- Weber, Frederick P
Forest Service - U.S. Department of Agriculture
Since the beginning of the current spruce budworm (Choristoneura fuminferana (Clem.) infestation in norther Minnesota, over three-fourths of a million acres of white spruce (Picea glauca (Monech) Voss) and balsam fir (Abies balsmea (L.) Mill) type have received varying degrees of defoliation. This includes approximately 274,000 acres of severely defoliated stands, characterized by extensive top killing and tree mortality.
Early operation recorder surveys beginning in 1957 showed where the damage was occurring; however, operation recorder surveys provided information only on where the host type is, the degree of defoliation, and the location of dying tress. They do not tell the volume of timber that has been killed. To estimate the volume loss, a new type of survey was designed which incorporates both the operation recorder method and anew photo measurement method, supplemented by ground sampling. It was conducted in July 1962, and the results are presented in this note.