ROOT WOUNDS AND ASSOCIATED ROOT ROTS OF WHITE SPRUCE

The root systems of 656 trees from 7 to 180 years old at three locations in Manitoba and Saskatchewan were examined for wounding and root rot. Twenty-seven per cent of 1170 diseased roots bore wounds caused by Hylobius spp. larvae which were associated with the entry of root-rotting or staining fungi. The fungi appeared to have entered mainly through insect-girdled roots, one-half inch in diameter or smaller, and to a less extent directly through the decorticated wood of larger roots. In individual trees, root rot and stain was highly correlated (r = 0.5357) with Hylobius wounding. Wounds caused by excessive moisture, root compression, and animal trampling were associated with the entrance of fungi in 7.1, 4.7, and 1.5 per cent, respectively, of the diseased roots. Eight per cent of the diseased roots were infected from established decay in the root crown. Root cankers and dead root ends, both of unknown cause, were associated with the entry of root fungi in 7.3 and 5.7 per cent of the roots respectively.