Yellow to brown spots appear on the upper surfaces of leaves, starting in the spring or late fall. On the undersides of leaves are spots or blotches containing a red, orange, or black powdery material that can be scraped off. Infected leaves may become twisted and dry and drop off the plant. Twigs may also be infected. Severely infected plants lack vigor.
At the first sign of rust, pick off and destroy the infected leaves and apply a fungicide labeled for this disease, following label directions. Rake up and destroy infected leaves in the fall. Prune off and destroy infected twigs. Plant resistant varieties.