"Cass" wrote, after Allegra pondered about this:

I've got some kind of garden contagion this year. Very odd, obviously
some microbial contagion because it enters pruning cuts. I don't think
it's dirty pruners because only certain roses get it, and not just, or
even primarily disease prone roses. sigh At the moment, I'm just
cutting it off.

Okay: here are the two pix. The first something I cut off a brand new
rose that came from Sonoma County, where they have it too. And they
spray.

http://home.earthlink.net/~cbernstei...isease2003.jpg

The second is off of Safrano. This lesion actually killed the cane. I
don't show the rest of the stem with the leaves fizzled on the end, but
take it from me, they fizzled:

http://home.earthlink.net/~cbernstei...DiseasePix.jpg

This stuff does not penetrate the pith right away. I can see the
maroonish discoloration of the bark spreading several inches in both
directions, up and down the cane. If I cut through the discolored cane,
the pith is white and healthy.

I'm sure you know I'm not much for spraying, but even if I were, I
wouldn't do it unless I knew what I was spraying for. Tom Liggett says
he's seen a lot of botrytis this year, and the estimable Paul Barden
told me that he thinks it looks like the botrytis he sees up his way.
Which makes perfect sense because it is eVerYwHeRe in this damn county.

I have to add my vote to that. I have seen this here last year and I am sure
I will see it again this year in the roses that have yet to be pruned. It was
disconcerting at first encounter, since for who knows what reason I always
look for the polka dots first ( the cart ahead of the horse syndrome when you
have much too much in your head I guess). The dead giveaway for me is the
"burnt" blackened look of the periphery of the dead tissue. BH sprayed with
Mancozeb twice and that got rid of the problem. He just told me he didn't
work "real hard" at it. We cut the infected canes first, took off all the blossoms
in each of the plants and some around it, and we have yet to see it, but given
the present weather condition, I am willing to bet this wouldn't hold for long.

Here is a valuable address in case you don't already have it to check cause
and effect of using it in your area. You know I am not a forceful advocate of
chemical spraying, in spite of my reputation. I just simply no longer believe
you can fight Panzers with violets, if you catch the meaning here. So when my
roses in spite of cleaning the beds and letting air flow at the expense of more
roses still doesn't work because Oregon is Wet Country, then my dear, I am
too old to accept that I can only grow certain roses and no others. It is not
stubbornness, it just simply a matter of a bit of selfishness and the hope that the
roses will bring the same joy to others that they bring to me. Particularly to those
who have no idea what an old garden rose really looks like.

http://ace.orst.edu/info/extoxnet/

Try it solely on one plant and see what happens. Of course methods and amounts
vary according to locale and infestation. But if you get a clean rose with very little,
that is the amount you need. Good luck, don't let it spread, and just cutting the
canes alone is not going to do it, unfortunately.

Allegra