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Evaluation of Douglas-fir beetle infestations, North Fork Clearwater River Drainage, Idaho, 1974 Public Deposited
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Douglas-fir beetle, Dendroctonus pseudotsugae Hopk., has caused extensive tree mortality in the North Fork Clearwater River drainage since 1971. In 1974, survey estimates indicated a continued decline in the infestation. Average group size decreased from a high of 158 trees per group in 1971 to 17 in 1974. Average area occupied by each group declined from a high of 4.1 acres per group in 1972 to 0.65 acre in 1974. Attack densities decreased; however, brood-to-parent ratios increased. Natural enemies are having a limited impact on population densities. Availability of susceptible host material may be the primary limiting factor on increased infestation potential. Continued salvage logging of infested trees and susceptible stands is encouraged.
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