Your Ash Tree and the Emerald Ash Borer: Treat It or Take It Down?
Every untreated ash in Flint is on a clock. Here's how to read where yours stands, using the state's ID guide and the research from Michigan State and Ohio State.
Three ways to tell if it's an ash, and if it's infested
Ash trees have compound leaves: several leaflets on one stem, arranged directly across from each other on the twigs. If that's your tree, look for the signs listed by the Michigan Invasive Species Program: Emerald Ash Borer:
- D-shaped exit holes in the bark, left as adults emerge
- Thinning from the top down, as larvae tunneling under the bark cut off water and nutrients
- The beetle itself: bright metallic green, about half an inch long, small enough to fit on the head of a penny
The state notes EAB has killed tens of millions of Michigan ash trees, in forests and neighborhoods alike, since it was first found here in 2002. In Flint, that means a lot of dead and dying ash in yards, on parkways and on vacant lots.
Save it, or take it down?
The best research on this comes from Michigan State and Ohio State. The Herms, McCullough, Smitley et al., "Insecticide Options for Protecting Ash Trees from Emerald Ash Borer" (2nd ed., multistate bulletin) gives a clear framework:
| Your ash right now | What the research says | Our usual advice |
|---|---|---|
| Full canopy, no exit holes | Best time to start treatment | Treat it if it's a tree you value. Otherwise plan its replacement |
| Some thinning, less than half the canopy lost | Treatment can stop further damage but can't reverse what's done. Recovery takes time | Treat, and expect a slow turnaround |
| More than half the canopy dead | Probably too late to save | Ash tree removal |
| Dead, bark falling off | Not a candidate | Remove before limbs start dropping. Sooner if it's over the house or the street |
What treatment actually involves
In MSU and OSU studies, a single trunk injection of emamectin benzoate in mid-May or early June gave excellent control for at least two years, and up to three depending on the rate and how heavy the infestation was. The bulletin also found that soil and base-of-trunk applications are taken up better than spreading product in a grid under the canopy.
Expect patience. A tree that was already thinning can look worse during the first year and only start to come back in the second.
What you can do on your own
- Identify every ash on your property and note how full each canopy is, with photos each summer.
- Don't move ash firewood. The state stresses that people moving firewood spread the beetle much faster than it spreads itself.
- Know when to stop. Dead ash near a house or driveway isn't a weekend chainsaw job.
Dead ash and Michigan winters
A dead tree doesn't get stronger with time. Snow and ice loads and spring winds bring down limbs from trees that are already dying. When a storm puts one on the house, that's emergency ice storm tree removal. We'd rather take it down on a calm day.
What sets the price
Estimates are free. Removal price depends on trunk diameter, height, how dead the tree is (brittle trees can't always be climbed safely and may need a lift or crane), and what's underneath: house, garage, wires or fence. Stump grinding and haul-off are quoted separately. Treatment cost depends on trunk size, and treatment has to be repeated every few years. We'll compare the two over time for any tree you're unsure about.
How a visit goes
- We find and identify every ash on the lot.
- We rate each canopy and check for exit holes and bark splits.
- You get a written recommendation for each tree: treat, remove, or monitor.
We're insured. If your ash is healthy and worth saving, we'll say so, even if removal would be the bigger job.
Flint ash tree questions
Is emerald ash borer still a problem in Genesee County?
Yes. The state says EAB is established across Michigan's Lower Peninsula and has killed tens of millions of ash trees since it was first found in Michigan in 2002. You no longer need to report it. Michigan.gov points homeowners to a qualified arborist instead.
My ash looks healthy. Should I treat it anyway?
If it's a tree you want to keep, yes, sooner rather than later. The multistate insecticide bulletin says treatment works best while ash trees are still relatively healthy. By the time most people notice thinning, the beetle has already done significant damage.
How do I know if it's too late?
The bulletin's rule of thumb: if more than half the canopy has been killed by EAB, or the tree carries less than half the foliage it should, it's probably too late to save.
We started treating and the tree looks worse. Did it fail?
Not necessarily. According to the bulletin, a tree that was already declining can keep getting worse in the first year of treatment. If treatment is working, the canopy usually begins to improve in the second year.
Can I keep the wood for firewood?
Burn it where it is. The state's message is simple: don't move firewood. The beetle only flies about half a mile on its own, so the real spread comes from people moving infested wood.
What should I plant instead?
Anything but ash. Mix species so one pest can't wipe out a whole street again. See our tree planting page or ask during the visit.
Sources
- Michigan Invasive Species Program: Emerald Ash Borer: identification, Michigan losses, 2002 discovery, firewood and flight range, reporting.
- Herms, McCullough, Smitley et al., "Insecticide Options for Protecting Ash Trees from Emerald Ash Borer" (2nd ed., multistate bulletin): treatment timing, the 50 percent rule, recovery lag, emamectin benzoate results, application placement.