Rust on rose leaf

Rose rust is a disease specific to roses and is caused by the parasitic fungus Phragmidium tuberculatum along with some other closely related species. This disease occurs during spring and persists until the leaves fall. This images shows rose rust on the surface of the leaf - tiny pores in the leaf (called stomata) are also visable, which are essential for plant gas exchange. The main group of spores from the fungus is 200uM.