Cactus rot

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Spikylover
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Cactus rot

Post by Spikylover »

This is gonna sound stupid but why do cacti rot? We know that when cacti are wet and cold, they rot. But why? I understand that some pathogen is involved, but why and how does it happen? :-k
If a pathogen is involved, if someone would put a sterile cactus in a sterile pot with sterile soil and water in the lab. Would that mean the cactus would not rot? Or the pathogen is inside the roots?

Thanks for shedding some light on this matter.
Rachel.
Rachel
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Spikylover
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Re: Cactus rot

Post by Spikylover »

Anyone?
Rachel
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DaveW
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Re: Cactus rot

Post by DaveW »

In many cases I presume the cactus has died from some other reason, like overwatering and then as with all dead bodies they start to rot due to pathogens as you say. Strange to say I often find a cactus that is rotting often has a larger infestation of mealy bugs than one that is not. I doubt the mealies killed it, so possibly they even prefer sick plants?
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Spikylover
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Re: Cactus rot

Post by Spikylover »

Thanks for the reply but now i have other questions. How does overwatering kill a plant or a cactus? I know roots need O2 but then what?
DaveW wrote: Mon Feb 05, 2018 5:46 pm Strange to say I often find a cactus that is rotting often has a larger infestation of mealy bugs than one that is not. I doubt the mealies killed it, so possibly they even prefer sick plants?
Do plants have like an immune system or something like that? I saw once a plant that was sickly and they gave it small dose of aspirin and the plant became greener and better. Not that it had a cold :lol: but aspirin is derived from plant matter (as are most medications) so something should be in line in that department maybe?
I thought the process of why a cactus rots is fairly understood [-(
Rachel
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Pompom
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Re: Cactus rot

Post by Pompom »

Spikylover wrote: Mon Feb 05, 2018 6:05 pm Do plants have like an immune system or something like that? I saw once a plant that was sickly and they gave it small dose of aspirin and the plant became greener and better. Not that it had a cold :lol: but aspirin is derived from plant matter (as are most medications) so something should be in line in that department maybe?
I recently read an article about plants communications. There was a mention about them feeling a touch. When plants in study were touched, they started to release some toxins which prevent the plant from bugs. When they released toxins, their growth slowed. Anyways, plants cannot tell the differences between touches, so even the wind could trigger the mechanism. Cacti weren't used in this study, but they are plants, so why wouldn't they have it too? That's some kind of immune system?
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Re: Cactus rot

Post by DaveW »

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TimN
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Re: Cactus rot

Post by TimN »

My experience has been that most cactus rot is caused by an injury of some sort. Could be an insect, some sort of physical damage, repotting and trimming roots, etc. One thing that complicates determining the source of rot is that a cactus will rot on the inside for quite some time without showing significant external clues.

I've had a few cactus split from too much water, but even those healed without rotting. I had 17" of rain in three months (Jan - Mar) a few years ago and I didn't experience any higher than normal mortality, so I don't think over watering causes it. Water may transport pathogens but I don't think it causes rot.
Disclaimer: I'm in sunny Arizona, so any advice I give may not apply in your circumstances.

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Spikylover
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Re: Cactus rot

Post by Spikylover »

That's very interesting pompom! I'll look search about that
Dave so essientially what they're saying is that the roots behave idependantly from the plant. So when they become deprived of O2, it's not supplied from the plant to the roots (so it's 1 way then?). And when roots suffocate, they die and decay and that's where rot sets in and speads.
TimN that's some very interesting insight. So theoretically a healthy cactus can be watered in sterile water indefinitely without rot. Interesting
So now i understand that if a cactus stays still with no ropotting or anything, there still is a chance of rot because maybe insect (could even be harmless) made a tiny injury to the roots or plant and that where a pathogen already in the ground enters in the plant and stars slow and then multiplies exponentially. Or maybe even wind in a storm could have broken the very fine roots by rocking the plant and then rots set in from the rain. Or if a cactus is dry, pathogens can enter that wound. And sonce they are microscopic, then only need a microscopic wound.

