Recent Tree Health Threats

Recent Tree Health ThreatsWhat’s New in Tree Health & Forest Threats- Wisconsin Department of Natural Resources (DNR)’s 2025 forest-health alerts

In December 2025, the DNR advised property owners to watch for woodpecker “flecking” on ash trees — a tell-tale sign that Emerald Ash Borer (EAB) may be present. This invasive beetle remains “the most damaging threat to Wisconsin trees,” capable of killing ash trees over a few years if untreated. forestrynews.blogs.govdelivery.com+1

Also in late 2025: DNR foresters are continuing to monitor other invasive pests even if some outbreaks have subsided. For example, while the statewide surge of Spongy Moth appears to have ended, local “hot spots” may still see a resurgence depending on weather. forestrynews.blogs.govdelivery.com+1

What this means for you:

Keep an eye on your ash trees this winter and spring. Look for bark “flecking,” woodpecker holes — early signs of EAB.

Even if spongy moth outbreaks are declining, it doesn’t mean your trees are safe — other pests or stressors like drought can make them vulnerable to new threats.

Emerging Threat: First Case of “Sudden Oak Death” in Minnesota

In November 2025 researchers confirmed the first ever case of Sudden Oak Death (caused by the pathogen Phytophthora ramorum) in Minnesota. MPR News+1

This disease has been devastating oak and rhododendron populations elsewhere in the U.S. — and now it appears to be spreading eastward (or at least into new locales).

Implication for the Upper Midwest region:

This is potentially very important: Minnesota isn’t far from Wisconsin, so the disease’s spread could threaten oak and other susceptible trees here. Even if not immediate, it’s a good reminder to check oaks for unusual die-back, leaf damage, or bark issues — especially if you have older or mature trees.

What Landowners & Tree-Stewards Should Do Right Now

Here are practical steps to help protect trees, whether in your yard, street, or woodlot:

Inspect ash and oak trees this winter and early spring. Look for woodpecker activity, bark damage, thinning canopy, and early wilt signs.
For oak owners: consider avoiding pruning or wounding during high-risk periods, especially during times when spores or beetles are active. That reduces risk of diseases like oak wilt. Wisconsin DNR+1
Be cautious moving firewood or wood debris. Many pests — like EAB — spread via infested wood. Avoid transporting firewood long distances; use locally or burn it near source.
Stay informed about local forest health bulletins. Agencies like your state DNR often publish alerts when a new pest or disease appears nearby.
Consider consulting a certified arborist — especially if you own mature or valuable trees — if you notice symptoms (leaf loss, bark damage, unusual pest presence)

Need help protecting your trees?

Johnson Ops Tree Care is here to help diagnose issues, prevent pest damage, and keep your trees healthy year-round. Our Certified Arborists serve Holmen, Onalaska, La Crosse, West Salem, and surrounding areas with expert tree care. Call 608-526-6297 to schedule your consultation today. Johnson Ops Tree Care — Professional. Knowledgeable

Recent Tree Health Threats