Ash Tree Chemical Treatment Successful, So Far

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The largest ash tree in Schiller Park is this white ash which is estimated it to be about 200 years old.(Photo: Mandie Trimble, WOSU News reporter)
The largest ash tree in Schiller Park is this white ash which is estimated it to be about 200 years old.(Photo: Mandie Trimble, WOSU News reporter)

The fight against the Emerald Ash Borer in the Midwest is nearing its 10th anniversary. Scientists and tree experts have tried many ways to stop the infestation. But it has spread from Southern Michigan throughout Ohio, threatening the state’s 4 billion ash trees. WOSU has an update on the fight and possible signs of hope.

For most of the past decade the primary weapon to fight the emerald ash borer was a chainsaw.

By year’s end, Columbus’ forestry department will have cut down about 6,000 ash trees along city streets and in public parks – at a cost of $2 million.

Many are scheduled for removal. In all, the city expects to remove 32,000 ash trees.

Once Emerald Ash Borers infest a tree it dies in about three years.

In neighborhoods, the city is targeting ash trees that could pose a public safety hazard. So if you have an ash tree in an easement – which is city property – you likely received a letter from the city stating it has to come down.

More Choices

But there is another option. You can treat the tree if it’s healthy enough – on your own dime.

“The thing that makes a successful treatment is that the tree has a full canopy or, at the very least, 70 percent of the canopy,” city forester Joe Sulak said.

Sulak recommends the trunk injection treatment the department uses.

“We feel the most successful treatment is the trunk injections with the chemical called emamectin benzoate,” he said.

The trade name, fittingly, is TREE-age (pronounced triage). Click here for up-to-date information on EAB from Ohio State.

“We drill a number of holes at the base of the tree and inject the chemical into the tree,” Sulak said. “And it’s a system insecticide, and so it’s taken up by the tree and then the larvae that eat underneath the bark and also the adults that feed on the leaves will actually be affected by the chemical.”

The treatment, which can be costly – $5 to $10 a diameter inch – has to be done every year or two for the life of the tree.

Signs of Success

Arborists and entomology researchers once were skeptical about any kind treatment. But OSU entomology professor Dan Herms said that’s not the case anymore.

“The trunk injection with TREE-age and some of the other treatment options can be quite successful.”

“[In Toledo,] the only living ash trees that are left, literally, are trees that have been treated with insecticide.” Dan Herms, Ohio State entomologist.

Friends of Schiller Park began injecting their ash trees – 30 of them – last May.

“A lot of them are on the eastern part of the park. There’s one, a great big huge one right here by the rec center, that’s at least 167 years old,” German Village resident Lindy Michael described.

Michael, a retired school teacher, spearheaded the treatment efforts at Schiller Park.

She said the largest ash tree in the park is a white ash – which is estimated it to be about 200 years old.

“This is it right here. And it’s just the most amazing tree,” Michael said. “It has this lower branch that reaches out, which ash trees don’t usually do. You rarely see them that old, and so far so good with this guy.”

There are a couple of green ash trees – which are more susceptible to the borer – that have some foliage loss.

“Possibly they were infested a little bit Emerald Ash Borer and nobody knew because we treated them fast enough that they should be okay if we’re able to repeat treatment,” Michael said.

The treatments cost about $5,000. The city paid for about half with a grant. Michael, who’s readying for another fund drive, says she hopes the city will help again next year especially given the chemical’s effectiveness.

EAB In The Future

Entomologist Dan Herms warned the insecticide is not a panacea. It will not kill the borer in the tree. It will cause them to just move on, but it will prevent new insects from infesting it.

“There’s so many infested trees now it’s not practical to treat anything but more than just a tiny fraction of the ash trees,” Herms said. “And only then high-value trees such as trees in somebody’s yard, trees in a city. It’s not economically feasible to treat trees in the forest.”

There are only a few counties in southeastern Ohio where the insect has not been detected. But as the borer moves through the state it kills off its food source, leaving behind seedlings and saplings. That leaves researchers with more to study.

“Can EAB persist at low levels on these juvenile orphaned ash? Or will Emerald Ash Borer go locally extinct? If it goes locally extinct, the question is then, will EAB recolonize after there’s enough larger trees. We don’t know the answer to those questions, but we’re studying them,” Herms said.

Herms expects every county in Ohio to eventually be affected by the Emerald Ash Borer.

  • Able

    Nice article.

  • Treedoctor

    Actually, there is one mistake, a misquote I am sure. When trees are injected with TREE-age, the adult beetles which feed are killed, and any larvae already in the tree are also killed. They can’t and don’t move on, they are inside the tree, eat the insecticided and are then killed.

  • Mandie

    Perhaps I misunderstood Dr. Herms. I will check on that and make any necessary corrections to the article. Thanks for bringing this to my attention.

  • Mandie


    According to the interview with OSU entomologist Dan Herms, “insecticides aren’t effective at slowing the spread [of the EAB] because if you have a tree that’s infested already and you treat it the insects will emerge. It won’t kill the insects that are already in the tree. It prevents new insects from infesting the tree.”

    I hope this helps. Perhaps reach out to Dr. Herms with additional questions/concerns.

    Thank you, again, for your comments and for choosing WOSU as a source for your news!