Just about a year ago, Bar Harbor arborist Jamie Lambert drove down Indian Point Road and noticed the trees were blonding.
It’s the kind of sight that makes an arborist stop his vehicle, which is exactly what Lambert did.
Blonding is when the woodpeckers start to remove the outer bark of the tree to go after an insect’s larvae and pupae, so Lambert stopped to confirm what he thought might be happening under the surface of those ash trees: emerald ash borer infiltration. He checked the trees and told the state.
The state quickly went into action, he said.
And what did the state find?
Exactly what Lambert, the local manager and arborist representative at Bartlett Tree Experts in Mount Desert, feared.
The emerald ash borer was definitely in the trees.
“They’re super invasive,” Lambert said at the time.
So invasive that just since the beginning of 2026, the insect has been detected for the first time in 16 Maine municipalities: Bangor, Benedicta Township, Benton, Bowdoinham, Buckfield, Dixfield, Greenwood, Harpswell, Hartford, Palermo, Rumford, Stockholm, Sumner, Topsham, West Paris, and Wilton.
In late April, the Maine Department of Agriculture, Conservation and Forestry expanded the emerald ash borer (EAB) quarantine in Maine.
Since that expansion the borer was found in Franklin County, in Wilton, and — for the first time — in Bangor. The city has a response plan to manage the impacts of emerald ash borer on the city’s trees.
All of Mount Desert Island has been in an active quarantine zone after Lambert’s 2025 discovery.
There is now a quarantine of all ash tree material except for ash chips. The quarantined tree material cannot be transported off the island, but must stay on-site or at MDI-based disposal facilities. This is meant to slow the borers’ spread to other areas.
The ash borer was first found in Maine in 2018.
According to a research report from Bartlett Tree Experts, it was first found in Michigan in 2002. It is not native to the continent and arrived via “solid wood packing material from Asia,” the report says.
Emergence Magazine further explains, “In the early 1990s, a cargo ship arrived in the port of Detroit, carrying pallets made of unprocessed ash wood from East Asia, where cousins of North American ash trees live. Along for the ride were several emerald beetles, each only half an inch long.”
The borer already has infested millions of Maine ash trees. After that infestation, trees typically live only 2-3 years.
It’s an environmental and cultural worry.
According to the U.S. Forestry Service, “Deeply rooted in tribal culture, the brown ash tree is not only the principal building material for baskets produced by tribal artisans, it’s also referenced in the Wabanaki creation story. This association of brown ash both to basketry and the creation story of the people clearly shows that the species is a part of the cultural identity of all the Indigenous peoples of the region.”
Treatment
According to the Bartlett Tree Experts lab report directed by Dr. Kelby Fite, the best treatment when dealing with the borer is early application of insecticides.
“Once an ash shows greater than 40% crown decline, however, treatment efficacy is significantly impaired. Recovery, even after effective treatment, may not become apparent until the second year. Trees with greater than 50% dieback should be scheduled for removal as soon as practical to prevent hazardous conditions due to the brittle nature of dead ash wood,” the report states.
One of the problems is that it’s hard to find trees that have a low density of larva. It’s also not desirable to put insecticide in a location before the insect invades that area.
According to the Bartlett report, “Treatments should ideally begin when EAB is found within 10-15 miles of an ash tree’s location. Research has shown that management techniques change as population levels build. Emerald ash borer population dynamics typically follow a pattern:
- Early Stage (Cusp of invasion) – Over three to four years, populations slowly build; losses from EAB are less than 8% of the total ash tree population. Annual preventive treatments with soil-applied imidacloprid will protect ashes during this stage.
- Peak Stage (Crest of tree mortality) – By year five of an infestation, EAB populations are very high. Most unprotected ash trees will be killed over the next four to five years. During this stage, root flare injection with emamectin benzoate every other year has been shown to be the most effective treatment to protect ash trees from the severe pressure presented by this pest.
- Late Stage (Core infestation) – By this stage, most unprotected ashes have been killed and beetle populations are declining. Annual preventative treatments with soil-applied imidacloprid will again protect ash trees at this stage.”
Containment via quarantine is a major strategy. That’s because if people didn’t cut dead ash, chop it, and carry it into other areas for campfires, the borers would move just about a half a mile each year.
This story was originally published by The Bar Harbor Story. To receive regular coverage from the Bar Harbor Story, sign up for a free subscription here.
