Mortalité du sapin baumier défolié par la tordeuse des bourgeons de l'épinette dans la région de la Gatineau au Québec

Abstract

This paper presents a method of analysis which differentiates between spruce budworm caused mortality and regular mortality on balsam fir in the Gatineau region in Quebec. A first attempt was made using multiple linear regression and a uniform random number generator. In order to overcome the bias inherent to the least squares method when dealing with a binary (0,1) dependent variable, a profit analysis was also conducted. In this case, the parameters and their variance were estimated using likehood method. These two approaches proved to be equivalent when percent budworm caused mortality was compared within the 1958 to 1979 period covered by the data at hand, while the outbreak lasted from 1968 to 1975.In 1979, approximately 55% of the stems had been killed by the budworm, accounting for 53% of the volume. Maple-yellow birch associations were more affected than fir associations although no significant difference was found. Fir mortality was delayed by aerial spraying of insecticides but this advantage disappeared as soon as the spray operations came to an end.

Wood losses and economical threshold of Btk aerial spray operation against spruce budworm

“…At the end of the study (2003), SBW killed 29% of balsam fir trees. These results were below the 55% mortality shown by Beaulieu and Hardy 42. For the period 1967–1975, Blais43 similarly found a high level of balsam fir tree mortality (44%) at the end of the last SBW outbreak in the Ottawa River watershed, but his result represented the average mortality for both coniferous and mixed stands.…”

Réduction de croissance en volume occasionnée au sapin baumier, suite à la défoliation par la tordeuse des bourgeons de l'épinette

“…communication personnelle, la mortalite du sapin baumier attribuable a la tordeuse totalisait en 1979, dans les 130 placettes 26,89 mslha, soit pres de 55% du volume potentiel total (Tableau 2). 11 est a noter que certaines de ces placettes ont fait I'objet de pulverisations aeriennes entre 1971 et 1974 mais cette variable n'a pas ete prise en consideration puisqu'il semble que I'effet global de ce traitement ait ete nu1 (Beaulieu et Hardy 1982 …”

Stand-level prediction of balsam fir mortality in relation to spruce budworm defoliation

“…defoliation can produce varying levels of mortality in stands dominated by its preferred host, balsam fir (Abies balsamea (L.) Mill.) (Belyea 1952;MacLean 1980;Beaulieu and Hardy 1982;Bergeron et al 1995;MacLean and MacKinnon 1997;Erdle and MacLean 1999). A reconstruction of the past spruce budworm epidemics since the mid 16th century in Quebec, Canada, suggests that outbreak frequency has remained quite stable, with a mean interval of about 40 years (Boulanger and Arseneault 2004).…”