Problem: Rust (Rose)
Rose rust is caused by any of several species of fungi (Phragmidium species) that infest only rose plants. Rose varieties differ in their susceptibility to rust. Wind spreads the orange fungal spores to rose leaves. With moisture (rain, dew, or fog) and moderate temperatures (55° to 75°F), the spores enter the tissue on the undersides of leaves. Spots develop directly above, on the upper surfaces. In the fall, black spores develop in the spots. These spores can survive the winter on dead leaves. In spring, the fungus produces the spores that cause new infections. Rust may also infect and damage young twigs.
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.