Biology and Control of the Engelmann Spruce Beetle in Colorado

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The Engelmann spruce beetle (Dendroctonus engelmanni Hopk.) is the most serious pest of the Engelmann spruce forests in the United States. From time to time epidemics of the insect have destroyed this spruce over large areas, especially in the Rock Mountain region (fig. 1). Damage by the beetle was reported as early as 1898, when Sudworth (4, p. 137)1a reported that 10 to 25 percent of the spruce on the White River National Forest, Colo., had been destroyed, supposedly by climatic factors. The timber he observed was later examined by entomologists and the death of the trees was attributed to the Engelmann spruce beetle. The species was described by Hopkins in 1909 (1). He reported that approximately 90 percent of the spruce in the White Mountains of the Lincoln National Forest in New Mexico was killed by the insect, and found evidence of beetle damage that had occurred 50 years earlier on the Pike National Forest in Colorado (2).


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