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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Annuals and Perennials > Phlox > Discolored leaves

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Phlox > Discolored leaves

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  • Image: powdery mildew 1
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Powdery Mildew
Erysiphe cichoracearum

  • Powdery, fluffy white spots and blothces 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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Aster Yellows
The Aster Yellows Phytoplasma

  • Leaves and stems may be yellow, stunted and spindly
  • Flowers are small and distorted, petals may remain all or mostly green
  • A brush-like mass of weak shoots may arise from the stem
  • Occurs most often in mid to late summer
  • More information on Aster Yellows...
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Leaf Drop

  • Problem with water movement in some cultivars - not a disease
  • Yellow or brown patches on leaves on old stems, often leaf veins remain green
  • Older leaves on the lower part of the stem turn brown and dry up
  • In severe cases leaves may fall off
  • Occurs only on some cultivars
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Virus
Tomato spotted wilt, Tobacco rattle virus and others

  • Yellow or light green rings, wavy lines or spots on leaves
  • Leaves may be smaller than normal, plant may be short and grow poorly
  • Lab test required to distinguish between viruses and verify infection
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  • Image: southern blight 1
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Southern Blight
Sclerotium rolfsii

  • Leaves turn yellow then brown from the edges inward and wilt
  • The base of the stem may be brown or discolored
  • Tiny tan to reddish brown hard spheres and white cottony growth can be seen at the base of infected leaves or in the soil around infected plants
  • Often seen after warm wet weather
  • More information on Southern Blight...

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