ALERT: Bronze Leaf Disease Affecting Trees in Westpark

This notice was shared to us via the Westpark Residents’ Association:

Dear WPRA Residents:

One of our residents noticed recently that some of the aspen trees near the mailbox on 81st Street were showing signs of Bronze Leaf Disease.  The City was notified and they confirmed the presence of the disease and pruned off the affected branches.

Bronze Leaf Disease (BLD) is a fungal disease that affects poplars and aspens, overwhelmingly the Swedish Columnar aspens, and has been spreading throughout Calgary since about 2007.  It spreads via air-borne spores in the early spring. If left untreated, it will advance through the leaves, down the branches, and right into the tree’s lifeline.  BLD can kill an infected tree within 3 – 5 years.  There are no known chemicals to treat BLD, so it is important to take preventative actions to save affected trees and limit the spread of this infection.

Please inspect any columnar aspens in your yard for signs of this disease, and take action if you find it.

Signs of BLD start showing up in late summer and fall.  Infected leaves will turn a bronzy colour, but the leaf stalk and mid-vein will remain green at first, and then eventually turn yellow.  Infected leaves will often remain on the tree through the winter.  If your tree has BLD, it is important to prune off any diseased branches 8 – 12 inches below visible signs of infection, and thoroughly clean up and dispose of the cuttings at the landfill (don’t compost, chip or burn it).  It is also important to clean up the fallen leaves of these trees in case spores are present.  If left on the ground, infected leaves can begin spreading their spores next spring.

More information can be found on the City’s website – and at

Leave a Reply

Your email address will not be published. Required fields are marked *