EXTENSION REPORT: Landowners can fight bark beetle infestation

Recent fires and last winter’s ice storms created a great late season smorgasbord of susceptible pine trees for the California fivespined Ips bark beetle. Top-killed ponderosa pine trees and dead young and old pines scatter the landscape in the eastern Gorge with small outbreaks occurring in Mosier, and Hood River Oregon and in Washington around Underwood, White Salmon and Catherine Creek Trail Area, just west of Lyle.

This level of mortality due to California fivespined Ips has not been previously reported in the eastern Gorge area.

Entomologists and foresters from the U.S. Forest Service, Oregon Department of Forestry and Washington Department of Natural Resources and extension specialists from both states met in early December to tour areas of the eastern Gorge where bark beetle outbreaks are occurring. The reddening tops of the infested trees became more abundant in November.

Due to outbreak conditions, experts recommend landowners do pruning and thinning work before January or wait until mid-October next year.

“Normally pruning and thinning work can be done from July through December but since we are experiencing small outbreaks, we would suggest landowners prune trees before January or wait until mid-October next year to do pine tree pruning and thinning work. This is also a good time to remove recently killed or dying pine trees that show evidence of being infested by bark beetles,” stated Rob Flowers of Oregon Department of Forestry.

“Tree volatiles from slash piles and fresh pruning wounds seem to be attractive to flying beetles in the spring and summer months during this period of high beetle populations. Otherwise healthy trees that should normally resist bark beetle infestations are getting mass-attacked,” added Glenn Kohler, entomologist with Washington State Department of Natural Resources, emphasizing conditions characteristic of outbreaks.

Bark beetles love to take advantage of stressed-out trees. Adult beetles lay eggs underneath the bark where larvae feed on the living tissue of the bark. High populations can kill both young and old trees alike. Normally, healthy trees naturally defend themselves from bark beetle attack by “pitching” them out with sap.

The California fivespined Ips was recorded in the Underwood area of Washington state for the first time in 2010. This species was unknown to occur at damaging population levels in eastern Oregon until then. The range of this Ips beetle had recently been documented to extend throughout the Willamette Valley.

Now experts have found the beetle as far north as Fort Lewis, Wash., in Thurston County and as far east as The Dalles.

The California fivespined Ips only feeds on pine trees and can affect ornamental trees as well as those in the forest.

“In the previously known ranges of this bark beetle, outbreaks are short-lived, only lasting for a year or two. If no new fires or storms create slash and stressed trees this next year, I expect populations to return to normal levels,” said Todd Murray of WSU Skamania County Extension.

To avoid beetle populations building up on your healthy pine trees, prune trees only from mid-October through December during these outbreaks. Right now, weather permitting, is a great time to work on pruning or removal of infested trees. Clean up all debris and chip or burn it before next spring when adult beetles emerge.

If you have pine trees whose foliage has rapidly changed to yellow, orange, or red in the past season, it is best to remove these trees. Beetles within these trees will continue to develop, even if they are felled, unless the materials are destroyed or de-barked before next spring.

Always check with your local fire district on burning regulations prior to burning debris. If using trees for firewood, be sure to debark the logs. Promote drying of the logs as soon as possible and do not stack wood near other pine stands.

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To learn more, WSU Extension has developed a factsheet, “Pest Watch: California Fivespined Ips — A pine engraver new to Washington state,” which can be downloaded for free at: http://cru.cahe.wsu.edu/CEPublications/FS085E/FS085E.pdf.

For more information, contact Glenn Ahrens, OSU Extension forester, at 503-655-8631 or glenn.ahrens@ore-gonstate.edu, or Todd Murray, (tmurray@wsu.edu or 509-427-3931, at the WSU Extension office.

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