Posted: 04/07/2013 at 23:12
You need to spray them with something like Fungus Clear which you can buy in a garden centre. Some roses are more prone to black spot than others and it is catching. If the rose is well fed and watered it is more resistant to disease. They should be sprayed fairly early, after the leaves come out. Not always easy when it keeps raining. I water my roses at the roots too. The diseased leaves should be put on the bonfire or thrown away, not on the compost heap.
We went to the RHS garden, Rosemoor, in Devon last year. The rose gardener told me that they only plant disease resistant roses there.