Lesions appear as raised purple-red irregular blotches, later becoming blackened and blistered. Wet conditions of at least 7 hours with temperatures between 60-80 C are required for infection. Proper sanitary practices are essential, because the black spot fungus overwinters on infected plant material. Gather and destroy fallen leaves. Remove old infected canes by cutting them back as severely as possible without cutting too close to the graft.
Plant roses far enough apart to allow good air circulation between plants.
Do not wet the leaves or flowers when watering. Protective fungicide sprays should be applied as soon as the growing season starts. Continue the sprays at 7-12 day intervals until fall. The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.