Identification and Pathogenicity of the Fungus Isolated from Butt Rot of Japanese Cypress, Chamaecyparis obtusa

Butt rot of Japanese cypress, Chamaecyparis obtusa, in three 25-year-old stands with 178, 70 and 45 trees caused 69.1%, 75.7% and 76.1% of the respective stands to rot. In the field survey, corticioid basidiocarps with yellowish hymenia were sometimes observed on the cut ends of trunks and cut surface of stumps of C. obtusa and a few species of hardwoods. These basidiocarps were identified as Phlebia chrysocrea by morphological studies. The isolates were classified into six groups based on their colony characteristics. The basidiocarp isolates belonged to one of six groups. The isolates from C. obtusa proved to be P. chrysocrea by mating experiments. In inoculation experiments, P. chrysocrea was pathogenic to C. obtusa.