Jem, I have 7 or 8 rose bushes. The rose trees have the black spot. What do you do for it besides ripping all of the leaves off them?
I douse them with fungicide I buy at Lowe’s. You could make a wash of water and baking soda and pour that over the plants. Fungus, iirc, grows in an acidic environment so washing the plant with something base ought to help. That’s theory I’ve read about online.