Bath has a new invasive species of insect to contend with, one that has been ravaging ash trees in southern and northern parts of the state.

Jack Hernandez, an arborist for the City of Bath, discovered the emerald ash borer in Bath last month. This is the first time the bug has been reported in Sagadahoc County.

He found the insect while removing a dying white ash tree at the intersection of Edwards and Dummer streets in Bath. Michael Parisio, an entomologist in the Insect Disease Lab for the Maine Forest Service, later confirmed Hernandez’s discovery.

“When we got there, I started cutting it and noticing some pretty telltale signs,” Hernandez said.

Hernandez said the emerald ash borer larvae are more aggressive than other borer species found in Maine. They feed underneath the bark of a tree for about two years, creating an S-pattern of feeding galleries. The emerald ash borer is difficult to detect because of its size and its preference for hiding under the bark of trees.

“It’s a very serious threat, and unfortunately, all these things don’t sink in until they hit home,” Parisio said. “We have a series of management tools that help a little bit, but unfortunately, there is no cure-all for emerald ash borers.”

Preventative measures against the emerald ash borer include licensed pesticides applied as soil trenches about 18 inches of the trunk and 2-4 inches deep. However, home products for soil application differ from professionally made products.

Another measure is systemic insecticide injections in ash trees that protect them for up to three years. Some parasitoid species native to North America and also brought in from Asia will attack and kill the emerald ash borer larvae.

“From an urban forestry standpoint, it can be very difficult because a lot of these urban trees are under a tremendous amount of pressure anyway,” Hernandez said.

In late August 2023, another case was discovered in Brunswick at Mid Coast Hospital. Parisio said the trees planted in islands near the hospital were moderately infested with emerald ash borers, but the forest grounds around the hospital had no ash trees.

Parisio said the emerald ash borer made its way into Maine more than five years ago. The emerald ash borer has killed millions of ash trees across North America.

Emerald ash borer has also been spotted in York, Cumberland and Aroostook counties after spreading south from Canada and north from New Hampshire.

Parisio said the emerald ash borer can only move a couple of miles at a time when the females fly to look for new areas to lay eggs. The tiny insect’s movement is aided mainly by humans, with the borers hitching a ride on the ash logs used for firewood.

Maine Forest Service regulates the movement of firewood by banning untreated out-of-state firewood and offering municipalities educational webinars about emerald ash borers.

Emerald ash borers originate from northeastern Asia and coevolved with the ash trees there, but when they arrived in North America through the port of Michigan by untreated pallet wood, they were able to go after the North American ash trees, which hadn’t developed any defenses to the invasive species.