If you’ve noticed your ash tree looking thin at the top, or you’ve spotted small D-shaped holes in the bark, you’re probably already wondering how bad it is. Maybe a neighbor just had one taken down and now you’re looking at yours differently. Either way, you’re in the right place.
The emerald ash borer has been working through Oakland County for over two decades. We hear the treat-or-remove question constantly from homeowners across Milford, Clarkston, Lake Orion, and throughout the county. There’s no universal right answer — it depends on your specific tree, how far along the infestation is, and what makes financial sense for your property. Here’s how to think through it.
How Emerald Ash Borer Insecticide Treatment Works
Treating an ash tree for emerald ash borer isn’t as simple as spraying something on the bark and calling it done. The insecticide needs to get inside the tree — into the vascular system — where it can reach the larvae feeding beneath the bark before they cut off the tree’s ability to move water and nutrients.
There are a few ways to accomplish that, and they’re not all equal. The method matters a lot, especially for larger trees. Understanding the difference helps explain both why professional treatment works and why timing is everything.
Treat Ash Trees for Emerald Ash Borer: Which Method Works Best
The most effective professional method is trunk injection — specifically using an insecticide called emamectin benzoate, sold under the brand name TREE-age. It’s injected directly into the tree’s vascular tissue, and it’s the only EAB treatment proven to protect a tree for more than one year from a single application. In most cases, a professionally applied trunk injection provides two to three years of protection before it needs to be reapplied.
Soil drench applications — where imidacloprid is poured around the base of the tree and absorbed through the roots — are another option. They work reasonably well for smaller ash trees, roughly under fifteen inches in diameter, but their effectiveness drops off significantly for larger trees. The product has to travel a long way up through the root system, and in a big tree, the concentration that actually reaches the canopy may not be enough to do the job.
Bark sprays are a third option, applied to the lower portion of the trunk where the insecticide can penetrate and move systemically. They’re used less frequently in professional settings compared to trunk injection.
Here’s the important thing about all of these methods: they require the tree to be actively moving water to work. That means spring — when ash trees are leafing out and transpiring — is the primary treatment window in Michigan. Treating in late summer or fall, when the tree has slowed down, is far less effective. If you’re in Milford, Clarkston, or anywhere else in Oakland County and you’ve been putting this off, mid-April through early summer is when the clock really matters.
Many of the products that can effectively treat EAB — especially trunk injection — can only legally be applied by a licensed pesticide applicator. This isn’t just a technicality. It’s part of why lawn care companies that add EAB treatment to their service menu can create real problems. If the person applying the treatment isn’t qualified to assess the tree’s condition first, they may treat a tree that’s already too far gone — and you end up paying for a service that can’t save it.
How to Tell If Your Ash Tree Is Still a Good Candidate for Treatment
This is the question that actually determines whether treatment makes sense — and it’s one that requires someone to look at your tree in person. That said, there’s a useful benchmark that arborists consistently apply: the 50% rule.
If your ash tree has lost less than half of its canopy — meaning the top still looks reasonably full and the thinning hasn’t spread too far — it’s generally a strong candidate for treatment. Trees in that range can often be stabilized and preserved for many years with a consistent treatment program. If the canopy has thinned by more than 50%, the tree has likely sustained too much internal damage for treatment to reverse the decline, and removal becomes the more responsible call.
The tricky part is that EAB infestations are invisible for the first year or two. The larvae are feeding under the bark, cutting off the tree’s vascular system from the inside, long before you see anything on the outside. By the time you notice thinning at the top, D-shaped exit holes in the bark, or heavy woodpecker activity — which is actually the birds going after the larvae — the infestation is already well established.
Oakland County has been inside the EAB quarantine zone since the pest was first discovered near Detroit in 2002. Michigan eventually lifted that quarantine in October 2018, not because the problem was solved, but because EAB had spread so widely across the state that the quarantine no longer served a practical purpose. What that means for homeowners here is simple: every ash tree in Oakland County is presumed to be at ongoing risk, whether or not you can see symptoms yet. Waiting until something looks obviously wrong is often waiting too long.
Trees that are dead or nearly dead from EAB also become physically dangerous faster than most people expect. Unlike a lot of species, ash becomes brittle quickly after dying — branches snap without warning, and the structural integrity of the trunk degrades within a season or two. A dead ash near your house, driveway, or a fence line isn’t just an eyesore. It’s a liability.
Emerald Ash Borer Treatment Cost vs. Removal: Running the Numbers
The financial side of this decision is where most people get stuck. Treatment feels like an ongoing commitment with no guaranteed end. Removal feels final and expensive upfront. Neither feeling is wrong — but the math is worth actually looking at.
