Answer: Black spot is a disease spread by water on the foliage. It can be held in check if you have only a few bushes and like to spend time in your garden. If you keep a close eye on your plants, you can catch the disease early and pinch off the affected leavesand dispose of them far from your roses. Then you can spray with a solution of compost tea, made by mixing one part mature compost that contains some manure with 5 parts water. Let the mixture sit for 2 weeks, then filter and spray at 2-week intervals. Other routine maintenance can help prevent black spot. Avoid getting the leaves wet when you water your plants, and water early in the day. Keep the mulch around the roses free of dead leaves and replace it every spring. Trim your roses to remove old blooms. In late winter, prune the bushes hard to remove all leaves left from the previous season and remove canes to open the center of the bushes. There are some rose varieties that are more tolerant of black spot, so you may want to look for them when buying new plants. Incidentally, yellow roses are the most susceptible to the disease.
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