I thought that I had black spot, which has taken off dramatically on a standard rose over the last two weeks such that existing rose flower buds look healthy but the new leaves and flowers are wizen. The bushes are well fed with blood and bone (2 months ago), worm wee, iron chelates, well composted area, potash. The leaves have been sprayed a week ago with your aphid insecticide. In winter I cut all the foliage off and sprayed with your Lime Sulphur (4 coats over 2 weeks). Normally I don't experience black spot till end of season in March and this is very upsetting. In addition to the yellowing leaves and black spot, this morning I noticed that the 'old wood' branches have large orange patches on them and it appears to be Rose Rust which I've never had before. I have 10 rose bushes and don't want the others to get infected. I'm thinking that I'll just take off all the new growth on the affected rose and take it back to bare wood and spray that with Lime Sulphur and start the year all over. On reflection this will be easier than having to spray again and again.
Certified GKH Gardening Expert
I can sense the frustration in your words and am so sorry you are confronted with this problem.... I highly recommend spraying all of your rosebushes with a product called Mancozeb. I have found it to be the only thing that will stop a full on overwhelming black spot attack in its tracks! It will also defeat the rust problems. It does leave a yellowish powdery residue on the foliage and such, but that is part of how it works. Spray the rosebushes with it at 5 to 7 day intervals for three sprayings to gain control of full on attacks of the black spot and rust. That should gain control. Keep in mind that the foliage and such with black spot will continue to display its marks but new foliage coming on should be free from such markings if the fungus was killed. Here is a link to one place to get the product for you: https://smile.amazon.com/Bonide-Chemical-Mancozeb-Flowable-Fungicide/dp/B000BWZ9JO/ref=sr_1_1?ie=UTF8&qid=1474813708&sr=8-1&keywords=mancozeb
I spray all of my roses at 14 to 20 day cycles with an Earth Friendly product called Green Cure, at the label listed Cure Rate. So far it has worked to keep the rust, black spot and powdery mildew at bay and I have been using the product for over 5 years now.
Stan The Rose Man
Master Consulting Rosarian
Gardening Know How