Forest Health Summary for the Pacific Northwest Region 2022

The adjacent map is interactive. There is a legend that will open in the lower left corner. Red denotes tree mortality, purple denotes tree defoliation, and yellow denotes miscellaneous forest damage. Use the + and - buttons in the lower right corner to zoom in and out. Use your mouse to pan around in the map. Click on an affected area to learn more about the forest damage associated in that location. The home button will return the map to the original extent.

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The adjacent dashboard is interactive. To select a certain tree species or specific area of interest, click on the filter located on the left. Forest damage detected in 2022 is illustrated in multiple ways on the right. The top bar graph displays the number of acres with damage associated with each bark beetle. The middle bar graph shows acres with all the miscellaneous forest damage that does not fall into either the bark beetle damage or defoliation category. The bottom bar graph shows acres with defoliation damage. The pie chart on the right shows the percentage of total damage for each type of insect or forest disease.

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After an abnormally dry couple of years, evidence of drought stress was observed in all tree species across the drought impacted areas of the Northwest. At the landscape level, drought stress occurred most heavily across Oregon from the center of Oregon around the Ochoco Mountains to the California border. Drought-stressed Douglas-fir and true fir species located on ridges and upper slopes in the central and southern part of the Oregon became too weak to fight off insects and diseases in 2022. Abiotic stressors, such as drought, can increase the susceptibility of trees to insects and diseases that do not normally affect healthy, vigorous trees.

  Climate projections predict  increases in temperature and possible changes in levels of precipitation across the Northwest as a consequence of climate change, potentially leading to fundamental and drastic ecosystem shifts. Data from the  USFS National Insect and Disease Risk Map  highlight the risk of substantial tree mortality from insects and diseases through 2027. Continued region-wide monitoring of forest health is imperative for effective forest resource management in a changing climate.

The fir engraver beetle (Scolytus ventralis) is a bark beetle which attacks true firs, such as white fir, Shasta fir, red fir, grand fir, and noble fir. Fir engravers are opportunistic tree killers that become major contributors to mortality events when firs are weakened, especially after drought events. The 2022 outbreaks of this pest in Oregon are associated with the exceptional drought which has plagued the state over the past couple of years. Additionally, other stressors such as root disease and forest competition for limited resources on a drier, warmer landscape can contribute to increased susceptibility to fir engraver attacks. True firs are highly susceptible to multiple root diseases, which are very widespread and caused by native fungi in Oregon and Washington. Trees infected by root disease are much more prone to mortality under drought stress compared to trees that are non-infected.

The fir mortality is widespread and quite severe in some locations. Fir mortality has been detected across Oregon and Washington, but the elevated and more severe fir mortality was observed across the Ochoco, Malheur, Fremont, and Winema National Forests from Central Oregon to the California border. More than 1.2 million acres have been impacted with fir mortality across the Pacific Northwest, with ~1.1 million of those acres all being recorded in Oregon. Nearly double the acres impacted compared to all the previous year's data on fir mortality in Oregon. In the most extreme cases, we estimate over 50% of the fir had recently died in some areas. If a fire should occur at these locations, areas impacted with fir mortality  could have an increased risk of severe wildfire  (crown fire) especially while the dead dry needles are retained in the canopy of the recently killed trees for the next two years.

Douglas-fir is one of the most important tree species in the Pacific Northwest. It can be found in abundance across Oregon and Washington growing from sea level to 7,000 ft. in the Cascades. Unfortunately, elevated levels of Douglas-fir mortality have been detected in parts of Oregon and Washington during the annual forest health survey of 2022. A variety of insects and diseases can contribute to Douglas-fir mortality. Which insect or disease is attributed to the death of the Douglas-fir may not be the same when comparing Washington to Oregon, or even when comparing areas within just one state. Often it is a complex of factors such as drought, insects, and diseases contributing synergistically to the demise of Douglas-fir.

Across the forests of southwest Oregon, surrounding the Medford area, aerial surveys detected elevated levels of Douglas-fir mortality. As previously mentioned, the drought, which has impacted forests across Oregon, predisposed the Douglas-firs in this area to attacks from what are typically considered secondary pests. The flatheaded fir borer (Phaenops drummondi prev. Melanophila) often attacks trees in poor health, but can also kill apparently healthy trees, especially on dry sites or during unusually, droughty conditions at elevations below 3,500 ft. above sea level. In this area, the Douglas-fir damage ranged in severity from very light (1-3% mortality) to severe in some places with 30-50% of the trees killed for a given location. In 2022, the aerial detection survey detected 463,900 acres with Douglas-fir mortality which is a dramatic increase compared to the historical data over the past twenty years. The last time Forest Health Protection detected a similar level of acres with Douglas-fir mortality was in 1989-1990.

In Washington, the main area of elevated Douglas-fir mortality occurred in the northeast portion of the state in and around Colville National Forest. Additional areas include the southern Washington Cascade Mountains, especially around relatively recent fires. Douglas-fir mortality at these locations was attributed to Douglas-fir beetles (Dendroctonus pseudotsugae). Collectively, Douglas-fir beetle activity in Washington increased to over 100,000 acres in 2022. Most of the acres impacted were rated as having low levels of severity with mostly light and scattered mortality across the landscape. Some of the mortality attributed to Douglas-fir beetle may in fact be secondary bark beetles that are causing the mortality, similar to what is happening in southwest Oregon, but further investigation and ground plots are needed to verify the damage agent. Root diseases are also common in Washington.

Additionally, in Washington, elevated levels of Douglas-fir pole and engraver beetle activity were detected throughout the state and appear to be impacting lower elevation areas which are more prone to water deficits. Douglas-fir pole and engraver beetles attack smaller diameter trees as well as tops or branches of larger trees, compared to Douglas-fir Beetles which tend to attack larger diameter trees. Douglas-fir pole and engraver beetles attacked about 10,000 acres in 2022. This damage is likely underreported due to the difficulty in seeing flagging branches, dead tops, and smaller diameter trees that are difficult to see from the air.

Mountain pine beetle (Dendroctonus ponderosae) can attack various pine tree species across Washington, but it is most prevalent in lodgepole pine. During outbreaks, the mountain pine beetle attacks apparently healthy trees and can cause extensive tree mortality over large geographical areas. Stand susceptibility to mountain pine beetle is strongly correlated with high stocking levels and tree age.

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Mountain pine beetle continued to affect lodgepole pine in Washington in 2022. The area affected in Washington is around 67,000 acres of lodgepole pine mortality due to mountain pine beetle in 2022. This is an increase from approximately 59,000 acres recorded in 2021.

Mountain Pine beetle activity was heaviest in the mountains surrounding the Kittitas valley. The map to the right shows the areas where the heaviest mountain pine beetle activity was observed. The areas on the map depict stands that had greater than 30% tree mortality. New outbreak areas were observed near the Mission Ridge Ski Area as well as the Gypsy peak area in northeast Washington.