At some time during the winter months, remove all leaves from the plants and discard or compost. In fall prune hybrid tea roses to about 18 inches and destroy the prunings. In spring prune again to about 10 inches and destroy the prunings. The characteristic white mold can occur on the surface of young leaves, shoots and flower buds. The disease causes leaf distortion but less leaf drop than black spot.
Powdery mildew is usually more severe in shady areas and during cool periods.
The fungus is windborne and can increase during periods of heavy dew. Remove and destroy diseased foliage and canes during the growing season and follow a rigorous fungicide program. Spray applications should be made every 7-10 days. Spray thoroughly to completely cover all plant surfaces. Follow all directions and precautions provided by the manufacturer on the label.