In West Virginia's scenic Canaan Valley National Wildlife Refuge, with its gently sloping mountains and emerald expanses of timber, Mike Powell relishes the perks of his job as a caretaker of the land: the sounds of a gurgling stream and the fresh pine scent of evergreens.

But one sight deeply troubles him: the haggard look of the valley's fabled Christmas trees. Some are bent like old men. The eye-popping green hue that makes people want to adorn them with ornaments has yellowed. A few are covered with hideous waxy balls, a telltale sign that they are under siege by the balsam woolly adelgid, a tiny insect with a notorious reputation among entomologists, who call the species "the bug that ate Christmas."

Along the southern Appalachian range, they are eating two of America's most popular wild Christmas trees — Canaan and Fraser firs — to death.