Emerald Ash Borer
Emerald ash borer (Agrilus planipennis) is an invasive insect that has proven to be one of the most destructive forest pests in North America. Since its initial detection in the United States two decades ago in Michigan, emerald ash borer (EAB) has wiped out more than 100 million ash trees throughout the country.
All true ash species (Fraxinum), including Oregon ash, the Pacific Northwest’s native ash, have proven vulnerable to EAB. A mortality rate as high as 90-100% is expected in both forested and urban settings over the next 10-12 years. Read the WSDA Bulletin to learn more.
Forest management options for EAB focus on reducing the rate of spread to provide forest owners with time to transition ash-dominant forests toward other species. To learn more, visit the WSU Extension EAB Guide.
Web Sites
USDA Forest Service, Pacific Northwest Region, Forest Health has links to many resources about forest health, including
- Forest Disease Management Notes, which describe various diseases that can affect native trees
- Forest Health Highlights by state and year
- Links to many more publications about diseases and insects in the Pacific Northwest
Forest Pests of North America. Native and Non-native insects, diseases, and weeds of urban, managed, and natural forests. Website developed, maintained and hosted by The University of Georgia, Center for Invasive Species and Ecosystem Health. Contains lists by tree species and disease type, but no identification keys or photos.
Publications
Forest health highlights in Washington 2024. A summary of insect,disease, and other disturbance conditions affecting Washington’s forests. Washington Department of Natural Resources, 2025. 64 p.
Disease and Insect Damage, Chapter 8 in Forest Management for Small Landowners by Bryon Loucks. 2020. Covers only a few of the most significant diseases and insects in western Washington.
A field guide to the common diseases and insect pests of Oregon and Washington conifers. USDA Forest Service, Pacific Northwest Region. 2006.
A field guide to forest damage in British Columbia. British Columbia Ministry of Forests, and Canadian Forestry Service, Joint Publication No. 17. 2014.
Forest Insect and Disease Leaflets. A series of leaflets covering diseases and insects throughout the U.S.
Webinars
Abiotic factors impacting forest health in Washington. Presented by Dr. Betsy Goodrich. May 29, 2024. Sponsored by WSU Extension and women Owning Woodlands. 60 minutes.
What’s Bugging You? A review of native and invasive forest pests in Washington , by Molly Darr. Presented April 24, 2024. Sponsored by WSU Extension and Women Owning Woodlands. 50 minutes.
Emerald Ash Borer. November 2023, Link to recording and additional information.
Common tree diseases of western Washington forests. Presented by Dan Omdal to Lewis County Farm Forestry Association, April 11, 2023.
Forestry Lunch Breaks – Root Diseases, February 2023
Separate sessions cover:
- Symptoms of common root rotsw
- Root rot signs and disease cycles
- Root rot management
- Lesser known root rots
Forest health highlights. A webinar presented by Glenn Kohler. Sponsored by WSU Extension Forestry, August 17, 2021. 1 hour, 7 minutes.
Forest health watch: Tracking forest health with iNaturalist. A webinar presented by Joey Hulbert, WSU Extension, May 14, 2021. 30 minutes.
Forest health in eastern Washington. A webinar presented by Melissa Fischer at the WSU Forestry Extension 2021 Forest Owners’ Winter School, February 27, 2021.
Forest health in western Washington. A webinar presented by Rachel Brooks at the WSU Forestry Extension 2021 Forest Owners’ Winter School, February 27, 2021.
Field trials of the addition of potassium to Douglas-fir seedlings with associated laminated root rot. Presented by Dick Hopkins, Hopkins Forestry, 2021. 50 minutes. Dick also discussed other options for establishing a new plantation where Phellinus root rot is known to exist.
Why are so many conifers dying? A look at current forest and tree health issues. Presented by Kevin Zobrist. Washington State University Extension Forestry. 2020. 1 hour, 30 minutes.
Climate change effects on forest insects and diseases. Presented by Glenn Kohler. 2019 Fall Forestry Seminar, sponsored by Washington Tree Farm Program. 42 minutes.