Answer: Roses can develop powdery mildew, rust and other diseases - some are more resistant that others - so if this is an ongoing problem and fungicide applications are not working, you may want to replace the roses with more resistant varieties. Make sure your roses are getting at least 8 hours of sunshine a day and that they have plenty of room to encourage good air circulation. Try to keep water off the leaves when you water them. You might try pruning them back to remove the infected leaves and stems and continue to apply the fungicide as often as recommended on the label. Best wishes with your roses.
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