Insects and Disease Monitoring

The insect and disease monitoring team at the Washington State Department of Natural Resources (DNR) tracks insects and diseases that affect forest health. Their work includes conducting aerial surveys of forest health conditions that results in the annual Forest Health Highlights report. This team of forest pathologists, forest entomologists, and forest health specialists also provide technical assistance to forestland owners. Explore the drop-down menus below to learn more.

Annual Forest Health Highlights Report

The Forest Health Highlights in Washington report is published annually by DNR’s Forest Health and Resiliency Division and the USDA Forest Service each spring. It summarizes the major forest insect and disease conditions from the previous year across all ownerships throughout Washington. Much of what is reported are results of aerial surveys and ground based surveys, but it also includes information on special monitoring projects, suppression projects, and other forest-health related projects and initiatives. It also includes information on recent forest damaging weather events, droughts, and wildfires. Printed copies are available on request by contacting 360-902-1300 or

Past reports

Forest Disease Information

Up close of Dothistroma Needle Blight

(Joseph OBrien/USDA Forest Service photo)

Our trees and forests are subject to a wide variety of pests and diseases, which are usually caused by bacteria, viruses, and most commonly, fungi. Tree diseases can decay wood, decrease tree growth and cause tree mortality in both forested and urban environments. Overall, forest diseases can impact carbon sequestration, purification of water, reduction of flood risk and cultural and recreational values. Many of our diseases in Washington are native and have been here a long time, often directly influencing the biodiversity and nutrient cycling in forests. All parts of a tree, including roots, stems, branches, and foliage, can be infected by the different organisms that cause diseases, resulting in different impacts on a tree’s health. They often have specific host preferences and environmental conditions in which they live, reproduce and spread. Non-native and invasive diseases are a constant threat to our forests since our trees have no natural defenses against the pathogens. Information about specific diseases and projects we are working on can be found below.

If you have questions about tree diseases or other forest health questions, including management and treatment options, please contact our State Forest Pathologist, Dan Omdal, at 360-902-1692 or email

Forest Management Guides
Forest Insect and Disease Leaflets

Foliar Diseases

Root Diseases

Dwarf Mistletoes

Other Diseases

Additional Resources

Forest Insect Information

Douglas-fir tussock moth

(Donald Owen/California Department of Forestry and Fire Protection photo)

DNR’s forest entomologists provide technical assistance to private landowners and state land managers with identification and management of forest insect pests. The primary focus is on insects that cause mortality such as bark beetles, those that cause growth loss and stress such as defoliators, and those that affect wood quality. We emphasize integrated forest pest management methods that focus on increasing stand resistance to insect attack and resilience following any damage that may occur. Management strategies that can increase resistance and resilience include increasing vigor of leave trees through selective thinning, reducing the proportion susceptible hosts, altering stand structure and/or age classes, planting species appropriate for the site, and reducing available breeding material (slash management or salvage following storms and fires). We annually monitor populations of Douglas-fir tussock moth and western spruce budworm in eastern Washington. We assist with the annual aerial survey. When unexpected levels of damage occur, we may conduct special monitoring projects to determine levels of mortality and potential causes. We also provide assistance to state and private land managers with specific insect monitoring, stand evaluations, and suppression projects. In some stands where forest health treatments have been applied, we install long-term plots to monitor changes in insect activity.

If you have questions about forest insects in Washington, please contact our State Forest Entomologist, Glenn Kohler, at 360-902-1342 or email

Forest Management Guides
Forest Insect and Disease Leaflets

Bark Beetles


Sucking Insects

Additional Resources

Aerial Survey Information

Map showing routes of 2018 aerial forest health survey

Systematic aerial surveys are conducted to collect and report on forest insects, diseases, and other disturbances across federal, state, tribal and private lands. These surveys have been conducted annually since 1947 in the Pacific Northwest by USDA Forest Service (USFS) with the cooperation of State and private partners since 1948. Aerial surveys have proven to be an efficient and economical way to detect and monitor forest change events over large forested areas. Statewide aerial surveys are conducted each year to assess forest health in Washington State. They capture mortality and discoloration caused by insects, diseases and abiotic disturbances. This relatively low cost remote sensing method gives a coarse, landscape-level overview of forest conditions. The data collected are then used with other remote sensing and ground sampling techniques to further enhance the data accuracy of significant forest health events and changes.

Aerial Survey Data Collection Methods

The primary data collection method is known as aerial sketchmapping. Data are collected by specially trained aerial observers from the USFS and Washington Department of Natural Resources (DNR). The necessary components to make this survey happen are a high-winged aircraft that provides good visibility and can fly at relatively slow speeds between 1,000 to 2,000 feet above ground level, a safety conscious pilot, and an experienced sketchmapper who can identify forest damage observed on the ground and plot it on a map while moving in the air. Areas of forest damage are recorded as polygons using a Digital Aerial Sketchmapping System (DASM). The DASM uses a moving map display, GPS, and a touch screen to create a digital version of the data while in the aircraft. The polygons are coded with attributes such as tree species affected, number of trees (or trees per acre) affected, likely cause of damage, and severity of damage. This advanced digital sketchmapping system allows rapid summarization and near real time reporting of tree mortality and damage. This is an extremely valuable tool for forest managers and other clients who can use the data to make timely decisions and assessments.

For more information on the aerial survey program, please contact Glenn Kohler at 360-902-1342 or

Additional Resources
  • Access the Washington Aerial Survey GIS data (under Forest Disturbance category)
  • Find the aerial survey data for your area on a 100K quad map
  • An interactive web service for the Forest Health Aerial Survey data can be found here. This is the place where the most current Annual and Cumulative Aerial Survey data are displayed. Users can create their own PDF, JPG, and PNG maps of the field of view by clicking on the printer icon in the upper right corner. Note: The Cumulative Aerial Survey data set contains several million polygons, so to speed up the loading process, the user may want to zoom in until “15 Year Mortality Indicator 2001-2015” title on the left switches from grey to black.