Equipment trials for uprooting root-rot-infected stumps.
Residual roots from Douglas fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) were measured following stump-root extraction one yr after harvesting a 55-yr-old, 314 stems/ha, 47% Douglas fir, 17% maple (Acer macrophyllum), 16% red cedar (Thuja plicata), 6% western hemlock stand with 20% infection by Phellinus weirii in the Cowichan valley, Vancouver Island, Canada. Extraction was by a Caterpillar D8H with brush-clearing blade, a 180-hp backhoe or a 115-hp backhoe. All 3 machines recovered more than 90% of root vol. The small backhoe left significantly greater numbers and lengths of root residues per m3 soil, though the vol. of residues was greatest for the Caterpillar. An earlier study suggested that a root density of 32 roots/m3 was needed to produce one root contact; as the least efficient treatment by the Caterpillar left 23.2 roots/m3 in the ground, it is suggested that this would provide insufficient contacts with a new tree crop to transmit infection.