Image of HWA from a scanning electron microscope, photo by Kelly Oten, North Carolina Forest Service,

The hemlock woolly adelgid (HWA) has been present in North Carolina since the mid-1990s and has occupied nearly the entire range of eastern and Carolina hemlock in the North Carolina for several years.  However, HWA is still only found in about half of the overall range of the eastern hemlock, but unfortunately it continues to spread.  Just this summer, HWA was found in Nova Scotia, which is the first instance of HWA in the Atlantic provinces of Canada.  It has also been found in new areas of Ohio, and New York.  The discovery of HWA in the Adirondack Mountains of New York is troubling because eastern hemlock can make up as much as 70% of the trees in that region, and a full infestation of the HWA could mean a devastating loss to those ecosystems.

HWA woolly egg sacs on hemlock branch, photo by Margot Wallston

HWA has spread much faster in the southern range than the northern range of hemlocks.  One factor slowing the spread in the northern areas is colder winter temperatures.  With increased winter temperatures due to climate change, we may see an increased rate of spread in the north.  States like North Carolina, where the spread of HWA has been relatively rapid, have had to implement aggressive and efficient strategies to protect our hemlocks.  Programs like the Hemlock Restoration Initiative in North Carolina and in other southern states (Kentucky and Tennessee Divisions of Forestry, Georgia Forestry Commission, Save Georgia’s Hemlocks) can serve as models for other states to adopt and modify to their needs to fight the HWA.

Volunteers under Carolina hemlock, photo by Margot Wallston

To help control the spread of HWA to other parts of its range, you can help by not purchasing infected nursery stock (possibly the cause of the spread to Nova Scotia) and monitoring hemlock trees on your own property, in your local forests and parks, and at school or work if the landscaping includes hemlocks.  If you find HWA on your own property, you can learn more about how to protect your hemlocks on our Info for Landowners page.  You can also help preserve hemlocks on public lands in North Carolina by joining one of our volunteer workdays.  Email us at to sign up.

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