Moon cactus rotting?

[Otan]

My office mate asked if I could help her fix this moon cactus. When I was initially checking it, I noticed that it had a lot of scales. After that, I proceeded in cleaning the scales and found out that it is rotting in the apex part. The bottom part of the moon cactus is soft but not mushy but it has a weird color (looks like its going to rot.) should I slab graft this or would coring the top part of it will do the trick?

[gemhunter178]

I'm not the most experienced when it comes to rotting from the apex, but I do know these grafts on Hylocereus don't tend to last long, regardless of quality of care.
So, if your office mate really wants to keep this plant, you're going to have to regraft it on a much better rootstock (and fix the rotting problem while you're at it)
The Hylocereus stock tends to grow pretty well after degrafting. Perhaps if you have the time and room it could produce some dragon fruits.

[Aloinopsis]

Neither the Hylocereus cuttings nor unpigmented Gymnocalycium are meant to last very long. Both are often already dying when you buy them. They're decorations.

[Otan]

Thank you for your insights. My office mate told me that I could do whatever I think would help her plant and won't take it against me if this plant dies.

Hopefully, I have a blue boy at home that I could use as a root stock. Will try to clean the apex and the bottom part of the Gymnocalycium and do a slab graft if the rot is too advance

[TimN]

I'm pretty sure the Gymnocalycium part is dead. The stock might be savable.

If you want to try to salvage the top, get some anti-fungal/anti-bacterial spray at your local plant shop and spray it thoroughly.