Spruce Budworm Damage Symptoms Related to Radial Growth of Grand Fir, Douglas-Fir, and Engelmann Spruce
External damage symptoms in Abies grandis Dougl. (Lindl.), Pseudotsuga menziesii (Mirb.) Franco and Picea engelmannii Parry subjected to defoliation by the spruce budworm are described by four damage classes based upon the amount of dead branches and twigs, and the extent of top killing seen in the crowns. Radial growth before and during a 1944-1956 infestation was determined by analysis of sample disks. Graphical, covariance, and multiple-range tests showed that damage symptoms were related to reductions in radial increment. Reduction in radial increment generally differed significantly between damage classes. Radial increment varied along the tree boles; the greatest reductions occurred at midcrown and the least near the ground. Top killing occurred often among moderately damaged trees, particularly in grand fir. The study suggests that crown vigor symptoms, can be grouped into several classes suitable for use in damage surveys.
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Document Type: Journal Article
Research Entomologist, Pacific Southwest Forest and Range Expt. Sta., Forest Service, U.S. Dept. Agric., Berkeley, Calif., was Research Forester, Pacific Northwest Forest and Range Expt. Sta., Portland, Oreg.
Publication date: 01 September 1967