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During outbreaks the mountain pine beetle (Dendroctonus ponderosae Hopkins) kills large lodgepole pine trees (Pinus contorta Dougl. ex Loud.) more frequently than smaller ones. There is, however, considerable variation in the relation of diameter to incidence of attack. In a meta-analysis of published data we found that the relationship was primarily determined by geographic location (elevation, latitude, and longitude). We propose a new tree mortality measure, the probability of death index, defined as the average percentage of mortality for trees >23 cm. The index may improve the precision in predictive modeling of tree mortality, as it provides a biologically relevant measure of mortality, since it only includes trees that contribute to the growth of an epidemic and is not influenced by the number of trees within a diameter class. To be useful to forest managers, it must be possible to predict the index from stand parameters that are easily measured. The usefulness of the index was supported by a meta-analysis, which showed that 53% of the variation in the mortality index was explained by geographic location. Tree density did not explain any additional variation. Future research is needed to evaluate the performance of the probability of death index compared with that of other mortality measures. [ABSTRACT FROM AUTHOR]

Abstract: Stand-level planning of lodgepole pine management can benefit from the use of mountain pine beetle susceptibility-risk model analyses to assign treatment priority. Priority is currently assigned based solely on relative levels of expected volume loss in the event of a mountain pine beetle outbreak. We evaluated the possibility to predict the relative contribution of brood beetles, by infested stands, to the next beetle generation. Existing data were used to develop generalized parameters for inclusion in predictive models of stand-level mortality and brood production. Model output for independent stands achieved a highly significant relationship with measured outcomes of brood productivity, indicating that relative levels of brood production can be predicted and incorporated into decision-models. [Copyright &y& Elsevier]

A diameter distribution survey at three sites in the interior of British Columbia revealed that the western balsam bark beetle (Dryocoetes confusus Swaine) predominately attacked trees from the three to four largest diameter classes at each site. However, the mean diameter of attacked trees was significantly different among sites, indicating that factors other than diameter contribute to the susceptibility of subalpine fir (Abies lasiocarpa (Hook.) Nutt.) to the western balsam bark beetle. A number of tree characteristics, including measures of growth, age, crown size, and phloem thickness, were compared among a total of 22 successfully attacked, 26 unsuccessfully attacked, and 28 unattacked trees at three sites. Of the 12 tree characteristics measured, five showed significant differences between successfully attacked and unattacked trees. Successfully attacked trees had a lower percentage of the bole covered with constant crown, lower crown volume, lower radial growth in the last 5 years, and were older than unattacked trees. Successfully attacked trees also produced less induced resinosis than unsuccessfully attacked trees. The results of this study suggest that western balsam bark beetle mortality may be limited by the presence and distribution of susceptible hosts. The study also identifies a number of variables that could be used in a susceptibility and risk rating model for western balsam bark beetle. [ABSTRACT FROM AUTHOR]

A survey in a lodgepole pine, Pinus contorta var. latifolia Engelm.,provenance trial showed that the western pine moth, Dioryctria cambiicola (Dyar) (Lepidoptera: Pyralidae), was the most prevalent pitch moth, and stalactiform blister rust, Cronartium coleosporioides Arth.,the most prevalent stem rust. Also present were the Douglas-fir pitch moth, Synanthedon novaroensis (Hy. Edwards) (Lepidoptera: Sesiidae), comandra blister rust, Cronartium comandrae Pk., and western gall rust, Endocronartium harknessii J.P. Moore, and the stem canker Atropellis piniphila (Weir). Results from a likelihood ratio test indicatedan association of western pine moth with stalactiform blister rust and of Douglas-fir pitch moth with both western gall rust and stalactiform blister rust. Western pine moth attacks are most commonly found along the active edge of stalactiform blister rust cankers, suggesting that the moth larvae derive some specific benefit from the fungus. The association of Douglas-fir pitch moth with the rusts appear to bea result of the physical wounding caused by the fungi, since attacksby this pitch moth are also frequently found at pruning wounds or other injuries. [ABSTRACT FROM AUTHOR]