Answer: Sounds like a very diseased rose bush. The white areas are probably powdery mildew and the brown spots are either another fungal disease or the beginning of a disease called black spot. If most of the leaves are infected you might want to simply prune your rose bush down to remove all the the diseased leaves and stems and give your plant a fresh new start. It is easier to prevent these diseases than to treat them. Pruning is also a good way to open the plant up to better air circulation. Roses need to be in full sunshine (minimum 8 hours) and have good air circulation all around to help keep them disease free. Good luck with your roses.
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