University of Vermont

Scott Costa

Entomologist, research professor

Dana Walrath

An invasive pest, hemlock woolly adelgid which has been marching and munching its way north along the Appalachians — killing pretty much every hemlock tree it can sink its sap-sucking mouthparts into. The adelgid recently arrived in southern Vermont. Its arrival was noticed by entomologist Scott Costa, and he's hoping to provide a tool for forest managers and homeowners to fight back.

Hemlock is the third most common tree species in Vermont. But it soon may drop off the list, going the way of the now-vanished chestnut and elm.

Working with the U.S. Forest Service, the State of Vermont, and others, Costa, an entomologist and research professor in UVM's Department of Plant and Soil Science, has been developing a novel method of putting an insect-killing fungus, lecanicillium muscarium, to work protecting hemlock trees.

Protecting a keystone species

The entire range of eastern hemlock and the less common Carolina hemlock, from southern Canada to Georgia, is currently at risk from the adelgid, a bug native to Asia that arrived in the United States in the 1920s and made its way to the East Coast in the 1950s. The stakes are high: hemlock provides habitat for dozens of mammals and birds. Arching over streams, it creates deep shade critical for the survival of trout and other fish. Some scientists think hemlock is a so-called keystone species, holding up a whole ecosystem.

Nobody thinks the adelgid pest can be eliminated. But Costa has had success with field trials on one-acre forest plots in Tennessee, using helicopters to drop the fungus — mixed with his proprietary blend of growth-enhancing ingredients — into the epicenter of the adelgid's devastating attack. These trials reduced the growth rate of adelgid by fifty percent — "that's the first time that's been demonstrated with an insect-killing fungus," Costa says — and it seems likely to give trees a fighting chance of recovery.

Last modified January 07 2013 03:42 PM