Credit: USDA Forest Service, Region 6, State and Private Forestry, Forest Health Protection. Collection: Region 6, Forest Health Protection, Aerial Survey Program slide collection.
For additional information see: Greeley, A.W., Wright, K.H. and Pope, R.B. 1953. Final report on the 1952 blowdown bark beetle survey in the Douglas-fir region of Oregon and Washington. USDA Forest Service, Pacific Northwest Forest and Range Experiment Station. Portland Forest Insect Lab.
For related historic program documentation see: archive.org/details/AerialForestInsectAndDiseaseDetection... Johnson, J. 2016. Aerial forest insect and disease detection surveys in Oregon and Washington 1947-2016: The survey. Gen. Tech. Rep. R6-FHP-GTR-0302. Portland, OR: USDA Forest Service, Pacific Northwest Region, State and Private Forestry, Forest Health Protection. 280 p.