Pacific Southwest

Title: Impact of Precommercial Thinning on Development of Heterobasidion annosum in Western Hemlock

Author: Edmonds, Robert L.; Shaw, David C.; Hsiang, Tom; Driver, Charles H.

Date: 1989

Source: In: Otrosina, William J.; Scharpf, Robert F., technical coordinators. 1989. Proceedings of the symposium on research and management of annosus root disease (Heterobasidion annosum) in western North America; April 18-21, 1989; Monterey, CA. Gen. Tech. Rep. PSW-GTR-116. Berkeley, CA: Pacific Southwest Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture; p. 85-94

Station ID: GTR-PSW-116

Description: The impact of precommercial thinning of western hemlock (Tsuga heterophylla) on the development of Annosus root and butt rot (caused by Heterobasidion annosum) in coastal Washington has been followed for more than 20 years. Infection of stumps and wounds was high following thinning and there was a high probability of residual tree infection. Eleven years after precommercial thinning tree infection was high, but after 20 years levels of infection were low in both thinned and unthinned stands (averaging <5 percent). Volume losses were even lower (<1 percent). Host tree defense mechanisms, including wetwood, appear to be effective in minimizing losses due to H. annosum. Precommercial thinning did not appreciably increase the incidence of H.annosum in the current rotation but problems could occur in future rotations. Borax treatment of precommercially thinned stumps was not effective in reducing the incidence of H. annosum.

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Citation

Edmonds, Robert L.; Shaw, David C.; Hsiang, Tom; Driver, Charles H.  1989.  Impact of Precommercial Thinning on Development of Heterobasidion annosum in Western Hemlock .   In: Otrosina, William J.; Scharpf, Robert F., technical coordinators. 1989. Proceedings of the symposium on research and management of annosus root disease (Heterobasidion annosum) in western North America; April 18-21, 1989; Monterey, CA. Gen. Tech. Rep. PSW-GTR-116. Berkeley, CA: Pacific Southwest Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture; p. 85-94.