Rose
Black spot is a common rose disease often reaching epidemic proportions after a long wet, warm period in the spring. The disease is caused by a fungus.
Symptoms occur on rose leaves initially as black circles with irregular margin. These more or less circular black spots as they grow may be surrounded by a yellow halo. Affected leaves turn yellow and drop. Repeated severe defoliation weakens the plant so that it produces fewer and poorer quality blooms, and is more sensitive to winter cold.
Prevention and treatment includes planting resistant varieties, maintaining good sanitation, removing infected areas, and keeping leaves dry by watering early in the day, and using drip irrigation methods. You can also use fungicide sprays.