Are they sick?

[anna_sweden]

Hi everyone,

This is my first post here, and I'm writing because I have a Mammillaria that was planted in one pot with four stems, two of the stems have rotten (one even rotted while I hadn't watered it for two months) and now I noticed on the largest one that there is a miscoloration... What do you think this is? Could it be red spider mite? I tried looking with a loupe but couldn't see anything moving... see picture below (I know it's difficult to see much in the picture, sorry)

Also I have a Lobivia backenbergii that has been sitting close to the Mammillaria and it looks like something might be wrong with it too...

What is happening? I'm worried about the rest of my cacti now

Any help is greatly appreciated!

Best,
Anna

[crispy224]

It's hard to see the first one through but it looks like it got damaged maybe bumped into. For the second pic I would take a magnifying glass and look for pest. I know thrips will damage a cactus making the skin look dry and flaky like that.

[anna_sweden]

Thanks for your answer crispy224, I have checked both plants with a magnifying glass and can't see anything moving... I don't think the Mammillaria have been physically damaged but I'm not 100% sure.. I guess I will just have to keep them away from the other plants and see what happens. I just hope my other plants aren't affected by whatever it is.

[Grimm]

Looking at the second pic, it looks like there is hardening of tissue close to the growth point, which would suggest pests to me (but it could be other things). Thankfully you don't seem to have lost the growth point itself though. I would spray them both, just in case. I use an Acetamiprid based spray - just keep them out of the sun for a week or so after spraying.