White blister rust is a disease that is mis-named as it is not actually caused by a rust fungus. The perpetrator is an oomycete. This group have traditionally been included in the fungi and have long been studied by mycologists but DNA evidence shows that oomycetes are more closely related to brown algae than to fungi or green plants. It was an oomycete that was responsible for the Irish potato famine in the 1800s.
White blister rust is common on Shepherds purse (Capsella bursa-pastoris) on campus and throughout Reading, especially on road sides. It develops into a thick white layer of sporangia that smother contorted and, often, enlarged parts of the plant. The causal organism, Albugo candida, is capable of infecting other members of the cabbage family. It was recently observed on Thale cress (Arabidopsis thaliana) near the Harborne Building.