A preview peek into the health of Washington’s forest

In 2016, DNR and the USFS discovered more than 450,000 acres of insect and disease damage in Washington's forest. Photo DNR
In 2016, DNR and the USFS discovered more than 450,000 acres of insect and disease damage in Washington’s forest. Photo DNR

While your trees are resting in the cold,
Little bah-hum “bugs” wait to be bold.
As you warm your toes by the fire,
Learn what forest damage did transpire.

This year marks the 70th year of the annual insect and disease aerial surveys in Washington. The survey is conducted cooperatively by the USDA Forest Service and Washington Department of Natural Resources (DNR). The survey information is collected by observers using digital navigational system-equipped airplanes flying at low altitude. The 2016 data has been finalized and resulting maps and data will be available to the public in March 2017.

Maps and data from past surveys are available at the following sites:

In its 70th year, the aerial survey dataset will be getting a new name: the Forest Health Aerial Survey. For many years it was known as “Bugs n Crud.” Certainly a fun name, but not terribly aligned with growing concerns regarding the state of our forest.

What damaged Washington’s forests this year?

The survey found that insects, disease and other types of damage affected more than 450,000 acres, including areas of defoliation and an estimated 2.4 million trees killed. The number of acres is relatively low compared to the last ten years, which have averaged about one million acres of damage per year. Though damage from forest pests was down from historic norms, over the last decade, it has had a cumulative effect; reducing stand productivity, affecting critical wildlife habitat and increasing wildfire risk.

A big forest health story in Washington was the statewide effects of a severe 2015 drought followed by an abnormally dry summer in 2016. Unusually high levels of drought-related damage to many different tree species was reported in both years, including entirely red crowns, red tops and scattered red branches. Many sampled trees showed little indication of being killed by primary pathogens, insects or other animals. In some cases, there were not even signs of opportunistic wood infesting insects. The drought alone was enough to cause their deaths. In other cases, drought-impacted trees may easy targets.

Damage by all major species of tree-killing bark beetles went up in 2016. Related secondary bark beetles, which attack smaller diameter trees and branches, also increased. Many types of bark beetles are known to take advantage of drought-stressed conifers, such as fir engraver, western pine beetle, Ips pine engravers and secondary engraver beetles in Douglas-fir.

About 126,000 acres of forestlands east of the Cascade Mountain Range showed especially high levels of pine tree death caused by pine bark beetles, an increase from the 65,000 acres reported in 2015. Damage from Douglas-fir beetle, fir engraver and spruce beetle also at least doubled in this area from the previous year.

There was a bit of good news, however. The 46,000 acres of damage caused by western spruce budworm, a major defoliator of firs east of the Cascades, was at the lowest level since 2002. Outbreak activity in central Washington appears to be declining, though northeast Washington activity continues to increase.

The 2016 conditions of Washington’s forested lands will be reported fully in March 2017 in DNR’s Forest Health Highlights in Washington report. Until then, the latest 2015 report is available at: www.dnr.wa.gov/ForestHealth

Learn how to identify major insects and diseases and get the latest information and trends on exotic pest problems, insects and disease outbreaks with DNR’s Forest Health program.

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