Answer: Roses require a lot of care but you'll be rewarded by your efforts. What you describe are the symptoms of the most common rose diseases; black spot and powdery mildew. Each has its own set of control options. Rather than attempt to cover all of the options in this forum, I'm going to provide a website address sponsored by the American Rose Society. Everything you need to know about growing roses and controlling diseases is explained in detail. I'm sure this website will provide lots of help in getting your fabulous rose collection back into shape:
When you get to this page, click on Powdery Mildew, and the Black Spot and when you've finished reading the basics, you can surf the site for info on feeding, pruning and watering your roses.
Best wishes with your roses!
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