Abstract: The powdery mildew,caused by Uncimdiella australiana,occurs commonly on Lagerstroemia indica in Kunming.The fungus chiefly attacks the shoots,young leaves and flowers,causing a spotting of the leaves,and occasionally defoliation and fall of the flowers.This article deals with the disease cycle of this mildew in Kunming.Preliminary results are presented of studies on this disease in 1982.The environmental factors which affect the outbreak and development of the mildew are discussed.The morphological characteristics of the conidial stage of this mildew are described.It has not been reported in our country.The authors have found that this mildew is also parasitized not uncommonly by Cicinnobolus cesatii de Bary which sometimes aids in checking it.