A comparison of mountain pine beetle (Coleoptera: Curculionidae, Scolytinae) productivity and survival in lodgepole and whitebark pine after a region-wide cold weather event

Warming has allowed mountain pine beetle (Dendroctonus ponderosae Hopkins) to move higher in elevation and cause extensive mortality of whitebark pine (Pinus albicaulis Engelm.). Although mountain pine beetle prefers whitebark pine to its historic host, lodgepole pine (Pinus contorta Douglas ex Louden), it is not known whether the two host trees differentially affect the beetle. We compared emergence rates of the beetle in both species by monitoring numbers of beetles attacking and brood emerging from whitebark and lodgepole pines growing in mixed stands experiencing an ongoing beetle outbreak. We measured sizes of the emerging beetles. During the study, most beetles at our study sites died. A combined phenology/cold tolerance model driven by local temperatures indicated that cold weather events probably caused this mortality. The mortality events offered a unique opportunity to assess how cold weather events interact with the tree host to affect beetle emergence rates and survival. The numbers of beetles emerging from the two tree species after the cold events did not differ. Relative to attack densities, beetle emergence rates from whitebark pine were significantly higher and more beetles emerged from small diameter whitebark pine than from similar sized lodgepole pine. We found no difference in sizes of beetles emerging from the two species.