The Identity of the Oak Powdery Mildew in South Africa

Abstract

Oak powdery mildew, which since 1923 has been recorded to occur in South Africa, was originally caused by Microsphaera alphitoides, the European oak mildew. At present it has been overtaken by another powdery mildew very similar to the North American oak mildew Microsphaera extensa. As a result of the absence of sexual fruit bodies a definite identification is not yet possible. Probable ways and time of introduction of the new pathogen are discussed.