First and foremost, give your Rose plant what it needs. A healthy plant is less susceptible to problems and diseases.
Ensure good air circulation for your Roses by not planting them close together and pruning often when they become dense.
Avoid overhead-watering, especially later in the day and mulch well beneath your plants to reduce water splashing up on leaves.
Plant resistant cultivars and last but not least, treat the bush with preventive sulphur spray in spring, before new growth arises. Spores won’t grow on sulphur and you will need to repeat the application after each rain as it will wash off.