What are these black spots?

Trouble shoot problems you are having with your cactus.
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Ozgur
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Location: Houston, TX USA

What are these black spots?

Post by Ozgur »

I love this cactus on the right, but lately it developed some black spots. Any idea what they are, and how I can treat them?

Thank you all in advance...
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LophoFan
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Re: What are these black spots?

Post by LophoFan »

That looks like some kind of fungal infection to me. I would personally cut out the black spots, cover with sulfur powder, and stop watering for a month or two. How fast have they been spreading?

You may want to get some other opinions though before chopping up your beautiful plant.
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Ozgur
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Re: What are these black spots?

Post by Ozgur »

Thank you LophoFan.
They've been there for a while, I'd say about 2 months.
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Steve Johnson
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Re: What are these black spots?

Post by Steve Johnson »

LophoFan wrote:That looks like some kind of fungal infection to me.
Try again -- those black "cigarette burn" lesions look suspiciously like mechanical damage. Getting poked by the spines of another cactus tends to be the #1 culprit, and it can take a good while before we see the full extent of the damage. Ozgur, I don't know if you went through any frost 2 months ago, but your overnights may have been cold enough to turn the lesions dark. If they're calloused, I wouldn't worry about it. Just keep an eye out in case they get bigger and/or turn mushy. Hopefully this won't happen to you. But if it does, come back and someone should be able to help you in case some cactus surgery is warranted.

Best of luck!
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Ozgur
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Re: What are these black spots?

Post by Ozgur »

Hi Steve,

Thank you for writing. I don't think this is a mechanical damage; the spots are mainly at the tip and I don't think any other cactus hit it. I live in Houston, TX. Since summer 2013, temps briefly touched the 31F-32F range on 11/28, 12/10, 12/16, 12/24 and 1/3. And then on 1/6 and 1/7 we hit the 23F-27F range here during night. In all these events, I covered this cactus with a plastic bag.

I will watch for callouses, size and consistency (mushiness) of the spots. If this is a fungal infection, do you think it will spread to other cacti?
LophoFan
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Re: What are these black spots?

Post by LophoFan »

If it's an infection I doubt it will spread to other cacti without direct contact. Have they been spreading on this plant?

And Steve, I've seen fungal infections that look exactly like this. I'm not saying they are for sure, but it's possible.

Just watch them and if they start spreading and getting mushy it probably is an infection.
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greenknight
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Re: What are these black spots?

Post by greenknight »

I've seen cacti with a kind of black rot that grew very little, if any. It was a dry rot, never got mushy. I don't know how it originated, but these plants grew right around it, lived for years with these black dead patches.

The infection may have already run its course, you may not need to do anything. Keep a close eye on it, if it doesn't grow any it's probably dead.
Spence :mrgreen:
Cool Potter
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Re: What are these black spots?

Post by Cool Potter »

I had the same trouble and was advised to cut the top of the plant off and start again. I wanted to follow their advice but couldn't bear the thought of the attack!
Therefore, I decided to leave it and see what happened. The black spots, which were twice as large as those you show, slowly paled in colour and now look like pale grey scabs. I'm so glad I decided on the patience option. None of the other cacti in the immediate area were affected and the lesions are no longer horrible to see. I think now that the temperature drop must've just damaged cells on the outer layer of the plant, but only to a minimal degree. I hope this is what has happened to your plants. It is about 5 months now since I first noticed the trouble, (about the end of our cool temperate winter in Tasmania, Australia). It is now summer and the cacti have grown about 6 inches since their shock!

Good luck with your plants. Incidentally, this only happened to those cacti that were bluish in colour and at first the black spots seemed to be very dark blue. They are now thriving!
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Ozgur
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Re: What are these black spots?

Post by Ozgur »

Thanks for all your replies. I showed these pictures to the owner of the nursery I bought it from and asked him what to do - he said it was an infection and that I should use systemic insecticide and pesticide. In that same visit, I bought another Pilosocereus.

Turned out that new one I purchased had the same problem. I used systemic insecticide and pesticide but they didn't work. In just a few weeks both cacti started to rot and I had to cut the top. When I did, I saw many of those spots inside the plants.

Bottomline: They are both dead. I chopped both into 3-4 inch blocks. Half got rotten, with a terrible smell. I planted the others; hoping that they will take root.
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jp29
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Re: What are these black spots?

Post by jp29 »

Not unusual on blue ceroid cacti - especially Brazilians - mostly likely caused by low temperatures in concert with elevated atmospheric humidity. As others have mentioned they are usually of no great concern and will soon heal on their own in a drier location with warmer temps.
Last edited by jp29 on Fri Feb 28, 2014 5:17 pm, edited 1 time in total.
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Saxicola
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Re: What are these black spots?

Post by Saxicola »

Ozgur wrote:Thanks for all your replies. I showed these pictures to the owner of the nursery I bought it from and asked him what to do - he said it was an infection and that I should use systemic insecticide and pesticide. In that same visit, I bought another Pilosocereus.

Turned out that new one I purchased had the same problem. I used systemic insecticide and pesticide but they didn't work. In just a few weeks both cacti started to rot and I had to cut the top. When I did, I saw many of those spots inside the plants.

Bottomline: They are both dead. I chopped both into 3-4 inch blocks. Half got rotten, with a terrible smell. I planted the others; hoping that they will take root.
Too bad. It sounds like this guy may not know as much as he thinks he does. Among other things I'd question why he recommends an insecticide for an infection instead of a fungicide. It may all be to the unusually cool winter you had in Houston combined with wet weather, but the nurseryman should know that and he should at least refund your money for the plant that died shortly after purchase.
I'm now selling plants on Ebay. Check it out! Kyle's Plants
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