Black spots on Tephrocactus geometricus

Trouble shoot problems you are having with your cactus.
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Cacidy
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Black spots on Tephrocactus geometricus

Post by Cacidy »

Hello everyone!

I just picked up a Tephrocactus geometricus cutting and I noticed small black spots around the body and some black around the cutting. This was from a grafted geometricus. Any ideas of what it could be or what I should do about it? I would like root this guy. I also just thought about grafting it but I have never tried grafting a cactus.

Thanks for the help and advice!
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hegar
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Re: Black spots on Tephrocactus geometricus

Post by hegar »

Well, this is a difficult one to answer. One thing that I believe is present on your Tephrocactus geometricus stem piece are armored scale insects.
You can go ahead and check in order to verify this by clicking on the tab "Pests and Disease" at the top of the homepage of CactiGuide.
I photographed the round, dirty-white scale, which is commonly found infesting cacti. You will need to take care of this problem, before you should even think about doing anything about the black spots.
Because your stem segment is rather small, you may actually kill it, if you were to cut around near those lesions. There are at least two of those circular black spots visible, plus something that looks like a discolored crack near the part that was attached to the main plant.
Because you seem to have multiple problems, consisting of a stubborn insect pest and perhaps also a pathogen and perhaps already a rot, it may be best to cut off those two black lesions and check what the plant tissue looks underneath. If it is uniform in color (no brown streaks, etc.), then the cut area should heal within a few days, unless you transferred any microorganism onto the cut part, because the knife blade was not sterilized before doing the procedure.
The other two areas near the base on image 1 showing a blackened area with two female scale insects attached, and also the deep crack visible near the top on image 2, should also be inspected further. Cutting them off may, however, remove so much of that small stem segment, that it may not be big enough afterwards to grow it into a plant.
In short, I would only do what I suggested above, if the stem piece were rather important to me and out of curiosity.
The logical thing to do would be, to throw the cactus piece into the kitchen garbage, in order to keep the scale insects from spreading and attacking your other cacti, if you do have any additional ones at your place. Sorry, to have no good news for your T. geometricus stem segment's treatment and rescue.

Harald
Cacidy
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Joined: Fri May 19, 2017 5:05 pm
Location: Sacramento, (Zone 9b)

Re: Black spots on Tephrocactus geometricus

Post by Cacidy »

Harald,

Thanks for taking the time to give such an in depth analysis. You are spot on about the scale, while I was scraping them off I noticed what I think are red spider mites...

I found a bit of information about the black spots on mycotopia.net, a monstrose bridgesii had very similar spots, the owner seems to think it may be from puncture wounds or possibly some kind of surface infection, he claims they usually heal. Heres a link to the post.

https://mycotopia.net/topic/76540-black ... m-of-this/

I'm not going to try to root it now, but I was a little confused by whay you meant by not enough stem segment. Does the head need some stem tissue to get roots? Like I need to have an axillary bud to get roots to form or something? I have no experience with propagation but have taken botany courses.

All in all this has been a great learning experience, taught me to really give a plant an inspection before buying from an unfamiliar nursery.

I really am in love with this species and have been trying for a while to get it in my collection. It seems this species is hard to come by either because it is hard to propagate or susceptible to disease. I've only seen them once a recent show and they were $100 USD for a 3 headed grafted plant. That's why I asked for a cutting of one (cladode?), and he sold me the one pictured for $25. Any advice on how to acquire a healthy plant?

Anyway, this is how the geometricus is looking this morning.
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hegar
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Re: Black spots on Tephrocactus geometricus

Post by hegar »

Hello Cacidy,
I am sorry to have come across in such a pessimistic way. The cladode you purchased, and which cost you an unbelievable price or $25.00, is from a cactus, that I would not mind having in my own collection. I do admire the nice geometric tubercle design. I wonder, where you do live, because it should be possible to obtain a replacement specimen perhaps even for free. I did have two kinds of Tephrocactus papyracanthus (with soft, wide, papery spines) and T. papyracanthus var. diadematus ( a spineless kind) given to me by fellow local cactus club members. The former I am already giving away to anybody who wants it. If a segment of the latter breaks off, it too will go to someone who would like to have it. I am waiting to have enough segments form for the plant to flower. Is there a cactus club somewhere in the vicinity of where you live?
Also, there are perhaps people here on CactiGuide who do have this plant in cultivation and would give/sell you a healthy replacement cladode or plant.
When I mentioned the difficulty about growing the cladode after you had done some "surgery", I was indicating, that it is not easy to grow or keep a plant alive that has been reduced to just a few tubercles, once parts of it have been cut off. I do have a Master's degree in Horticulture and I do have rooting hormone, but I would not be 100% convinced, that I would be successful at keeping the plant alive and growing.
Also, I am a little bit surprised, that you tossed the cactus segment into the trash, without having heard from someone, who may or may not have agreed with my assessment. If you are correct about the presence of spider mites, in addition to armored scale insects and possibly a pathogen on the outside and/or inside of the cladode, then most likely it was the correct decision to discard the cactus.

