Barrel cactus turning yellow at the base?

Question

My fiance has a barrel cactus he's really, really, really attached to. It's about a foot high, and the bottom 2-3 inches has started turning yellowy brown, and the spines in the discolored area are turning black.

Is this a rot of some type? Over watering? Fungus? I'd like to help him save it if possible.

The cactus is potted in soil with large rocks at the bottom of the pot for drainage. He's watering it every couple of weeks for the growing season, and adding cactus food every second time it's watered.

Answer 1

Barrel cactus will also turn yellow and or brown at the base if it is being watered too much or is not getting enough water.  Some cactus do not store their water like others for example a pole cactus does not store its water like the paddle cactus do.

Answer 2

I think they might go through stages but not sure my mom has had a cactus plant that just sits in a window for as long as i can remember and im 36 the same cactus

Answer 3

From everything I can find, there really aren't any diseases that cause your problem.  It sounds like it is not drying out completely before you water it again and you are over fertilizing it.  Plants don't need fertilized more than quarterly.  I would try repotting it in a larger pot if it seems to need it and water it only when it is completely dry.  Fertilize it only once every 3 months or so.  These plants seem to thrive on neglect.

Answer 4

Something similar happened to my cactus a while back, and it finally collapsed at the base.  It turned out that some flys had bored into the cactus and had eaten it from the inside out.  I don't know how to treat it, if that's what is wrong, but I do know that you need to quarantine it from all other cactuses, because it affected the rest of my collection soon after.

Check and see if the base feels squishy at all.