Dear Cactus Jungle,

I was recently examining my cacti and noticed two very strange (maybe) fungus/viruses on two of the four.

(one is a ‘Fairy Castle’/Cereus tetragonus,

Cactus #2

the other might be a Coryphantha georgii,

Cactus #1

though I’m not sure about that).

I scoured the internet in search of identification for these possible fungi or viruses, but was unsuccessful. I noticed this blog when looking for answers, and would be so grateful if you could help me. I love these little buggers and would hate to see them go. I’ve attached two photos to this e-mail.
Thank you very much for your time and help!


I’m not seeing any fungus on the Cereus. Maybe there’s some rot on the inner branch, but it doesn’t look like a fungus. If it’s soft it may be a problem of overwatering, or if the plant has been in the pot for a long time it may not have enough soil left. It looks like it’s ready to be potted into a larger pot – the brown things coming out of the branches are aerial roots looking for more soil.

The other cactus (possibly a Coryphantha, although I would guess a Mammillaria, but I would need to see the blooms to know for sure) looks like a fungus, possibly Rust. You can spray fungus with standard organic fungicides. We like to use Neem Oil.