Timely warning about oak wilt

The Canadian Food Inspection Agency is sharing a reminder to nurseries, garden centres, homeowners, and tree professionals: Please do not prune oak trees from April until December.

Oak trees, of any size, especially red oaks are susceptible to a pathogen that causes Oak Wilt (Bretziella fagacearum), transmitted by sap beetles. This invasive fungal infection is so serious that red oaks can die within two to 12 months.

What to look for:

• Discoloured and wilted leaves, starting at the top of the tree. Discolouration begins at leaf tip and moves inward to the base. Premature leaf-drop mid to late summer.
• Black sooty stains form at the base of trees.
• White, grey, or black fungal mats forming just under the bark. Bark will smell fruity.
• Cracking tree bark as fungal spore mats push bark and large branches outward.

What do to:

• Prune in winter (December-March) when trees are dormant.
• Paint over any wounds that occur during this high-risk time.
• Use local firewood.
• Remove and burn infested trees and stumps.
• Break root connections with nearby oak trees.
• Report infected trees to the Canadian Food Inspection Agency by emailing OakWiltReportingOntario-Fletrissementduchene@inspection.gc.ca.

Oak wilt disease was first found in Canada in 2023, and unfortunately identified near us, in the Barrie area and Springwater Township.

Submitted by the Simcoe County Master Gardeners.