The roots look fine, but the stem at the soil line has been infected by fungus. This will be fatal without intervention.

You must transect the stem (cactus) above the level of infection. Using a clean knife, cut as low as you can, then keep cutting upwards until there is no dark infected tissue in the cross-section.

Callous by drying in air for several days, and place on damp to dry well- draining soil. Then wait for roots to form. This will take several weeks. Do not water until the plant has roots. Good luck.

Brad

Getting rid of the old C&S soil of the root ball is important, I think you did the right thing. Otherwise the roots in that area have no access to water (as you suspect). Those roots look very healthy to me.

As a comparison, here are the roots of an Aloe that I repotted today. It was doing very well in gritty mix, but I wanted to transfer it into a different pot.

Thank you both for the advice.

I think I cut off a bit more than needed, maybe twice as much. We'll see what happens.

Thanks again - Mark

Good luck! I'm no cactus expert, but the rest of the plant looks quite healthy and I think you have a chance!

It's always good to err on the side of caution with fungus/rot - the healthy looking part immediately adjacent to the mushy part is actually where the attack/rot progression is taking place.

I'm done with gritty mix for cacti. It has killed a whole bunch of great plants (due to rot) including some that I've had for many years. I'm either going back to my old 50/50 pumice/potting soil mix, or a mix of pumice and lava rock.

Oh, and hi Brad, haven't seen you around for some time!