Phloespora ulmi is a fungal plant pathogen that affects the leaves of Elm species, usually recorded as the asexual anamorph.  Irregular brown spots in yellow patches appear on the upperside of the living leaf.  Underneath, white strands of conidia emerge from small brown spots, or acervuli.  Eventually the underside of the leaf is covered in white fuzzy masses of conidia.  Each conidia is falcate (sickle- or banana-shaped)

There are numerous leaf spot diseases of Elm.  

microscope

Photograph on host plant.  Note substrate and associated plant species.  Detailed photos of conidial masses on underside of leaf.  Microscopic examination of conidia may be needed, and we recommend that your record is verified by an expert before submission to NatureSpot

Elms