where can I purchase Banner Maxx or Honor Guard
I want to use Banner Maxx or Honor Guard to prevent black spot on rose bushes.
Certified GKH Gardening Expert
For black spot on roses, our rose expert here recommends a product called Mancozeb, which is available at http://www.rosemania.com, It will leave a yellowish powdery residue on the foliage for a while, but that is part of how it works. You may need to spray again in 7 to 10 days to be sure you get the black spot stopped, as the black spots never really go away but the fungus is dead. New foliage will grow back once the black spot is under control. Here is more information: https://www.gardeningknowhow.com/ornamental/flowers/roses/black-spot-roses.htm