According to Wikipedia (accessed 4/1/2023) "Puccinia poarum, the coltsfoot gall rust ... forms a yellow to orange gall, 1–2 cm in diameter, on the underside of leaves of coltsfoot (Tussilago farfara). It also infects, but does not gall grasses of the family Poaceae. P. poarum is a genetically diverse species that has been reported on at least seventy plant hosts.