The best spray I have found to stop Black Spot in its tracks is called Mancozeb fungicide. It will leave a yellowish powdery residue upon the foliage but that is part of how it works. Spray the rosebushes affected with the black spot with this fungicide three to four times 7 to 10 days apart. The Mancozeb is avaialable from http://www.rosemania.com. After that you can use fungicides such as Honor Guard or Green Cure to keep it at bay. Once the fungus has been killed all new foliage coming out should be clear of the black spotting, if not, do the same spraying again. Once the black spot is on the foliage it will never go away. However you do not need to remove those leaves unless so desired.As the affected leaves will still function for the health of the rosebush until new ones take over.
Answered on August 1, 2015
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