Carlson, Clinton E.; Pfister, Robert D.; Theroux, Leon J.; Fiedler, Carl E. Release 

 of a thinned budworm-infested Douglas-fir/ponderosa pine stand. Research 

 Paper INT-349. Ogden, UT: U.S. Department of Agriculture, Forest Service, 

 Intermountain Research Station; 1985. 8 p. 



Eighty-year-old Douglas-fir (Pseudotsuga menziesii) in a thinned stand of 

 mixed conifers in western Montana showed less impact due to defoliation by 

 western spruce budworm (Choristoneura occidentalis) than firs in an adjacent 

 unthinned stand. Radial growth of thinned fir increased 57 percent; ponderosa 

 pine (Pinus ponderosa), 38 percent; whereas unthinned fir grew very slowly. In 

 both stands, radial growth of pine increased substantially, even before thinning, 

 probably because defoliation weakened the competing fir. Thinning may reduce 

 budworm impact by increasing larval mortality, enhancing host tree growth, or 

 stimulating the tree's defensive chemistry. 



KEYWORDS: Choristoneura, budworm, silviculture, thinning, stand density, bud- 

 worm impact 



