Witches Broom is a viral disease called Rose Rosette disease. Once the rosebush contracts the disease it will continue to have it as there is no known cure. Pruning out the canes that are diseased and burning them is okay to do. Be sure to clean the pruners so as not to help infect others. Here is a link to an article for you: https://www.gardeningknowhow.com/ornamental/flowers/roses/rose-rosette-disease.htm
Answered on October 20, 2014
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