Hi ST
''Black spot'' thrives on dry conditions and so if you can water well and even spray the roses innthe evening when cool this will help.If treated this way roses rarely die from this but look dreadful.
Gather all fallen leaves and burn them and remove (within reason) the worst from the plant as well. Fallen leaves go on to reinfect next year. If you can find a friendly soil disinfectant this can help.
I sometimes water with ''Jeyes Fluid'' in weak solution as this is effective and a pretty safe formulae, however this is the UK name and may be different in US.It is a coal/tar product. There are some harmless soil sterilizers.
Good Luck,
Roses are so rewarding.
Roger
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