Photo: Maine Forest Service entomologist Colleen Teerling gently places a colony of Laricobius nigrinus beetles on the tip of a hemlock branch. Photo courtesy the New England Forestry Foundation.
By Emmett Gartner
Published in The Maine Monitor on November 21, 2025
The hemlock woolly adelgid is indifferent to property lines as it marches inland to Maine’s hemlock belt.
The frontline of Maine’s battle against the invasive hemlock woolly adelgid is concentrated in the Midcoast, where the tiny insect is wreaking havoc on its namesake evergreens.
After arriving in Kittery more than two decades ago, the adelgid has traveled up Maine’s coast largely unrestricted and bypassed a state quarantine on moving hemlock saplings designed to prevent the adelgid’s spread.
Hailing from East Asia, it has no natural predators in New England. Maine’s eastern hemlock trees are largely defenseless against the swarms of adults that pitch tents of protective white fluff and siphon sap from the tree’s deep green branches until the host dies.
The adelgid has wiped out scores of hemlocks in southern Maine and is creeping further inland each year, threatening to infiltrate the state’s so-called “hemlock belt” in the western mountains, where mature sections of Maine forests are nestled in the foothills.
In recent years, however, a coalition of Midcoast land trusts, private landowners and Maine Forest Service officials have ramped up their efforts to control the hemlock woolly adelgid by recruiting the help of a familiar foe: two species of beetle that prey on the adelgid in Asia and the U.S. Pacific Northwest.
It’s a counteroffensive that forest managers hope will knock back the adelgid to both relieve the recently infested hemlocks in the Midcoast and thwart the insect’s inland expansion.
“The more we do to reduce the population of hemlock woolly adelgid in the Midcoast area will probably [determine] how fast it moves into more inland areas and our big hemlock belts,” said Colleen Teerling, the Maine Forest Service entomologist overseeing Maine’s adelgid response.
