Black Spot of Rose: Diplocarpon Rosae- Black spot is the most common pest with roses. Black spot causes the entire plant to become weak and to slowly begin to produce less blooms. Infected plants will begin to show black spots on the top of the leaf surface, the spots will eventually spread to 1/2″ and typically have a fringed border, yellowing will begin to surround the spots on the leaves, causing the leaves to ultimately fall off. Black spot will sometimes infect cones where lesions appear purple colored and later turn black. To help control black spot, rake and remove all foliage that has fallen from the plant, this is the main source of fungal spores in the early spring, also be sure to remove any infected cones that may be present with a light pruning. Always plant roses in full sun to encourage the foliage to dry quickly after rain or irrigation. There are several fungicides available to control black spot. Contact you nearest plant shed for questions or concerns