Nov 08th, 2016

If you notice that your Columnar Aspens have leaves that are bumpy and irregularly changing colour, this may be an indication that your tree has Bronze Leaf Disease (BLD). BLD is caused by a fungus that affects Poplars, especially Swedish Columnar Aspen, Tower Poplar and Poplar hybrids. The disease can kill an infected tree within three to five years.


It is easy to confuse a BLD-infected leaf with normal leaf colour changes in the fall, or with the new growth leaves in the spring. A BLD-infected leaf is usually seen in the late summer to early fall. The infection may be limited to a few leaves or branches but can spread around the tree and cause branches to die back. It can also cause the bark under an infected branch to brown. Infected leaves turn orange-brown to red-brown; typically, this colour change starts at the outside edge of the leaf and moves inwards, while the leaf’s veins remain green. Affected leaves often remain on the tree throughout the winter. In the spring, they have a bumpy texture, which is caused by the growth of spore-producing structures.

Best care practices

The best thing you can do for your tree is to try to prevent the infection in the first place. When planting, space your trees appropriately to allow for proper air flow / reduced humidity, and do not plant in an area where the disease is already present. Ensure you keep your tree well-pruned and well-watered. If your tree does become infected, the most effective treatment is pruning out the infected leaves or branches. Pruned wood needs to be burned, or bagged and disposed of in the garbage. Pick up and dispose of any leaves on the ground to keep the fungus from overwintering. If the tree is severely infected, it may be best to remove it. There are no chemical treatments for BLD.

Interesting Facts about Bronze Leaf Disease

  • Some cities and counties track infections of the fungus.
  • The Latin name of the fungus is Apioplagiostoma populi.
  • The fungus is spread by airborne spores. The spores are released more quickly if the weather is rainy and warm.

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