comments:
As others have said, this is Rust. Best way to treat it is to purchase Copper Fungicide (Amazon) and use it to treat your rose. Remove infected leaves. As many as possible. Mix your copper fungicide according to the instructions. Get a sprayer and mist the mixture onto the remaining leaves. The copper fungicide does some fancy chemistry stuff that I don't really understand, but it's something to do with the copper ions disrupting the rust from being able to latch on to your leaves, as well as preventing future spores. Spray the leaves (top and bottom, all around) and it'll dry and leave a teal film on your leaves. If you get rain, it'll wash it away and you'll have to reapply. The last time I had an infestation of spore (wet and rainy weather) it took several weeks before they were treated. Reapply as needed. Copper fungicide is only preventative. It doesn't cure it. When you roses create new leaves, spray those to prevent rust from claiming them.