Das Projekt "The powdery mildews of Switzerland" wird/wurde gefördert durch: Bundesamt für Landwirtschaft. Es wird/wurde ausgeführt durch: Bundesamt für Landwirtschaft.This monograph is based on morphological and anatomical studies of herbarium material from the author's own collections, made between 1954 and 2004 and preserved in the Conservatory and Botanical garden of the city of Geneva. Complete description, with more than 125 original figures, are given for the species newly discovered in Switzerland and for the already known, but insufficiently described species.