Emerald Ash Borer in Bloomington-Normal, IL

What Is the Emerald Ash Borer?

The emerald ash borer (EAB) is a small, metallic-green beetle native to Asia that was first detected in the United States near Detroit in 2002. Since then it has spread across the Midwest, and Illinois has been hit hard. Adult beetles are only about half an inch long and do little damage themselves — the destruction comes from their larvae, which burrow under the bark and chew through the tree's vascular tissue in winding S-shaped galleries. Those galleries cut off the flow of water and nutrients, and within a few years the tree starves to death from the inside out.

EAB attacks all North American ash species — white ash, green ash, black ash, and blue ash — and untreated trees have essentially no natural resistance. In practical terms, that means every untreated ash tree in McLean County is on borrowed time. The insect doesn't care whether the tree is in your yard in Normal, along a street in Bloomington, or on acreage outside Lexington.

Why Central Illinois Ash Trees Are Dying En Masse

Ash was one of the most widely planted shade trees in the Midwest for decades. Developers and municipalities loved it: fast-growing, hardy, tolerant of compacted soil and road salt. In the 1980s and 1990s, entire subdivisions in Bloomington and Normal were planted with green ash as the default street and yard tree. That monoculture is now the problem — when every third tree on a block is ash, EAB moves through the neighborhood like wildfire.

Compounding the issue, infestations often go unnoticed for the first year or two. The larvae work under the bark, invisible from the outside, and by the time the canopy shows symptoms the tree has already sustained heavy internal damage. Many homeowners discover their ash is infested only when the crown starts thinning — at which point removal becomes a matter of when, not if.

Signs of Emerald Ash Borer Infestation

Check your ash trees — especially in late spring and summer, when symptoms are most visible. Look for:

• Canopy dieback: The top of the crown thins first. Branches at the very top die back while the lower canopy still looks okay. This is often the earliest visible sign.
• D-shaped exit holes: Adult beetles chew their way out of the bark in holes about 1/8 inch across, shaped like a capital D. Finding these confirms an active infestation.
• Bark splitting: Vertical cracks appear in the bark as the larval galleries disrupt the wood underneath. Bark may also slough off in patches, revealing the serpentine tunnels beneath.
• Woodpecker damage: Woodpeckers strip bark to get at the larvae underneath, leaving pale, flecked patches sometimes called "blonding." Heavy woodpecker activity on an ash in winter is a strong indicator.
• Epicormic sprouts (water sprouts): The stressed tree pushes out clusters of leafy shoots from the trunk and major limbs in a last-ditch effort to survive.
• Thinning leaves and bare branches: In advanced stages, the canopy looks sparse, leaves are undersized, and large sections of the crown are simply dead.

If you see two or more of these signs, have the tree evaluated promptly. An arborist or experienced tree crew can confirm EAB and tell you how far the decline has progressed.

Treatment vs. Removal: An Honest Assessment

Here's the truth most homeowners need to hear: treatment only works if it's started early, on a tree that is still largely healthy. Systemic insecticides must be applied by a licensed, certified pesticide applicator — but once a tree is too far gone, tree removal is the next step.

Treatment is not a realistic option when the tree has lost more than about 30–40% of its canopy, shows heavy woodpecker damage, or has significant bark splitting. At that point the vascular system is too compromised for the insecticide to circulate, and the tree will continue to decline. For most infested ash trees in McLean County, removal is the responsible choice — safer for your property, and it eliminates a hazard that will only get worse.

Removal Urgency: Don't Wait on a Dead Ash

A dead ash is one of the most dangerous trees a homeowner can have. Unlike some species that rot gradually and lean before they fail, dead ash becomes brittle quickly — limbs can drop in calm weather, and trunks can snap mid-height in a storm. After Central Illinois' spring severe weather season, dead ash failures are one of the most common emergency calls in Bloomington-Normal.

There's also a cost angle: a dead ash that is still standing whole is a routine removal. A dead ash that has partially collapsed onto your roof, fence, or garage is an emergency removal — with the 25–50% surcharge that comes with it. Removing it while it's still standing saves money and risk.

Replanting: Diversify This Time

Losing an ash is an opportunity to plant smarter. The lesson of the emerald ash borer is diversity — never plant a whole street or yard with one species. Good replacements for Central Illinois include:

• White oak and bur oak: Native, long-lived, and well adapted to McLean County soils. Slow to establish but worth the wait.
• Sugar maple and red maple: Excellent fall color; sugar maple is slower-growing and sturdy, red maple faster but weaker-wooded — pick based on your site.
• Honey locust (thornless cultivars): Tough, drought-tolerant, and a fine lawn tree — though it's now overplanted in some areas, so mix it in rather than relying on it alone.
• Kentucky coffeetree, hackberry, and ginkgo: Unusual but hardy choices that add diversity and resilience to your landscape.

Avoid replanting ash, and be cautious about overplanting any single species. A mixed canopy is the best insurance against the next pest — because there will always be a next pest.

Frequently Asked Questions