Emerald Ash Borer in St. Charles County: Treat or Remove?

With emerald ash borer in St. Charles County, treat an ash tree only if it still has most of its canopy and is worth the ongoing effort of protecting it. If the crown is heavily thinned, plan removal sooner rather than later, because a dead ash turns brittle and gets more dangerous to take down every season you wait.

Key Takeaways

• Emerald ash borer has been in St. Charles County since about 2014, and Missouri's forest entomologists say it is probably in every county (St. Louis Public Radio, KSMU).
• Treatment works best before about 30 to 50 percent of the canopy is lost, depending on which university you ask.
• Treatment is done by certified arborists or pesticide applicators. We do not inject trees; we handle hazard assessment and removal.
• Dead ash wood becomes extremely brittle, and limbs can break high in the tree even on calm days.
• Once an ash is past saving, removal is the safer, more predictable choice.

How do I know if my tree is an ash?

Ash trees have leaves that grow in opposite pairs along a stem, and each leaf is made of several smaller leaflets. The Missouri Department of Conservation describes ash leaves as opposite and pinnately compound, with mostly 5 to 11 leaflets (MDC Ashes). Ash bark on mature trees forms a network of ridges with diamond-shaped furrows.

Branches on an ash also tend to sprout in opposite pairs, which is a quick way to separate it from an oak or hickory whose branches alternate. If you are unsure, take a photo of a leaf and a patch of bark and send it to us or a certified arborist before you decide anything.

It matters because the borer does not pick favorites. MDC says all of Missouri's native ash species are vulnerable, including green, white, pumpkin, and blue ash, along with cultivated varieties like Autumn Purple (MDC Emerald Ash Borer).

Is emerald ash borer really in St. Charles County?

Yes, emerald ash borer is in St. Charles County. The insect was first found in Missouri in July 2008 at Wappapello Lake in the southeast part of the state (MDC Emerald Ash Borer). St. Louis Public Radio reported it in St. Charles County since about 2014 and in St. Louis County since 2015 (St. Louis Public Radio).

By July 2021, MU Extension counted the insect in 89 Missouri counties plus the City of St. Louis (MU Extension). A Missouri Department of Conservation forest entomologist told KSMU it is probably already in every county, and that infested ash trees are mostly dying or dead about 8 to 10 years in (KSMU).

Only about 1 in 1,000 ash trees is naturally resistant, according to KSMU's 2021 report on Missouri Department of Conservation guidance. Assume an ash in your yard is at risk, not the lucky exception.

Adult beetles generally fly less than half a mile to lay eggs (MU Extension), so a neighbor's infested tree is a real threat to yours.

What are the signs of emerald ash borer?

The clearest signs are dieback in the upper part of the crown, small D-shaped holes in the bark, S-shaped tunnels under the bark, and woodpecker damage that leaves the bark looking pale. Several of these together mean the tree is infested, and the more you see, the further along it is.

According to the Missouri Department of Conservation (MDC Emerald Ash Borer), watch for:

• Upper-crown dieback. Thinning and dead branches start at the top of the tree.
• D-shaped exit holes. The adult beetle leaves a hole about 1/8 inch across.
• S-shaped galleries. Peel back loose bark and you may find winding tunnels packed with sawdust-like material.
• Blonding. Woodpeckers strip the outer bark while hunting larvae, leaving pale patches.
• Trunk sprouts. New shoots low on the trunk mean the tree is severely stressed.

Adult beetles are metallic green and about half an inch long, but you will rarely see one. Most homeowners notice the canopy first. For a broader walk-around checklist, see our guide to inspecting your own trees for hazards, and for other causes of thinning crowns, read about common tree diseases in St. Charles County.

Should I treat or remove my ash tree?

Photo: Zack Masters / Unsplash. Judging canopy loss up close is how an arborist decides which side of the treat-or-remove line a tree falls on.

Treat an ash if its canopy loss is limited and the tree is valuable to your property. Remove it if the crown is heavily declined. Universities draw the cutoff at slightly different points, between 30 and 50 percent canopy loss, so a tree in the middle ground calls for a certified arborist's opinion before you spend money either way.

Table: canopy-loss cutoffs for treating an ash tree, by university source

Source	Canopy loss threshold	What it says
MU Extension	Under 40% dieback	Trees can be protected with insecticide before 40% dieback; injections by a certified arborist work better than soil drench.
Purdue Landscape Report	30%	Over 30% loss, plan removal now; under 30%, hire professionals to treat.
Wisconsin Extension	Under 50% thinning	Insecticide works significantly better below 50% thinning; above that, remove.

