It sounds like you have Powdery Mildew fungus on your rosebush. If so, you need to spray the bush with a fungicide that will get rid of powdery mildew. Such as either one called Milstop or one called Green Cure. Both are available on-line, however Green Cure went out of business so the availability is dwindling. The Milstop is the same type of product and it is available at Amazon.com. Check out this article on Powdery Mildew and other rose diseases as well: https://www.gardeningknowhow.com/ornamental/flowers/roses/rose-bush-diseases.htm
roseman
Answered on July 14, 2020
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