I have had this very problem. The only solution is to try to get as long a bit of stolon with leaves as possible, preferable a few, and retart the clone in fresh uninfected media.
On a hopeful note, my original infected pot hosts both species in harmony. In fact, the U. sandersonii seems to use the subulata as a preferred medium! I try to remove all the scapes of U. subulata, but some slip by from time to time. The simultaneous flowering of both species is really very pretty. I do however keep this pot totally isolated from my other CP species.
I have had quite a time with U. sandersonii. The original start that pyro sent was reduced to bits by the postal service, no part larger than 2 mm. It seemed remarkable that it would be possible to so pulverize anything so small into even smaller bits in a padded envelope, but such was the case. The ingenuity of those postal workers has to be respected. I now have 2 uncontaminated pots of U. sandersonii, but none show the steady and prolific flowering that the infected pot does.
Go figure.
