Trunk sap rot of Japanese cedar (Cryptomeria japonica) caused by Fomitiporella sinica

Trunk rot caused by the wood decay fungus Fomitiporia torreyae is a serious disease of Japanese cedar. The rot is characterized by white sap rot with brown zone lines and vertical depressions on the trunk. During our field investigations on this disease, we found another sap rot on Japanese cedar, characterized by white rot with brown zone lines, with or without less obvious depressions on the trunk. The results of phylogenetic analysis of the most frequently isolated fungus from the diseased trees and morphological observation of basidiocarps previously identified as Fomitiporella umbrinella showed that both represented Fomitiporella sinica. Our inoculation tests using Japanese cedar showed that F. sinica caused longer discoloration in sapwood compared with control treatment. Therefore, we concluded that F. sinica was the cause of trunk rot on Japanese cedar as reported for F. torreyae, but trunk depressions were not obvious in the trees infected with F. sinica. Moreover, branch scars were found around the middle of decaying parts of diseased trees infected with F. sinica, and infection with this fungus was assumed to occur via dead branches or pruning scars.