Factors Affecting Spruce Beetles during a Small Outbreak
- 1 September 1972
- Vol. 53 (5) , 830-839
- https://doi.org/10.2307/1934298
Abstract
In 1957, spruce beetles, Dendroctonus rufipennis developed into outbreak numbers in logging slash at a north—central Colorado site, entered living spruce trees, but remaining epidemic for only two years. Reduced beetle fecundity was the first indication of outbreak decline; this was caused by nematodes and unknown agents. Significant summer mortality agents were pitch, intra— and interspecific competition for food, predation by woodpeckers and flies, and parasitism by wasps. Desiccation of both food and beetle larvae, enhanced by woodpecker feeding activity, contributed significantly to outbreak decline. Winter mortality was attributed mainly to woodpeckers, although temperature of —29°C caused additional losses. The effects of the outbreak on the spruce were considerable. Large diameter trees in small patches were killed, and species composition was altered in favor of subalpine fir and lodgepole pine, but mean tree diameter was not significantly reduced.Keywords
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