Treatment cost is primarily driven by the size of the tree, measured by the diameter of the trunk at chest height. Removal cost depends on size too, but also on location — how close the tree is to your house, power lines, or other structures. Both numbers vary, but they’re not impossible to compare.
What to Expect: Emerald Ash Borer Treatment Cost for Oakland County Trees
For a typical residential ash tree treated with trunk injection, professional treatment generally runs in the range of $150 to $400 per application, depending on the tree’s size. That treatment needs to be reapplied every two years to maintain protection. So over a ten-year period, you’re looking at five treatment cycles — a total cost somewhere between $750 and $2,000 spread out over a decade, for a tree that stays alive and continues to provide shade, curb appeal, and property value.
Compare that to removal. Taking down a large ash tree — especially one near a structure, power lines, or in a tight yard — can cost anywhere from $500 to over $2,000, and that’s before stump grinding. If you want the stump gone too, add that to the total. Replacement planting is a separate cost on top of that, and a new tree won’t reach the canopy size of a mature ash for decades.
For a large, healthy ash with less than 50% canopy loss, treatment often wins the financial comparison — especially when you factor in what that tree is actually worth to your property. Mature trees in Oakland County’s wooded suburban neighborhoods — places like Milford, Lake Orion, Highland Township, and White Lake Township — add real, measurable value to residential properties. Removing a mature tree isn’t neutral. It changes what your yard looks and feels like, and it doesn’t come back quickly.
That said, treatment isn’t always the right answer. If the tree is already too far gone — more than half the canopy thinned, significant dead wood throughout, or structural issues that make it a hazard — spending money on treatment is unlikely to change the outcome. In those cases, removal is the honest recommendation, and getting it done before the tree becomes a danger is the smarter move.
Trees over roughly fifteen inches in diameter should always be assessed and treated by a professional. Homeowner-grade products simply don’t move through large trees reliably enough to be depended on. If your ash is a big one, this is not the situation to DIY.
When Removal Makes More Sense Than Treatment
Removal becomes the clearer call in a few specific situations, and being honest about them upfront saves homeowners both money and frustration.
The most straightforward case is a tree that’s already past the 50% canopy threshold. At that point, the vascular damage is too extensive for insecticide treatment to reverse. The tree will continue to decline regardless of what’s applied, and removal — done while the tree still has some structural integrity — is safer and less complicated than waiting.
Location matters too. An ash tree in an open part of your yard, away from structures, gives you more flexibility on timing. But an ash tree leaning toward your roof, positioned over your driveway, or growing near power lines is a different situation entirely. As EAB damage progresses and the tree weakens, the risk of a branch failure or full tree failure increases. That risk doesn’t go away with treatment if the tree is already structurally compromised.
We’re line-clearance certified, which means we’re qualified to work safely around utility lines — meeting the standards set by DTE and Consumers Energy. That’s relevant for a lot of Oakland County properties, where ash trees in older neighborhoods often grew up alongside power infrastructure. Not every tree service can legally or safely work in those zones, and it’s worth asking about before you hire anyone.
For homeowners in communities like Clarkston, Orion Township, or the wooded stretches of Milford Township, where properties often have multiple ash trees, the treat-or-remove decision sometimes needs to be made tree by tree. A healthy ash in the back corner of your property might be worth treating. A declining one near the house might not be. Getting an honest, on-site assessment — one that gives you a straight answer rather than a sales pitch — is the only way to know for sure.
We offer free on-site estimates with no obligation, and we’ll tell you plainly what we see. If a tree can be saved, we’ll say so. If it can’t, we’ll say that too.
Making the Right Call on Ash Borer Treatment in Oakland County
The emerald ash borer isn’t a future problem for Oakland County — it’s been here since the early 2000s, and every ash tree in the county is living with that reality. The question isn’t whether to pay attention. It’s whether your tree is still in a position where treatment can make a real difference, or whether removal is the more honest path forward.
The 50% canopy rule gives you a starting framework. The treatment window — spring, when the tree is actively moving water — gives you a timeline. And the cost comparison between biennial treatment and one-time removal gives you the financial picture. Put those three things together and most homeowners can get to a reasonable answer.
If you’re still not sure, that’s exactly what a free estimate is for. Ivan’s Tree Services is based in Milford and serves homeowners across Oakland County. Reach out and we’ll take a look — no pressure, no guesswork, just a straight answer about what your tree actually needs.