Evaluation of the Douglas-fir beetle along the North Fork of the Shoshone River and the Clarks Fork of the Yellowstone River, Shoshone National Forest, Wyoming

Douglas-fir beetle (Dendroctonus pseudotsugae) infestations frequently result from disturbance events that create large volumes of weakened Douglas-fir (Pseudotsuga menziesii) trees in the vicinity of susceptible stands. In 1988, extensive wildfires occurred in Yellowstone National Park and the Shoshone National Forest. Populations of Douglas-fir beetle increased in the fire-scorched trees. Subsequent generations of the beetles moved from these injured trees to undamaged trees in neighboring stands on the Shoshone National Forest, Wyoming. This outbreak has moved from the Clarks Fork/Sunlight Basin area and now affects almost the entire drainage west of Cody along the North Fork of the Shoshone River. Beetle populations have erupted in the past few years within the large expanse of susceptible forest, killing many tens of thousands of Douglas-firs. Mortality evident in 2002 from beetle attacks in 2001 was far more extensive and intense than at any time since the current outbreak began. Brood sampling indicates another year of strong increase in the Douglas-fir beetle population. Because the current outbreak will continue to expand and intensify, continued high levels of mortality can be expected along the North Fork. Deployment of anti-aggregation pheromone has successfully protected three US Forest Service campgrounds for three years. Continued use of anti-aggregation pheromones and, where possible, sanitation harvest is recommended. Long-term planning and public education with respect to this large scale change in the forest is advised.