Puccinia sessilis is a fungal plant pathogen, also known as Arum Rust or Ransons Rust. It commonly infects Arum maculatum and Allium ursinum causing yellow to orange circular patches on leaves. On the underside it produces raised orange aecia commonly covered in spores. It is common in Eurasia in the Spring. Other species affected by this rust include Convallaria majalis, Dactylorhiza fuchsii, Dactylorhiza incarnata, Dactylorhiza majalis, Gymnadenia conopsea, Neottia ovata, Paris quadrifolia and Phalaris arundinacea