Bath City Arborist Kyle Rosenberg stands in front of the Bath tree nursery. NATHAN STROUT / THE TIMES RECORD

BATH — Bath has an invasive bug problem, and the city is trying to raise trees that stand a fighting chance against the pests.

The Bath Forestry Division launched its tree nursery in 2015, largely in response to the damage caused by the browntail moth.

The nursery, located next to the cemetery by the middle school, originally contained 100 trees — all species that the browntail moth was adverse to.

“The importance of diversity is that it allows for the impact of a pest like the emerald ash borer to be spread over the forest better,” said Kyle Rosenberg, Bath’s city arborist.

American Sycamore, Red Maples, and other trees will be planted in the city to diversify the urban forest. In some instances, the forestry division will remove trees susceptible to invasive insects and replace them with a tree from the nursery that is resistant to them, strengthening the core of Bath’s arboreal resources.

Invasive insects like the winter moth and browntail moth have devastated trees in the city, defoliating many. Over time, the trees could die if these pests continue to strip them every season.

To counter the threat, the city regularly injects trees with chemicals that repel the deadly browntail moth. The city also wraps trees that are the regular prey for the winter moth, another insect that slowly kills trees over the years by consuming their leaves. The wraps can prevent the moths from climbing up the trees in their caterpillar stage, when they’re looking for a meal.

And the city also launched a plan with the Maine Department of Forestry to eliminate the wintermoth in the Midcoast area, by burying hundreds of parasitic flies in the Bath woods. When they hatch in the spring, the flies will prey on the moth’s eggs, eventually depleting the population to a manageable or nonexistent level.

In addition to the two moths plaguing Bath’s urban forest, the city, along with the rest of Maine, faces an additional invasive insect with a penchant for killing trees: The Emerald Ash Borer. This insect, which has been found in northern Maine and York County, specifically targets Ash trees.

“We bought (trees) at different sizes, but ironically a lot of them have all caught up to each other,” said Rosenberg, who said the original plan was to by them at different sizes so as to stagger the plantings over the years.

Rosenberg said the city hopes to distribute the trees currently at the nursery in the spring and plant new trees after that. NATHAN STROUT / THE TIMES RECORD

The sycamores have close to tripled in height since they were purchased three years ago.

Rosenberg said the town plans to sell off excess trees next year, which will help fund the Forestry Committee’s work with the nursery. The Sycamore trees, for instance, which were purchased when they were smaller for $22-$41 , would now sell for $250-$300 each. Selling off just a few trees can help bring the nursery closer to being self-sustainable.

“It also allows people to contribute in a different way to what the Forestry Committee is doing,” said Rosenberg.

Besides the labor provided by the Forestry Division, the only costs of the nursery are occasionally buying new trees and the cost of water for irrigation, which is minimal. The benefits, however, only grow over time. According to the National Tree Benefit Calculator, an American sycamore 12 inches in diameter would provide $125 in economic benefits to Bath every year.

Rosenberg said that they’ll try to distribute or auction off most, if not all, of the trees in the spring, and then replant the nursery with an added focus on growing varieties resistant to the winter moth and emerald ash borer. One of the species grown to deter browntail moths, basswood, proved to be attractive to winter moth, so in the next planting, the division will choose a species that neither insect is interested in.

In the coming months and years, the city is looking to expand on the nursery site as a center for the city’s forestry efforts. The woods behind the nursery could be expanded into an arboretum, Rosenberg said. They’re building a small building to the side that will serve as the Forestry Center. The building will primarily be for forestry related storage, but it will also work as a meeting place for volunteers.

Rosenberg said both Portland and Lewiston had their own tree nurseries, but both those cities dwarf Bath in terms of population and municipal government size. Rosenberg credits the nursery to the active work of the Bath Forestry Committee, as well as the community’s unique value of their urban forest.

“Every municipality has the potential to do something like this, it just depends on what sort of committees they might have,” he said.

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