Answer: Roses are prone to a disease called powdery mildew, and the symptoms include a white substance on the leaves. If there are just a few leaves, pick them off and destroy them before the disease spreads. Then try pruning the plant back to increase air circulation and to allow for additional sunlight penetration. When watering, keep the water off of the leaves and try to water early in the day so the plant can dry out before nightfall. If all else fails, a good garden fungicide will protect the rose leaves from developing powdery mildew.
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