Bangor is committed to protecting its ash trees from the Asian ash borer, an invasive insect that could invade the city before the end of the year.
Four forestry students from the University of Maine spent the summer counting, categorizing and studying every single tree on public land in Bangor. Trees on private property, including residential yards, were not included.
In total, the students counted 8,574 trees, 20 percent of which are ash trees, said Sophia Cameron, a master’s student in forestry at the University of Maine’s School of Forest Resources. Ash trees are the second most common tree species on public lands in Bangor, just behind Norway maples.
As they counted the trees, students looked for signs of the Asian ash beetle, an invasive insect species whose larvae eat away at the inner bark of ash trees. This part of the tree carries water and nutrients to the leaves, and if it is damaged, the tree slowly dies.
“This is becoming a much bigger problem than we realize,” said Aaron Huotari, Bangor’s public works director. “On a clear, dry, beautiful day, the trees simply collapse under their own weight because they become so brittle. That poses a danger to the public.”
An ash tree has only a two percent chance of survival when infested with the Asian ash beetle if it is not treated.
Losing 20 percent of trees would likely have surprising consequences in Bangor. It would destroy the city’s stormwater management system and raise temperatures in urban areas filled with materials like concrete that trap heat, Cameron said. Trees also filter air, increase property values and are aesthetically pleasing.
The brown ash is also culturally significant to the Wabanaki Nations because of its use in basket weaving, which is why Cameron advised the city to include Wabanaki voices in future discussions about preserving the ash.
The metallic green, penny-sized bugs probably entered the United States on wooden pallets in 2002 and spread to 36 states. They were found in Maine in 2018, and an infestation was discovered in Hermon just last year.
“It’s only a matter of time before we’re dealing with that too,” Cameron said. “We wouldn’t be surprised if we had the Asian ash borer in 2024. But we have an advantage now because everything we do is preventative, not retroactive.”
Cameron recommended that the city monitor its ash trees and look for signs of infestation. If the beetles are found in a tree, it should be removed and replaced with a healthy tree, she said.
Detecting an infestation can be challenging because the beetles burrow into the tree trunk at the top and work their way down through the wood, Cameron said.
“By the time you notice an insect infestation in the tree, it’s usually almost too late unless you’re looking for it,” Cameron said. “If you see the upper branches dying and then moving downward, that’s a pretty clear indication that it could be the Asian ash borer.”
To protect the healthy trees that are especially valuable, such as those that provide shade in a public park, the city should treat the trees next spring and summer by spraying insecticide into the trunk, Cameron said. The insecticide in the wood would kill the insects as they feed. This method is similar to the one the city has used to kill brown-tailed moths in public parks.
The city plans to set up a database where residents can report ash trees on their private property, Huotari said. The city will also advise residents on how to care for their ash trees.
To control the spread of the Asian ash beetle, the Maine Forest Service recommends not transporting ash firewood from areas where an Asian ash beetle infestation has been confirmed, Cameron said.
