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Understanding the California Fivespined Ips and Its Outbreaks
By Todd Murray, Washington State University Extension Skamania County, and Glenn Kohler, Washington State Department of Natural Resources
In 2010, a concerned homeowner in Underwood, Wash., reported dying ponderosa pine trees. Both mature and small trees were affected, many showing the top-killed stems that are characteristic of Ips beetles. This wasn’t a huge surprise as recent fires in the area commonly caused bark beetle flare-ups. What was a surprise was that the Ips were identified as Ips paraconfusus, the California fivespined Ips (CFI).
The Range of the Beetle
CFI is a native bark beetle known to occur in California and the western valleys of Oregon. Until now, the most northern known distribution was the Willamette Valley in Oregon. In 2010, approximately 100 acres of killed and top-killed ponderosa pine were recorded in Skamania and Klickitat counties near the town of White Salmon.
As of early 2013, small outbreaks still continue in the area, causing significant tree mortality near Lyle, Wash., in the Catherine’s Creek Trail area of the Columbia River Gorge National Scenic Area and the small community of Mosier, Ore.
Thanks to a handful of volunteers and pooled resources, Washington State Department of Natural Resources, USDA Forest Service R6 Forest Health Protection, and Washington State University Extension have led a trapping program since 2010 to determine the range of CFI in Washington.
During the flight period of adult beetles, Lindgren Funnel traps (a specialized pheromone trap specific to forest insects) were used at each site and baited with CFI pheromones. After counting beetles for the past three seasons, entomologists have determined that CFI can be found in trapping sites in Clark County heading north along the Interstate 5 corridor up to Fort Lewis in Thurston County. CFI is also found east through the Columbia River Gorge in Skamania and Klickitat counties and as far north as Trout Lake.
CFI can infest numerous species of pines and has been a serious pest of young ponderosa pine in Oregon’s Willamette Valley since it was first reported there in 1999. CFI can rapidly increase its population in small diameter (but greater than 3 inches) dead pine slash created by storms, fires, logging, or thinning. Offspring produced the same year can then successfully attack nearby live trees.
The risk of outbreak is much higher during drought conditions when live trees are stressed. Outbreaks of CFI typically subside within a year unless fresh breeding material becomes available a second year. As with other pine engravers, the likelihood of outbreaks is reduced by assuring that breeding material has time to dry out or is removed before beetles fly in spring.
Logging practices and stand age spurred the pest nature of CFI in its known historic geographic ranges in California. Logging of second growth pines and slash management practices created a mass food source for CFI, and it quickly became known as another bark beetle pest of pines in the 1940s.
After investigations into the nature and habitat of CFI, forest practices changed to avoid CFI outbreaks. In its historic ranges, a CFI outbreak typically lasts for only one year’s season, and populations quickly subside as its preferred food of pine slash piles are used up.
During ‘normal’ periods of beetle activity, Columbia Gorge landowners now take precautions to prevent beetle population build-up by not making fresh slash piles available from January through June. During this time, slash should be treated or removed promptly to avoid attracting adult beetles. However during outbreak times, foresters are recommending that tree work such as pruning and thinning be postponed until mid-October through December.
Landowners with red trees should down the trees as soon as possible and debark them before beetle flight takes place. Exposed beetles during the dormant season are easy prey for hungry critters like rodents and birds.
It is unclear if we are witnessing CFI expanding its range or if CFI is reclaiming a historic natural range. Droughty periods during July through October are definitely affecting tree health in the region. While a changing climate is a readily available reason for an insect like CFI to expand its range northward, other historic factors are likely allowing CFI to repopulate a historic geographic range.
Investigations into CFI by Oregon entomologists found that CFI populations are much higher in stands of 60 years and older. Willamette biotype ponderosa pines have been newly re-introduced to the region and now provide an ecology suitable for the beetles that used to be present before pioneer settlement removed older pine stands. In the Columbia Gorge, similar logging of old and second growth pines has occurred since pioneer settlement and now the preferred age classes of CFI are beginning to establish again in the region. ‘Fort Lewis’ ponderosa is another Westside adapted variety of pine increasingly planted within the range of CFI in western Washington. CFI isn’t expanding its range, maybe CFI is coming home.
For more information, Murray and Kohler have developed the free, WSU Extension Factsheet 085E, Pest Watch: California Fivespined Ips–A New Pine Engraver in Washington State.
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