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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Deciduous Trees > Willow > Unusual growth or swelling on trunk or branches

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Willow > Trunk/Branches > Unusual growth or swelling on trunk or branches

1 of 4
  • Willow pine cone midge gall 1
  • Willow pine cone midge gall 2
  • Willow pine cone midge gall 3

Willow pine cone midge gall
Rhabdophaga strobiloides

2 of 4
  • Crown gall 1
  • Crown gall 2
  • Crown gall 3

Crown gall
Agrobacterium tumefaciens

  • Round to irregular woody overgrowth or tumor at soil line or on roots
  • Small round woody galls can occur on branches
  • Young galls are soft, light green or white
  • Old galls are hard, dark colored or black
  • Occasionally galls are seen higher on the stem
  • More information on crown gall
3 of 4
  • Willow witches’ broom 1
  • Willow witches’ broom 2
  • Willow witches’ broom 3

Willow witches' broom
Aster yellows group phytoplasma

  • Witches' brooms, a cluster of numerous small weak shoots arising from one point on a branch, occur randomly throughout the tree
  • Leaves on branches within witches' broom are stunted
  • Twigs within witches' broom often die over winter
  • More information on Willow witches' broom
4 of 4
  • Poplar gall borer 1
  • Poplar gall borer 2
  • Poplar gall borer 3

Poplar gall borer
Saperda inornata

  • Twig becomes swollen where larvae are feeding under bark
  • Branch tips die and/or break above the gall
  • Also found on aspen and poplars
  • Fully grown larvae are up to 1" long, cylindrical body, creamy-white and legless
  • More information on Poplar gall borer

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