Recurrence of Spruce Budworm Outbreaks for Two Hundred Years in Western Quebec

The history of spruce bubworm (Choristoneura fumiferana (Clem.)) outbreaks for the past two hundred years in the Ottawa River Valley in Quebec was retraced through radial-growth studies on old white spruce (Picea glauca (Moench)) and black spruce (Picea mariana (Mill.) B.S.P.) trees. The radial-growth profiles clearly indicate three suppression periods resulting from outbreaks that occurred in the twentieth century, each starting about 1910, 1940 and 1967. There is no evidence of an outbreak during the nineteenth century in this region. However, a reduction in radial-growth starting in 1783 observed on the only three specimens of white spruce over 200 years old, has the characteristics of that caused by a budworm outbreak. An interval of 127 years between this and the 1910 outbreak is similar to other long intervals between outbreaks recorded prior to the twentieth century for some other regions in eastern Canada.