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Can we Save our Hemlocks?

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—Photo courtesy of Margot Wallston

When you gaze out at our mountains in the winter, the magnificent dark green stands of Eastern and Carolina Hemlocks used to stand out against the winter browns of decidous trees. However, as many of us have observed, these trees seem to be losing the battle with the invasive wooly adelgid (HWA) –  a tiny aphid about the size of a poppy seed that suck the sap from new shoots. Foresters estimate that nearly 80% of our southern hemlocks may already have been killed by this tiny insect.  Infected trees are easy to spot from the white cottony egg sacs that cling to the smallest twigs.

But there is hope. The Hemlock Restoration Initiative (HRI), headquartered here in Asheville, is working  with a variety of partners to restore hemlocks to long term health throughout North Carolina and ensure that both the Eastern and Carolina hemlocks can withstand attacks by the invasive HWA and survive to maturity on public and private lands.

Right now the primary treatment for infected hemlocks is chemical –  injecting  a systemic pesticide into the ground underneath affected trees. But this approach is costly and temporary – it buys time but does not provide a permanent cure.  HRI and its partners are looking at more permanent solutions.  Scientists such as  Ben Smith of the Forest Restoration Alliance in Waynesville and Albert Mayfield  of the US      Forest Service’s Southern Research Station in Asheville are currently working on several fronts:

  • Building our knowledge base on the physiology of hemlocks and how they respond to severe conditions such as HWA, drought, air quality, and warming temperatures.
  • Breeding hybrid species with greater resistance to the HWA, starting by developing a cross between the Carolina hemlock and a Chinese hemlock and by finding resistant individual trees in the forest.
  • Developing forest restoration techniques to give new seedlings the best chances of success.
  • Studying the potential for biological control by introducing insects that will prey on the HWA. Two promising species from the Pacific Northwest are a beetle (Laricobious nigrinus) and a predatory cousin of the eastern silver fly.

Want to know more? The Blue Ridge Naturalist Network will present “Save the Hemlocks” on February 21, 2017 from 5:30-7:00pm at the West Ashville Library. Margot Wallston and Sara deFossett of the Hemlock Restorative  Initiative will discuss where we stand now with the hemlocks and the ways in which these magnificent trees can be saved. This presentation is free and open to the public.