Bark beetle problems continue to worsen on Northern Idaho forest lands, a university forester says. Drought stress from several years ago has led to the increased pressure now, said Chris Schnepf, University of Idaho Extension forester in Coeur d’Alene, Idaho.
Western pine beetles, pine engraver beetles, fir engraver beetles and Douglas fir beetles all are more active this year, he said. “All of these bark beetles are native insects, they’re always around at some endemic level,” he said. “But when you have stand conditions that favor them, they start to take off.” Pine bark beetles are particularly bad on lands with too many trees per acre, Schnepf said. “With many of these beetles, they may take out the most stressed trees first, but they don’t necessarily stop there,” he said. Pine engraver beetles and Douglas fir beetles can breed in downed trees, which can make the situation worse.
The problem is worse in private and U.S. Forest Service stands compared to industrial stands, Schnepf said. Private forest landowners can hesitate to take action because they fear making a mistake, he said. “The default position there is forests continue to get overstocked,” he said.
Schnepf recommends favoring the best tree species for a site and reducing stocking. “Sometimes thin it out a lot,” he said. “If you’ve got 6,000 (trees) per acre of lodgepole, you can remove three-quarters of those trees and still be overstocked.”
The most recent winter weather and increases in moisture in June are hopeful signs, Schnepf said. But a longer than usual growing season could mean more bark beetles. Last year, three generations of the beetles were found in some areas of Northern Idaho, compared to the usual two. It means bark beetles could remain active into the fall instead of slowing down by the end of July.
From Capital Press: https://www.capitalpress.com/20170622/bark-beetles-getting-worse-forester-says