Bronze Leaf Disease


This fungal disease affects many Poplar and Aspen species. Both Tower Poplar and Swedish Columnar Aspen are highly susceptible to the disease, which is unfortunate due to the number of these trees in Calgary. Bronze Leaf Disease affects only Poplars but not all poplar species are susceptible. Fungal Spores are transferred by air causing infection of the trees.

Tree Damage

  • Symptoms of the disease appear in mid to late August.
  • Infected leaves turn a reddish-brown colour from the edge towards the base.
  • Damage can be limited to a few leaves or all the leaves on a branch.
  • Infected leaves often persist on the tree throughout the winter.
  • Disease moves systemically within the branch, eventually causing tree death.
  • Trees may die within three to five years.

Control Measures

Bronze leaf Disease cannot be controlled by chemicals. Early detection and treatment are important to save trees and prevent widespread infection. The disease can only be managed with good sanitation practices which include:

  • Removing leaves from tree in fall soon after they drop.
  • Pruning to remove diseased material below lowest point of visible infection.
  • Trees that are so badly infected that pruning is not possible or trees that have been killed be Bronze Leaf Disease should be removed to prevent spread.
  • Keeping your tree healthy with regular maintenance will help ensure it is best prepared to resist the disease!