I used to think foliar feeding was a good idea. I did it, and thought it was possibly helpful. Then I heard that it is a myth that it does any good, that plants don't take up nutrients through their leaves. But rose leaves apparently do absorb something like a systemic fungicide like Bayer. Or Bayer claims the chemical actually gets into the leaves.

When Vernon Rickard, who owned Almost Heaven Roses was alive I valued his advice very much and he liked Neptune's Harvest as a foliar food. I tend to think foliar food might help. I don't know that any study that proves it is useless is final. Probably it would be good to look in to what farmers do to their crops in terms of foliar feeding.