HEMLOCK WOOLLY ADELGID

February 1, 2024

The Hemlock Woolly Adelgid, (Adelges tsugae or HWA), Is a tiny sap-sucking insect that feeds on sap at the base of needles of North American Hemlocks, (Tsuga canadensis and T. caroliniana). Native to Asia and the Pacific Northwest, these insects were first seen in the eastern United States in 1951 in a park in Richmond, VA and they were seen in Connecticut in 1985. The most obvious sign of infestation is the presence of white woolly egg sacs on the underside of hemlock needles, especially on new growth. Other signs include thinning of needles and grayish needle color. HWA can kill infected trees within 4-9 years depending on conditions and infestation severity. There are treatments with horticultural oil or insecticidal soaps to prevent HWA which are best applied in the spring. If a tree is already infested, there are systemic insecticides that are low in toxicity and can be applied via soil or injected directly into the trunk. We prefer to use the trunk injection method because there is little to no effect on surrounding environment.

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