
About this Tree Concern
Oak wilt is an introduced fungus in Ontario and was discovered for the first time in 2023 in the Niagara Falls area of Southern Ontario. It has also been discovered near Barrie and has likely spread in other places of Southwestern Ontario. The red oak species has been found to be the most susceptible.
Oak wilt can be spread by beetles or through connected tree roots. Fungal mats develop on tree stems in spring and fall and spores can move throughout the tree to the roots. It can persist in the roots after the tree dies and infect adjacent oak trees.
Sap beetles are attracted to the fungal mats to feed and then spores from the mats stick to the beetles and are moved to wounds of healthy trees.
When infected, oak leaves wilt or discolour, starting at the top of the tree. Leaf colour change starts at the leaf tip and moves inward towards the base. Leaves may drop prematurely in mid to late summer and a black stain forms in the sapwood of the tree.
White, grey or black fungal mats form just under the bark that may smell fruity. Trunk and large branches may develop bark cracks as the fungal spore mat pushes outward.
Red oaks can die within 2Â to 12Â months of infection.

Remediation
Oak wilt must be pruned from the tree and the wound must be painted to prevent infection in the fresh wound. Oak wilt can be spread by moving firewood from one zone to another. Oak wilt can be moved by other insects so contact us immediately if you suspect oak wilt.