How do I treat these spots? What is it? What causes it?
Once the leaves get the spots (Bs fungus), they will sooner or later turn yellow and fall off the bush. Nothing you can do to rid the leaves of the spots (fungus) or to save those infected leaves. Blackspot is a rose fungal disease.
Prevention is the key to stopping Blackspot.
Blackspot info below:
Here is a link that might be useful: Blackspot
Your zone is completely different than our zone. So, if you have anymore specific questions about your area and roses, try making a new thread with the word "Florida" in the
"Subject of Posting" box to target Florida rose growers.
Take care ;-)
I live in South Carolina and we have the hot humid summers, not as long as you, but we sure get hot during the summer and the humidity is so thick you can hardly breathe.
There are some hybrid teas that are very black spot resistant, I would research that onine and ask in this forum for some names of some of them.
You really can't ever get rid of black spot on a rose.
You can spray all kinds of expensive sprays dilligently on the rose bush and canes, constantly keep the rose bush real clean, don't let the infected leaves blow into other roses, and they will always have it.
I bought for the first time this spring a knock out rose, double red.
It is the only rose in my garden that doesn't have black spot. It is absolutley gorgeous! Clean foliage, and grows fast.
When I get tired of all the nonsense for my hybrid tea rose trees and black spot, I will buy another knock out.
All you ahve to do is water them, don't even dead head them.
Low maintance, it is a beautiful thing.