Cereus tetragonus is turning white

Question

Hello, I’ve had this cactus for about 3 1/2 years now, he’s gotten quite large and has a few little sprouts coming up in the soil as well. Recently one of the larger prongs has started turning white and going soft from the bottom up and the four little sprouts have wilted and fallen over. I’ve never had a problem with this cactus before and my family and I love it and are fearful we might be losing it, does anyone know how to save the rest of it?

Answer 1

Does the white area feel soft or mushy, which would indicate rot? Also check the sprouts that have fallen over to see if they are mushy.
https://www.gardeningknowhow.com/ornamental/cacti-succulents/scgen/cactus-going-soft.htm

Removing the plant from its pot and checking to see whether the roots are mushy is probably necessary. You will also need to cut out any mushy aboveground parts of the plant as described in the article. If the roots are are mushy or overly moist, you can let them dry out overlight, then repot the cactus in clean soil and be careful not to overwater, since it will probably use less water while recovering.

If any of the small sprouts still seem healthy, you can use them to take a cutting:
https://www.gardeningknowhow.com/ornamental/cacti-succulents/scgen/propagating-cacti-and-succulents.htm