I've been noticing these weirds orange/rust colored spots on my astrophytum asterias. Does anybody know what this is and how to remove it?
I don't know what it is. All I know is that I had a Euphorbia obesa with similar lesions that eventually rotted through. I noticed them when they were about the same size as the ones on your plant. I found another affected euphorbia but caught it when the spots were first developing, about the size of a BB. I cut them out and dusted the cuts with sulphur. So far so good.