• Mott, D.G.
  Fredricton Forest Biology Laboratory
  
• Nairn, L. D.
  Winnipeg Forest Biology Lab
  
• Cook, J. A.
  Calgary Forest Biology Lab
  

It is well recognized that radial growth in forest trees is influences by many factors, including climatic fluctuations, site, variable stand conditions, and defoliation. Severe or prolonged insect defoliation may cause modifications of the normal ring pattern that are useful in assessing the risk of imminent mortality and the need for control action. If old surviving trees are available, the modified ring patterns may be used in the reconstruction of outbreak histories many decades after the event (Swaine and Craighead, 1924; Blais 1954). critical cross-dating techniques are available for assigning year dates to ring sequences from dead trees (Ghent, 1952.)