Oak wilt is a fungal disease that has killed oaks across Wisconsin. It spreads two ways: through roots grafted between neighboring oaks, and by small sap beetles that carry spores to fresh wounds. That second route is why timing your pruning matters.
The Rule: Avoid Pruning Oaks April Through July
Wisconsin DNR guidance identifies April through July as the high-risk period. During these months, beetles are active and fresh cuts are most attractive to them. Avoid pruning, wounding, or even bumping oak trunks with equipment during this time unless a limb is a genuine hazard.
The Safe Window: Late Fall Through Winter
We schedule most oak work from November through March, when trees are dormant. It's also a great time to see structure without leaves. Our month-by-month pruning calendar covers other species too.
Signs of Oak Wilt
- Leaves wilting, browning from the edges inward, and dropping in early to mid summer
- Symptoms starting at the top of the crown and moving down quickly
- Nearby oaks dying in a spreading pattern
Other problems can look similar. See our tree fungus and disease guide.
Summer Storm Damage on an Oak
Safety comes first. If a limb is broken or hanging, it needs to come off. Make a clean cut and cover the wound right away with wound dressing or latex paint. Call us for emergency tree removal if the damage is large.
If an Oak Dies
Dead oaks become brittle and should be removed before they drop limbs. Don't move the wood off site as firewood. We handle tree removal and disposal.
