If you learned one thing from the ash borer, learn this. The county sits directly across the water from a place where the next problem is already established.
Oak wilt is a fungal disease. It kills oaks, and it kills red oaks fast, sometimes inside a single season. It has been in Michigan for decades. It is now confirmed in Ontario, and Essex County is about as exposed as a place can be, being the first landfall for anything moving east.
We are not trying to alarm anybody. We are saying that the pattern that played out with the ash is available to be avoided this time, and the thing that matters most is boringly simple. When you cut.
What oak wilt does to a tree
The fungus gets into the tree's water-conducting vessels. The tree responds by plugging its own vessels to wall the fungus off, which works about as well as it sounds. The tree ends up cutting off its own water supply.
Red oak group: red, black, pin
These decline fast. Leaves go bronze or brown from the outer edges inward, often with a sharp line between the dead tissue and the green. They drop while still partly green, which is unusual and worth noticing. A red oak can go from healthy-looking to dead in a few weeks to a few months.
White oak group: white, bur, swamp white
More resistant. These decline over years rather than weeks, branch by branch. Better news, but it also means it is easier to miss.
How the disease moves
Beetles, which you can control
Sap-feeding beetles are drawn to fresh wounds on oaks. If a beetle has been on an infected tree and then lands on a fresh pruning cut on yours, that is a new infection. This is the transmission route you have power over.
Root grafts, which you cannot
Oaks of the same species growing near each other graft their roots together underground and share a circulatory system. The fungus travels through those grafts, which is why oak wilt kills in expanding patches rather than scattered single trees. If your neighbour's red oak goes down and yours is within about fifteen metres, yours is at real risk regardless of how carefully you have pruned.
The pruning window, which is the most useful thing in this article
Do not prune oaks between April and the end of October.
The beetles are active in the warm months and they find fresh cuts within hours. A wound made in June is an open door. The same cut in December is not, because nothing is flying.
So prune oaks November through March. Late fall and winter. That is the rule.
The awkward part is that this runs against how most homeowners think about yard work. People want the tree tidied up in May when they are outside looking at it. If it is an oak, wait. Our tree trimming and pruning service schedules oak work into the dormant season for exactly this reason.
If a limb breaks in July and you have no choice, that is different. Get the wound dressed immediately rather than leaving it open. But elective pruning waits for the cold.
What to do if you think you have it
Do not cut it and do not move the wood. Firewood from an infected oak can carry the fungus, which is the same mistake that spread the ash borer across the province.
Get it looked at. If it is confirmed, the response usually involves severing root grafts between the infected tree and its neighbours before removal, trenching a line deep enough to break the underground connections. Take the tree out without doing that and you can push the infection into the healthy oaks next to it.
That is a real reason to have somebody who knows the disease handle it rather than the first outfit with a chainsaw.
Why we care about this locally
Essex County is Carolinian country. We have oak here that does not grow most other places in Canada, in yards, in the remnant woodlots, around Point Pelee and the Ojibway complex. Some of those trees are two hundred years old.
The ash is gone. We watched that happen from the front row. There is no reason to run the same play twice.
If you own an oak
Get it assessed, and get your pruning scheduled for the winter rather than whenever you happen to think of it.
Tree Removal Windsor prunes and removes oak across the county. We schedule oak work in the dormant season on purpose, we handle root graft severing where it is needed, and we can write an assessment if you need one for a development application.
- Tree trimming and pruning in Windsor
- Arborist reports and tree risk assessments
- Tree removal
- Emergency response if an oak is failing fast
Serving Windsor, LaSalle, Tecumseh, Amherstburg, Leamington, Kingsville, and Essex.
If you think an oak is going down fast, get in touch now rather than waiting on a form.