Insects and Disease Monitoring

The Insect and Disease Monitoring Program at the Washington State Department of Natural Resources (DNR) monitors the impacts that insects and diseases have on forest health. A central component of the program is working with the U.S. Forest Service on an annual aerial survey of millions of acres of forested lands in Washington. The data collected by the aerial survey, along with the work of DNR scientists on the ground, informs the annual Forest Health Highlights report.
This team of forest pathologists, forest entomologists, and forest health specialists also provide technical assistance to forestland owners. They play a crucial role in the planning of forest health treatments, providing the scientific backing for implementation of those treatments, and post-treatment monitoring of those lands.

Choose a section below to learn more:



the cover of the 2023 Forest Health Highlights in Washington report
The Forest Health Highlights in Washington report is published each spring by DNR’s Forest Resilience Division and the U.S. Forest Service. It summarizes forest insect and disease conditions from the previous year across all ownerships throughout Washington, as well as contributing factors such as heat and drought. Much of what is reported is a direct result of the annual aerial survey and additional ground- based examinations of new or changing conditions in specific locations, as seen from the air.
The report also includes information on special monitoring projects, suppression projects, and other related projects and initiatives. It also includes information on damaging weather events and wildfires.
Printed copies are available on request by contacting 360-902-1300 or 
Past reports


Up close of Dothistroma Needle Blight
(Joseph OBrien/USDA Forest Service photo)
Washington forests and trees are subject to a wide variety of pests and diseases, the latter of which are usually caused by bacteria, viruses, and most commonly, fungi. Tree diseases can decay wood, inhibit tree growth, and cause tree mortality in both remote and urban environments. Outbreaks of harmful forest insects and diseases can negatively impact carbon sequestration, water quality, aquatic habitat, outdoor recreation access, economic opportunities, and cultural values.
Many of the disturbance agents affecting Washington forests are native to the region, or have been here for a long time. They often have direct influence on the biodiversity and nutrient cycles of the forests. All parts of a tree, including roots, stems, branches, and foliage, can be infected by the different organisms that cause disease, which results in different impacts to tree health. Insects and diseases 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. Climate change and emerging threats from insects and diseases new to Washington add additional stressors to the challenges our forests face.
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
Information about specific diseases and projects we are working on can be found below.
Forest Management Guides
Forest Disease Leaflets 
Foliar Diseases
Root Diseases
Dwarf Mistletoes
Other Diseases
Additional Resources


Douglas-fir tussock moth
(Donald Owen/California Department of Forestry and Fire Protection photo)
DNR’s forest entomologists provide technical assistance to public land managers and private landowners and assist in identification and management of forest insect pests. Their primary focus is on insects that cause mortality (such as bark beetles), as well as insects that cause growth loss and stress, such as defoliators, and those that affect wood quality.
DNR emphasizes 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, such as slash or salvage wood left after storms and fires.
We monitor populations of Douglas-fir tussock moth and western spruce budworm in eastern Washington on an annual basis and participate in the annual aerial survey with the USFS. When unexpected levels of damage occur, we may conduct special monitoring projects to determine levels of mortality and potential causes. We also aid land managers with specific projects related to insect monitoring, stand evaluation, and suppression. We install long-term monitoring plots in some stands where forest health treatments have been applied, to track 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 Leaflets
Bark Beetles
Sucking Insects
Additional Resources


a map of Washington with colorful lines indicating aerial survey flights
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 the Forest Service, with the cooperation of state and private partners. Aerial surveys have proven to be an efficient and economical way to detect and monitor forest change events over large, forested areas.
Aerial surveys use trained scientists and cutting-edge technology to capture mortality and discoloration caused by insects, diseases, and abiotic disturbances. This relatively low-cost remote sensing method gives a broad, landscape-level overview of forest conditions. The data collected is then used with other remote sensing and ground sampling techniques to further improve the accuracy of reports and ongoing study of significant forest health events and changes. 
Aerial Survey Data Collection Methods
The primary data collection method is known as aerial sketch mapping. Data is collected by trained aerial observers from the USFS and DNR. Resources necessary for a successful aerial survey include 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 sketch mapper who can identify forest damage observed on the ground and plot it on a map while moving through the air.
Areas of forest damage are recorded as polygons using a Digital Aerial Sketch mapping 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 sketch mapping system allows rapid summarization and 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 datasets 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.