Q.My Knockout Roses Have Yellow Leaves
My roses were doing great but something was eating them, so we put liquid Sevin on the them and fed them with rose bush food. Now the leaves are turning yellow. I am watering them to keep them alive. I have 3 bushes; only 1 is doing this. What can I do to get it back to health?
This link will take you to several articles about roses: http://www.google.com/cse?cx=012078378210706707791%3Af1h5n_k1r5e&ie=UTF-8&q=black+spot+on+roses&oq=black+spo&gs_l=partner.3.0.0l5j0i5l2.10972.15364.0.182188.8.131.52.0.0.0.913.3387.2j1j1j5-3j1.8.0.gsnos%2Cn%3D13..0.0.6425j8497011j10..1ac.1.ifany6VYYt8#gsc.tab=0&gsc.q=black%20spot%20on%20roses&gsc.page=1
This particular article might be the one to answer your question: https://www.gardeningknowhow.com/ornamental/flowers/roses/yellow-rose-leaves.htm
A few yellow leaves aren't too troublesome for the most part, but if 20% or more of the plant is involved, something should be done to correct the situation.