Sharlene .....
For a long time I thought bs was a non-issue as far as being a problem over wintering in mulch, but I've since been proven wrong.
I did some more research and found that Dr. David Zlesak said the spores do over winter in the old mulch.
Here's a link to an article where this is mentioned as part of the evaluation of the Earth Kind Trials
http://hortsci.ashspublication...
You will have to click the FULL TEXT link to the right and drop down to the Horst and Cloyd, 2007 paragraph I've copied below to see it in context.
Diplocarpon rosae is capable of infecting only the genus Rosa. Asexual spores (condia) overwinter on stems and fallen leaves and are transported to new growth in the spring through water droplets. If free water remains present, the conidia form germ tubes that penetrate the leaf epidermis. Lesions may appear in as little as 4 d as sub-cuticular mycelia radiate from the point of infection. Condia-bearing acervuli burst through the leaf cuticle followed by leaf abscission in susceptible cultivars (Horst and Cloyd, 2007).
I hope this helps answer your question.
