• CANUSA
  

The western spruce budworm was first reported in the Northern Regions in the early 1920's. Only scattered and insignificant infestations were reported from time to time for the next 30 years, although outbreaks occurred over large areas in two northern Idaho National Forests to the early 1930's, and small outbreaks persisted until the early 1950's on one or two Ranger Districts east of the Continental Divide in western Montana. The first significant outbreak in the Northern Region began about 1948, reached two million acres by 1952, and has persisted until now, fluctuating between two and four million acres infested per year. The gross infested acreage during the 30-year period exceeds ten million acres.