Roses always look their best during their first bloom in the spring. Fresh, green leaves and bright blooms beautify the garden at this time of year. A month or so later, though, leaves start to yellow and develop spots. This is black spot, a fungal disease affecting roses worldwide. If left untreated, black spot will cause leaves to drop and the plant to die. Fortunately, there is a way to effectively treat black spot. Season-long attention to your roses will ensure their health and the beauty of your garden.
Remove dead and severely affected branches. Remove yellow leaves, but don't cut leaves that have spots, but are still green
Rake up leaves and branches that have dropped to the ground.
Prepare triforine fungicide in a garden hose sprayer or pump-type garden sprayer according to label directions.
Spray the flowers and leaves, top and bottom, as well as the canes. Spray the ground underneath the plant. A fine spray ensures even coverage, while a courser spray is less likely to become airborne and get breathed in. Follow all label precautions and don’t spray on a windy day or around other people or pets.
Repeat spraying every seven to 10 days to continue black spot control. You will need to spray more often if the season is rainy. Continue to rake up dropped leaves. Remove spent blooms, which can harbor black spot.