Consecutive harsh winters hammer hemlock-killing insect

After one of the coldest months on record in East Tennessee, many people are more than ready for some warm weather. But the especially frigid winter has been a life-saver for some of the mightiest trees in the forest.

This winter’s sub-zero temperatures in the Great Smoky Mountains National Park have devastated the once unstoppable Hemlock Woolly Adelgid. The adelgid is an invasive insect from Asia that has killed millions of hemlock trees in the eastern United States. They first arrived in the Smokies in 2002.

“You know adelgids have been devastating in the Southeast,” said Jesse Webster, a biologist with the National Park Service who has coordinated the efforts to fight the adelgid in the Great Smoky Mountains. “We’re not just losing this one species of tree. We’re losing all of the associate species, the hundreds of species that rely on this tree.”

Scientists have worked non-stop to save any hemlocks they could. Their efforts are the reason many hemlocks are still alive at campgrounds and other locations in the Park as they were doomed for eradication as the adelgid flourished in the warm Tennessee climate. After more than a decade of taking it on the chin, the last two winters Mother Nature finally helped fight back with a stone-cold combination.

“We know the adelgids start to die when it reaches 3 degrees. We had the really long freeze in 2014 during the polar vortex with the temperature far below zero. That killed 80 to 90 percent of the adelgids in the park. Then this year we had another prolonged cold snap. One night it was -23 at the top of Mount LeConte. We believe that will result in another 80 to 90 percent mortality rate for any of the insects that survived last year. It is really going to help with Hemlock Woolly Adelgid control.”

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