Canadian Forest Service Publications
Tree-ring growth of interior Douglas-fir after one year's defoliation by Douglas-fir tussock moth. 1991. Alfaro, R.I.; Shepherd, R.F. Forest Science 37(3): 959-964.
Issued by: Pacific Forestry Centre
Catalog ID: 3069
Availability: PDF (request by e-mail)
Reductions in ring width of Douglas-fir, Pseudotsuga menziesii [Mirb.] Franco, trees defoliated for 1 year by the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), are reported. Trees were treated with a nuclear polyhedrosis virus, but the resultant epizootic which killed larvae and reduced defoliation took several weeks to develop and trees sustained varying degrees of damage. No negative effects of defoliation were noted in the year when feeding took place; on the contrary, a growth stimulation occurred. Defoliation levels above 50% resulted in growth reduction for 2 years following defoliation relative to nondefoliated trees. The implications of these growth changes for cost/benefit analysis of control options are discussed.