Harald

P.S.: Did you cut into the tissue underneath the darkened lesions and the other discolored areas, in order to see, if the interior tissue of the plant part was discolored/infected?
Cacidy
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Location: Sacramento, (Zone 9b)

Re: Black spots on Tephrocactus geometricus

Post by Cacidy »

Thanks for the follow up, I suppose I can pull it from the trash and attempt to root it on the other side of my house in quarantine. Regarding cutting the cladode, not having any propagating experience, and the delicate nature of the procedure, I think I would do more harm than good.

I think I should just stick it in wet soil away from my other cactus and hope for the best.

Thank you very much for your advice and for offering the T. papyracanthus and T. papyracanthus var. diadematus. I am very thankful to have those cactus in my collection.
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hegar
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Re: Black spots on Tephrocactus geometricus

Post by hegar »

Hello Cacidy,
it is not difficult at all, to cut off a discolored spot on a cactus in order to find out, if there is a rot present underneath. A rot and pathogens will cause a discoloration, which may be as obvious as a browning or slightly different from the normal color like a "water-soaked looking area" or a chlorotic area.
Once the plant's tissue does have a uniform color it can be considered to be healthy. The only care you would need to display is to make the final cut with a disinfected cutting tool, general a knife. Isopropyl alcohol (rubbing alcohol) can be used to disinfect the knife. The cactus should then be placed in such a way, that the cut area is exposed to the air, so the wound will dry and heal, forming a callus layer.
Then the cactus can be placed in the growing medium. However, it is a mistake to put it into very soggy soil. That would once again encourage the growth of fungi that could lead to a rot of the plant.
This one lesion, which I had described as a deeper cut, also should be examined the same way the black spots are. Cut away anything that looks discolored and then let the cactus rest in a shady location to heal itself.
If there is an internal rot present in the cladode, your stem segment will within a few weeks become totally discolored and probably even very soft.
At that point the plant is gone.
You can give it a try and place that cladode away from the other plants in a pot. However, before I would do that, I would definitely check those lesions and get rid of the bugs (armored scale insects and possibly spider mites). The best way to tell, if you do actually have spider mites, is to check for some fine webbing. The animals are very tiny and do not move rapidly. Their color is in most cases a bit mottled with reddish-brown being the base color of the body. Some of these mites do have two red dots on their cephalothorax. If you use a small brush and a white piece of paper, you can brush the mites off the plant and should be able to see them crawl around on the paper.
You can remove spider mites mechanically or with a sharp spray of water. The armored scales do not wash off as easily. There may be some miticide/insecticide combination pesticides that can be used to kill both of these pests. Once a plant does have roots though, the easiest way to keep these plant pests at bay is to use a systemic insecticide/miticide. The problem is of course, that by repeating the treatment year after year, some of the plant pests may develop resistance and will no longer be controlled. So it is advisable, to switch pesticides and use different classes of chemicals with different modes of action, which will delay or prevent the pest from developing resistance to the pesticide.

Harald
Cacidy
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Re: Black spots on Tephrocactus geometricus

Post by Cacidy »

Alright, I decided I should try what you suggested and cut out the black spots. Those spots just flaked right off with the edge of a razor. I tried to take a closeup of it. And I just took a thin sliver off the base, enough to remove the black, although the tissue underneath doesn't seem totally uniform. I'm not sure if it seems that way because of the angle of the cut though. Maybe you guys can tell from the pics.

I didn't like the idea of cutting out that callous, it looked a like a big area to cut out for a small cladode so I left it.

The head honestly feels a little squishy...I have been handling the $#!% out of it though...
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hegar
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Re: Black spots on Tephrocactus geometricus

Post by hegar »

OK, what you are telling us is not too bad at all. If the black spots just flaked off and the tissue underneath is not discolored, there is still hope for your stem piece. Also, the cut that removed a bit of the plant pieces base does look normal. This could mean, that there is no rot pathogen present, which looks like a positive thing to me.
Now you only need to let the cut base heal and form a callus layer and you are ready to give it a try to grow this plant. I hope, that you have taken care of the scale insect and mite infestation. Keep the plant under observation for any changes be they caused by arthropods or perhaps plant pathogens. I wish you good luck und success, resulting in a positive outcome.

Harald
Cacidy
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Re: Black spots on Tephrocactus geometricus

Post by Cacidy »

:wink: Finally got around to grafting the T. Geometricus. A nearby cactus master was gracious enough to try to save the little guy and show me how he likes to graft. I hope it takes. I'll post updates soon. We put it on Trichocereus (Echinopsis) spachiana.
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hegar
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Re: Black spots on Tephrocactus geometricus

Post by hegar »

The graft looks good to me. I hope, that your Tephrocactus geometricus will grow well for you. :)

Harald
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ElieEstephane
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Re: Black spots on Tephrocactus geometricus

Post by ElieEstephane »

Any updates?
There are more cacti in heaven and earth, Horatio, than are dreamt of in your philosophy.
One of the few cactus lovers in Lebanon (zone 11a) :mrgreen:
Cacidy
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Re: Black spots on Tephrocactus geometricus

Post by Cacidy »

The grafting has done well. Those black spots have dried up and scabbed over, after this picture was taken I flaked them off to reveal mostly healthy tissue underneath. There are two areoles near the cut that have developed some red hair amd will hopefully produce new cladodes next growing season. It has inceased in size a good amount, I am very happy. :D
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