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| A Hemlock Woolly Adelgid was attached to a hemlock tree in the Rock Creek Park area of the Cherokee National Forest in Erwin,
Tenn. Ron Campbell/Johnson City Press/AP |
Hemlocks threatened by an unwelcome guest
Scientists are working to stop the hemlock woolly adelgid from killing trees in the Eastern US and spreading northward.
from the August 2, 2007 edition
Page 3 of 3
Scientists also are studying an even better candidate: a Japanese relative of the laricobius. "We're pretty happy about it because this is an insect that's adapted to [the eastern US] strain of hemlock woolly adelgid," says Scott Salom, a professor of forest entomology at Virginia Tech in Blacksburg, Va.
Approaching the problem with fungus
For years, Scott Costa, a research assistant professor at the University of Vermont in Burlington, and his graduate student, Stacie Grassano, have been developing a slightly different approach. He aims to jump-start a disease that would kill the adelgid. He mixes a naturally occurring fungus with sweet whey, a protein- and sugar-rich byproduct from cheesemaking, and sprays it onto infested trees. Prompted by the food source, the fungus emits hundreds of spores, eventually killing the bugs.
"You want to get enough spores out there so that a disease outbreak does occur," he says.
If effective, this approach has the advantage of not introducing potential pests into the equation, and of being considerably cheaper compared with other methods.
"If we get nature to work for us, there's a potential for economic windfall," he says.
The adelgid's historic trail
The saga of the hemlock woolly adelgid begins in Eastern North America almost 90 years ago. Scientists think that, perhaps as early as the 1920s, an ornamental tree infested with the bug arrived at a private plant collection in Richmond, Va. That plant enthusiast's estate, which still housed the tree, eventually became Maymont Park, where scientists first detected the adelgid in the early 1950s.
From there, maybe by hitching a ride on migratory birds or through inadvertent human transport, the adelgid jumped to wild hemlocks.
By the late 1960s, it was established in Pennsylvania. After Hurricane Gloria in 1985, it appeared in Connecticut, causing many to suspect that winds play a role in its dispersal. In 1991, it showed up in Springfield, Mass. (It only arrived in parts of Southern Appalachia in the early 2000s.) Earlier this year, the adelgid was found in Vermont.
"At my house, I always thought I was safe; I live in northern Vermont," says Scott Costa, a research assistant professor at the University of Vermont in Burlington. "I don't feel particularly safe anymore."
– Moises Velasquez-Manoff
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