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

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Maple > Trunk/Branches > Growths or bumps on branches or trunk

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  • Image: Cottony Maple Scale 1
  • Image: Cottony Maple Scale 2
  • Image: Cottony Maple Scale 3

Cottony maple scale
Pulvinaria innumerabilis

  • Nymphs are brown-translucent, 1/5 inch; females lay eggs in the white marshmallow egg-sac along the twigs and small branches
  • Young insects remove sap from leaves creating a speckled appearance and possibly yellowing leaves in mid to late summer
  • Excrete honeydew, a sticky, shiny material, on leaves and branches; sooty mold may also result from honeydew
  • Heavy infestations cause premature leaf drop and branch dieback
  • Silver maple is preferred host
  • More information on Cottony maple scale
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  • Image: Phomopsis galls 1
  • Image: Phomopsis galls 2
  • Image: Phomopsis galls 3

Phomopsis galls

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  • Image: Oystershell scale 1
  • Image: Oystershell scale 2
  • Image: Oystershell scale 3

Oystershell scale
Lepidosaphes ulmi

  • Heavy infestations of “shells” 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: Burls 1
  • Image: Burls 2
  • Image: Burls 3


  • Large round to semi-circular swellings along main trunk or large branches
  • Many buds or sprouts may be present on the exterior of the burl
  • Common on sugar and Norway maples
  • Burls continue to grow as the tree grows
  • While burls do not kill trees directly they can reduce a tree's health and lifespan
  • There is no known cause for burls
  • More information on Burls

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