• Hamel, L.
  Laval University
  

The characterization of the vegetation found in seven epicenters where the current spruce budworm outbreak got underway in Quebec has allowed for the elaboration of new concepts on the epidemiology of the spruce budworm. The epicenters were found to be mostly covered with mixwood stands and the presence of meridional species such as sugar maple, yellow birch, and white pine was common to every epicenter. Softwood stands occupied less than 30 percent of the cover and the most common age class of the host species, balsam fir and white spruce, was 50. Moreover, every epicenter had been subjected to some ecological perturbation that resulted in the presence of pioneer species which in turn seem to exert an influence upon the abundance of the host species. Applied to the current outbreak, the concept of zones of abundance stated by Cook indicated that the outbreak developed in a concentric manner with differential periods of occupation, which in turn could affect the control strategies commonly in use against this insect.