Many thanks to everyone!
Rachel
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ElieEstephane
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Re: Cactus rot

Post by ElieEstephane »

Sometimes it's not the water itself Rachel. If the surface stays wet for too long, fungi can start to form on the skin and eventually break in at some point (sort of like powdery mildew on roses). Cacti with a depressed apex where water can accumulate are also susceptible to crown rot. The same can happen to cacti with wooly apices. Fungi can also infest a wet organic soil and suffocate the roots leading to root rot.
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:
DaveW
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Re: Cactus rot

Post by DaveW »

There are very few situations where anybody or anything is in a pathogen free environment, unless you live in one of those sterile hospital bubbles. Even if you watered with sterile water there are pathogens in the soil and air. Even with sterilising the soil, as soon as it is exposed to the air pathogens rain down on it. Therefore you would even need to sow seeds in a laboratory clean room to avoid that when sowing. If you open the bag if using "baggies" for seed raising to either sow them or look at them you automatically introduce pathogens.

Really even with soil sterilisation you are simply growing in a reduced pathogen environment, not a pathogen free one. Just as the Advertising Standards Authority in Britain will not allow disinfectant manufacturers to claim they kill all known germs, but only 99.9% since 100% germ free is unprovable in science.

All living creatures depend on some degree of immunity, or the ability to fight pathogens to survive. As Elie says plants can rot from the top down as well as from the roots up, though we usually loose most cacti from rotting from the base and over watering or the soil remaining wet too long, though of course with cold sensitive plants it us usually the stem above ground killed by the cold, since the soil itself provides some insulation from the cold.
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Robb
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Re: Cactus rot

Post by Robb »

DaveW wrote: Tue Feb 06, 2018 1:26 pm Therefore you would even need to sow seeds in a laboratory clean room to avoid that when sowing. If you open the bag if using "baggies" for seed raising to either sow them or look at them you automatically introduce pathogens.
I often notice that seedlings that seem to be doing fine inside their bags will suffer a high mortality rate when I open them. Maybe this could be due to the fact that growing in a reduced pathogen environment, the seedlings don't have the same sort of immunity to fungi etc that seedlings have grown out of the bag? While no doubt the fact that they are changing from a high humidity environment to one of comparably low humidity contributes to this by stressing the plants out, I have not considered that there may be some sort of immunity at play.
Buying a cactus a day will keep the madness away.
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ElieEstephane
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Re: Cactus rot

Post by ElieEstephane »

This calls for an experiment. Next batch of seeds i sow, i will compar bagged and unbagged (if i have the time to keep misting) and we'll see who turns out to be stronger
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:
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greenknight
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Re: Cactus rot

Post by greenknight »

The problem with saturated soil isn't too much water, it's lack of air - water has filled up all the air spaces. If it stays that way too long, all the oxygen gets used up. Plant roots need oxygen. Also, different microbes grow under those conditions that produce toxic waste products - the soil sours.
Spence :mrgreen:
DaveW
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Re: Cactus rot

Post by DaveW »

We often forget that the seed itself usually contains pathogens on the seed coat since we seldom disinfect them too. It being difficult with small seed and even more so if you set about 20-50 different species at a time. Usually they have grown on the dried mucilage from the fruit originally. Also everything we touch or breath over we transmit bacteria and pathogens to, or obtain them from what we touch or breath in. Luckily most of these are not harmful to us or to the plants. We think since we got rid of visible fleas we are super clean, yet all animals including humans are covered with millions of bacteria etc, invisible to the human eye. Therefore there is virtually nothing that is actually sterile in the world.

In fact now we use disinfectants so frequently in the quest for super cleanliness we are no longer gaining natural immunity and over cleanliness is put down to the large rise of children with different allergies. You never heard of nut allergy when I was young. I was never vaccinated because my dad had a thing about it, so have had Mumps, Whooping Cough and Measles and am still here. The strange thing was all the kids around me that were vaccinated seemed to get them too.
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ElieEstephane
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Re: Cactus rot

Post by ElieEstephane »

Yeah and when we were kids mud was actually very entertaining to play with :lol: :lol:
With kids always inside these days and the news strains of viruses, natural selection is gonna play a very important role in the future of humanity. When humans were still nomads and hunters, only the strong and smart survived. The rise of farming saved the lives of the weaker humans buy providing them with food they can't get and now we all have some of their DNA
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:
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