San Pedro white spots

[Solidsnake1]

Hi Team,

I'm just wondering if anyone knows what these white spots are and how to remedy them? I've tried upsizing the pot with new soil and a little fertiliser so I don't think its nutrient deficiency.

Would it be a case of the mature one sacrificing itself for the younger ones..... they seem to be doing fantastic and super green.

Conditions are rather hot atm here in Perth Western Australia. Mostly 28-38 degrees centigrade. But we have had a few 40+ days sometimes even 44.

Any help would be appreciated.

[Steve Johnson]

First of all, please see this:

https://www.cactiguide.com/forum/viewtopic.php?t=43816

And also see this:

https://www.cactiguide.com/forum/viewtopic.php?t=46111

Your thread should go into the Sick Cacti forum. I'm one of the moderators, and I can move it there if you'd like.

[Solidsnake1]

OK sure

[Steve Johnson]

OK sure

Done.

The spots appear to be callused-over water blisters, also known as edema. This article on succulent edema applies to cacti as well:

https://thesucculenteclectic.com/unders ... ucculents/

Are you growing your San Pedro in straight potting soil? If so, you'll need to mix it with some sort of mineral gravel for better drainage and aeration of the roots. The 2 best options are pumice and calcined clay granules. You can find both products on Amazon Australia:

https://www.amazon.com.au/s?k=pumice+fo ... doa-p_1_10

The mix I'll recommend is 50% mineral gravel and 50% soil. If the spots are being caused by edema, that mix should take care of the problem.