A little story...

A couple of days ago I noticed a few little mites (what I thought to be mites) on some of my potted Trichocereus. I wasn't too worried. I figured I would just give them a good spray with something and give the rest of my greenhouse a good preventative spray. No worries I thought. Good greenhouse management. I'm so smart.

I grabbed the confidor... nah, kinda gone off confidor recently

I grabbed the Rogor... nah, kinda smelly - and I don't want to spray it to excess in the confines of my greenhouse without a mask. Although I'm sure it would work wonders.

So I grabbed the Natrasoap... hmm organic specifically for mite. Cool... so I loaded up my 5 litre sprayer with a week solution and sprayed every single plant in my greenhouse - I’m so smart....

Anyway - I returned a couple of hours later and was happy that the soap spray had not marked my plants.


Ok yesterday I notice a couple of my Astrophytum myriostigma nudum have a funny pale marks - must have been the soap! Oops. I put them in the shade and crossed my fingers.

I return today and noticed the pale marking on the astro was going away. Great!

Anyway while kicking around in there I noticed one of my trichocereus had lots of blisters on the flesh. Fluid filled blisters that join up into large bumpy mountain ranges. On the larger peaks the flesh has turned black and a few of them are weeping a dark goo…. On closer inspection there were a load of my Trichos that have the same blistering. It almost looks like there is something under the surface tunnelling just under the flesh. I counted about 15 or 20 plants with the same damage. I will have a better inspection tomorrow and take some pics.

It’s going to be messy…


It’s funny but at the time I was thinking about the effects of soap on the waxy skin and if it could cause damage. Grrr… so stupid.


The only comforting thought I have is that I’m in this for the long term - so in 5/10 years this will just be a learning experience.

i noticed the same thing when i used pyrethrum+big killer. (basically pyrethrum with some potent non organic additive) on my echinopsis eyresii when i saw mealies. exactly as you describe.. big black blisters which weep goo. i was so alarmed i threw the plant away. im so glad i only used it on one plant. i never used it again.. except to kill those pesky native cockroaches which are present in plague proportions in my area in summer.

I reckon anything thats going to mess with the waxy skin is bad news.

I have noticed that a lot of natural products contain surfactants to assist the active ingredients.

I think I will stick with my harsh toxic chemicals from now on

Pyrethrum based sprays should be kept well away from any cacti. It melts Pereskiopsis into a mush and does major damage to many plants.

Thanks for the info on Natrasoap. Only thing is I have used Natrasoap on my trichos before and had no dramas. Check the ratio and make sure you don't have a pest, especially if you are seeing tunnels on the skin.....sounds like a pest.....Caterpillar or larvae ???? some burrow in to the plant

So this is basically what’s happened - I had more pics but they all are essentially the same.
The tunnelling I talked about is really just on this plant and can be seen on the lower left. I feel like these are just small abrasions on the skin that have allowed the soap to enter.
It’s interesting that although all the plants had the same treatment only some got damaged. For example the Astrophytum were actually (A. myriostigma nuda x A. myriostigma strongylogonum ) and the neighbouring A. myriostigma nuda are fine.
Pictured below. The pale areas are now hard lumps.



I just hope the worst of the damage has shown it’s self and doesn't keep happening. There are some Tricho that have some small bumps which I think should be fine.... as long as they don't start rotting....

what do you think I should do now? a part of me wants to give them a good water which might help then deal with the stress...? but the first rules when these things happen is usualy don't water!.