Deep freeze helps fight tree-killing insect in the Smokies

Biologists in the Great Smoky Mountains say there is a bright side to the recent spell of frigid temperatures. The deep freeze is a life-saver for some of the mightiest hemlock trees in the Smokies.

“Definitely, these cold extremes help with the invasive hemlock woolly adelgid,” said NPS forester Jesse Webster. “It will not get rid of them completely, but we will take every bit of help we can get.”

The hemlock woolly adelgid (HWA) invaded the Great Smoky Mountains National Park in 2002. The tiny insect from Asia has killed millions of hemlock trees in the Eastern U.S. The pest gets its name from the white woolly coating that surrounds and protects the nymphs while they feast on hemlock trees in the winter.

“Adelgids are a little bit of a different insect. They are completing a lot of their life cycle during the winter. Most insects are not active in the winter,” said Webster. “But it can get too cold for them. They have not survived as well in the northern parts of the country. You start seeing mortality when it gets around 4 or 5 degrees Fahrenheit.”

The national park is able to treat some hemlocks with chemicals, but terrain only allows crews to reach 15 percent of the hemlocks in the Smokies. Predatory beetles were also introduced to combat the HWA and have brought some balance to the pest population.

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