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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Deciduous Trees > Elm > Colored patches or bumps on branches or trunk

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Elm > Trunk/Branches > Colored patches/bumps on branches/trunk

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  • Image: Lichens 1
  • Image: Lichens 2
  • Image: Lichens 3

Several species

  • Colorful patches on the bark of trunk and/or branches
  • Can be wrinkled, in scalloped sheets, lace-like pads, bushy tufts, paint-like spots or splashes
  • Forms can be flat against the bark surface or raised in leaf-like lobes, finger-like or hairy projections
  • Colors may be shades of gray, green, blue, yellow, orange, or red
  • More information on Lichens
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  • Image: Oystershell scale 1
  • Image: Oystershell scale 2
  • Image: Oystershell scale 3

Oystershell scale
Lepidosaphes ulmi

  • Heavy infestations can completely cover bark
  • Feeding can cause foliage to yellow
  • Twig and branch dieback can occur when branches are heavily infested
  • Light to dark brown, elongated, 1/10 to 1/8 inch long, found feeding on branches
  • Damage occurs during summer
  • More information on Oystershell Scale
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  • Image: European elm scale 1
  • Image: European elm scale 2
  • Image: European elm scale 3

European elm scale
Gossyparia spuria

  • Yellow leaves on lower branches
  • Heavy infestations cause premature leaf drop and dieback of branches
  • Excrete honeydew so leaves and branches may be covered by sooty mold
  • Dark gray oval body outlined by white wax
  • Found mainly on American and rock elm
  • More information on European elm scale

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