This disease blemishes plants, but does not kill them. Powdery mildew, too, usually becomes less of a problem as summer wears on. Antique roses will get the same disease as modern roses, but are usually so vigorous, they dropped diseased foliage and continue to grow. And, of course, gardeners' experiences differ. Abundant sunshine, good air circulation and healthy soil are the first steps toward good resistance.
Organic matter is beneficial, and fish emulsion is helpful in boosting soil health.
Many gardeners discourage blackspot and mildews by spraying a fungicide every seven to 10 days. While I tend to shy away from printing product names, the following have gotten good reviews from various gardeners. Funginex is popular. Safer's manufactures a sulfur-based fungicide that helps control powdery mildew and blackspot. Rose Defense, which contains neem oil, fights mites as well as powdery mildew.