Abstract
Perennial canker due to Guignardia cryptomeriae, the casual fungus of Guignardia dieback, was first found on the stem of Cryptomeria japonica in Shimane Prefecture. The disease occurred in a 17-year-old Cryptomeria planted stand in Hasumi-mura. Frequency of infected trees was about 25% of all the trees examined at each middle and lower part of the slope and 3% at upper part. The canker lesions mainly expanded vertically in oblong shape around pruning scars. On the lesions, diameter growth was stopped because cambium was necrosed, and callus developed around them. The causal fungus, G. cryptomeriae, was isolated from stained xylem of the lesions. The sunken lesions were observed on the stem from the base to 4m above the ground and the xylem was stained to 6m. Diarrieter growth of the infected trees was extremely reduced in 1994 and stopped in 1995 on the lesions. Symptom of the disease, accordingly, was considered to develop between fall 1994 and 1995. The disease heavily occurred on trees on a steep slope in 35- and on gravel-mixed soil. Furthermore, drought was recorded in July and August in 1994. These ecological factors that caused water stress in Cryptomeria trees were supposed to predispose the trees to the disease.
