Urocystis occulta
Urocystis occulta is a smut fungus which attacks the leaves and stalks of rye.
It is found in Australia, Europe, and North America. The fungus was first described by German botanist Karl Friedrich Wilhelm Wallroth under the name Erysiphe occulta in 1833, before being renamed as Urocystis occulta in 1857 by German botanist and mycologist Gottlob Ludwig Rabenhorst.