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!

Sincerely,
Sophy

Sophy,
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.

Peter