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[Fontoking61777]

Got some black spot on them wanted to how to fix it or if its problem

[Solipsis]

It's weeping black rot i'm pretty sure..

It is often considered to only be an aesthetic problem and it is common. The spots can dry out and become a lighter color but also ooze stuff that I think makes it highly infectious esp to other Trichs but bridgesii seems to be more vulnerable to it just like fricii seems to be more vulnerable to rust than the average Loph.

Anyway, if you grow outdoors it is less likely to become a problem but it is still infectious and if you keep having conditions that favor the rot and also potentially kinds of damage may cause it. Perhaps especially insect damage from insects that are infected with the mold.
Indoors which is how i grow... it is bad imo and should be quarantined outside of the house.

I guess high humidity but especially poor ventilation can cause it.

Very small spots that ooze, i have personally just put a little glue on to prevent it from spreading that way. I'm looking into agents that can be applied to plants that would stop spores from ever germination, like I think sulfur can.

I really don't recommend cutting into your plant unless in very particular circumstances to save the plant/genetics. What I would like to know is if the mold can eventually go systemic (so like into the 'bloodstream' of the plant) like i think rust can.

[cactusman]

It's weeping black rot i'm pretty sure..

Is that the real term for it? I always just called it benign black rot

[Shamichael]

I'm guessing you're somewhere humid.  I am in a very humid area and I have several cacti right now with this.  I cut it out and treated a couple of the cacti but it only came back in another area. 
I was told that the humidity is the major cause but that chemical ferts also play a role, and that trichocereus don't like them. I will try using only organic fertilizer and see how they do next summer in the humid weather.