows 2

    Credit: Michelle Grabowski, University of Minnesota Extension

  • Zinnia aster yellows 3

    Credit: Karen Blaedow, University of Minnesota Extension

  • - CLICK PHOTOS TO ENLARGE -

green arrowAster Yellows
Phytoplasma

  • Part or all of the leaves may turn yellow
  • Flowers fail to develop, remain small green and may be distorted
  • Clumps of weak shoots known as witches broom develop throughout the plant or on flower stalks
  • More information on Aster Yellows

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