Dwarf mistletoe infection centers 1/10 acre in size were visible on infrared color film at scales as small as 1:118,000. Detection of 1/10 acre centers was easily accomplished at scales of 1:31,680. Individual aspen trees killed by the hypoxylon fungus were detected with relative ease at scales of 1:6,000. Armillary root rot in red pine was detectable only after the trees had died and the foliage had turned from green to brown.
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