Cymadothea trifolii is a fungal pathogen causing Black Blotch or Sooty Blotch disease on clovers.   The sexual state produces small black pustules, the stromata, on the lower side of clover leaflets.  The asexual state is more often recorded, and sometimes referred to Polythrincium trifolii; thick-walled, blackish conidiophores with a spiral appearance are produced in tufts on the undersides of the leaf, with corresponding yellowish spots on the upper side.  

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

See page on Plant Parasites of Europe website