The Register-Herald, Beckley, West Virginia

March 10, 2013

Woolly adelgid endangering state’s hemlocks

By Clint Ferguson
For The Register-Herald

— A small insect is wreaking havoc on West Virginia's hemlock populations, and it’s spreading into more counties every year.

The hemlock woolly adelgid is native to Asia and is believed to have been brought to the U.S. via a shipping crate in 1924. Since then, it has established populations from the Smoky Mountains north to southern New England and is having devastating affects on the eastern hemlock stands.

The adelgids attach themselves at the base of the needles and suck the sap from the young twigs, which retards or prevents the tree from having new growth. In result, the needles turn from their normal dark green color, to a drab grayish-green color. Eventually, the needles fall off and the defoliation caused by these pests will result in the trees dying within three to five years.

The best way to tell if there is an infestation of hemlock woolly adelgid is to look on the underside of twigs, and egg masses appear as very small cotton balls. The white cottony sacs are present throughout the year, but are more prominent in the early spring. The adelgids are inside the cottony sacs and feed during all seasons, with the greatest damage occurring in the spring when the hemlocks are putting out new growth.

Humans play a role in transporting this insect into new areas. Since West Virginia provides ample outdoor recreation, we need to be careful not to relocate these pesky little critters. As more people camp and hike in infested areas, the adelgid can get on camping gear, vehicles and even clothing to hitch a ride to a new location. Wind, birds and other mammals also disperse these insects.

The Eastern Panhandle in West Virginia has been hit extra hard and numerous dead hemlocks are present since the insect has been there longer than the rest of the state. The first infestations discovered in West Virginia were found in Grant, Pendleton, Hardy and Hampshire counties in 1992. Currently, hemlock woolly adelgid is present in 42 of the 55 counties in West Virginia.

There are only 13 counties that hemlock woolly adelgid hasn’t been found; Hancock, Brooke, Ohio, Marshall, Wetzel, Pleasants, Doddridge, Ritchie, Gilmer, Calhoun, Jackson, Mason and Putnam counties haven’t had any adelgid documented for now. These western counties lack large hemlock populations and what hemlock trees that are found there are in small stands and yard trees.

These insects are small and you will need a hand lens or magnifying glass to see the actual adelgid. The problem with adelgid and other invasive insect species is that there are no natural predators, fungi or diseases to keep the populations in balance.

The West Virginia Department of Agriculture (WVDA) began treating hemlock trees in 2004 to highly visible hemlocks in state parks and state forests throughout infested areas in the state. They’ve continued treatments as the adelgid keeps spreading westward into new counties. So far, the hemlock trees that have been treated are looking much better and free of adelgid.

Last year, the WVDA was the first state in the country to start a hemlock woolly adelgid Cooperative Pilot Project for landowners in Fayette and Nicholas counties. The program was set up to help landowners control hemlock woolly adelgid by treating hemlocks on private wooded property with a minimum of five acres and more than 50 percent canopy cover of hemlocks. The project has been continued this year to include Raleigh and Summers counties. This area of the state was chosen because of its high hemlock content, and the trees aren’t too far gone to treat.

The treatments are applied through the soil by tablets. The tree uptakes the chemical and when the adelgids suck the sap they get a mouth full of the chemical in the process.

The only problem with the chemical treatments is they are costly and trees need to be retreated every four to five years. It will really be a task to treat every tree in the forest, but if nothing is done the hemlock’s future is looking grim to say the least.

The decline of hemlock trees will have devastating effects on many shade-tolerant plant species. Hemlocks provide ample shade and, without them, plants that require shade will suffer.

Another risk that has me concerned is the warming of our trout waters. Scientists are worried that eliminating the shade will cause the water temperature to rise and could hurt trout populations and habitat. Trout are coldwater fish and raising the temperature only a couple degrees could have a negative impact.

Since 2005, the adelgid has progressed westward and 20 new counties have been added to the list as infested. It was first documented in Raleigh County in 2001.

I hate to be a Debby Downer, but the fate of our hemlocks is looking bleak. The hemlock woolly adelgid could potentially wipe out our hemlock trees and is a serious invasive insect species that unfortunately also calls West Virginia home.   

For more information, contact the WVDA’s plant industries division at 304-558-2212.