Microbotryum piperi (Clinton) Vánky, 1998
pustules at the underside of the leaf, mainly along the margin, often confluent. They contain a purplish-brown mass of spores.
Polygonaceae, narrowy monophagous
Aconogonon alpinum (= Polygonum, Persicaria).
Ustilago piperi Clinton, 1904. Ustilago polygoni-alpini (Cruchet) Zundel, 1951 is taken as a valid species by the Index Fungorum (2014), but on the base of Vánky (1994a) is a synonym of piperi.
Brandenburger (1985a: 86), Klenke & Scholler (2015a), Vánky (1994a).