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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Deciduous Trees > Poplar > Discolored bark on branch or trunk

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Poplar > Trunk/Branches > Discolored bark on branch or trunk

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  • Image: Hypoxylon canker 1
  • Image: Hypoxylon canker 2
  • Image: Hypoxylon canker 3

Hypoxylon canker
Entoleuca mammata

  • Leaves on one or more branches are undersized, turn yellow then to brown and remain attached to stem
  • Cankers begin near wounds or at the base of a branch
  • Infected bark initially turns yellowish-orange; older infections are black at center with yellowish-orange margins
  • Bark first appears blistered and raised, then falls off to reveal blackened wood
  • Clusters of raised buff white to black bump like fungal stromata can be seen on 3 year old cankers
  • Damage most common on trembling aspen


  • There are no fungicides that prevent or cure Hypoxylon canker.
  • Avoid planting species that can become infected where existing Hypoxylon infections are found on neighboring trees.
  • Prune to remove dead or dying branches during dry periods, before the canker reaches the main trunk.
  • Remove structurally weak trees that have cankers along the main trunk in order to avoid damage to people and property from tree breakage.
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  • Image: Valsa and Leucostoma cankers 1
  • Image: Valsa and Leucostoma cankers 2
  • Image: Valsa and Leucostoma cankers 3

Valsa and Leucostoma cankers
Valsa sordida and Leucostoma niveum

  • Random dead branches seen throughout canopy
  • Sunken irregularly-elongated cankers with cracked bark at the edges occur on branches or the main trunk
  • Leaves on random branches wilt, turn yellow then brown
  • Cankers are brown to black at the center with salmon to orange discoloration of the bark at the edges
  • In wet weather curled tendrils of orange spores emerge from pimple like fungal structures within infected branches
  • Common on trees stressed by drought, winter injury, wounds, insect feeding or other factors
  • More information on canker
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  • Image: Cryptodiaporthe canker 1
  • Image: Cryptodiaporthe canker 2
  • Image: Cryptodiaporthe canker 3

Cryptodiaporthe canker
Cryptodiaporthe populea

  • Multiple thin weak adventitious shoots develop
  • Bark on cankers may or may not be discolored, but the tissue beneath the bark will be brown to black
  • Callus tissue formed around edges of cankers causing bark to fall off and expose the wood beneath it
  • Leaves on infected branches turn yellow and drop prematurely
  • Random dead branches caused from girdling cankers seen throughout canopy
  • Common on Lombardy poplars
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  • Image: Wetwood or bacterial slime flux 1
  • Image: Wetwood or bacterial slime flux 2

Wetwood or bacterial slime flux
Several species of bacteria

  • Streaks/columns of water-soaked bark discoloration on the trunk or branches that is gray to yellow-brown when dry and black to brown when wet
  • Discoloration commonly starts at bark cracks, wounds, or branch unions
  • Fluid may ooze or bleed out of openings in the bark and may have a yeast-like odor
  • More information on wetwood
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  • Image: Leaf spot and canker blights 1
  • Image: Leaf spot and canker blights 2
  • Image: Leaf spot and canker blights 3

Leaf spot and canker blights
Marssonina spp., Septoria spp., Colletotrichum

  • Dark, sunken cankers can develop on stems of Septoria infected
  • Irregular dark spots (angular to round) to large blotches on leaf surface
  • Severe infestations may lead to leaf yellowing full defoliation by late summer
  • Lower branches are infected first
  • More information on Leaf spot and canker blights

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