Well if we are not 100% sure what the problem is, I'm thinking mites, then lets go with a Sulphor spray it will slow down and kill some mites and will only help any rot issue ??


Or you could just start wth a systemic fungicide and see if that helps. If not move to a miticide.

sounds logical

The world of cacti does not allways follow logic

thanks guys - I appreciate the help. I have had
a bad week as far as plants go!

To add more info and answer a few more questions. they are kept in
a cupboard like setup with a number of levels and fluros. all sides are
closed in. they sit in a plastic tub - so Its quite humid.

I should have mentioned this before but ages ago the all the pereskoopsis
developed funny looking leaves. like below.
it looks like mite damage right? but where are
the mites?


could it be that the mites are just too small to see?
I have used up to 40x magnification and can't see anything.

I'm also thinking about degrating the lot, grafting the pups and getting
them on their own roots. then take them to the greenhouse where they can
get some real sunlight.

what do you think? a number of the grafts are not doing that well anyway
and have developed their own roots already.

grrrrrr

also - I'm pretty sure it (the nastyness) has spread to other plants in the same area.

cheers

Hmm this is a pickle. After reading about your setup i'm now leaning more towards kada's idea. You need to open it up and allow air flow.

I have never been able to see mites but you can easily see their webs !. Its kinda like a silky white sheet over the skin. Have a good look for silky webs, They (mites) don't seem to attack pereskiopsis much but build nice webs on them.

I woudln't degraft whilst under stress they will really struggle. The scions must be healthy to degraft.

That leaf does look like mite damage but again you would see the webs.

I think the original damage resembles a lot lightburn, like Kada said....