Phylum: Basidiomycota Family: Pucciniaceae
Puccinia poarum E. Nielsen
Common on the large leaves of Colt's-foot Tussilago farfara. An early flowering plant, the rust can be found about May time
References:
Ellis & Ellis (1997) - Microfungi on Land Plants
Termorshuizen & Swertz - Dutch Rust Fungi