To best control pesky problems such as black spot (for more care tips about black spot click here), rust, powdery mildew, and others it is important to maintain a regular, fungicide spraying regimen.
You can protect your roses from diseases during the dormant phase by spraying them with a liquid copper fungicide like Liqui-Cop every 10-14 days. Liqui-Cop is extremely weatherproof and will stay on the leaves and stems after they are dry.
Once your roses wake up from dormancy and new leaflets start to form, or if your roses never fully go dormant, it's a good idea to spray a fungicide such as Dr. Earth Final Stop Disease Control Fungicide once every 10-14 days.
This simple regimen will ensure your rose’s health and allow you to enjoy the beauty of your garden all year long.