What do you do, spray to get rid of black spot on knockout roses? Black spots on leaves and leaves turning yellow.
Black Spot on Leaves of Knock Out Roses
Certified GKH Gardening Expert
The quickest way to stop black spot in its tracks is to spray the rosebushes well with a product called Mancozeb. You can get it at Amazon.com. Part of how it works is to leave a light yellowish powdery residue on the foliage. But it does work very very well. If it is a severe case of black spot it may take two to three sprayings 7 to 10 days apart. Keep in mind that even when the black spot fungus is killed it will not just disappear from the foliage. It leaves its mark! However the new foliage coming on should be free of the black spot if the fungus has been killed. Take a look at this article too: https://www.gardeningknowhow.com/ornamental/flowers/roses/disease-resistant-rose.htm