Erysiphe cruciferarum. [Descriptions of Fungi and Bacteria].
Abstract A description is provided for Erysiphe cruciferarum. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Chiefly on members of the Cruciferae but also reported on Papaveraceae (Junell, 1961). DISEASE: Powdery mildew of swedes and tumips. The first signs of mildew consist of small patches of a thin white mycelium arising at various places on the leaf, often appearing first on the under surface. These soon merge forming larger areas of mycelium. The leaves of the swede, B. napus, may support heavy mildew growth for many weeks before they become chlorotic and die. GEOGRAPHICAL DISTRIBUTION: World-wide. TRANSMISSION: Wind-borne conidia. The method of ovewintering is uncertain but myelium may be able to survive on winter Brassica spp. in the form of 'subinfections' (Searle, 1919).