In autumun 1997 powdery mildew of perennial statice was found in Mie and Oita prefecture, Japan. Many white, powdery mycelial colonies appeared on leaves, stems and branches of the plants. The fungus successfully caused disease on perennial statice after artificial inoculation, but not on Limonium sinuatum. Conidia were cylindrical, (29-) 36-54 (-62)×14-20μm in size, formed singly on conidiophores straightly erected on the aerial mycelia. Lobed appressoria differentiated on the germ tubes from conidia. No cleistothecia were observed. On the basis of morphological characters of the conidial stage, the fungus was found to be an Oidium sp. of the Erysiphe polygoni type.