Uprooting and trenching to control annosus root disease in a developed recreation site: 12- year results
Six annosus (Heterobasidion annosum) root disease centers in a proposed campground on the north shore of Big Bear Lake in southern California were treated in 1989. Trees, stumps, and roots were removed in six disease centers, and in two cases, soil trenching was used to stop the progress of the disease. A total of 154 trees and 26 stumps were removed; 300 linear feet of trenching was done around two disease centers. Of 101 trees sampled, 47% were infected with H. annosum. Sixteen percent of infected trees exhibited no visible crown symptoms. The pathogen was isolated from 50% of roots that showed resinosis and 14% of roots not exhibiting resinosis. Only the P biological species was present on living, infected Jefrey pine and juniper roots. Twelve years after treatment, all six sites appear to be disease free with no aboveground symptoms of root infection. Tree mortality is continuing on untreated disease centers in this recreation area.