City arborist Mark Reiland inspects an ash tree near the intersection of Spring and High streets in Portland on Wednesday. A row of ash trees there have been treated against an infestation by emerald ash borers, insects that are responsible for the deaths of many ash trees throughout the city. Ben McCanna/Staff Photographer

Mark Reiland traced his finger along a groove in the bark of an ash tree on the corner of Spring and High streets in Portland. The tree was bushy near its patterned trunk, but higher up its spindly branches stretched out like spider legs into a bare canopy. Reiland pointed to a deep semicircular hole in the bark.

“That’s where they got in,” he said, referring to the emerald ash borers, a species of beetle that has been decimating New England’s ash trees for years and is killing hundreds of trees in Portland.

Reiland, the city arborist, estimated there are 600 ash trees in the city and most of them are infected. In the next five years, he said about 500 will have to come down.

“Unfortunately there are entire streets we’ll have to clear cut,” he said.

The city had tried to save some trees last spring by injecting insecticide into their trunks in an effort to kill the beetles, but the treatment wasn’t as successful as they hoped and “there just aren’t many trees that are in good enough condition to save,” Reiland said.

He gestured down Spring Street, where several ash trees lining the electric vehicle charging station are slated to be removed. A row of trees in front of the Holiday Inn by the Bay already have come down.


“This street used to be lined with trees,” he said.


The emerald ash borer is a little green beetle, about a half an inch long. It was first detected in the United States in the early 2000s, though it is native to Asia. Reiland said it decimated the Great Lakes region where it was first discovered, then it went south and now is making its way through the Northeast.

The beetles bore their way into the bark of ash trees and lay pancake-shaped eggs inside. They eat through the inner layer of bark, which serves like a second, thinner skin protecting the tree’s vascular system, leaving the tree unable to move nutrients and water.

This D-shaped hole beneath the bark of an ash tree is the telltale sign of an emerald ash borer, an insect that is responsible for the deaths of many trees throughout Portland. Ben McCanna/Staff Photographer

“So it dies from the outside in,” said Reiland, pointing to the deteriorating outer branches, too far from the tree’s center for any nutrients to reach them with a shredded circulatory system. Once the trees begin to die, they’re more susceptible to falling in storms.

It can be hard to tell at first whether a tree is infected, he said. The early signs of the ash borer, like dying outer branches and unusual bushiness closer to the trunk, also can indicate drought stress or poor soil quality, common issues for trees growing in urban areas like Portland.


But trees infected by the beetle will die quickly.

“The structural decline of ash trees impacted by emerald ash borers is much faster than when they die of natural causes,” Reiland said. “If an ash tree were to die out in the woods it would be a much slower process.”


By last fall, about 20 of the ash trees the city had tried to treat the previous spring had declined to the point that they’d need to be removed.

“We realized there were more emerald ash borers than we thought,” said Reiland.

The city then conducted a survey of all the ash trees and rated them on a scale of 1 to 4, with 1 being the healthiest. They created a map with the results.


City arborist Mark Reiland leans against an ash tree near the intersection of Spring and High streets in Portland on Wednesday. Ben McCanna/Staff Photographer

On Tuesday, the city received results from a condition survey conducted this spring. Reiland said those were again discouraging.

“I’m not confident that we’ll be able to save as many trees as we’d initially hoped,” he said.

It’s not the first time New England has seen a widespread decimation of a tree species.

In the early 20th century, the majority of the nation’s American chestnut trees were killed by a fungal disease known as chestnut blights. Then in the 1970s, elm trees were hit with Dutch elm disease. Elm trees had been widely planted all over Portland, an in many other American cities, so the epidemic was devastating for urban tree canopies.

“That lead to entire landscapes being clear cut,” Reiland said.

The city widely planted Norway maples to replace them. It was common practice at the time to replant entire areas with the same species.


“We didn’t know back then how important it is to plant a diversity of trees,” he said.

Planting only one or two new species is risky, he said, because that leaves the tree canopy susceptible should another pest or disease come through. Over the last few decades, it has become widely recognized that a diversity of species creates a healthier ecosystem and prevents against a large loss of trees.

This time, as the ash trees come down, a variety of new tree species will go up. Reiland and his team are already in the process of planting “a whole smorgasbord” of new trees, including oak, hackberry and blackgum trees.

He hopes with this new approach that Portland’s trees will be more successful in the future. If a beetle or fungus or disease comes to the city again someday – an exceedingly likely possibility with more frequent ecosystem disruptions due to climate change – perhaps just 50 or 100 trees would be lost instead of 500 all at once.


Helping with those replanting efforts, which the city says could take years, are neighborhood efforts like the Bayside Tree Planting Project and the city’s tree co-op program.


The city announced this week that the Bayside project, paid for with a combination of American Rescue Plan and Community Development Block Grant money, will plant 150 new trees in the neighborhood, where historically there has been markedly less tree cover than in other parts of the city. They’ll get to work this month planting 20 trees.

A national tree equity score, which indicates whether there are enough trees in the neighborhood for everyone to experience the health, economic and climate benefits that trees provide, shows Bayside has a significantly lower score than other parts of the city.

The city is working with a contractor to build new tree wells along streets, a labor-intensive task because the area was not originally designed with space for greenery.

Sarah Michniewicz, the president of the Bayside Neighborhood Association, said there “are only a few heritage-sized street trees” in the neighborhood, which has struggled to find ways to get new greenery in the area.

“More populous, wealthier neighborhoods have the bandwidth to do that advocacy and really stand up and say ‘We don’t want that tree cut down,’ ” Michniewicz added.

Bayside Neighborhood Association President Sarah Michniewicz, photographed in April 2023, says the area has struggled to find ways to get new greenery in the neighborhood. Gregory Rec/Staff Photographer

In the West End, a group of neighbors worried about the ash borer infestation took an active role in trying to maintain the city’s tree canopy by recruiting neighbors to participate in the city’s co-op program.


The program allows residents to purchase a tree from a local nursery and select where it will be planted. The city provides a team to transport and plant the tree once a planting site has been approved. Trees can be planted on public or private property so long as that property is close to the street.

“That way those trees are still providing shade and other benefits to the community, even if they are growing in someone’s private yard,” Reiland said.

Rob Adams, a West End resident and landscape architect, said that he inherently “cares a lot about trees” because of his career. When he learned about the ash borer infestation, he got a group of neighbors involved in the co-op program to replant parts of their neighborhood.

“I’m happy to be the middleman,” he said.

More than a dozen neighbors were interested in participating and they were able to put through seven applications to plant two species – sugar maple and a hybrid American elm – on the Western Promenade. The tree sites are still pending review, Adams said.

“Rather than waiting until they’re all dead, we decided to start planting next to and around the trees with different species so that when the ash trees die, they can be removed, and the new trees will have … a head start,” he said.

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