What is it?

Oak wilt, is a fungal disease caused by the bacteria Bretziella fagacearum. The fungus is typically spread by insects that are attracted to the sap from fresh wounds or pruning cuts, but can also spread through the root systems of infected trees to non infected trees. The disease infects the xylem of Quercus species, inhibiting the trees ability to transport water and nutrients, causing discoloration, defoliation, and eventual decline of the tree.

Signs

• White, grey, or black fungal mats, also referred to as “pressure pads”, just under the bark that sometimes emit a fruity smell 
• Dark rings (vascular streaking) can be seen in the cross-sections of infected branches

Symptoms

• Wilting and bronzing of the foliage, starting from the top of the tree and moving down 
• Discolouration of the leaves, beginning at the leaf margin and progressing to the midrib 
• Premature leaf fall 
• Vertical bark cracks in the trunk and large branches from the fungal spore mat exerting outward pressure on the bark

Images provided from Invasive Species Centre

What Should you do?

The best practice to stop the spread of Oak wilt is to only prune oak trees between November to mid March. Another way the general public can help is to only use firewood that is from the area and never transport firewood long distances.

If you suspect your Oak Tree may be affected,  have one of our ISA Certified Arborist visit to confirm and provide next steps. Secondly, report the diagnosis to the Invasive Species Centre.

​More information can be found here.

Download Fact Sheet from Invasive Species Centre Above

Impacts

• ​​Impacts Property values and neighbourhood aesthetics
• Increased costs with tree maintenance, removal and replacement
• Loss of valued shade tree
• ​Negative impacts to the Forestry industry and production of high value oak products
• Reduction in food source for forest animals provided by oak trees
• Loss of habitat for some species
• Reduction of ecological services (air and water filtering)
• Safety and Liability Issues