Hemlock Woolly Adelgid



Hemlock woolly adelgid invaded the United States in the 1920’s when accidentally imported from Japan into the Pacific Northwest. Since then, adelgids have spread rapidly and are found in most regions of the U.S. where hemlock and spruce grow.

Woolly adelgid prefers Canadian (eastern) hemlocks. If you have hemlocks on your property you need to be concerned. Adelgids have already defoliated and killed large numbers of native Canadian hemlock trees throughout American forests.

A Woolly adelgid infestation causes hemlocks trees to become weak and eventually die. Infested trees first begin to look thin with a lighter green color. This happens because the insects feed by sucking sap from twigs and foliage causing the trees to become weak and the needles to fall off. A serious infestation can defoliate a tree in as little as one year.

Adelgids are well adapted to the northern climate because they are actually cool weather insects. Look for white globular masses of cottony/waxy tufts on bark, foliage, and twigs. Check the base of needles and small twigs especially close. The tufts are actually protective covers for the adelgid’s body that remain in place throughout their lifetime.

If you find them on your hemlock - or neighbors in your area have had problems with hemlock woolly adelgids - do not panic. Treatment options are available for hemlocks.

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