Dark brown leaf spots often with concentric rings.

Close-up of dark brown leaf spot with concentric rings.

Conidia enbedded in infected leaf tissue under darkfield observation.

Asexual spores of the fungal anamorph, Phoma cucurbitacearum.

Asexual spore-producing structures "pycnidia" with spores oozing out, seen in infected tissue.

Stained, asexual spores of the fungal anamorph, Phoma cucurbitacearum.

Dark brown leaf spots often with concentric rings.

Close-up of leaf spots with concentric rings.

Close-up of leaf spots with concentric rings. Spots often occur along margins of leaves.

Earlier stage of leaf spot development before all infected tissue turns dark brown.