SUMMARY
On purely nomenclatural grounds, the powdery mildew passing in the literature as Uncinula polychaeta (Berk. & Curt.) ex Ellis, on Celtis spp., if retained in the genus would need to be called U. lynchii Speg.
On taxonomic grounds it should be placed in another genus than Uncinula, and in the subfamily Phyllactinieae. The species has been shown to have an Ovulariopsis of the “subspiralis” type imperfect state and both epiphytic and endophytic mycelium.
On the basis of priority, the generic name Pleochaeta Sacc. & Speg. in Sacc. descr. emend. Kimbr. & Korf is accepted for such a genus with an Ovulariopsis imperfect state of the “subspiralis” type and an Uncinulalike perfect state. Uncinulopsis Sawada is a synonym. Only two species of the genus are known, both on Celtis.
The species occurring on Celtis in both North and South America with about 60, 2-spored asci must be called Pleochaeta polychaeta (Berk. & Curt, in Berk.) Kimbr. & Korf.
The species occurring on Celtis in Asia with about 30, 3- to 4-spored asci is treated as a distinct species, Pleochaeta shiraiana (Henn.) Kimbr. & Korf.