Why do treatments for blackspot on my roses not work?
Why Do Treatments for Blackspot on My Roses Not Work?
Even when the black spot fungus has been killed, it leaves its mark upon the foliage of the roses. The new foliage should be free from the black spots though if the fungus was killed by the spray being used. If I have big problems with black spot, I use a product called Mancozeb available from http://www.rosemania.com , it is the only thing I have found that will stop black spot in its tracks. It does leave a yellowish powdery residue on the foliage. That is part of how it works. Once it is under control I keep my rosebushes sprayed with Green Cure fungicide every two to three weeks depending on how damp it has been. Here is an article for you too at this link: https://www.gardeningknowhow.com/ornamental/flowers/roses/black-spot-roses.htm
use 1 tbs epson salt to 1 gal water and use a hand sprayer and spray ur roses once a wk.....or when spots show up.bk spot usually shows up when to much moisture is on foilage.