Very sick Monvillea Spegazzini

[Medusa]

Can anyone help with my very sick plant?

Medusa is a beautiful Monvillea Spegazzini but has recently started to shrivel and turn brown/grey (see photos) in large patches. Can anyone suggest what might be wrong with her? Its getting to the point where I am worried she wont recover.

Many thanks

[tumamoc]

To start, remove all of the dead/rotten portions back to the healthy part of the plant immediately. I think I can see succulent green growth above the dead portion. If so, it may be possible to root those cuttings, if you want to start new clones. It's hard to tell how much is affected, but the front portion of the plant looks pretty bad. Once that brown stuff is gone, we can make a better assessment of the plant's overall chances.

[hegar]

To me it looks odd, that only the front portion of the plant seems to be affected. Was that part of the cactus subjected to either possible frost or perhaps sunburn?
Also, did the die back occur rapidly - out of the "blue" - or was there a slower, but steady progress of the malaise?
Just looking at your image suggests, that most likely the plant stems in the background are not suffering from the same problems than those in the front of the image.
If you are dealing with a pathogen, you will see the thus far healthy stems to take on the appearance of the frontal area of your cactus.
Then you have to act quickly and may need to cut off the still healthy stems, let them callous over with or without using a rooting hormone, and then replant them in a "clean" growing medium. In case the problem does not worsen, the only thing you need to do is to remove the dead stems.

Harald

[Medusa]

Thank you both for posting replies and apologies for not getting back sooner. The good news is Medusa has not got significantly worse but she is still in a bad state. I have cut away the shriveled areas to see if this improves her condition and will also re-pot her. She has definitely not suffered from frost bite and it is unlikely that it was sun burn, although she has occasionally been in direct sunlight. What has confused me most is how some of the tendrils that have gone brown and look as though they are dead are still green and, to the eye at least, alive.

Any more thoughts greatly received, I will be more active on the forum from now on.

[Medusa]

I forgot to say that it has been a steady onset over several months and has not spread to the other areas of the plant.