If your ash tree in St. Charles County has less than 30 percent canopy dieback and a sound trunk, treating it for emerald ash borer is usually worth it. Once dieback passes 50 percent, removal is the safer and cheaper long-term choice, because a declining ash turns brittle within a year or two of dying.
Emerald ash borer has been established across the St. Louis metro for roughly a decade, and on the properties our crews maintain from Wentzville to Creve Coeur, untreated ash trees are now rare. The question for most homeowners is no longer whether the beetle will arrive. It is whether the tree in your yard can still be saved.
How to Check Your Ash Tree This Season
Walk around the tree in late May or June, when the canopy is fully leafed out and thinning is easy to spot. Look up first, then work down the trunk.
- Canopy thinning from the top down, with bare twigs poking above the leaves
- D-shaped exit holes about 1/8 inch wide in the bark
- Blonding, where woodpeckers strip outer bark and leave pale patches as they hunt larvae
- Epicormic sprouts, clusters of leafy shoots growing from the lower trunk
- Vertical bark splits that reveal S-shaped tunnels underneath
Estimate dieback by picturing the canopy as a whole and judging how much is bare. If you see heavy woodpecker activity on the main trunk, the infestation is usually further along than the canopy suggests.
Measure the Trunk Before You Decide
Measure trunk diameter at 4.5 feet above the ground, called DBH (diameter at breast height). Wrap a tape around the trunk and divide the circumference by 3.14. Treatment products are dosed and priced by the inch, so this number drives both the method and the cost.
Your Two Treatment Options
Homeowners in St. Charles County generally choose between these approaches:
- Soil drench with imidacloprid: works for trees under about 15 inches DBH. Apply in April or early May while the soil is moist, and repeat every year. Heavy clay soils slow uptake, so pull mulch back and soak the drench zone within 18 inches of the trunk.
- Trunk injection with emamectin benzoate: the most reliable option for larger trees. Apply after full leaf-out, typically mid-May through June in zone 6. One injection protects the tree for two to three years.
Injections are a professional application in Missouri. Retail drench products are available at garden centers, but follow label rates closely, since overdosing will not rescue a tree that is already in heavy decline.
When Removal Makes More Sense
Ash wood dries out fast after the tree dies, and dead ash limbs snap without warning in Missouri summer windstorms and winter ice. Removal also gets more expensive as the tree weakens, because crews cannot safely climb it and need a lift or crane instead.
Removal is the better call if any of these apply:
- Canopy dieback is over 50 percent
- The trunk shows extensive blonding or bark splitting
- The tree leans over a house, driveway, or power line
- The ash is a low-value tree in a spot you would rather replant
- You do not want to commit to treatment every two to three years for the life of the tree
Good Replacements for Clay Soil in Zone 6
If you remove an ash, plant something suited to our wet springs and compacted clay. Trees that perform well across St. Charles and St. Louis counties include:
- Swamp white oak
- Kentucky coffeetree
- Bald cypress
- Hackberry
- Black gum
- Shingle oak
Plant in October or early April, and set the root flare at or slightly above grade so water does not pool around the trunk in clay.
Getting a Second Opinion
If you are unsure where your ash falls, our crew can measure it, assess dieback, and give you a straight answer on treatment or tree removal. Call (636) 293-6322 or Contact Us to set up a visit.