Wooly Adelgid continues to expand in Maine

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Maine Forest Service

Hemlock Woolly Adelgid Populations
Continue to Expand in Maine

Maine community members and Maine Forest Service staff are steadily uncovering new beachheads of hemlock woolly adelgid populations in Maine. Most recently, new areas around Sebago Lake and forests in two Kennebec County towns have been found to be infested. Maine Forest Service is requesting your help in discovering additional locations of this pest.

What can you do?

Now is a terrific time to get out and look for this pest in your backyard. Most of the year, white, waxy tendrils cover the insect’s body, making it resemble a miniature cotton ball. It is most visible from late-October through July. The woolly masses can be found attached to hemlock twigs at the bases of needles. Although there are adelgids on other conifers, hemlock woolly adelgid is only found on hemlocks.

You can reduce the chance of adelgid spreading by pruning live hemlock branches from areas people visit. Hemlocks around driveways, pools, edges of lawns, trails and other places that expose them to visitors, vehicles and other equipment are often the first to show signs of attack. Cutting hemlock back from where we work and play can help reduce spread from infested areas and to new areas.

If you think you have found evidence of hemlock woolly adelgid in Maine please call or email the Maine Forest Service at foresthealth@maine.gov or (207) 287-2431.

Hemlock exposed to visitors

Prune hemlocks such as these to reduce the risk of accidental spread of the pest.

What is hemlock woolly adelgid?

Hemlock woolly adelgid is a small, aphid-like insect. It causes premature needle drop and twig dieback and can eventually lead to tree mortality. In Maine, it has been found in forested areas in a band along the coast from Kittery to Mount Desert Island and in inland locations such as the forests surrounding Sebago Lake and now southern Kennebec County.

hemlock woolly adelgid infestation

White tufts of wool on the base of hemlock needles show the presence of hemlock woolly adelgid.

What is happening with hemlock woolly adelgid in Maine?

In 2022, hemlock woolly adelgid was found in 15 additional towns and one new county. Although some of these finds fill logical gaps in known distribution, others reflect spread to more interior hemlock forests.

Hemlock woolly adelgid presence was confirmed for the first time in 2022 in: Acton, Casco, Dresden, Gardiner, Gray, Limington, Litchfield, Naples, Nobleboro, North Haven, Pownal, Sebago, South Thomaston, Whitefield and Windham. Detections in Litchfield and Gardiner represent the first known location of this insect in natural forests in Kennebec County.

In some Maine communities with hemlock woolly adelgid, populations of the insect are scattered and hard to find. In others, almost every tree seems to be infected. Especially in coastal regions, adelgid-related  hemlock decline and mortality are apparent. Recent drought conditions, high adelgid populations, warmer winters and challenging site conditions have led to more rapid impacts to hemlocks in these coastal areas.

Towns with detections of hemlock woolly adelgid in the forest in Maine.

Towns with detections of hemlock woolly adelgid in natural (vs. planted) trees in Maine. Hemlock woolly adelgid was confirmed in natural hemlock in fifteen additional towns in 2022.

Why does it matter?

Hemlock woolly adelgid causes significant damage to hemlock trees and forests. Hemlock trees are a significant Maine species. Often found near lakes and streams, hemlocks contribute to Maine’s water quality. They also buffer stream temperatures which can affect species such as brook trout, and are important in deer wintering areas. Hemlocks are a favored landscape tree, as well as contributing to the state’s forest economy.

Hemlock next to a vernal pool

Hemlocks are an important tree in Maine’s forests.

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