Abstract
In November 1998, powdery mildew was observed on African violet (Saintpaulia ionantha H. Wendl.) in Morioka, Japan. There are no descriptions of the symptoms of this disease on African violet and the morphology of this fungus in Japan. A white, powdery mycelial colony appeared on petals and flower stalks of the plant. Conidia with fibrosin bodies were cylindric to doliform, 24-43×14-22μm in size and born in chain on conidiophores. Germ tubes from conidia were straight or occasionally nippleshaped. No cleistothecia was observed on the diseased plant. From the morphology at the conidial stage, the fungus was identified to be a species of Oidium.
