Hemlock Woolly Adelgid

The hemlock woolly adelgid (HWA) is an invasive insect posing a serious threat to hemlocks in Greater Boston and throughout the eastern US.  HWA is an aphid-like insect that feeds off the nutrients from its host tree.  HWA is most recognized by the white “woolly” masses of wax produced by the insects at the base of hemlock needles. HWA are most recognized by the white “woolly” masses of wax produced by the insects at the base of hemlock needles.

Hemlock woolly adelgid was first reported in the eastern United States in 1951 and has been a problem in Massachusetts since the mid-1990’s.  HWA infested hemlocks can now be found from northeastern Georgia to southeastern Maine.

Unlike most insects, HWA grows throughout the winter.  The tiny insects produce a dense mass of waxy hairs protecting it during cold weather.  Often hemlock woolly adelgid can be easily detected by looking at the undersides of hemlock branches.

In their native range in Asia, HWA cause little damage to hemlocks.  In North America, the pest attacks both Eastern and Carolina hemlock.  If left unchecked, HWA can suck needles dry, causing them to shed.  Premature needle drop can cause entire trees to die from only four years of infestation.

It is important to inspect Eastern and Carolina hemlocks to see if HWA is present on important trees. Once detected, options exist to control infestations and limit damage to trees.

BTSE has successfully managed HWA with appropriately timed horticultural oil applications and the selected use of systemic insecticides.  If you have concerns with the health of your hemlocks, contact our Certified Arborists to help develop a plant health care plan for appropriate for your property.