Fungal species of Phaeoacremonium are known vascular plant pathogens causing wilt and dieback of woody hosts. The most prominent diseases in which they are involved are Petri disease and esca, which occur on grapevines and are caused by a complex of fungi, including Phaeomoniella chlamydospora and several species of Phaeoacremonium. Various Phaeoacremonium species are also opportunistic on humans, where they are known to cause phaeohyphomycosis. Togninia was confirmed as the sexual state of Phaeoacremonium. Seven species of Togninia and 15 species of Phaeoacremonium were newly described during the course of this study. Identification tools including online polyphasic keys as well as species-specific primers were developed for the known 22 species of Phaeaocremomium. This will enable scientists in the plant industries as well as pathology units of hospitals to correctly identify all the known species. The genetic diversity among isolates of Pa. chlamydospora on grapevines was also investigated and a low level of genetic variation confirmed asexual reproduction to be dominant in vineyards.