OIDIUM

in fungi (division Mycota), a single-celled asexual spore (arthrospore) produced by fragmentation of fungal filaments (hyphae) in lower fungi; the asexual stage of Erysiphaceae (powdery mildew fungi); or, in Basidiomycetes, both an asexual spore (microconidium) and a male cell (spermatium).