When forestry crews in Portland first found the invasive emerald ash borer in Payson Park in 2019 they were relieved to not find any damage caused by the bright green beetle to the city’s hundreds of ash trees.

But they knew it was only a matter of time until that changed. Now the city has begun removing trees with the heaviest damage.

“It’s something we’re concerned about,” city arborist Jeff Tarling said. “Ash trees can decline pretty quickly. We’re hoping the public will see this and if they have ash trees make plans to monitor their tree and do some preventative treatments. … People should at least be aware of it and monitor it.”

Earlier this year, crews noticed a decline in a group of ash trees on District Road near the Westbrook town line off outer Congress Street. Tarling said they initially thought the damage might be due to drought, but upon further inspection they realized the trees had been badly damaged by the emerald ash borer.

Four large trees were cut and removed with a crane late last month, in part out of concern that the trees can become brittle and a safety hazard from the damage. The city also is planning to remove seven infested trees outside Lincoln Middle School in the Deering Center neighborhood, as well as another group of trees at Riverton Trolley Park and the Riverside Golf Course.

“This is something that will probably ramp up in the next year or two and it’s something everyone in southern Maine and New Hampshire should know about,” Tarling said.

“We’ve heard about it, but you think, ‘It’s somewhere else. It’s not going to affect me.’ I think seeing it here in Portland, even though I’ve known about it for years, it makes us realize we have to deal with it.”

The recent discovery of damage from the emerald ash borer in Portland is part of a broader spread of the invasive insect into Maine. The beetle was first discovered in Aroostook County in 2018 and in York County later that year. In Cumberland County, it was detected first in Portland in 2019.

“As far as how big of a problem it is, it does threaten all ash trees in Maine,” said Allison Kanoti, director of forest health and monitoring for the Maine Forest Service and the state entomologist.

Maine has 400 million ash trees, though they make up only 2 percent of all trees in Maine, Kanoti said.

“I would say almost anybody in Maine should have a plan if they have ash trees around their home or other infrastructure,” she said. “It doesn’t mean everyone in the state or city needs to take action today, but if you have trees in decline or threatening structures that action may need to be sooner than if you have healthy trees.”

The emerald ash borer is a small wood-boring beetle originally hailing from Asia and first identified in the U.S. in the Detroit area in the early 2000s. The beetle attacks native (not mountain) ash by burrowing through conductive tissue, cutting off the flow of food and nutrients and eventually killing the tree, typically in five years or less.

Signs of infestation include “blonding,” which is the result of woodpeckers peeling away the outer layer of bark to look for the beetle larvae to feed on; bark falling off; S-shaped tunnels left by the beetles on the bark; and D-shaped holes made by the beetles as they exit the tree. Abnormal shoots and sprouts may also appear as the tree compensates for the damage done by the beetles.

An insecticide – emamectin benzoate – can be injected into trees to prevent damage, though Tarling said its potency only lasts two to three years. He said homeowners may want to consider consulting a professional applicator if they have a tree they’re concerned about.

“People could consider between now and spring if they want to treat their ash tree and enlist services to decide what they want to do,” he said, adding that the treatments are usually done in spring.

In Portland, the city has treated some trees, but it’s neither time- nor cost-effective to try and treat all of the roughly 600 ash trees on public property in the city, Tarling said. The largest green ash tree in Maine is in Deering Oaks, and Tarling said the city treated that tree last year.

Next spring, he said, the city will also plan to release parasitic flies as a means of “biological control.” There are also a small number of ash trees that appear to be immune to the emerald ash borer for unknown reasons. “It’s not like every single ash tree will die,” Tarling said. “There will be a recovery aspect of trying to find the seeds of those ones who made it.”

The state offers grants to municipalities through its Project Canopy program to support towns in understanding and mitigating the impacts of the emerald ash borer, Kanoti said.

The insect hasn’t been detected yet in all parts of Maine and is currently known only in York, Cumberland, Oxford, Androscoggin, Aroostook and Kennebec counties.

PROACTIVE TREATMENT ADVISED

Last summer, Yarmouth proactively treated 120 ash trees for emerald ash borer after reports of the beetle on the outskirts of town prompted concern it could become widespread.

“We haven’t actually seen the effects of the emerald ash borer in town yet, but we … have quite a few prestigious ash trees and want to make sure they don’t get infected,” said Scott Couture, Yarmouth’s tree warden and a licensed arborist.

The cost of the treatment wasn’t cheap – Couture said it cost Yarmouth $21,000 for the 120 trees they injected – but officials are advising residents to consider it themselves.

“If you have an ash tree you really care about, you should look into getting it treated,” Couture said.

Officials in Westbrook also are monitoring their community for the emerald ash borer. Arborist Doug Eaton said in an email that the city was contacted by Tarling about the tree removal on District Road, and they have also been made aware that the Maine Forest Service has detected emerald ash borers near a movie theater on County Road.

“I hope to connect with Portland soon to discuss how things went and what we need to do to work together to help fight the spread of emerald ash borer,” Eaton said.

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