We recently moved into a new house with existing rose plants, many of which are diseased. The obvious problems are the orange spots that puff into dust when you touch the plant, and black / brown patches on the leaves.
I tried a compound from Bayer that was said to resolve all problems with roses including the ones I described, but it had no effect. It was pellets that you put onto the soil.
I'm wondering if it's worth trying to save these plants, or if I should simply pull them out and plant new ones.
I have some Daconil fungicide on hand, which I understand can be used to treat some things. That would be my next attempt.
EDIT: Some of the plants have a whitish color on the leaves / stems, wbich I understand is also fungus related.