Published on January 29, 2025

Pruning Diseased Branches: What You Need to Know About Our City Bylaw

Trees in our city are not just beautiful additions to our landscape—they are vital to our environment and well-being. However, they can fall prey to diseases like Dutch elm disease (DED) and black knot, which spread rapidly and threaten the health of our urban forest. Understanding how to manage these diseases is crucial for all residents.

Dutch Elm Disease

DED is caused by a fungus spread by elm bark beetles. The disease blocks the tree's water-conducting system, leading to severe leaf wilt and eventually the death of the tree. Although there is currently no confirmed Dutch elm disease infected trees in St. Albert, pruning elms to keep them healthy is critical, but it must be done during the beetles' dormant season, between October 1 and March 31. This prevents attracting beetles to the fresh cuts.

Remember, it's illegal to prune elms between April 1 and September 30 without written permission from the City, as per Bylaw #5-98.

Black Knot

Black knot, a fungal disease affecting trees in the Prunus family (like Schubert chokecherry, Mayday, and plum trees), forms distinctive black cankers on branches. To control its spread, prune infected branches 15 to 20 centimeters below the affected area during the winter when the fungus is dormant. Ensure your pruning tools are sterilized with a 10 per cent bleach solution or a multi-purpose cleaner like Spray Nine.

Proper Disposal

After pruning, dispose of diseased branches responsibly. Diseased branches cannot go in the Green Organics Cart as the City’s outdoor composting process cannot ensure that fungal spores are destroyed. Residents can dispose of small diseased branches infected with black knot in a sealed bag in their Brown Garbage Cart to prevent the spread of spores.

Elm wood and infected tree prunings must be brought to the Mike Mitchell Recycling Depot during the winter months. This helps prevent the spread of diseases and keeps our city healthy.

Protecting Your Trees

Any work near trees should be done cautiously to avoid damaging their roots, trunk, or crown, as this can make them more susceptible to diseases and pests.

By following these practices, we can collectively protect our city's trees and maintain our beautiful urban canopy.