In Cass wrote:
Everyone in the past 300 years has recommended cleaning up under roses.
The persistence of spores is the primary reason. And blackspot isn't
the only fungus - anthracnose, rust, powdery mildew, cercospora,
botrytis, brown canker, brand canker and other things that go bump in
the night.

Where possible I follow the conventional wisdom. One year I didn't, and
the difference was too big to dismiss or attribute to something else.

I wouldn't go see Dr Lyle if I had a cold :-)