The teleomorph of Erysiphe takamatsui, a powdery mildew of lotus, was found in 2012 at a lotus pond of Niigata-shi, Japan, where this species was first found in 1974. This is the second record of teleomorph of E. takamatsui. Morphological and molecular analyses revealed that the asexual stages of the lotus powdery mildews found in Aichi, Osaka and Tokyo represent the anamorph of E. takamatsui. The nucleotide sequences of the internal transcribed spacer (ITS) and 28S rRNA gene were identical to those of E. aquilegiae, E. catalpae, and E. macleayae. These species formed a homogeneous clade together with E. sedi, Pseudoidium neolycopersici, and Pseudoidium spp. occurring on a wide range of plant families with only five base substitutions of ITS sequences in maximum. These results suggest that E. takamatsui is a fungus that appeared as a result of recent host expansion.