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Answer

Blackspot What you are experiencing is "Blackspot" a fungus that affects the foliage on rose bushes. It starts with black spots appearing fringed with yellow rings on both sides of the leaves. Eventually, as the disease spreads, the entire leaves will go from green to yellow and eventually drop off. In sever cases the rose bush may loose all of its foliage. The fungus is most active in humid or moist conditions above 75 degrees. Once you discover you have Blackspot prune out the infected stems and dispose of them properly, do not compost that will only spread the fungus. After removing the diseased parts from your rose bushes it is necessary to apply a preventative formula to minimize additional damage. Using fungicidal soap or sulphur several times throughout the summer and reapplying after it rains. To defend against Blackspot from the start of the season the shrubs need to be treated during the dormant season with fungicidal soap and wettable sulphur. Removing canes from the shrub will increase air circulation and reduce moisture build up which will reduce infestation, there are also many disease resistant verities of roses on the market.