"Uncle-C" wrote
Hi folks, an old chesnut no doubt, but i suffered terribly from "black
spot" last year and although I got a reasonable bloom of roses the
leaves look seriously ill. snip

I would rather avoid the use of nasty chemicals if possible !!!!!

I think the only sure-fire way apart from regular spraying is to stick
to growing the most resistant varieties. Rugosas for instance don't seem
to get affected. Other than that, making sure that the plants are well
fed and watered, as stressed roses are likely to be worst hit.
Christopher Lloyd once recommended mulching thickly underneath with
grass clippings to keep the spores down, but then he dug up his rose
garden so maybe it didn't work all that well after all!

--
Sue