Insects of whitebark pine with emphasis on mountain pine beetle

Few insects that live on whitebark pine (Pinus albicaulis) are considered pests or potential pests. Those that inhabit cones can cause reductions in reproduction of the tree by destroying seed crops. Decreases in food for animals ranging from squirrels to grizzly bears may also result. A single insect species, mountain pine beetle (Dendroctonus ponderosae) (MPB), may cause serious damage to whitebark pine over much of its range by killing mature trees. Through periodic epidemic outbreaks, the resultant tree killing causes reductions in seed cones and so decreases food supplies for various animals. Excessive mortality of whitebark pine can lead to increases in other tree species, and decreases in whitebark pine, in some future stands. A survey of MPB damage in the whitebark pine zone was conducted in Yellowstone National Park, Gallatin National Forest, and Flathead National Forest from 1983 to 1988. Preliminary results show 22 to 44 percent of the whitebark pine had been killed by MPB during the recent past. Losses were strongly related to elevation-decreasing mortality with increasing elevation. Losses were heaviest in the lodgepole pine-whitebark pine ecotone. Implications of such losses are discussed.