Answer: The symptoms of black spot begin with circular black spots, frequently with fringed margins. Yellowing and defoliation are common in susceptible cultivars. In wet weather, spots may become very severe and run together, making large irregular spots. Control practices include avoiding dense plantings (good air circulation all around the plant is important). Avoid overhead watering. Rake up and remove all leaves at the end of the season. You can try removing the yellowing leaves as soon as you notice them, but I suspect the canes might also be infected. A copper-based fungicide should stop the disease in its tracks. Or, since it's early in the season, you might try pruning your plants to remove any suspect wood and foliage. If you use a preventative spray in May and June, your rose should not develop black spot in July. Try putting your rose on a regularly scheduled spray schedule. If it still develops black spot, regardless of treatment, you might consider replacing it with a more resistant cultivar. Best wishes with your roses.
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