Occurrence and life-history of pink disease caused by Erythricium salmonicolor in northern Kanto, Honshu, Japan

Since 1989, a serious concentrated occurrence of pink disease caused by Erythricium salmonicolor (BERKELEY et BROOME) BURDSALL has been observed in an arboretum of Gumma Forest Experiment Station, where is the most northeastern place of the disease occurrence in Japan. A total of 25 tree species of 19 genera belonging to 15 families have been infested. Mycelial mat and hymenium producing basidiospores are formed on stem lesions, from June to September, in this place, in contrast with the tropics, where they are formed throughout the year. Mycelial mat and hymenium gradually disappear in October on most of infected lesions. On concave parts of the bark of highly susceptible species, for instance Ginkgo biloba, Fraxinus excelsior, etc., small ,and white mycelial masses of the fungus are formed and overwintered to the next June. In early June, new and thin mycelial mat extended from the mycelial masses, then, hymenia and basidiospores were produced and began to disseminate by wind. This seems to be the characteristic overwintering procedure of the fungus in temperate regions having cold winter season. Optimum temperature range for the germination of basidiospores on Ginkgo biloba was from 20 to 25 degrees C. All isolates of the causal fungus obtained from 9 different host trees showed the same mycelial growth pattern having the best at 25 degrees C among various temperatures. Generally, the tropical isolates of the present species has the optimal temperature range from 28 to 30 degrees C for their mycelial growth. From the facts mentioned above, it is presumed that the pink disease fungus originated from the tropics adapts itself to the cool temperate region in its characterized life-history and relatively low temperature activity