The sources differ, so a tree under about a third canopy loss is a strong candidate for treatment, one past half is a removal, and the middle needs an arborist's eyes.

Beyond canopy loss, weigh these factors:

• Tree value. Wisconsin Extension lists health, shape, location, seasonal appearance, and shade as reasons a tree may be worth saving (Wisconsin Extension).
• What it could hit. An ash beside a house, driveway, or play area carries more risk than one at the back of a lot.
• The commitment. Treatment does not cure the tree; it has to be repeated. Homeowner soil products are applied yearly, while professional injections of emamectin benzoate protect for about two years (Wisconsin Extension).
• Tree size. Soil drenches are not effective on trees 20 inches in diameter or larger, and MU says injections by an arborist are far more effective than homeowner drenches (MU Extension).

To be clear about who does what: treatment is done by certified arborists or licensed pesticide applicators, and B. Woody's does not perform injections. MDC also says a heavily infested tree showing multiple stress signs is a poor treatment candidate and should be removed (MDC Emerald Ash Borer). Where we come in is the hazard assessment and, when the answer is removal, the work itself. Not sure whether your tree is a removal or a repair? Our comparison of tree removal versus tree trimming can help you frame the question.

Why do dead ash trees become dangerous so fast?

Dead ash wood becomes extremely brittle and breaks easily, so limbs and even whole trees can fail with little warning. Purdue forestry specialists say ash use only a thin ring of conducting tissue, which is one reason decline hits the structure so hard (Purdue Landscape Report).

That same report says it is not uncommon for sizable limbs to snap 30 feet off the ground on a calm day. It also cites an Ohio study finding that an ash can lose structural integrity even while two thirds of the canopy is still intact. A tree that looks mostly green from the street may already be unreliable.

The Purdue Landscape Report's advice is blunt: delaying removal lets the tree become more brittle and the problem more dangerous.

This is the part of the job Bryan Wood, our owner, takes most seriously after more than 20 years in the industry. Brittle wood changes how we approach a tree. It limits how much we are willing to trust a climber's weight in the crown, and a badly declined ash may call for a lift or crane rather than a climb. That is our own practice, not a published rule, and every tree is different. The point for you is simple: an ash removal that is planned costs less risk than one done after a storm. For general warning signs across all species, see our list of 7 warning signs a tree needs to come down.

What happens when a dead ash comes down?

We start with a hazard assessment to decide how the tree can be taken down safely, then plan the method around the tree, the site, and anything in the drop zone. Removal may be a straightforward climb, or a lift or crane when the wood is too brittle to trust. Our tree removal service covers the full job, including cleanup.

A few practical notes:

• Emergencies. If an ash has already dropped a limb onto a structure or is leaning over a roof, our emergency tree service line is staffed around the clock.
• The stump. Once the tree is down, stump grinding clears the space for whatever you plant next.
• The wood. MDC advises that removed ash wood be burned or chipped (KSMU). MDC also notes that ash nursery stock, tree parts, and hardwood firewood should not be moved out of infested counties without authorization (MDC Emerald Ash Borer), so do not haul it off yourself.
• Permits. Rules vary by city, so check our guide to tree removal permits in St. Charles County before scheduling.
• Cost help in the City of St. Charles. The city runs a 50/50 cost-share program for trimming or removing dangerous, dead, or damaged trees in the city right-of-way, and the owner pays the other half (City of St. Charles). It applies only to right-of-way trees, funds are limited, and it is not a county-wide program.

What can I plant instead of ash in St. Charles County?

Plant a mix of native species rather than another single-species row. The Missouri Department of Conservation recommends replacing lost ash with native trees such as white oak, tulip tree, and sycamore, so that no single pest can take out every tree on your property again (KSMU).

Diversity is the real lesson from ash. Yards and streets that leaned on one species had a lot to lose when one pest came through. Choose a species that fits the space, since a sycamore or white oak needs far more room than a small ornamental. If you are planning around a lot of stumps and open ground, our St. Charles County service area page shows how we work across the county.

Who should I call?

Call us for the removal and hazard side of an ash problem, and a certified arborist or licensed applicator if you want to try to save the tree. If you are unsure which category your ash falls into, we will look at it with you. Contact us for a free estimate. We are bonded and insured, we offer military and senior discounts, and we provide 24-hour emergency service for trees that cannot wait.