Black spot is a common fungal infection in roses that develops circular or irregularly shaped black spots on the leaves. It festers in moist areas with little airflow. If your rose has black spot, it’s not the end of the world! There are a few easy ways to manage it:
Cut off any infected leaves. Disinfect your pruner between cuts to prevent the spread to other areas of the plant
Discard any cut or fallen leaves around the plant, especially in fall.
Avoid wetting the leaves. Wet leaves are most susceptible to black spot disease. Avoid overhead watering, especially on dark and cloudy days.
Ensure adequate air circulation. Prune the plant in spring to ensure proper airflow. Space the plants apart to allow them to breathe.
Spray fungicides. There are several fungicides on the market for controlling black spot disease. Visit your local gardening store for options.