Hemlocks flourish after polar vortex kills adelgid

(WBIR - Sevier County) The old saying "April showers bring May flowers" held true this year as wild blooms once again flourish in the Great Smoky Mountains National Park. But it was the winter's deep freeze that put fresh green on the trees.

Specifically, the polar vortex during this year's wicked winter helped wipe out a destructive insect that feasts on hemlock trees.

"You see a lot of growth this year on the hemlock trees. They're covered in the new bright green terminals," said Jesse Webster, coordinator of the GSMNP program to control the hemlock woolly adelgid. "We had plenty of rain last year, the winter killed the adelgids, and that equals healthy hemlocks."

In January, WBIR reported predictions the deep freeze would put a big dent in the destructive hemlock woolly adelgid.Webster says now that spring surveys have been completed, those predictions proved true.

"We had from 80 to 97 percent mortality of adelgid," said Webster.

The tiny insect from Asia invaded the Great Smoky Mountains in 2002 and has killed millions of hemlock trees across the eastern United States. In the time since the pest invaded, it never tasted a winter as cold as 2014. The frigid air with lows dipping into negative temperatures served as an icy grip of death for the pests.

Webster says this winter's polar vortex was more than a cold killer for the hemlock woolly adelgid. It also slowed the reproductive rate of the survivors.

"The ones that survived are also producing a lot fewer eggs. We've done surveys that show some of the adelgids only laying 10 eggs. In the past, one adelgid would lay anywhere from 30 to 60 eggs. So with the cold kill mortality along with lower egg numbers, those are all just win-win situations for us."

While Mother Nature gave the trees a breather in a long-standing fight with the invasive adelgid, biologists anticipate the bug will make a comeback. The park will treat trees that are especially vulnerable to the insects with chemicals. Scientists also continued the program that releases predator beetles to hunt the adelgid.

For now, the mightiest trees in the forest enjoy a respite that makes it a little easier being green.


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