• Witter, John A.
  United States Department of Agriculture, Forest Service, Cooperative State Research Service
  
• Lynch, Ann M.
  United States Department of Agriculture, Forest Service, Cooperative State Research Service
  

Numerous studies in Eastern North America during the last 40 years have recorded the amount of tree mortality in individual spruce fir stands during outbreaks of the spruce budworm (Witter et al. 1984). Mortality in mature balsam fir stands often ranges from 70 to 100 percent; in immature stands, mortality often ranges from 30-70 percent (MacLean 1980). However, mortality in an individual stand can be less.