This is an introductory paper on the outbreak of Scleroderris canker of Todo‐fir (Abies sacbalisnensis Mast.) in Hokkaido, northern Japan. Symptoms, distribution of the disease, and features of infected plantations are described. The variability of disease intensity is also described.
Ascospore and pycnospore discharge and germination were examined. The causal fungus was psychrophilic, with an optimum growing temperature of 10 °C. Pathogenicity to Abies sachalinensis was ascertained by artificial inoculation, and symptoms were induced also by spraying a pyenospore suspension on to untreated shoots.
Climatic data during the past six years associated with the outbreak of Scleroderris canker in 1970 were analyzed. Exceptionally low air temperatures from late September to early October 1969, and a subsequent long period of deep snow were considered the main factors favouring the outbreak of the canker.-ur.
The first symptom of canker on Todo‐fir appears in spring, although infection of current year shoots by spores must be established early in the growing season of the previous year. Isolation experiments demonstrated the presence of dormant infection of the causal fungus in the shoots and invasion of new bark tissues under snow cover during the winter.
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