Spruce Budworm Outbreaks in the Past Three Centuries in the Laurentide Park, Quebec

Abstract

Abstract The history of spruce budworm outbreaks for the past three centuries in the Laurentide Park region of Quebec was determined through radial-growth studies of basal discs from budworm-host and non-host trees collected from 102 locations. Evidence was obtained of six past outbreaks beginning about 1704, 1748, 1808, 1834, 1910 and 1947 respectively; hitherto only the last two were documented for this area. The outbreaks of 1704 and 1748 are the oldest recorded to date in any region. The time intervals between outbreaks shows that, in the past, budworm gradations recurred at irregular intervals. More recent outbreaks have apparently been more severe than those prior to 1900; increase of balsam fir at the expense of spruce after clearcutting may account for this situation. The last four outbreaks that occurred in the Park were also recorded in certain other regions in eastern Canada, but at least two were less severe in the Park than elsewhere. In the past 200 years, two major outbreaks took place in southeastern Quebec and in adjoining regions in Maine and New Brunswick that did not occur in the Laurentide Park. It is postulated that spruce-fir stands in the study area appear to be less susceptible and less vulnerable to budworm attack than in other areas; reasons for this are discussed.