Oak Wilt the Silent Killer

Nov 6, 2023

What is Oak Wilt and why should we be concerned?

Oak wilt is a vascular disease of oak trees, caused by the fungus Bretziella fagacearum. This disease can decimate a thriving oak stand with in a year. The pathogen is spread by sap and bark feeding beetles. While feeding on an infected tree the beetles can pick up the pathogen on their bodies, when they travel to the next tree they carry the pathogen with them. Once a tree is infected the pathogen can travel through the root system to the next healthy oak and so on. Although all oak trees are susceptible, our native red oak Quercus rubra is most at risk. Once the fungus is in the vascular system of the tree it stops the transfer of water and nutrients and eventually cause tree mortality.

Although the pathogen is not yet known to be here in Ontario it is right on our doorstep! In 2016 oak wilt was discovered on Belle Isle which is only 1km from the Windsor boarder. Even more devastating is the discovery of eDNA in Ontario in 2020. This discovery of eDNA does not mean that the disease is here in Ontario but it does mean that the beetles that carry the pathogen have been detected.

What can we do to help stop the spread?

One of the main things you can do as a home owner is to be a responsible caregiver of your oak trees.

  • Do not let anyone prune your oak trees during the months when your trees vascular system is active, so to be safe no pruning from April – November.
  • Have a Certified Arborist come inspect your oak tree, especially if you see sudden signs of decline.
  • Keep an eye out for decline, such as discoloration of leaves in the upper canopy. Red oaks react to to disease much faster then white oak. A red oaks canopy will turn a bronze colour while white oak tend to dieback one branch at a time.

Oak trees are a major component to our natural ecosystem and a vital piece of our urban landscape. It is our duty to help stop the spread of these types of diseases. It is up to us to be vigilant and keep our eyes open for any signs that could potentially cause catastrophic damage to our oak population. If you have an oak tree on your property or notice the decline of one on your favourite hiking trail, please feel free to contact us or you can report it directly to the Canadian Food Inspection Agency.