Abstract This paper reports the relationship of site quality, crown closure, and percent Douglas-fir (Pseudotsuga menziesii Mirb. Franco) to defoliation caused by spruce budworm (Choristoneura fumiferana Clem.) on a western Montana forest. Significantly less defoliation was observed on moist bottomland sites than on drier hillsides. Open stands, and stands with low percentage of Douglas-fir also incurred considerably less defoliation than did dense stands and stands composed mostly of Douglas-fir. Silvicultural control of budworm defoliation seems unfeasible on the area studied. Defoliation on good quality sites is not severe enough to warrant such control measures; on poor sites, only undesirably low-stocking levels, or low percentages of Douglas-fir would create a condition having low defoliation risk.
Fauss et al. (Thu,) studied this question.
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