In article , Mark. Gooley
wrote:

wrote :
remove all the black spot leaves before spraying them? On some of my
bushes there wouldn't be much left and I wondered if that would
interfere with the stem development

I've read claims that so long as the leaves are still green enough to
function, it just cripples the plant further to remove them. They're
lost anyway once black spot has taken hold. Try to kill the spores
and halt the progress with the spray, and remove the fallen leaves.

Opinions? I vaguely recall having read that what I wrote above was
confirmed by scientific studies.

Yes, the non-stripping was the opinion of a Texas plant pathologist
back in the late 70's, from what I read he

http://www.rosekinggardens.com/faqs/blackspot.htm

Makes sense.