Black spot in roses: it is caused by a fungus which grows into the leaf and forms the familiar black spots by which the disease gets its name. Little black pimples also appear in the spots. The diseased leaves should be removed, picked and burned. The flowers should be kept away from rain and too much water collecting on the plant.
After removing all the diseased leaves, the soil should be allowed to bake in the sun to dry out the wetness. Planting onions, garlic and edible onions around the plant also helps to keep pests away.