• Morris, R.F.
  
• Webb, E.
  
• Bennett, C.W.
  

To ensure correct sequence in the timing of insect sampling or control operations over a large forest area it is desirable to know what phenological differences may be expected. Measurements of shot elongation provide a simple and objective method for comparing a large number of phenological stations in one season. By this method one or more reference stations have to be visited weekly to permit the plotting of growth curves but the great majority of the stations have to be visited only twice a year. At any one station the major source of variance in cumulative shoot growth on a given date is between trees and the optimum allocation of sampling resources will usually be based on the selection of one shoot per tree and 10 or more trees of balsam fir per station. The variance is greater for cherry and larger samples are necessary.