Salem, Oregon – A new aerial forest‑health survey released by the Oregon Department of Forestry (ODF) and the U.S. Department of Agriculture Forest Service shows encouraging progress for the state’s woodlands. In 2025, only about 0.7% of Oregon’s roughly 30 million forested acres displayed signs of tree death or damage, down from 0.8% in 2024 and far below the 1.8% peak recorded in 2022.
Improved numbers, but challenges remain
The survey identified 181,500 acres with visible damage or mortality, a figure well below the ten‑year average and less than half of the 2022 high. While the decline signals healthier forests, experts caution that drought continues to stress trees, making them more vulnerable to insects and disease.
ODF forest entomologist Christine Buhl explained that drought often coincides with rising temperatures, creating a perfect storm for tree stress. “Together these are often the underlying cause of tree deaths in our state,” Buhl said. “Drought reduces tree growth and lowers their defenses against insect pests and some diseases, which healthy trees may otherwise resist or tolerate.”
Drought‑linked beetle damage dominates
According to the report, 78% of the damage detected in the 2025 aerial survey was linked to the combination of drought and opportunistic beetles attacking stressed Douglas‑fir, true fir and pine species. Eastern Oregon recorded the highest percentages of forest death and damage, with Union County at 2.4%, Umatilla County at 1.24%, and Harney County at 1.12%.
Coastal counties and areas bordering the Coast Range showed the lowest percentages, reflecting more favorable moisture conditions.
Other threats monitored
The survey also tracked disease, storms and wildfires. Levels of most common tree diseases remained relatively unchanged in 2025, though some illnesses are difficult to detect from the air. One notable exception is sudden oak death, caused by the water mold Phytophthora ramorum. First discovered near the California border in 2001, the disease continues to spread northward through Curry County, threatening native tanoak trees.
Oregon is collaborating with federal land managers to slow the spread of sudden oak death by identifying newly infected areas and removing or burning infected vegetation. Private forest owners are also treating affected stands.
Swiss needle cast remains a concern for Douglas‑fir, especially in the Coast Range where late‑spring atmospheric moisture is high. ODF forest pathologist Gabriela Ritokova noted the fungal disease can cause premature needle loss, leading to sparse crowns and slower growth. The report estimates Swiss needle cast can reduce volume growth by 20% to 50%.
Survey methods and history
The annual aerial survey is conducted by trained observers who fly fixed‑wing aircraft between 1,500 and 2,500 feet above ground, following a systematic grid spaced four miles apart. Flights typically travel at 90 to 140 miles per hour. Beginning in 1947, the survey is the longest continuous forest‑health effort of its kind in the United States, with the sole interruption in 2020 due to the COVID‑19 pandemic.
Ground‑level data collected by Oregon State University Forestry Extension staff, natural‑resource agencies, universities, landowners and volunteers complement the aerial observations, providing a more complete picture of forest health.
The full 2025 Oregon Forest Health Report is available through the Oregon Department of Forestry, and the underlying aerial‑survey data can be accessed via the USDA Forest Service.
Original reporting: KTVZ (Central Oregon) — read the source article.
