Hemlock-hunting bugs threaten Chattanooga area trees

Hemlock-hunting bugs threaten Chattanooga area trees

September 25th, 2013 by Alex Green in Local Regional News

Hemlock Woolly Adelgid

Photo by

Forester Eric Taylor looks for hemlock trees to inject with pesticide in the Cherokee National Forest.

Photo by Staff File Photo/Times Free Press.

The Hemlock woolly adelgid is bad news. It looks innocent enough, easily mistaken for a dandelion puff or a floating piece of cotton.

But the tiny, white wool-wearing adelgids are capable of wiping out the hemlock population.

Park Greer, park ranger at the South Cumberland State Park near Monteagle, Tenn., pointed out potentially endangered trees Tuesday afternoon near a 150-year-old hemlock tree.

"Hemlock. Hemlock. Hemlock. Hemlock," he pointed out -- about every fifth tree near a creek bed. On the way down to the site, he pointed out a 300-year-old hemlock tree.

At Tennessee state parks, rangers and arborists are trying to preserve a native Tennessee tree species against an exotic bug likely brought here by humans. But hemlock preservation has practical purposes, too, Greer said.

The adelgid has no natural predator in the United States.

Hemlocks are considered a keystone species. Their roots help hold soil in place. They provide habitats for dozens of species. They are vital to healthy stream and creek ecologies, providing shade for fish and dropping insects and other food into the water for them.

Remove the hemlocks, remove the shade and insects. Remove the shade and insects, remove the fish. Remove the root systems, increase the chance for flooding and mud slides.

It's not good for the area, especially on the heels of boll weevil and adelgid infestations that have hurt Tennessee's pine and Frazier fir populations.

The Great Smoky Mountains folks know all about it.

They've been battling the woolly pests for more than a decade. Like Chattanoogans, residents around the Smokies suddenly began to see the little bugs everywhere. That means they've established themselves, according to Kristine Johnson, supervisory forester at the Great Smoky Mountains National Park.

"It takes a while for the populations to build before they're really visible," she said. "Now is the time of year they're really starting to develop the wool again, and they're more visible."

She said the first Chattanooga adelgids showed up around Lookout Mountain. They first live in the high branches of tall hemlocks. Over time, they become more widespread and begin to attach themselves to lower branches, as well.

And don't mistake their drifting through the air as flying. Only mature adults, who are nearing death, develop wings and fly. The others develop wool and float. They travel on birds' feet. They travel on the wind. They travel extensively on nursery purchases and domestic tree trimmings. "They're very resilient," Greer said.

State authorities are fighting back. In the Smokies, in addition to tree insecticide trunk injections, park officials have released about 600,000 woolly adelgid-eating beetles since 2002.

Rangers at the South Cumberland State Park are sticking to insecticides. Greer said the state parks office doesn't have the money for the beetles, which are about $4 per bug, he said.

He said area residents who spot adelgids can apply Bayer Advanced 12 Month Tree and Shrub Insect Control to hemlocks. Now is the best time to manage the bugs, he said.

Contact staff writer Alex Green at agreen@timesfreepress.com or 423-757-6731.