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Hey all, have not checked in for a bit.

Just noticed this 2 days ago, and sprayed it with 3 in 1. It almost looks like mold, and is creeping its way to the growth point. I know we have high constant humidity here, but this is the only plant I see this issue with.

Hopefully you can clearly see the "green" stuff on the areoles.

Any thoughts? Thanks

It's some kind of micro-organism. Black sooty mold often grows on the aeroles of Tephrocacti and Glandulicactus, but it doesn't cause the plants any harm, just looks unsightly. I think this could be the same case for your plant. Unsightly, but nothing to worry about. Keep an eye on it though, just in case.

Did not realize this was a common thing, among some species.

I imagine hitting it with a dilute hydrogen peroxide be ok? Maybe can just spray it with a hose afterwards, and flush it off? Or a tooth brush, lol.

Yeah, you can go ahead with dilute peroxide, but I have a feeling it'd probably come back. Maybe paint a little fungicide onto the aeroles after peroxide treatment?

May just give that a try. Will be ordering some Fongarid here in the near future. See if that does the trick.

Otherwise, green areoles it is then