Willow scale spreading fast
ASPEN What would Aspen look like without aspen trees?That’s something city officials don’t want to find out, as they’re busy trying to quash parasitic willow scale, which is killing area aspen trees and narrowleaf cottonwoods.”We’re in a lot of trouble here,” Stephen Ellsperman, the city’s parks and open space director, said as he surveyed rows of dying trees near Original Curve on Aspen’s east side. “We’ve got this all over town.”Four years ago, city officials first observed tiny red bugs burrowing into area trees but had no idea what they were, Ellsperman said. And since then the problem has gotten worse.
Scale insects, which come in thousands of varieties, are parasites that embed in trees and plants, and secrete a protective wax while they draw sap and nutrients from the host tree. The insects move usually just once per year and survive winters in stasis, Ellsperman said.And while willow scale is native to the area, Ellsperman said, the bugs have become more prevalent and are reproducing more than usual.”It seemed to be concentrated on the east end of town, but now it’s throughout town,” said city forester Chris Forman, who manages some 8,500 trees in the city limits.The insects are moving unpredictably and “constantly reproducing,” Forman said. And Aspen’s willow scale is attacking 25- to 30-foot trees with 6- to 12-inch-diameter trunks.
“Those trees are going to be the big trees of tomorrow,” Ellsperman said. He is asking for cooperation from homeowners who can help stop the breeding populations.”Nobody knows much about this insect,” Ellsperman said. He said that either laboriously scraping the insects off the tree or injecting chemicals into the tree’s root system can eliminate the bugs.Willow scale is easy to spot as clusters of dark bumps on the surface of a tree, and Ellsperman urged Aspen residents to notify the city if they spot the bug. He recommends hiring a tree specialist to tackle major outbreaks, but said city staff is happy to advise homeowners.”You may not know this bug’s there until your tree starts to die. And then you’re behind the eight ball,” Ellsperman said. Early detection is the key.
“Keeping your trees happy is one of the best initial defenses,” Forman said, and that means watering , pruning and keeping an eye out for the parasite.Unlike other infestations such as the gypsy moth, which can kill large stands of trees rapidly, willow scale kills slowly. But Ellsperman stressed that 80 percent of trees in the area are of the Populous genus (which includes aspens and cottonwoods) and vulnerable to the infestation.Ellsperman and Forman urged Aspen residents who spot willow scale to contact the city at 920-5120.Charles Agar’s e-mail address is firstname.lastname@example.org
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