perhaps... but looks more like trauma lesions to me (like from hail or snail damage)

I agree, Some times it takes months for the damage to show itself. Like next to an agave leaf? Keep watch so infection don't set in. Maybe one of those Fungicides for Roses. Like Bayer 3 in 1.

Hi guys,

Thanks for your responses.

I really don't think these are trauma lesions. Towards the top of the cactus I have some trauma lesions from when the pot tipped over and fell a long time ago. Trauma lesions are biege and black in color. The main difference with these strange blotches are that a) there has been no trauma to the area, b) they have hundreds of tiny black pores if you look really closely, c) overall they are grey NOT biege/black, d) the surface of the blotches are raised. So there are many differences between the appearance of the trauma lesion and the strange blotches.

I have it near to a (healthy) Crassula ovata but it is not touching and they are a few inches apart. They are both indoor potted plants.

A couple weeks ago there was a frost overnight and I had the window open in the room where the cactus lives. Could cold cause this? It looks like some kind of microbiological thing to me though, especially with the hundreds of miniature black pores as you can see above.

This post was edited by stevelatinner on Sun, Dec 8, 13 at 4:37

Strange, can you collect the spores in a envelope and maybe watch to see what they do? Still, the Bayor 3 in 1 is good againest insects and fungus and only need a teaspoon to a gallon of water. I wonder if they are eggs? I heard stories of insects coming out of cactus. I thought they were not true.

Well they don't appear to be changing. I'm wondering what would make the surface of the lesions so bumpy, the trauma marks elsewhere are flat.

At first glance I thought there might me an aerial root forming, as I have on my similar Cereus...

Christopher

Hmm after googling some images, I don't think so. And they appear to be spreading upwards. The odd thing is, why are they only on this facet/side of the cactus? I forgot to mention that in my other posts.

This post was edited by stevelatinner on Thu, Dec 12, 13 at 5:01

I had alot of these little spots on one of my cereus about 2-3 years ago. They had the little raised bumpy pores as yours has, and then they erupted with black goo, and then just scarred over into trauma scars. nothing like it has happened to any other of my cacti.

Thanks for the post Microthrix. That seems to be exactly what is going on, but so far only one has erupted into the black goo. Just what the hell is it? Was your cactus getting enough light? I am thinking about using a fungicide as suggested earlier or vinegar which I hear works well against cactus mold.

I'd go with a copper based fungicide, or just cinnamon.

Have you tryied popping or poking one of the spots?

It looks like dead skin over top of rotting spots

I can't say I've seen this exactly, black goo and all, I have seem trauma spy's look very similar, if there's a way for moisture to be trapped in one if those spots it may begin to progress!

I'd open one up atleast!