Sue ...
We have a horticultural representative from UC Davis up here and I discussed this with her last year and she confirmed that spores cannot live on dead leaves.
As I said in my post above, it depends on the rose and the race of bs you have in your garden.
Not all roses are susceptible to all of the five strains/races of bs in the United States. That's why a rose might be very disease prone in one climate and the same rose be totally clean in another climate. The bs race in the second climate is different than the one in the first garden. The second garden may have roses that are bs magnets, too, but it's a different race of bs.
Thanks, Zuzu, for finding Gregg's article. I was looking for it this morning.
I was also going to post that in normal years, I always mulch my garden in fall and in spring because I had read that this prevents any pathogen that may have overwintered in the garden debris from surviving to infect plants in the new growing season. Just covering the old mulch in spring will catch any leaves that have dropped after I mulched in fall, so I know that the bs in my garden does not come from the dead leaves below the rose.
For some fun reading about bs, here is a link from the Rose Hybridizers Association.
http://www.rosebreeders.org/fo...
You can get a sense of what I mean about bs races.
Smiles,
Lyn
