Will this 'rot' cause any problems?

[duckworth]

Hello everybody!

I'm just wondering if this little black dot could cause any problems. I should mention that there was some dark, moist rot on the cutting, which I cut away about 2 months ago. I didn't cut ALL of it away though, it was discoloured. But it didn't seem to matter. Now, this little black dot has appeared about 1-2 weeks ago, in a different location (the original darkness wasn't in the core). I think the species is Trich. scopulicola, or a hybrid.

Also - it was in a pot of 100% dry perlite for 3 days - but this pot had another cutting in it beforehand (which also has some rot, more, and I don't know if that'll survive ). Could the disease from that other cutting in any way transfer to the cutting in this photo through the perlite?

Thanks people - and I want to thank you all for the time you put into answering questions here and helping out!

[hegar]

The picture showing the cross section of the stem with the yellow-orange spot, is that how your plant looks like now?
I would go ahead and make a fresh cut, in order to find out, it the discoloration does extend further into the interior of the cactus stem.
If so, it would be best, to slice some more of the plant off, until you do have no more discoloration visible. At least the last slice you make should be done with a disinfected cutting tool. Otherwise you may spread the infectious agent (bacteria or fungus) back onto the cactus.
Also, it is always a good idea to disinfect the pot and use a clean (new) growing medium, especially when placing a plant with a new callus tissue back into the pot for growing roots and becoming established. It will be a while, before the cut end has produced a sufficiently thick corky layer, which helps in keeping pathogens out. Some of the rot pathogens are present in practically all kinds of soil, but will not cause a problem, unless the plant's defenses have been weakened, e.g. root decay due to overwatering or mechanical injury (opportunistic pathogens).

Harald

[greenknight]

Agreed. When you're cutting off rot, you need to cut it clear of any discoloration.

You can reuse that perlite, but you should bake it or microwave it to sterilize it.

[duckworth]

Thank you, guys. Yep this is the current state of the cactus.
Can cutting into the cactus too many times shock or kill it? If I cut again, it will be the third time. It will only be around 10cm - 12.5cm long after the cut.

Could the cactus potentially be fine if I leave it? Or is it clear that rot is sealed behind the callous? The orange part is not soft.

[greenknight]

Cutting again won't shock it. 10cm long is plenty large enough to be a viable cutting, that's what counts.

Can't predict with absolute certainty that rot will spread from that spot, but it's likely. Safer to cut it off now, rather than risk having to cut off even more later, or maybe losing it completely.

[duckworth]

Okay, one concern is that the cutting is quite soft - i think because of lack of water. What if it doesn't have enough hydration to survive until it heals and gives out roots?

[greenknight]

As long as it's not really shriveling you should be ok. After it's planted you can give it a daily misting to reduce moisture loss - not enough to soak the soil under it, just dampen the surface to raise the humidity.

[duckworth]

Thank you, again!

[duckworth]

Hi everyone,

Here is the latest: I cut the cutting again. Almost within 1 day, this orange colour appeared. It happened so quickly! Is this anything to worry about?

[hegar]

Well, I certainly would worry about these two orange-yellow spots. Their quick appearance would indicate the presence of a pathogen, which seems to be rather aggressive. So I would not lose any more time and cut yet another slice off the stem base, perhaps 1/2 to one inch above the last cut.
Unfortunately, the presence of microorganisms like fungi and bacteria is very difficult to determine, except of course through viewing the damage these organisms cause, e.g. discoloration, rot, wilting, die-back, etc.
In some cases, the pathogen will already be present all the way to the tip of the plant, but the plant's tissue still looks healthy. Then, most likely even a very severe cut-back from the original point of infection would do no good and the plant would succumb to the invading organism.
I admit, that I have lost a sizeable number of my cacti over the years due to root rot organisms. Oftentimes it is already too late, by the time something seems to be wrong with the cactus.
This said, I would cut off enough of the stem piece - at least as much as I have mentioned above - from the point of where you cannot see any discoloration, using a sterilized cutting tool. You can brush some isopropyl alcohol (rubbing alcohol) on the freshly cut wound, apply some sulfur, or a fungicide if you do have this and let the cut remain dry until it has healed. If these are bacterial lesions, the sulfur or fungicide would of course not be effective. The goal is, not to have any of the rot organisms be present either on the fresh cut or inside the stem.
I hope, you do have enough of a stem size left to cut off enough of the diseased portion. Good luck with the task. I hope, that you will be able to achieve a healed cut that does not form new lesions.

Harald

[duckworth]

Thank you Harald once again, and to everyone else for all your help! Unfortunately I've had more bad luck with the cutting, and I'm not sure I have many options now. The orange spots have come back, and as you can see I've almost run out of cactus to cut!

With so little cactus left, maybe my best chance to leave it now and hope for the best.

Anyway thank you all for your help! I've learnt a lot