A rarely recorded species that seems to be host-specific to horsetails (Equistem spp.).

References: 
Ellis, M.B. & Ellis, J.P (1997 new enlarged edition). Microfungi on Land Plants: An Identification Handbook.
Grove, W.B. (1935). British Stem- and Leaf-fungi, (Coelomycetes), Volumes I: Sphaeropsidales.