Black/brown skin fungus, initially firm before rotting

Trouble shoot problems you are having with your cactus.
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Download
Posts: 251
Joined: Mon Mar 01, 2021 5:22 am
Location: Adelaide, Australia

Black/brown skin fungus, initially firm before rotting

Post by Download »

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I got this mystery cactus last Autumn (Australian, so we just started Spring) and put it under shelter with my other cacti for winter. I suspect it is a browningia or a pilosocereus. A few weeks into winter I noticed a few blackened areole near the base. I just figured it was some mildewy fungus so I put some mancozeb fungicide on and figured it will stop being a problem come spring and drier weather.

I moved my cacti out from under shelter over the last two weeks and noticed the black spots had spread. I gave it a poke and it didn't seem soft, so I set it aside, deciding to wait and see what happens before decapitating and propagating it. Then, today I found it at a 45 degree angle and decided it was stuffed if I didn't.

I'm not sure if this infection weakened the cacti so something else could get in and rot it, or if the original infection just progressed.

Given it seems to sprout from the areole I'm slightly worried about it being infectious. Anyone got any idea what it is and if it's treatable if it gets onto other things? I'm thinking or preemptively fungiciding all my cacti just in case.
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hegar
Posts: 4596
Joined: Mon Jan 23, 2006 4:04 am
Location: El Paso, Texas

Re: Black/brown skin fungus, initially firm before rotting

Post by hegar »

Hello Download,

I just noticed, that nobody did respond to your post. It may already be too late and your cactus has "kicked the bucket" due to the rot is was experiencing. Your first image does show what looks like two slices of a small cactus. The piece on the left is not discolored and more promising to survive. I do not know whch part you placed in the pot. However, that cut cactus does not look good, because there is some discoloration visible one one side of it. Most likely, you either already tossed the cactus, because it continued to rot.
It is difficult to grow a cactus, if all you do have is a slice of it, especially, if the plant is small. In that case I would try to graft an areole or stem piece to another cactus.
I did do some budding with fruit trees during my time as a horticulture graduate student, but I have yet to graft a cactus. I am going to try that once spring arrives in March/April of next year.
Well, you most likely will have to replace that plant and I wish you luck growing cacti. Don't get upset and become discouraged, if you do lose a plant every once in a while. I do not have a brilliant track record myself and just lost a flowering size Ariocarpus fissuratus, which had been in a pot for the second season. :(

Harald
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