Bah HumBUGs and disease are the problem in our forests

pine bark beetle
A pine bark beetle is the size of a grain of rice.

With milder winters, overstocked forests and past forest management practices, Washington’s forests are increasingly becoming a smorgasbord for tree-devouring insects.

The 2014 annual insect and disease aerial survey found that insects and disease killed more than 4 million trees on over 540,000 acres in Washington state.

About 143,000 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 107,000 acres reported in 2013.

You can now explore the latest aerial survey maps on the Department of Natural Resources’ interactive, web-based mapping site: Fire Prevention and Fuels Management Mapping. Click on the Forest Disturbance folder.

Aerial observers this year also identified nearly 740,000 trees across 30,000 eastern Washington acres that died as a result of 2012 wildfire damage or from the bark beetles that subsequently attacked damaged trees. Those numbers are well higher than typical.

Though damage from forest pests was down from historical norms in 2013 and 2014, the number of trees destroyed by insects in the last decade is unprecedented.

Widespread mortality caused by bark beetles and damage from defoliating insects is setting the stage for more wildfires. In some places, critical wildlife habitat is being destroyed.


Lots of reasons: mild winters, drought conditions, overstocked forests, past fire control techniques and logging practices of yesteryear.

Here’s an example of how those elements combine. Many eastern Washington forests are over-stocked with fir trees grown after the original pine was harvested intensively during the first part of the 20th century.

Fir does quite well in shady areas so these forests grow in thicker than the original stands. Fire management strategies of the past tried to suppress even periodic natural fires, allowing the stands to grow thicker with potential fuel.

bark beetle galleries
Adult bark beetles excavate galleries within a pine tree’s inner bark where they can lay eggs. The emerging young excavate galleries of their own. In sufficient numbers, the intricate galleries may kill the host tree. Photo: Robert Van Pelt/DNR.

Thus, a recipe for intense wildfire incidents and, in the meantime, a delicious salad bar for pests thriving thanks to milder-than-normal winters of recent years.

The aerial survey is conducted cooperatively by the USDA Forest Service and Washington Department of Natural Resources. The survey information is collected by observers using digital navigational system-equipped airplanes flying at low altitude. Every year in March, DNR produces the Forest Health Highlights report on the current condition of Washington’s forested lands; the latest report available is Forest Health Highlights in Washington Report – 2013.

Oregon Public Broadcasting reported on the disturbing impact of bark beetles on western forests.

Get the latest information on exotic pest problems, insect and disease outbreaks and trend information, and learn how to identify major insects and diseases from DNR’s Forest Health Program.

Follow DNR on: Facebook Fan See us on Flickr Watch us YouTube Follow us on Twitter Follow DNR Fire Twitter Join in the DNR Forum