A revision of a monophyletic group of Hypocrella species and their Aschersonia anamorphs with white effuse stromata is presented. In addition to taxon descriptions, distributions, and nomenclature, a synoptic key and a molecular phylogenetic analysis are also provided. A new holomorph, Hypocrella rhombispora sp. nov., is described. This study presents a revisionary treatment of Aschersonia aleyrodis (teleomorph: Hypocrella libera) and its allies. These fungi parasitize whiteflies and are promising candidates for whitefly biological control. Four species of Aschersonia and their Hypocrella teleomorphs are treated in detail: Aschersonia aleyrodis/Hypocrella libera; A. andropogonis/H. andropogonis, A. placenta/H. raciborskii, and A. sp./H. rhombispora sp. nov. A synoptic key including these and six other morphologically similar species is presented to facilitate identification in the field and laboratory. Phylogenetic analyses of partial DNA sequences from three genes (LSU, mtSSU, and RPB2) suggest that Aschersonia species with effuse white stromata form a monophyletic group of whitefly pathogens. Phylogenetically informative characters in the group include the colour and shape of the stromata, the arrangement of tubercles containing perithecia, the arrangement of conidial masses on the stromata, and the shape of conidia and part spores.