Detection of root disease in coastal Douglas-fir stands using large scale 70-mm aerial photography

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Abstract
Douglas-fir (P. menziesii (Mirb) Franco) stands 15, 40, and 100 yr of age containing root disease openings of various sizes were photographed using 70-mm Aerochrome color and color-IR film at scales of 1:1500 to 1:15000. Success in detecting disease centers varied with scale relative to stand age and disease symptomatology. Scales of 1:6000 provided adequate information for young stands 15-20 yr of age whereas scales of up to 1:15000 proved satisfactory for locating most centers in 100-yr-old stands. The large variation in symptomatology among stands in the midage class made accurate assessment of disease occurrence difficult at all scales used. Measurement of area within most disease centers in a stand using aerial photographs is probably feasible only in mature stands. Color photographs were superior to color-IR for detecting early foliage discoloration; the reverse was true when characterization of ground features and downed trees was desired. [Root diseases were caused by Armillaria ostoyae and Phellinus weirii].

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