"Holes" with dead, dying, and downed trees in the forest canopy could be reliably identified on 9- by 9-inch Kodak Ektachrome Infrared Aero film 2443 as root disease centers. Film scales larger than 1:4000 were best for detection of these "holes." Most commonly occurring causal organisms in root diseased trees were Armillaria mellea and Poria weirii. Although trees in latter stages of decline could be visually identified from photographs, red filter optical density measurements were extremely variable and inconclusive.
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