The Department of Natural Resources’ 2013 Forest Health report was released in March. It shows that while our forests continue to face forest health challenges, they also appear to be holding their own. What follows are a few highlights, with the full report available online.
In 2013, the area of forestland containing some level of tree mortality, defoliation, or disease was about half of that reported in 2012. Acres with mortality from bark beetles decreased and mortality from mountain pine beetle, Douglas-fir beetle, and fir engraver is at a ten-year low.
Pacific Northwest weather was influenced by the La Nada (neutral) effect in 2013, resulting in a moderately wet spring and above average temperatures from June to September. However, an unusual number of conifers in western Washington exhibited top-kill, dead branches, and whole tree mortality. Most trees examined showed no indication of being killed by pathogens, insects, or other animals. The damage was primarily the result of an extended period with little to no rain during August and September of 2012 and a drier than normal spring in 2013. Douglas fir trees 5 to 15 years old appeared to be the most commonly affected, but some larger trees also showed symptoms. Damage was most severe in areas with rocky soils, such as in glacial outwash around the Puget Sound.
The 2013 wildfire season began unusually early for western Washington due to abnormally hot, dry, and windy conditions in early May. Two small wildfires, the C Line Fire in Capital State Forest and the Dog Mountain Fire near Riffe Lake in Lewis County, each burned approximately 100 acres. In contrast, the eastern Washington wildfire season was delayed due to widespread rains in late June. Wildfire conditions worsened across Washington in July and August with warm, dry weather and the number of lightning strikes was above normal. Almost 70 percent of the fires in DNR’s jurisdiction were human caused, with approximately 126,000 acres burned – well above the 10 year average of 29,000 acres.
Insects and Disease
- Pine bark beetle activity recorded by aerial survey decreased in 2013 to approximately 107,000 acres compared to the 156,000 acres in 2012.
- Mountain pine beetle damage decreased to the lowest level in ten years, with declines seen in all pine hosts. The most concentrated areas of Mountain pine beetle-caused mortality occurred in Chelan County, western Okanogan County, northern Ferry County, and near the border between Yakima and Klickitat counties.
- Approximately 11,000 acres with Douglas fir beetle-caused mortality were observed statewide in 2013, down from 26,000 acres in 2012. This is the lowest level recorded in the last ten years. Concentrated areas with Douglas fir beetle- caused mortality were detected in western Okanogan County, likely associated with long-term defoliation by western spruce budworm.
- Western spruce budworm continues to damage trees in areas of eastern Washington; however affected acres were a third of those reported in 2012. A similar decline has also been reported in adjacent western states and British Columbia. Mid-elevation forested areas of Kittitas, Okanogan, and Ferry counties were most heavily affected.
- Approximately 14,000 acres with western blackheaded budworm defoliation were observed in western Washington, primarily on the east side of the Olympic Peninsula and west of Mt. Rainier in Lewis County. Both western hemlock and Pacific silver fir were moderately defoliated.
- An outbreak of Douglas fir tussock moth in the Blue Mountains from 2011 to 2012 has collapsed due to natural controls. A 2011 to 2012 outbreak of hemlock loopers in the vicinity of Baker Lake in Whatcom and Skagit counties has also collapsed due to natural controls.
- Needlecast diseases in eastern Washington affecting larch and pine decreased significantly in 2013. Approximately 11,000 acres of needlecast symptoms were observed in western larch, 4,500 acres in lodgepole pine, and 200 acres in ponderosa pine.