A new record of the powdery mildew Phyllactinia chubutiana, nom. cons. (= Oidium insolitum, Ovulariopsis insolita) was documented on pearl berry [Vallesia glabra (Cav.) Link]. No teleomorph was observed. This novel record was identified as a member of Ovulariopsis, based on the morphological characteristics of the anamorph (hyphae, conidiophores, and conidia), and its hemi-endophytic mycelium in V. glabra correspond to P. chubutiana, nom. cons. A Phyllactinia-specific primer pair was designed for the ITS region of the nuclear rDNA. Phylogenetic analyses confirmed the identity of the powdery mildew specimens found in V. glabra in Sinaloa, Mexico. This is the first ever report of this powdery mildew in V. glabra, and the second report world-wide on a member of the Apocynaceae.