20 Years After Emerald Ash Borer: The Surprising Science of Ash Recovery

Drive down an older Peoria street and you’ll see the gaps. Green ash used to line whole blocks — fast-growing shade trees that cities loved. Then the emerald ash borer arrived, and most of them are gone.

For years the story was simple: the beetle wins, the tree dies. Homeowners with an ash faced one question — take it down now, or wait until it turns into a hazard.

New research marking 20 years since the invasion is changing that story. The science came out more surprising than most people expected — and it changes how you should think about the ash tree still standing in your yard.

What 20 Years of Data Actually Found

The 99% number is real

Tayal and Perry’s 2026 analysis looked at research sites that have been tracked since the invasion began. At those long-term sites, over 99% of ash trees died. That number backs up what anyone who’s driven through Central Illinois already knows — this was one of the worst tree-killing events in U.S. history.

The surprise: the understory came back

Here’s what researchers didn’t expect. At those same sites, ash seedlings and saplings now dominate the regenerating understory. The beetle targets larger trees, so young ash slipped through — and nature started over.

Think about the woods at Forest Park Nature Center for a second. Old woods don’t bounce back overnight when a whole species is wiped out. But given decades, ash is quietly reclaiming ground where it was killed off. That’s a very different story than “the ash is gone forever.”

The survivors are doing better than expected

The study also found that 57% of the larger surviving ash trees retained healthy canopies. That’s important. It means some mature ash can live with the beetle around — or fight off attacks well enough to keep a full, healthy crown.

Those survivors matter for Peoria homeowners. They prove the species isn’t doomed — and they prove that a living ash with a good canopy is worth taking seriously instead of writing off.

The 20-Year EAB Timeline

It helps to see the whole arc at once. Twenty years is a long time in tree years — and the story has more chapters than most people realize.

What This Means for Your Ash Tree in Peoria

Green ash was a favorite street tree here for good reason — it grows fast and shrugs off tough city soil. Whole stretches along Sheridan Rd, Knoxville Ave, and War Memorial Dr used to be shaded by it. Much of that canopy is gone now, and the D-shaped exit holes the beetles left behind are still visible on dead trunks around town.

So if you still have a living ash — in the 61604 core, out toward 61615 and 61616, or in the 61548 and 61554 neighborhoods — you’re holding something the 20-year data says deserves a real decision. Not panic. A decision.

The treat-or-remove question

Here’s the rule of thumb that comes out of two decades of experience: treatment is worth considering while canopy loss is under about 30%. A tree that’s mostly full, with dieback limited to the top branches, is a candidate. A tree that’s half bare is probably past the point.

Treatment protects living wood from the beetle — it can’t bring dead branches back to life. That’s why the earlier call matters. If you’re on the fence, get the tree assessed before the canopy slips any further. You can read about how professional treatment works on our EAB treatment page.

Decision Card: Should You Treat or Remove Your Ash?

Whichever side your tree lands on, don’t wait until it becomes a hazard. Dead ash gets brittle fast — a dead limb over your roof or your neighbor’s fence on the Illinois River bluffs isn’t a problem you want to discover during a storm.

Reading Your Ash: The Signs That Decide It

You don’t need a forestry degree to size up your tree. Walk around it and look for these clues — they tell you which side of the 30% line you’re on.

• D-shaped exit holes: small, D-shaped holes in the bark — the classic sign EAB has been there.
• Thinning crown: the top of the tree goes sparse first; that’s where dieback usually starts.
• Bark splitting and woodpecker damage: woodpeckers strip bark hunting for larvae, leaving pale, flaking patches.
• Sucker sprouts: clusters of thin shoots popping from the trunk or base — the tree’s last-ditch effort to survive.
• Half the tree looks fine, half doesn’t: uneven dieback often means the beetle has been working for a couple of seasons already.

One or two of these with a mostly full crown? Worth an assessment. Most of the list at once, with big dead sections? That’s a removal conversation. Either way, knowing what you’re looking at puts you in charge of the decision instead of the beetle.

If Your Ash Is Already Dead, Here’s the Good News

Remember the seedlings from the 20-year study? That same regeneration logic applies to your yard. When a dead ash comes out, you get a blank slate — and the science says forests recover strongest with diversity.

So don’t plant another ash. Plant a mix: oaks, maples, and other species that fit zone 6a and your yard’s size. A varied canopy means the next pest can’t take everything at once. Our tree planting page covers how to pick the right tree for a Peoria yard.

October is actually a good season to plan this. First frost lands in Peoria around October 11–20, and fall planting gives roots a head start before spring. Whether you’re along Grandview Drive, near Bradley Park, off US-150, or along the Rock Island Trail in the river towns, one well-chosen tree now beats a rushed choice later.

Why This Story Hit the News Again in October 2026

On October 14, 2026, the USDA confirmed emerald ash borer on both sides of Washington state. Think about that: nearly a quarter-century after the first Michigan detection, the beetle is still expanding into new territory. This fight isn’t over anywhere.

Eleven days earlier, on October 3, Colorado Springs started active EAB removals under its brand-new management plan. A city hundreds of miles west of here, gearing up for the same battle Peoria has been fighting for years.

For ash owners from the I-74 corridor to the IL-29 river towns, that news is a reminder, not a reason to panic. EAB isn’t going away. But the 20-year science says we understand it far better now — and that ash, as a species, is tougher than the early years suggested.

The Bottom Line for Peoria Ash Owners

• Twenty years of data says the beetle killed over 99% of ash at long-term research sites — but young ash is regenerating on its own, and 57% of larger survivors kept healthy canopies.
• A living ash with a full canopy is worth protecting. Treatment is worth considering while canopy loss stays under about 30%.
• A mostly dead ash won’t bounce back. Removal keeps your home and family safe — and clears the way for a diverse new planting.
• October 2026 news proves EAB is still spreading nationwide, so ignoring the problem isn’t a plan.

The science finally caught up with the story. The beetle did its damage — and nature, given time, is doing its repair work. Your job is the part in the middle: decide what to do with the ash tree in front of you, while you still

have a choice.

Related Articles

• Emerald Ash Borer Signs in Peoria IL | Save Your Ash Tree
• Best Replacement Trees to Plant in Peoria, IL (After a Removal)
• Buying Firewood This Fall? How Moving It Spreads Tree-Killing Pests in Illinois

Frequently Asked Questions

Peoria Tree Removal Co. — 114 W Forrest Hill Ave, Peoria, IL 61604 — (309) 250-8333 — treeremovalpeoriail.com — info@treeremovalpeoriail.com