The White Mould Ramularia ulmariae causes purple spots to appear on the leaves of Meadowsweet. Small white tufts of conidia in caespituli, emerging from stomata, should be visible. 

Similar spots can be caused by pathogens or physical damage.

microscope

Photograph on host plant; note substrate and associated plant species. Microscopic examination is needed.  We recommend that your record is verified by an expert before submission to NatureSpot

Meadowsweet