Ecological analysis of butt-rot disease of Japanese larch

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1. Three hundred and eleven larch stakes (3 x 3 x 45cm) were driven to a depth of 30cm below the ground at 5 x 5m intervals in an experimental area (0.9ha) at Kawakami University Forest, University of Tsukuba, and furthermore 3 quadrates 10 x 10m were designated and 102 stakes were driven at 2 x 2m intervals. Six months after the stakes had been placed they were removed, and their surface was examined by eye. Generally, the stakes with the mycelial strands of unidentified basidiomycetous fungus were distributed on a ridge of the area in groups. Occasionally, the fungus was found sporadically.2. All of the live larch trees (901 individuals) in the experimental ares were examined for the rot in their butts by lasing a Shigometer on November and December, 1989.Ninety seven larch trees of the 901 trees tested have been affected with butt-rot disease.The diseased trees were distributed on a ridge of the area in groups, but occasionally, the trees with butt-rot were found sporadically on a r … More idge. Our data suggested that the distribution of unidentified basidiomycetous fungus mentioned above may coincide the distribution of larch trees with butt-rot in the experiment area.3. Soils were collected from 42 spots in the experimental area in order to test soil water content, soil pH, etc. Our data show that high water content of soil (over 80%) and soil acidity (pH 4.6-4.8) may be related with the distribution of butt-rot fungi and lurch trees with butt-rot.4. Isolation of fungi from trunks of about 25 years old Japanese larch trees with butt-rot, planted in central Japan, were performed. Furthermore, fungal isolation was made systematically from trunks of larch treed infected artificially with a buut-rot fungus, Phaeolus scliweinitzii, and healthy larch trees. About twenty non-basidiomycetous fungi were isolated from the sound areas adjacent to wood with visible decay and also from areas with advanced decay of naturally infected larch trees. Coryne dubia and M-1 (un- identified non-basidiomycerous fungus) were mostly isolated iron healthy-slightly discolored areas adjacent to the decay. Coryne dubia and M-1 were also isolated from inoculated parts and healthy-slightly discolored areas of the inoculated larch trees. Inoculated fungus was reisolated from inoculated parts only. The fungus grew very slowly in the trunk of larch trees. Less