Abstract
In autumn of 1972, a severe case of rust caused by Coleosporium xanthoxyli DIETEL et P. SYDOW was found on leaves of Fagara ailanthoides ENGL. at Asakawa, Tokyo. To identify the aecial stage of the fungus, needles of several pine species were inoculated with the sporidia from teliospores formed on Fagara ailanthoides. Immature spermogonia began to develop only on the needles of Pinus thunbergii about two months after inoculation. They overwintered on the needles and matured in the next spring. From mid April through early May abundant aeciospores were produced on them. No signs of infection were observed in the other pine species tested. Fresh urediniospores were produced only on the leaves of F. ailanthoides inoculated with aeciospores formed on P. thunbergii or urediniospores formed on F. ailanthoides, after two weeks incubation. Teliospores appeared on the same leaves about a month after inoculation. No signs of infection were observed on leaves of Fagara shinifolia, Xanthoxylum piperitum and X. planispinum. A life cycle of the fungus was determined from the results of field observation and inoculation experiments, and its aecial stage was newly described.
