A rose is a timeless classic that comes in a range of colors, each depicting a different emotion. These beautiful flowers are the perfect accent pieces, whether planted outdoors or inside. Despite their hardiness to most climates, however, they are susceptible to several diseases that include mildew, black spot and rust. All these diseases are fungal, therefore their cure is more or less the same. Maintain a healthy rose bush, prune diseased parts and discard them appropriately to prevent the infection from spreading.
Plant your roses in sunny spot that has well-drained soil and a pH between 6.5 and 6.9. Make sure they are spaced at least 3 feet apart, or more, depending on the cultivar, so they get good air circulation.
Water the roses infrequently, at least twice a week, but deeply. Roses thrive on plenty of water, so a deep watering two to three times a week is sufficient. However, depending on the weather, you can increase it up to four times in case it is very hot. Use a garden hose or drip irrigation system, and water at soil level as opposed to using sprinklers to avoid wetting foliage.
Check the leaves of the rose plants for circular black spots with a yellow halo around them, or tiny red or brown spots with a dried center. The former fungal disease is called black spot and appears in late spring, while the latter is called spot anthracnose and appears in early spring. Spores of both fungal diseases germinate in water.
Wear gloves and spray fungicide on the affected leaves regularly to prevent the fungal diseases from spreading. Prune affected leaves with clean pruning scissors to separate them from the plant, and spray fungicide on freshly sprouted leaves in spring to prevent them from being diseased.
Prune and then destroy all leaves, especially new ones, that are curled or twisted and covered in a thin layer of white powder. This disease is called powdery mildew, and occurs when days are dry and warm while nights are humid and cool. Make sure you burn affected leaves or collect them in a bag and knot it securely to prevent them from coming in contact with the remaining leaves. Spray your rose plants with fungicide late spring to early summer.
Cut off rosebuds that fail to bloom and are covered with fuzzy, brown mold. This disease is called gray mold or botrytis blight, a fungal disease that spreads in spring when the temperature is cool and moist. Also spray the plant with fungicide to prevent the disease from spreading.