Abstract
The scientific name, Uncinula Evonymi-Japonicae HARA(4) was given to the powdery mildew fungus of Evonymus japonictts THUNB. in 1921 by Hara. Later HINO(5) and KITAZIMA(8) reported respectively the impossibility to find the perithecia of this fungus and it was also in vain for the author to find them near the city of Fukuoka. It is a questiom how the fungus be possible to live. throughout the winter. The purpose of this paper is to find out the place of the hibernation of the mildew fungus and the form of tbe fungus at that time. The experimental results are as below:
(1) The perithecia were not found in any parts of the host plant.
(2) The conidia are ill-adapted to survive from one season to the next.
(3) The wind-borne conidia are unable to attack the old leaves when they become old.(Fig. 3, 4)
(4) The fungtis does not exist within the dormant buds with any forms.
(5) The first conidial formation in early spring is observed on tbe lesionsns of the preceding year's leaves and tbat after twenty days the first infection ocurs on the young emerged. 1eaves from dormat buds. (Fig. 1)
(6) Overwintering hyphae with haustoria are found on the lesions of the preceding year's 1eaves, which are capable to ovetwinter and to produce conidia in tbe next spring. (Fig. 9).
From this experimental results it is offered that the fungus overwinters on the lesions fo the preceding year's leaves of Evonymus japonicus (evergreen tree) ir the form Of the pecu1iar superficial mycdia with haustoria. Laboratory of Plant Pathology, Faculty of Agriculture, Kyushu University.
