Climate Factors Associated with Historic Spruce Beetle (Coleoptera: Curculionidae) Outbreaks in Utah and Colorado
This study investigated relationships between climate and historic spruce beetle, Dendroctonus rufipennis Kirby (Coleoptera: Curculionidae), outbreaks in northern and southeastern Utah and western Colorado between 1905 and 1996. A chronology of outbreak years was constructed from historic records, research papers, newspapers, and other sources of information. Historic climate data for the region included annual and mean monthly temperature and precipitation, in addition to Palmer drought
... lmer drought severity index (PDSI) values estimated from tree rings. ClassiÞcation and regression tree analysis (CART) was used to identify those climate factors most important for predicting historic spruce beetle outbreaks. The factors identiÞed by the best CART model included mean December temperature, mean September temperature 1 yr before outbreak years, the mean estimated PDSI value of the 5-yr period before outbreak years, and mean October precipitation. The resulting model correctly classiÞed nonoutbreak and outbreak years 67 and 70% of the time, respectively. a t, observed year; t-1, lagged 1 yr before observed year; A, average of the no. of years indicated before the observed year. 286 ENVIRONMENTAL ENTOMOLOGY Vol. 37, no. 2 lation suppression in northern Utah. Wes. J. Appl. For. 15: 122Ð128. Bentz, B. J., J. A. Logan, and G. D. Amman. 1991. Temperature-dependent development of the mountain pine beetle (Coleoptera: Scolytidae) and simulation of its phenology. Can. Entomol. 123: 1083Ð1094. Berg, E. 1999. Climate change on the Kenai Peninsula. USDI Fish and Wildlife Service, Alaska, Soldotna, AK. Ext. Rep. Version 1.22. Blackman, M. W. 1924. The effect of deÞciency and excess in rainfall upon the hickory bark beetle. J. Econ. Entomol. 17: 460 Ð 470.