Decay in white fir top-killed by Douglas-fir tussock moth.

Abstract

Stands heavily defoliated in 1936-37 by the Douglas-fir tussock moth, Hemerocampa pseudotsugata McD., at Mammoth Lakes, California, were studied to determine the incidence and extent of decay in top-damaged trees. This was done by dissecting the tops of trees felled during logging. Comparisons were made with white fir in a nearby logged area that was not defoliated during the old outbreak. Few decay organisms were isolated from trees top-killed by Douglas-fir tussock moth. However, old top damage and a condition known as wetwood were common in the infested area. Wetwood was found in 17 of 21 top-damaged trees in the infested area and in one of 50 trees in the uninfested area. We conclude, therefore, that in eastside Sierra Nevada white fir stands, the threat of defect is not economically serious in large trees that will be logged within 35-40 years after top damage.

Citation

Wickman, Boyd E.; Scharpf, Robert F. 1972. Decay in white fir top-killed by Douglas-fir tussock moth. Res. Pap. PNW-RP-133. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 12 p