By Sylvia Kantor, College of Agricultural, Human & Natural Resource Sciences
UNDERWOOD, Wash. – Five years ago, when entomologist Todd Murray received a call from a landowner in Underwood whose ponderosa pine trees were dying, he wasn’t surprised. The trees had been stressed by a nearby fire, a situation that commonly results in a flare-up of bark beetles that can kill the trees. But the calls kept coming.
“People were saying things like, ‘I’ve lived here all my life and have never seen pine trees die like this,’” said Murray, Washington State University Extension director in Skamania County. “The situation has worsened since then.”
At the time, Murray didn’t know that the culprit was a new pest on the scene, the California fivespined ips or Ips paraconfusus.
This summer, WSU Extension, along with the Washington Department of Natural Resources, Oregon Department of Forestry, Oregon State University and several other agencies and nonprofits, begins a coordinated effort to help landowners respond to emerging forest health concerns like the California fivespined ips with training, outreach materials and on-the-ground treatments.
Information about this pest and recommended forest management practices are described in the WSU fact sheet: California Fivespined Ips – A Pine Engraver Beetle New to Washington State,
Attacks between the urban and the wild
The new beetle is showing up in the wildland-urban interface: a designation for areas between unoccupied land and human development that are at risk for wildfires. In Washington, beetle damage thus far is limited to the Columbia River Gorge area. However, the beetle has been confirmed as far north as Fort Lewis, Wash.
The beetle favors the green, freshly broken branches of many species of pine including ponderosa, sugar, western white and lodgepole.
The male bores into the tree to create a nuptial chamber underneath the bark and then emits pheromones to attract females. Females, usually three at a time, come to mate and then carve out an egg gallery where larvae hatch and feed on the cambium layer of the bark.
“A healthy tree can easily spit out this (kind of attack) with pitch,” Murray said.
Trees can flush out the invaders by exuding sap, but this natural defense doesn’t work when the trees are stressed or the beetles are too numerous. During an outbreak, beetles actually coordinate their attack to overwhelm tree defenses.
Climate change or forest health?
It’s unclear whether the California fivespined ips has newly expanded its range north from Oregon and California or if it’s been in Washington historically and gone unnoticed. Until 2010, when the pest was officially documented in Washington, it hadn’t been found beyond the northern reaches of the Willamette Valley in Oregon.
The beetle may have moved northward as a result of climate change, but Murray suspects it is more likely that the insect has reclaimed an existing range that until now hasn’t had the right set of conditions to support the outbreaks.
“Bark beetles are there all the time,” Murray said. “It’s a condition of forest health when there are episodes of population flare-ups.”
Forests that are stressed by drought, fire and storm damage are susceptible to insect and disease damage. Ironically, the recent outbreaks may be due partially to forest health improvements that have resulted in a greater number of older trees. The beetles prefer trees that are over 60 years old.
More mature trees plus drought conditions, storm damage, fire suppression practices resulting in denser forests and poorly managed harvests can add up to stressed trees and habitat that the insects favor for breeding.
Mature trees overwhelmed by the California fivespined ips are easily identified by their red tops. The beetle tends to infest the tops of trees where branches are more likely to be broken by wind and where bark is thinner.
An infestation turns the needles pale green, then orange and finally reddish brown. Mature trees may recover, but young trees that are completely red are unlikely to survive.
Other signs of infestation include numerous exit holes in the bark and accumulations of reddish brown bark dust.
Adding insult to injury, adult beetles can introduce a fungus that kills tree tissue in the attacked area and further weakens the tree. The fungus stains the wood blue.
What can forest landowners do?
During an outbreak, the advice is to do nothing. From February through September, avoid pruning or creating any slash piles that could harbor the pests. Early season pruning especially can exacerbate the problem.
The recommended window for pruning, thinning, tree removal and slash management is between October and January, when the insects are dormant.
While commercial repellant lures have been developed for other bark beetles, none are effective for this species. The best medicine is prevention – improving and maintaining overall forest health.