A pathological study of the bacterial tree diseases found in Hokkaido, northern Japan

A new disease of Maackia amurensis var.buergeri was identified in Hokkaido. Affected trees were heavily damaged and had cankers on trunks and branches. The pathogen was isolated and characterized as Pseudomonas syringae. Inoculation tests confirmed its pathogenicity to the host. Hence, the disease was designated as a "bacterial canker of M. amuraensis var. buergeri" caused by P.syringae. Anatomical observations to elucidate the process of the canker formation were carried out. The initial symptoms included a longitudinal series of swellings and slightly swollen bark. First, abnormalities appeared near the cambial zone. Xylem formation was suppressed, hyperplasia of irregular ray parenchyma cells occurred, then the swellings appeared. The irregular cells increased in number; after that, the surface of the swollen bark burst open. The ruptured swellings coalesced to form long irregular cankers.