The same adelgid was detected in San Francisco in 1928 and has chomped through sub-alpine and silver firs in Idaho, Oregon, California and other areas of the Pacific Northwest in large numbers since the 1950s.
Adelgids are about the size of a freckle and about as hard to remove. They are all female and don't engage in sex. Eggs develop without mating. Two to four generations hatch each year. They have no natural predator.
"It actually feeds on the trunks or large branches of trees," Liebhold said. Their mouths are like a straw that punctures the bark. "When they're feeding, they release a chemical in the trees that cause them to deform. When they suck in large numbers, they take nutrients from the trees and they ultimately die."
The feeding process creates thousands of waxy, woolly balls, which give the adelgid its name. A similar insect, the hemlock woolly adelgid, lays up to 300 eggs in a single woolly ball.
They leave dead shoots and branches, swelling around the shoot nodes known as gouting, a stiff trunk and growth rings with red, hard wood instead of the healthy, creamy white wood, Sidebottom wrote.
Nature has its own way of dealing with problem parasitoids — organisms that kill their hosts — but nature takes its sweet time. "If we wait 100,000 years, the firs here will develop a resistance," Liebhold said, the way they probably did in Europe.