I just moved to a new house, where I have inherited a lovely garden from the previous home owners. I have noticed that almost all the roses have spots (yellowish-white) on the existing leaves – newer leaves do not have them yet. I know that most roses need to be cut down after summer, but I don’t think that these were. Do you think this is the reason for the spots, or do I have a bigger issue at hand?
The spots you describe could be a fungus attacking the foliage or could be insect damage if the spots are actually little holes or skeletonized areas on the leaves. It does not sound like a water on foliage related problem. I would recommend spraying them with an earth friendly fungicide such as one named Green Cure, mixed at the Cure Rate listed on the label. If the spots continue to appear, then a good insecticide application may be in order. If you see tiny webs on or around the foliage, it could be a spider mite problem which will require the application of a miticide as insecticides will not kill them.