This fungus disease, caused by Gymnoconia peckiana , infects black raspberry and blackberry. It is not know to infect red and purple raspberry varieties. Orange rust can be a serious bramble disease in the Northeast. These spores serve to spread the disease to other plants.
Orange rust invades the entire plant reducing blossoming and fruit set.
In addition, heavily infected leaves may die, infected shoots will be weak, spindly and have very few, if any thorns. Infected plants will not recover. To control orange rust, plant only healthy black raspberry and blackberry stock. Eradicate infected wild blackberries and black raspberries near your raspberry patch. Remove and destroy infected plants as they appear in spring.