Spruce Budworms Handbook: Regional Climatic Patterns and Western Spruce Budworm Outbreaks

摘要

To determine if the frequency of outbreaks of western spruce budworm (Choristoneura occidentalis) was related to selected climatic variables in Idaho, Montana, Oregon and Washington, defoliation histories were collected for a sample of 43 points across the four states. Three broad regional compartments of differing outbreak frequencies were identified. Mean maximum and minimum temperatures for January and July, as well as mean annual precipitation data, were collected from a four-State, stratified sample of 169 points where susceptible hosts occurred. Significant differences in climate were found among the three classes of outbreak frequencies identified.