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My cactus has these brown spots that are spreading and I’m not sure what they are? I’ve tried adjusting sunlight exposure and how much I water but it doesn’t seem to have changed anything. Some of the spikes are falling off too… Help a guy out please

2 Answers 2


Nope, that is not normal at all.

I am sorry to say that this looks like a rot to me, and probably it has spread out a lot. Though I have not faced such severe case of rot, still it looks like it had started with the root and now much of the central stem (if not the whole of it) is affected.

Now generally what I do with cactus that rot is

  • uproot it immediately
  • cut the portion that is already rotten with at least 1cm good portion with it or keep cutting it until you see a perfectly fresh part, else any tiny rotten portion can again start the whole process without you knowing it.
  • put some fungicide on the fresh cut
  • keep this in open air for 4/5 days so that it dries out properly
  • after 4/5 days repot it in well drained media, don't water it immediately, again keep it like that for 2/3 days, no direct sunlight
  • after 2/3 days water it thoroughly and place it in partially sunlit area
  • after that you start your cactus watering schedule, i.e., don't water it unless the media dries out properly, keep it in sunlight etc etc.

That is my normal procedure with cactus with rot. You can follow it, though I don't know how much the rot is spread in your case.

Or, this article suggests few things, you can go with that or google yourself about other measures. https://www.gardeningknowhow.com/ornamental/cacti-succulents/scgen/stem-rot-of-cactus.htm

Bottom line: looks like root and stem rot.


I've never grown this kind of cactus (and the affected parts don't look super clear to me), but the affected areas look a lot like parts of a pepper or tomato that some creature (such as a pill bug or slug) has munched on, and which have healed over. If this is the case, your cactus probably isn't under threat of dying by disease or something, but maybe it needs some potassium to help make it stronger against pests. The pests may be gone by now, though.

I don't see any yellowing or rotten-looking parts.

I wouldn't call this normal, though, but remember, I haven't grown this kind of cactus.

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