Help to recognize the disease

[Fohat85]

Dear friends,

I'm trying to understand why my ariocarpus are dying this year (and the other cacti aren't).
Before understanding the growing cause I am trying to classify the type of pathology they have.
It seems as if they were "boiled" but I would like to rule out that it is some type of fungus or other.
Some further details below:

- often it happens 5-10 days after I water (I always water in the evening);
- only happens to seed ariocarpus, grafted ones do not
- they are grown in greenhouses (day-night 45C°/20C° - 15%/90%)
- the greenhouse is totally open but I have no fans inside

After more of 25 days (august usually too hot). I gave them a little water and they started doing this.






What do you think is happening?

[ohugal]

They went into summer dormancy perhaps… but that doesn’t explain why it’s not happening to other genera. What else do you have growing?

[Fohat85]

They went into summer dormancy perhaps… but that doesn’t explain why it’s not happening to other genera. What else do you have growing?

I grow Turbinicarpus, astrophytum, geohintonia, copiapoa... several species!

[Tom in Tucson]

Dear friends,

I'm trying to understand why my ariocarpus are dying this year (and the other cacti aren't).
Before understanding the growing cause I am trying to classify the type of pathology they have.
It seems as if they were "boiled" but I would like to rule out that it is some type of fungus or other.
Some further details below:

- often it happens 5-10 days after I water (I always water in the evening);
- only happens to seed ariocarpus, grafted ones do not
- they are grown in greenhouses (day-night 45C°/20C° - 15%/90%)
- the greenhouse is totally open but I have no fans inside

After more of 25 days (august usually too hot). I gave them a little water and they started doing this.






What do you think is happening?

Your user profile doesn't reveal your location. If you live in the desert southwest, then your "boiled" reaction is possibly correct. Other than that I would suspect a soil pathogen such as root mealy bugs.

[jerrytheplater]

Your user profile doesn't reveal your location. If you live in the desert southwest, then your "boiled" reaction is possibly correct. Other than that I would suspect a soil pathogen such as root mealy bugs.

Tom, his signature shows he lives near Rome, Italy

[Steve Johnson]

Let's take a look at the following numbers:

• Daytime high 45C/113F

• Overnight low 20C/68F

Okay, overnight lows well below 75F indicate that you don't have a summer dormancy problem. Davide, were your Arios growing on their own roots grown from seed by a nursery, or were they collected in the wild? Knowing who the original seller is/was can be significant. Before I jump to any conclusions, let me know where the Arios originally came from.

Update: Now that I think about it, the Arios growing on their own roots might be uniquely susceptible to problems with extreme heat and lack of free airflow in your greenhouse. There's a good reason why experienced growers always use fans in greenhouses.

[ohugal]

Did you take a look at the roots of the affected cacti?

[Tom in Tucson]

Your user profile doesn't reveal your location. If you live in the desert southwest, then your "boiled" reaction is possibly correct. Other than that I would suspect a soil pathogen such as root mealy bugs.

Tom, his signature shows he lives near Rome, Italy

I rarely read tag lines "My Bad" (just profiles in user avatar box).

[Hanazono]

G'morning Davide,

only happens to seed ariocarpus, grafted ones do not
- they are grown in greenhouses (day-night 45C°/20C° - 15%/90%)
- the greenhouse is totally open but I have no fans inside

I have kept many Ariocarpus propagated from seeds in my greenhouse. I think our summer is a bit hotter than your place but I can not see any similar ploblem on my Ariocarpus species.

They are grown in a greenhouse (day 50 C' and night 20 C')
Since it exceeds 50 C' in normal condition easily and I cover the greenhouse by a shadecloth in summer to keep within 50 C'.

The greenhouse is not opened. There is a door attached shadecloth. Birds and insects go into greenhouse easily, the door is closed.
The greenhouse has no fans.

Frank

[Fohat85]

Let's take a look at the following numbers:

• Daytime high 45C/113F

• Overnight low 20C/68F

Okay, overnight lows well below 75F indicate that you don't have a summer dormancy problem. Davide, were your Arios growing on their own roots grown from seed by a nursery, or were they collected in the wild? Knowing who the original seller is/was can be significant. Before I jump to any conclusions, let me know where the Arios originally came from.

Update: Now that I think about it, the Arios growing on their own roots might be uniquely susceptible to problems with extreme heat and lack of free airflow in your greenhouse. There's a good reason why experienced growers always use fans in greenhouses.

Dear Steve, I obtained my Arios in different ways, for example through seed or through different European sellers, but never from nature.
The composition of the soil and the type of pot does not seem to be influential.

