Bronze leaf affects Swedish columnar aspen, tower poplar and poplar hybrid clones. The disease will develop over the summer and infections will spread internally to other parts of the trees. Symptoms typically appear in later summer (early to mid-August) or early fall (September). You will begin to see individual branches or a few leaves suddenly show symptoms.

image showing some leaves of a aspen tree infected with bronze leaf


  • Leaf tissues turn orange-brown to reddish-brown, starting from the edges of the leaf, moving inward towards the base of the leaf. Leaf veins and petiole remain a bright green colour. All leaves on a branch may be affected.
  • Discolouration deepens to a bronzy, reddish-brown colour as the season progresses.
  • Infected leaves will often remain attached to the tree over the course of the winter (they do not fall off).
  • Branches may dieback as the disease progresses systemically.
  • Leaves that overwinter may have a pebbly surface texture (like the surface of a curling rink), reflecting the development of spore-producing structures (perithecia).


Prune affected areas of the tree. Cut off leaves and branches, place in a sealed garbage bag and dispose of in your black waste cart or take to the landfill. The sealed plastic bag will help prevent spores from spreading the disease.

Please DO NOT do the following:

  • bring infected brush to the enviroservice station
  • place in your backyard composter
  • burn or place in your green cart
  • chip or use as mulch

What is Strathcona County doing?

  • Assessing trees listed in the Tree Inventory for signs on damage
  • Pruning affected trees and removing severely infected trees
  • Bagging the trees/branches/leaves and disposing of them in the landfill
  • Educating residents about the disease and how to care for their affected tree

Further information:

Trees in Sherwood Park and Hamlets
Recreation, Parks and Culture
780-416-PARK (7275)
Submit a tree pest inquiry

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Last updated: Tuesday, April 04, 2023
Page ID: 50133