• Karsh, M.B.
  Natural Resources Canada
  

A subset of 21 balsam fir abies balsamea mill. trees were completely re-measured from an existing database to determind the impact of eastern spruce budworm defoliation on tree growth. Reduction in growth were evident soon after the start of the infestation in 1971 but severe impacts were no observed until after 3 successive years of severe defoliation from 1975 to 1977. The budworm defoliation resulted in a 20% reduction in merchantable volume growth. The reduction in growth when combined with budworm related tree mortality was so severe in 29% of the pots that the stands were lost to production; i.e. there was less than 90% m3/ha merchantable volume on the site. The percentage of stands taken out of production may have been as high as 56% on less productive areas of the Island. There was an average of a 6-year increase in rotation length for budworm defoliated stands.