Experts issue warning as hidden pathogen threatens trees across vast area: 'Make sure there aren't any open wounds'

Ontario residents are being urged to hold off on pruning their oak trees until November to help stop the spread of a deadly, fast-moving fungus known as oak wilt.

What's happening?

Oak wilt is caused by a fungal pathogen that targets a tree's internal circulation system, cutting off its supply of water and nutrients. Once infected, the tree essentially suffocates itself trying to fight back. Red oaks are especially vulnerable, often dying within two to six weeks.

The disease spreads through beetles that are drawn to the sweet-smelling fungus. These beetles often carry the fungus from infected trees to fresh wounds on healthy oaks, making spring and summer pruning especially risky.

"Just go out and look at your oak trees and make sure there aren't any open wounds," said Vince La Tassa, project manager at the Invasive Species Centre. "If there are, apply shellac or wound paint to seal them."

Why is oak wilt concerning?

Oak trees are a vital part of both urban neighborhoods and natural ecosystems. From backyard shade to forest biodiversity, losing them at scale would be a major blow to local habitats.

And this isn't just a local issue. Oak wilt has already hit parts of the United States — particularly states along the Canadian border, such as Michigan and Ohio — hard.

The fungus first appeared in Canada in 2023, and experts fear it could spread rapidly if people continue to prune during high-risk months.

Invasive species including this fungus decimate native ecosystems by outcompeting local species for resources, altering forest composition, and leaving behind weakened species. And when foundational trees such as oaks disappear, it can lead to cascading consequences.

What's being done to stop the spread?

If you have oak trees on your property, avoid pruning them from April through November. If damage does occur — from weather, animals, or something else — seal any open wounds immediately with shellac or wound paint.

If you're in Canada and spot signs of oak wilt, which include wilting, bronzed leaves, early leaf drop, and a fruity smell, report it to the Canadian Food Inspection Agency. If you're in New York, report it to the Department of Environmental Conservation.

More broadly, planting and prioritizing native species in your yard helps prevent the spread of invasive species. Healthy local ecosystems are our first line of defense against pests and diseases.

Do you think governments should ban the production of gas-powered lawn equipment? Absolutely 💯 Yes — but not yet 👍 I don't know 🤷 Heck no 👎 Click your choice to see results and speak your mind.

Join our free newsletter for good news and useful tips, and don't miss this cool list of easy ways to help yourself while helping the planet.