We report the finding of the disease of pear (Pyrus communis ‘Konferans’, ‘Abate Fetel’) and nashi trees (Pyrus pyrifolia ‘Hosui’) in the Soča river valley in the westernmost part of Slovenia (E:13.58844°, N: 46.04117°). On healthy and moribund branches of host trees, the fungus Septobasidium marianii Bres. was identified with morphological and molecular methods. In the basidiomes colonies of European pear scale (Epidiaspis leperii (Signoret 1869)) were observed. Mutualistic symbiosis formed by the fungus and the scale insects is explained and the characteristics of felt disease affecting host plants is described. Listed are the disease control measures recommended in the literature. The article is the first report of the occurrence of felt disease in Slovenia.