# New Publication - Powdery mildews on Quercus April 13, 2022 - [ News ](/news-categories/news) HUH Research Fellow Michael Bradshaw and colleagues have [a new publication](https://doi.org/10.1111/efp.12742) in the journal *Forest Pathology*. In "Powdery mildews on *Quercus*: A worldwide distribution and rediscovered holotype provide insights into the spread of these ecologically important pathogens," the authors emphasize the importance of sequencing type specimens of powdery mildews, especially regarding morphologically alike species on similar hosts. **Abstract:** Powdery mildew on oak, caused by *Erysiphe* spp., has been shown to have serious ecological consequences on a range of *Quercus* hosts. *Erysiphe alphitoides* and *E*. *quercicola* are two of the most heavily studied and common powdery mildews known to occur on *Quercus* species. In recent years, these species have been noted throughout the world on a range of hosts within and outside the *Quercus* genus. Reports that *E*. *alphitoides* was absent in European herbaria before 1921 and the discovery of the holotype of *E*. *alphitoides* from 1911 in an American herbarium (FH) led to the current study in which we genetically analysed six specimens of *E*. *alphitoides* s. lat including, most importantly, the holotype of *E*. *alphitoides* from France collected in 1911. The results of our analyses revealed that: (1) The sequence of the *E*. *alphitoides* holotype falls within the *E*. *quercicola* clade, confirming that *E*. *alphitoides* did not spread to Europe until ~1921. (2) *E*. *alphitoides* var. *chenii* forms a monophyletic clade with *E*. *epigena* and should be reduced to synonymy with that species and (3) through sequence analyses *E*. *alphitoides* and *E*. *quercicola* are confirmed to have spread to North America. The sequencing results of the *E*. *alphitoides* holotype have severe nomenclatural-taxonomic consequences. A proposal was submitted simultaneously with the present manuscript to conserve the name *E*. *alphitoides* so that the traditional usage of the names *E*. *alphitoides* and *E*. *quercicola* could be maintained. The sequences obtained for the current study provide new insight into the taxonomy and spread of these ecologically significant, globally distributed species. The present study highlights the importance of sequencing specimens from type material, above all when morphological similar species are involved. Bradshaw, M., Braun, U., & Pfister, D. H. (2022). Powdery mildews on *Quercus*: A worldwide distribution and rediscovered holotype provide insights into the spread of these ecologically important pathogens. *Forest Pathology*, 00:e12742. Share on:- [ Facebook ](#) - [ Twitter ](#) - [ Linkedin ](#)