Can anyone identify this brown spot on my Totem Cactus? I'm not sure if it's from an animal, pest, or fungus. I rarely water it, and I live in the hot desert. Could it be from under watering? Thanks

Don't know. Let me tag another NGA member who might recognize the problem. @mcvansoest can you help?

They do that sometimes. I am not sure why and I suspect it may have different causes. I saw something like that on one of my Totem poles and could associate that with a spot of sunburn.

The main thing it appears to be is scar tissue in response to some sort of damage to the epidermis of the plant. So while I am not sure there could not be a fungal cause my first response would be to ask did that cactus possibly suffer some damage at those spots. The spot in the second picture almost looks like during growth the area was pulled apart/split. That second spot certainly does not look like a candidate for sunburn but the first certainly does.

If it is scar tissue I have noticed on both a totem pole and the regular version of the plant the senita that with time it may flake off to expose new healthy skin.

Keep an eye on it if this starts spreading it is probably a lot less benign that what I describe above.

In the past, I have had good advice from the Desert Botanical Garden in Phoenix. I think the garden itself is closed right now, but they might still be responding to e-mails. So, you might try sending your picture there: planthotline@dpg.org.
Great place to visit is you're into cactus and succulents, especially in the Fall, Winter and Spring. Meanwhile it's fun to browse their website.

Thank you for your prompt feedback, I really appreciate it! I guess I'll just monitor the area, and hope it doesn't get any worse. I'd hate to have to operate on it. Thanks again.