Abstract
The present paper deals with the results of experiments on the pathogenicity of Pythium ultimum, Fusarium sp. and Rhizoctonia sp. to young seedlings of red pine (Pinus densiflora), black pine (Pinus thunbergii), Cryptomeria japonica and Chamaecyparis obtusa.
Among the three pathogenic fungi used, Rhizoctonia sp. revealed the strongest pathogenicity upon the germination of seeds and upon seedlings, showing the symptoms of so-called damping-off. Fusarium sp. has the weakest. All the fungi used have no invading power upon comparatively large seedlings which grew for three months after the germination.
Red pine seedlings were attacked severely, when they grew under moist condition. In wet condition of soil, Rhizoctonia gained ca. 90 per cent attack on seedlings. In dry condition, however, it showed only 19 per cent infection. In the same condition, Fusarium has no pathogenicity upon the seedlings of red pine.
