An attempt was made to restrict the aerial distribution of Fomes annosus (now Heterobasidion annosum) through the cut surfaces of spruce stumps by inoculating the surfaces, immediately after felling, with mycelial suspension, grown in the laboratory on malt agar, of Fomes pinicola, Lenzites sepiaria, Peniophora gigantea (now Phlebiopsis gigantea), Polyporus abietinus and Trichoderma viride. Trees were felled once a month for a year. Samples were taken from the cut surfaces of the stumps approximately one year after the felling and the inoculation.
P. gigantea inhibited the infection of cut stump surfaces by airborne F. annosus. P. gigantea cut down both the total number and the number of the species of fungi infecting the stump through aerial distribution. T. viride had a parallel but less marked effect. F. pinicola, L. sepiaria and P. abietinus proved to be weak colonizers of spruce stumps. When they were used to inoculate the stumps, the number of fungi infecting the cut surfaces was larger than that infecting the stumps treated with P. gigantea and T. Viride. A year after the inoculation some stumps were excavated with their roots. Fungi from the discoloured spots of wood in the stumps were cultured for identification. It was found that many different fungal species from the soil and the points of root grafting had infected the roots of the stump in the course of the year. The majority of the identified microbes were non-Basidiomycetes fungi, and bacteria.
A year after the felling and inoculation, a white mycelial sheet was seen between the wood and bark of many stumps. Several fungi, including Armillaria mellea, Trichoderma viride, Penicillium species, and Peniophora gigantea were isolated from this sheet.
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