In fact, many roses get a little black spot, which can even be tolerated to some degree without any harm to plants. However, heavy infections can seriously defoliate plants. Rose black spot is caused by fungus. Dark-brown to black leaf spots develop on the upper leaves, which eventually become yellow and drop. Black spot can be distinguished from other leaf spot diseases by its fringed edges and dark black color. Raised, reddish-purple spots may also appear on rose canes. Warm, humid conditions favor its germination and growth. Black Spot Rose Disease Control Treating black spot roses begins with prevention. Black spot rose disease control includes adequate planting sites, the use of resistant cultivars, and pruning. Roses should be planted in areas with plenty of sunlight and good circulation. Good garden hygiene is important for treating black spot roses. During the growing season, overhead watering should be avoided. Removal of leaf litter and pruning of diseased canes (back to ...
Black Spot is a bothersome problem for many rose gardeners. Understanding how to recognize it and what causes it will help reduce your chances of getting Black Spot. If your roses do get it, there are both chemical and organic treatments.