Hemlock Woolly Adelgid—Adelges tsugae

Hemlock woolly adelgid (HWA) is a serious pest of eastern hemlock. Damage from HWA feeding causes needles to discolor and drop prematurely. This leads to crown decline, reduced growth and, in some cases, tree death. HWA is spread by wind, birds and mammals, and can be moved on live hemlock plants.

The most obvious sign of HWA is the covering of wool-like wax filaments produced as the insect matures. The woolly masses generally range from 1/16 inch to 1/8 inch across. They are found on the most recent hemlock growth, generally on the outermost branch tips.

Many coastal and southern towns in Maine are known to harbor infestations of this pest. A Hemlock Woolly Adelgid Quarantine is in place to reduce artificial spread of this insect to other parts of the state.

In Maine, please report sightings of this pest to the Maine Forest Service.

hemlock with hemlock woolly adelgid
needles with hemlock woolly adelgid
close-up of hemlock woolly adelgid

The most obvious sign of HWA infestation are the white cottony masses, resembling cotton balls, found at the base of the hemlock needles.

Click on images to view full-size

Identification and Control Information

More Information

[Photos, left to right: James Johnson, Georgia Forestry Commission, Bugwood.org; Connecticut Agricultural Experiment Station Archive, Connecticut Agricultural Experiment Station, Bugwood.org; Chris Evans, River to River CWMA, Bugwood.org]