Tom Briggs of Berwick stands on the land trust property where hemlocks were cut down to reduce the presence of the hemlock woolly adelgid. Briggs, who lives nearby, was surprised to see the cutting on trust land, but says he understands the need to fight the pest.

BERWICK — A tiny pest that has devastated hemlock forests from southern Appalachia to New England is steadily spreading in Maine, forcing some landowners to choose between saving and harvesting trees.

The hemlock woolly adelgid – a sap-sucking insect barely the size of a pinhead – first arrived in York County via natural spread of the insects in 2003. Since then, the adelgid has reached four other Maine counties and is now considered “established” in scattered areas of more than 40 towns.

“Landowners are going to have to adapt to it,” said Dave Struble, chief entomologist with the Maine Forest Service. “We have seen the hemlock woolly adelgid moving up the coast, and it is now established in Lincoln County.”

An invasive transplant from Asia, the hemlock woolly adelgid targets only the tree species that lends it its name. Hemlocks infested with the woolly adelgid in New England eventually turn brown from the top down before succumbing to the bugs. Often, an infestation is present for years before it is noticed.

In the York County town of Berwick, for instance, logging crews have been harvesting trees on a 100-acre parcel that is part of the conservation lands owned or managed by Great Works Regional Land Trust. Forester Jeffrey Williams said about 40 acres “were pretty well infested” with the woolly adelgid, prompting the Wright family that owns the land to approve a forest management plan to remove much of the juvenile-to-mature hemlock while thinning out the tree canopy to allow for more diverse regrowth.

“It’s been here for quite some time,” said Williams, owner of Maine Forest Management. “There has only been a little bit of mortality, but it was bound for more mortality in the next decade” if the infestation hadn’t been discovered.


The aphid-like insects are nearly too small to see with the naked eye, but normally manifest themselves as white egg sacs with a woolly or cottony appearance on the underside of the outermost branches or the base of needles. To control the spread of the woolly adelgid, the state of Maine has established a quarantine on hemlock plants or products in all of York, Lincoln and Sagadahoc counties, as well as parts of Cumberland and Kennebec counties. The quarantine prohibits movement to non-quarantined areas of rooted hemlock plants, hemlock branches or needles as well as hemlock chips and uncomposted bark containing branches or needles.

A tractor drags harvested hemlocks from the Great Works Regional Land Trust property in Berwick. The hemlock woolly adelgid first arrived in York County by natural spread in 2003, and has since reached four other Maine counties. The invasive pest is now considered “established” in parts of more than 40 towns.


The hemlock woolly adelgid is tiny, less than 1/16-inch long in its nymph stage, and varies from dark reddish-brown to purplish-black in color. As it matures, it produces a covering of wool-like wax filaments, below, to protect itself and its eggs from natural enemies and prevent them from drying out. The ‘wool’ is readily observed from late fall to early summer on the underside of the outermost branch tips of hemlock trees.

Individual trees can be treated with pesticides to kill or control the adelgid, but such an approach would have been unfeasible or cost prohibitive for an infestation the size of the one in Berwick. Forestry and entomology professionals in Maine also are experimenting with the release of predatory beetles – also from Asia – that feed exclusively on the woolly adelgid. Such natural-control methods are costly, however, and often take years to take root, if they ever do.

Williams, who has worked on adelgid infestations elsewhere in Berwick and in Cape Elizabeth, said landowners in southern and coastal areas should be aware of the potential presence of the destructive bug.

“It’s something to look for,” Williams said.

The sight of heavy equipment harvesting large stands of trees came as a surprise to some neighbors. When they bought their home on a secluded, rural cul-de-sac about three years ago, Debra and Tom Briggs were told the land had been permanently protected. But the conservation easement held by Great Works Regional Land Trust allows the Wright family to control for disease and insects as well as to manage the land for forest health. A member of the family, Michael Wright, serves as president of the land trust.


Watching from his backyard one recent afternoon as a skidder hauled piles of hemlocks out, Briggs said he and his wife were most concerned about the impact on the deer, birds and other wildlife living in the harvested areas. But Briggs said he understood the concerns about the woolly adelgid.

“Nobody caused this, and nobody created it,” Briggs said. “It just happened.”


Darrell DeTour, the land trust’s stewardship director, said the woolly adelgid also has been spotted on properties owned by the organization in Eliot and Ogunquit. While the Eliot land is largely hardwood trees unaffected by the adelgid, the Ogunquit property has more hemlocks that are more challenging to access. DeTour acknowledged that the trust has yet to decide on a path forward.

“It’s not so extensive yet where we are seeing devastated trees, but it’s not something that we have talked about how to address it yet,” DeTour said. “There is no easy response to the woolly adelgid.”

Struble, the forest service entomologist, said invasive pests such as the woolly adelgid can put land trusts and conservation organizations in awkward situations by forcing them to consider more heavy-handed cutting than some would prefer.


The good news, if there is any, is that the adelgid hasn’t spread nearly as rapidly in Maine during the past decade-plus as it has in many other states. Some parts of the southern Appalachians in Virginia and Tennessee, where hemlocks are a key species, have seen massive tree die-offs during the past 20 years.

“Our climate is marginal for it,” Struble said. “Our cold weather doesn’t eradicate the adelgid, but it will knock them back.”

Kevin Miller can be contacted at 791-6312 or at:

[email protected]

Twitter: KevinMillerPPH

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