Coleosporium tussilaginis is a heteroecious rust fungus in the family Coleosporiaceae, completing its life cycle alternating between pine (Pinus species) as the primary host and various herbaceous plants in the family Asteraceae, particularly coltsfoot (Tussilago farfara) and related genera, as alternate hosts. On pines, the fungus produces aecia that release aeciospores infecting alternate hosts in late spring; on Asteraceae, uredinia and telia form on the underside of leaves through summer and autumn. Infection of pine needles generally causes minimal economic damage, appearing as orange to yellow blistering of needle tissue. On alternate hosts, orange pustules on leaf undersides may cause cosmetic damage but rarely pose serious horticultural concerns. This rust is widely distributed across the Holarctic region wherever Pinus forests and Asteraceae hosts co-occur. Its complex host alternation reflects the evolutionary sophistication of rust fungi, which exploit different host species for different spore stages. Coleosporium tussilaginis belongs to a species complex that was formerly considered to include several morphologically similar rusts on different alternate hosts, and molecular studies have helped clarify species boundaries within this group.