Attack of the Woollys

Sunday, June 22, 2008

There was a recent article in the Louisville newspaper announcing that eastern Kentucky’s hemlock forest is now being threatened by a tiny insect called the hemlock woolly adelgid.

This reddish-purple insect, a non-native species originating out of Asia, kills giant hemlocks by depriving them of nutrients. The insect was first detected on the eastern seaboard in the 1950s before spreading to the Blue Ridge Mountains and then up through the northern Appalachians to Maine. In Shenandoah National Park alone, up to 90% of all hemlocks have already died due to the infestation.

Frequent travelers to Great Smoky Mountains National Park may already be aware of the presence of this tiny killer. Visitors may have noticed a fluffy white “wool” on the needles of the mighty hemlocks. As young nymphs, adelgids wraps themselves in a protective “wool” as they attach to the base of the needles in order to suck the sap out of the hemlock.

Infestations in the Smokies were originally discovered in 2002 and have spread throughout most of the park’s hemlock forest. Will Blozan, an arborist and expert on eastern hemlocks in the Smokies, was quoted in the spring issue of Smokies Life Magazine as saying that more than 95% of the hemlocks in the park already have adelgids. To give you an idea on the extent of the looming devastation, the Smokies has about 800 acres of old-growth hemlock trees and 90,000 acres of younger hemlocks. In some areas infested trees have already begun to die. It usually takes 4-10 years for the adelgids to kill a tree.

Known as the “redwood of the east,” eastern hemlocks can grow more than 170 feet tall and can have trunks measuring more than 16 feet in circumference. The tallest hemlock in the Smokies, located in the Cataloochee Valley, is listed at 173 feet in height. Hemlocks are known to live up to 800 years or more. The oldest in the Smokies is more than 500 years old.

Hemlocks play an important ecological role as well. They help maintain moisture and moderate temperatures on the forest floor. By providing deep shade, hemlocks keep streams cool which is critical for the survival of trout, crawfish, salamanders and other cold water species. The thick boughs of the hemlock also provide shelter and nesting for birds. Widespread loss of hemlocks will undoubtedly bring about significant changes to the Smoky Mountains.

What is the Park Service doing to combat the infestation?

Unfortunately there are no easy solutions. Insecticides sprayed from the air don’t work. Foliar treatments sprayed from truck-mounted trucks and pesticides injected into the tree are impractical for trees in the backcountry. One treatment with some promise is with the use of predator beetles which voraciously feed on the adelgids. The national park web site states that early results from the use of these beetles is encouraging, however, it will take several years before populations of beetles increase enough to control the widespread infestations.

Visit the Friends of the Smokies web site to find out how you can help save the eastern hemlock.


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