Answer: Sounds like your rose bush has powdery mildew. I would cut out the infected plant parts and clean up any fallen leaves and blossoms. Pruning will open your rose bush up to better sunshine penetration and good air circulation. There are a few fungicides on the market that you can use to stop powdery mildew if it becomes a problem again. The safest is one called 'Rose Defence'. It'sa neem oil based product, biodegradable and is safe for insects, animals and humans. If your roses are shaded by your birch trees, they may not be getting adequate sunshine and may be more prone to diseases. Eight hours is minimum for rose bushes. You may want to think about moving them this winter. Best wishes with your roses.
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