The data set provides information on the incidence and severity of a rust fungus Triphragmium ulmariae occurring in populations of the herbaceous perennial Filipendula ulmaria growing on a range of islands in the Skeppsvik archipelago, northern Sweden. These data, together with information on the size of individual host populations, is being used to monitor temporal and spatial dynamics in a natural plant pathogen - host metapopulation system. See Smith, David L., Ericson, Lars & Burdon, Jeremy J. (2003) Epidemiological patterns at multiple spatial scales: an 11-year study of a Triphragmium ulmariae– Filipendula ulmaria metapopulation. Journal of Ecology 91 (5), 890-903. doi: 10.1046/j.1365-2745.2003.00811.x for further details.