The First Record and Characterization of Powdery Mildew (Erysiphe pachypodiae sp. nov.) on Pachypodium lamerei (Apocynaceae)

During the summer and autumn of 1999, symptoms of powdery mildew disease were first observed on Pachypodium lamerei in the Czech Republic. White lesions of irregular shape appeared on leaf margins and spread towards the central vein of the leaf, often followed by necrosis of leaf tissue. In the spring of 2000, the sexual stage (cleistothecia) also appeared on infected leaves. Based on the observations of the morphology of its anamorph and teleomorph stage as well as on results from inoculation experiments, the identity and origin of this powdery mildew species are discussed. Based on the pseudoidium anamorph, this fungus may be clearly assigned to Erysiphe emendation, probably to section Uncinula, since the cleistothecial appendages are nonmycelioid and occassionally circinate at the apex. The fungus is described as a new species Erysiphe pachypodiae sp. nov.