My mexican fence post cactus has developed some sort of white/yellowish fungus(?) on it. Anyone know what it is? I hope it's not a goner!!!

Looking for some help to save this guy!

  • 1
    That is not a Pachycereus marginatus which normally has the common name of "Mexican fence post". As for your plant issue, it almost looks like it was sprayed with some substance that it didn't like. The damage looks like corking, sorta. It will never "recover" from this. These spots are permanent. I think the best you can hope for is to get a clean offset or stem from this one and start over. It could be insect damage, but that won't heal either. Good luck!
    – Tim Nevins
    Dec 19, 2017 at 14:55

1 Answer 1


How sure are you, that this is a fungus?

To me, it looks suspiciously like scale, although the photos are a bit blurry.

Try to pry off one of the bigger thingies. If my suspicion is correct, you'll find a shell-like object (actually an insect) that pops off in one piece.

We have more Q/As on scale, in short, typical treatments are spraying with neem or an insecticide, using a systemic insecticide or washing the insects off with a soft cloth or toothbrush. Better yet, a combination thereof, used repeatedly over a few weeks.

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