Tree and shrub services in South Portland, Maine.

The Maine Forest Service lists South Portland, like every Cumberland County town, in its quarantines for emerald ash borer, hemlock woolly adelgid, white pine blister rust and spongy moth. The city has inventoried its own ash trees and scheduled treatment for June 2025, and it is monitoring hemlock woolly adelgid. Browntail moth is at low populations for now, and a parasitic fly released in 2017 has knocked winter moth back to about 40 percent of its former numbers.

For a homeowner, that list shapes the pruning plan. Ash trees worth keeping are identified before borer damage shows. Browntail webs on oak, apple and cherry can be cut out in the October to March window the Forest Service recommends, before the caterpillars emerge. The Forest Service notes that browntail caterpillars carry toxic hairs that can cause a rash, which is one reason the agency points owners of larger infested trees to licensed arborists. Hemlocks are checked for adelgid on the undersides of the needles, since the city is still watching for that pest.