G'morning Davide,

only happens to seed ariocarpus, grafted ones do not
- they are grown in greenhouses (day-night 45C°/20C° - 15%/90%)
- the greenhouse is totally open but I have no fans inside

I have kept many Ariocarpus propagated from seeds in my greenhouse. I think our summer is a bit hotter than your place but I can not see any similar ploblem on my Ariocarpus species.

They are grown in a greenhouse (day 50 C' and night 20 C')
Since it exceeds 50 C' in normal condition easily and I cover the greenhouse by a shadecloth in summer to keep within 50 C'.

The greenhouse is not opened. There is a door attached shadecloth. Birds and insects go into greenhouse easily, the door is closed.
The greenhouse has no fans.

Frank

Thanks Frank for sharing. Honestly, it's the first time I've heard of the absence of a fan and such high temperatures suitable for air growth.
I hope it's a consequence of your climate or "cultivation school" otherwise I really don't understand what the cause of the death of my arios is!

[Steve Johnson]

Dear Steve, I obtained my Arios in different ways, for example through seed or through different European sellers, but never from nature. The composition of the soil and the type of pot does not seem to be influential.

Cacti being collected in the wild have all kinds of problems when they're brought under pot cultivation, so at least we can eliminate that as a cause for what happened. However, there is another possibility...

I got a Mammillaria deherdtiana dodsonii from the California Cactus Center (Pasadena CA) in May 2012:

Mammillaria_deherdtiana05062012.JPG (92.15 KiB) Viewed 3271 times

The plant was grown from seed by a collector who sold it to the CCC -- lucky find because they're rarely seen in US collections. The Pasadena area is very hot and dry during the summer, so the dodsonii grew up being acclimated to that level of heat. When I brought it home to my part of LA, it became acclimated to the more moderate Mediterranean coastal climate where I live. Highs up to a range of 32-35C -- no problem, and occasional highs up to about 38C aren't a problem either. Those are heat wave conditions in my area, and highs above 35C don't last long. Then came the summer of 2020 -- a week of highs around 38-39C in August, and the dodsonii was struggling. The worst was a sudden heat spike up to 46C one day in September -- here's what happened, 8/1/20 on the left and 9/16/20 on the right:

Mammillaria_deherdtiana0801-09162020_01.jpg (124.23 KiB) Viewed 3271 times

The plant simply wasn't acclimated to the sudden heat spike, and if I had some forethought, I would've taken it into my garage before the spike hit. Lesson learned -- the dodsonii recovered enough to start growing again (new offsets included) in 2021, and when I see highs above 36C in my immediate forecast, back down to the garage it goes. And if it needs watering, I wait until I place it back on my plant bench once the highs are below 36.

Why was my dodsonii so uniquely susceptible to getting hit? The only answer that makes sense to me -- Mammillaria deherdtiana (and its variety) is the slowest grower of the genus. Since Arios are very slow growers too, perhaps your Arios on their own roots exceeded the heat levels they're acclimated to under your normal greenhouse conditions. Even though your overnight lows have theoretically been fine for watering, IMO their susceptibility was to watering when they couldn't take it.

Davide, local conditions rule -- Frank's experience is based on his local conditions and growing practices, so I'm not sure if it can be applied to yours. Since you and I share a similar climate, I hope my experience can be at least somewhat helpful to you. Of course this is all just a guess on my part.

[keith]

I lost many seed grown Ariocarpus this year because of ? bad soil ? water too early ? too cool and humid ? Who knows but probably not heat.

Ariocarpus where I live do best in a almost soiless mix and clay pots. The ones that rotted were in neither because they were still small.

I would say from your picture either sunburn or fungus. They can sunburn in full sunlight even if its not hot. Mine turn a weird green or yellow color then rot. Often liquid will show up on the stem and that is not good. And the roots are usually not firm but like ripe bananas. Yuck.

[keith]

M. dodsonii I think they are just tricky to grow . Higher altitude cactus probably like wide temperature swings day to night. I have one left from seed hope it stays alive very hard to find now.

[Steve Johnson]

M. dodsonii I think they are just tricky to grow . Higher altitude cactus probably like wide temperature swings day to night. I have one left from seed hope it stays alive very hard to find now.

Day-to-night swing weren't the problem with my dodsonii -- daytime high about 98 one day and a high of 114 the next day was. That's the difference between a swing and a sudden heat spike, and as I just said, the plant wasn't acclimated to it. Your comment to Davide is probably the more accurate diagnosis of what happened to his Arios growing on their own roots.

[zpeckler]

I obtained my Arios in different ways, for example through seed or through different European sellers, but never from nature.

Off topic, but I just wanted to make a point of commending you for buying your plants from nurseries or raising them from seed yourself. Too many cactus and succulent species are being severely impacted by poaching.