I bumped into your blog while trying to research to check if my cactus is becoming healthy: in the center of each cactus stalk (not sure what to call it!), it looks like the center is starting to brown and decay. But I’m not sure exactly if it in fact it is doing it, and I’m getting concerned and wondering if I can catch this potential problem right now. Would you by any chance know what’s going on right now with my cactus? Any information would be helpful!
It looks like it could be a burn on the newly growing centers of each stem of the cactus. Was it recently brought out into sun, or turned around so a different side was facing the sun? Maybe it was under an overhang and the sun finally came around to its part of the yard? Also, it might have been from spraying it.
It looks like it has healed over enough that you probably don’t have to worry about it getting an infection. But watch for soft spots.