Bangor is on a mission to protect its ash trees from emerald ash borer, an invasive bug that could arrive in the city before the year is over.
Four University of Maine forestry students spent the summer counting, categorizing and inspecting 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, according to Sophia Cameron, a masters of forestry student from the University of Maine’s School of Forest Resources. Ash trees are the second most common tree species found on public land in Bangor, just behind Norway maple.
While counting the trees, the students were looking for signs of emerald ash borer, an invasive species of bug that, as larvae, eat away the inner layer of bark of ash trees. That part of the tree carries water and nutrients up to the leaves, so when it’s damaged, the tree slowly dies.
“This is going to be a much bigger issue than we can recognize,” said Aaron Huotari, Bangor’s public works director. “On a clear, dry, beautiful day, the trees just collapse under their own weight because they get so brittle. That presents a danger to the public.”
An ash tree has only a 2 percent chance of surviving an emerald ash borer infestation if left untreated.
Losing 20 percent of its trees would likely wreak havoc on Bangor in surprising ways. It would ravage the city’s stormwater management system and raise the temperature in urban areas, which are filled with materials like concrete that hold heat, Cameron said. Trees also provide air filtration, increase property values and are aesthetically pleasing.
Brown ash is also culturally significant to the Wabanaki Nations because it’s used in basketmaking. Because of this, Cameron advised the city to include Wabanaki voices in future discussions on ash tree preservation.
The bugs, which are metallic green and about the size of a penny, arrived in the U.S. in 2002, likely through wooden shipping pallets, and spread to 36 states. In 2018, they were found in Maine, and just last year an infestation was identified in Hermon.
“It’s a matter of time until we’re dealing with it as well,” Cameron said. “We wouldn’t be surprised if we had emerald ash borer within 2024. However, we’re at an advantage now because everything we’re doing is preemptive rather than retroactive.”
Cameron recommended the city monitor its ash trees and look for signs of an infestation. If the bugs 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 bugs burrow into trunks toward the top of the tree and work their way down through the wood, Cameron said.
“Usually by the time you can detect an insect infestation in the tree, it’s very close to being too late, unless you’re looking for it,” Cameron said. “If you start seeing the upper limbs start to die and then move downwards, that’s a pretty significant indicator that it may be emerald ash borer.”
To protect the healthy trees that are particularly valuable, like ones that shade a public park, the city should treat the trees by injecting insecticide into the trunk next spring and summer, Cameron said. The insecticide in the wood would kill the bugs when they eat. This method is similar to what the city did to kill browntail moths in public parks.
The city plans to set up a database for residents to report any ash trees on their private property, Huotari said. The city will also advise people on how to manage their ash trees.
To control the spread of emerald ash borer, the Maine Forest Service recommends people not transport ash firewood from areas that have confirmed emerald ash borer infestations, Cameron said.
