Stand Ratings for Spruce Beetles
Engelmann spruce-subalpine fir stands can be rated for potential spruce beetle outbreaks o the basis of physiographic location, tree diameter, basal area, and percentage of spruce in the canopy.
Schmid, J. and Frye, R. (1976). Stand ratings for spruce beetles. USDA Forest Service, Rocky Mountain Research Station, Research Paper RM-309, 4 pp.