Oak wilt is a serious tree disease affecting much of Wisconsin, including the greater Milwaukee area. It has been confirmed in 66 of the state’s 72 counties and continues to spread. Once a tree is infected, the disease can move quickly and cause permanent damage or death—especially in red oaks.

The best way to protect your oaks is through proper timing, pruning, and professional care.

How Oak Wilt Spreads

Oak wilt moves from tree to tree in several ways:

• Insects – Beetles are attracted to fresh tree wounds and can carry fungal spores from infected trees to healthy ones.
• Connected roots – Oaks growing close together may share root systems, allowing the disease to move underground.
• Pruning equipment – Tools used on an infected tree can spread the fungus if they are not disinfected before moving to another tree.

Signs of Oak Wilt

Watch for these common symptoms:

• Leaves turning brown, yellow, or bronze, often starting on one section of the tree
• Leaves curling, wilting, and falling early
• Cracks in the bark near branch joints or at the base of the tree
• Rapid decline, especially in red oaks, which can die within weeks of infection

Why Pruning Now Matters

Oak trees are most vulnerable to oak wilt between April and July, when beetles that spread the disease are active. Pruning during that time increases the risk of infection.

Winter and early spring are the safest times to prune. This allows damaged or weak branches to be removed without attracting insects that carry oak wilt and gives trees time to heal before the high-risk season begins.

How Oak Wilt in Wisconsin Is Managed

Our arborists use several methods to limit the spread of oak wilt and protect healthy trees:

• Pruning during the safe season
• Treating storm damage right away
• Disinfecting tools between trees
• Removing infected trees before the disease spreads
• Preventative fungicide injections that can protect trees for up to two years

White oaks are more resistant than red oaks, but all oak trees benefit from early care and proper pruning.

Have Questions About Your Oaks?

If you have oak trees on your property, now is the right time to have them evaluated and pruned. Our certified arborists can assess their condition and recommend the right steps to keep them healthy.

Contact American Landscape to schedule a consultation or winter pruning service.