Rainy weather has made conditions ripe for pathogen outbreaks
Patches of red needles on the ponderosa pine trees caught Kent Moline’s attention as he hiked the bluff below High Drive on Spokane’s South Hill this spring.
He knew the trees should have already shed their dead needles and “I wondered if it was a pine beetle outbreak,” said Moline, a board member for the nonprofit Friends of the Bluff.
But foresters say the unsightly appearance of the region’s ponderosa pines this year is caused by fungal infections and tiny insects called pine scale that thrive during cool, moist weather conditions. At least four different pathogens that attack pine needles are at work, said Guy Gifford, a Department of Natural Resources officer.
Though the pests seldom kill trees, the dead needles are triggering panicky calls from landowners, who wonder what’s attacking their ponderosas.
Steve McConnell, a Washington State University Extension forester in Spokane, is fielding two to three calls per day. And every other forestry agency he knows of is getting similar queries.
“Some people are worried that their tree is dying. They want to know what they can do to keep it from spreading,” he said. But if the tree is otherwise healthy, it should recover, though the pests can affect growth rates, McConnell said.
“This is the time of year that it’s going to look the worst,” said Paul Zambino, a plant pathologist for the U.S. Forest Service in Coeur d’Alene. “We should start to see the trees greening up.”
The pathogens are native to Inland Northwest forests. Last year’s wet spring, followed by a wet fall and a consecutive damp spring, created the conditions for them to thrive, Zambino said.
Normally, the outbreaks are smaller – DNR’s Gifford will notice one affected ponderosa in an area, or five or 20 affected ponderosas. This year, he’s seeing acres of affected trees and not just in typically moist spots, such as canyons or near creeks or ponds.
“It’s been a regionwide thing, and that’s very unusual,” McConnell said.
Pine scale can look like paint spatters, while fungi are identified by black or brown splotches on the needles.
In North Idaho this spring, Zambino is particularly noticing the red band needle blight fungus, which creates dark green spots on the needles that eventually turn brown. In drier years, the fungus attacks older needles. Last year’s wet conditions meant they attacked new growth as well, Zambino said.
A return to drier conditions should curb the outbreak, the foresters said. And for landowners who want to be proactive, Gifford recommends thinning dense stands of ponderosa pines to increase air circulation. Many stands are overcrowded, he said.
Moline, from Friends of the Bluff, said that effort is already underway on the bluff. Over the past several years, volunteers using hand saws thinned about 14 acres, and DNR got a grant to thin another 93 acres.
“The trees that were less affected (by the pests) were better spaced,” Moline said.