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Seeking help from everyone, what kind of bacteria is this and how to deal with it?
I planted a batch of young seedlings, and these white hyphae appeared about a month after they appeared. I don't know what to do, I used some thiofuramide drug particles on the soil surface, but it didn't work. I have also used a fungicide of ethyl allicin, but it has not worked. I humbly ask everyone how to handle this situation?

You know, I too am having the same problem and was gonna post about it about haven't gotten around to it yet. I've been using sulfur powder which keeps it at bay but it still comes back. I've tried letting the pots dry out completely for a few weeks but that didn't work either. It would be great if anyone knew of another treatment that might work. A different fungicide? Hydrogen peroxide?

It's only affecting my seedlings that are in a mix that's too rich in organic material--about 50%. I of course sterilized the mix before sowing. My different seedlings in a leaner mix (25% organic) aren't having this problem, so learning experience for this year's seeds.

I cannot use a completely dry method to remove these bacteria because these young seedlings are too small and die before the soil is completely dry.
My soil was also subjected to high-temperature sterilization and disinfection before sowing, but it should not have completely removed this bacteria. I want to know which beneficial bacteria can help me eat or kill these harmful bacteria. I have tested a bacterium called Bacillus subtilis. But it didn't work either.

Aztekium123 wrote: ↑Sat Nov 18, 2023 1:20 am I cannot use a completely dry method to remove these bacteria because these young seedlings are too small and die before the soil is completely dry.

Oh for sure. My seedlings are just shy of a year old so they can take a little dryness. Definitely not a possible solution for ones as young as yours!

My soil was also subjected to high-temperature sterilization and disinfection before sowing, but it should not have completely removed this bacteria. I want to know which beneficial bacteria can help me eat or kill these harmful bacteria. I have tested a bacterium called Bacillus subtilis. But it didn't work either.

For what it's worth, it's probably not bacteria that's causing your problem. Looks more like a fungus or mold. Hopefully one of the more expected members has a suggestion that helps both of us!

Definitely mold. Although I don't have any experience growing cacti from seed, this may provide y'all with a few ideas:

https://www.thespruce.com/white-fuzzy-m ... gs-3972289

Other ideas from Craig Fry of C and D Plants:

viewtopic.php?t=34225

Craig recommends Chinosol fungicide, and I think that could take care of your mold problem.

I'd lower the water a bit anyway, looks very wet, good for seed germination but seedlings don't need it to survive. Mostly it's gonna be the empty seed pods that start the mold and keep it growing. You could use tweezers, and take them out. Also a top layer of sand works well to keep the mold at bay, but I'd remove the seed pods first, that's the main cause.

I agree with Jangaudi's advice. Also, you may apply 3% hydrogen peroxide (H2O2) with an eyedropper, which might help.
What species are the seedlings?

Looks like fungus , hydrogen peroxide might help I use it at 3% , dry powder fungicide might work better . maybe use a fan on the pot for a hour or whatever it takes to dry out the fungus and not the cactus.

keith wrote: ↑Sat Nov 18, 2023 10:02 pm Looks like fungus , hydrogen peroxide might help I use it at 3% , dry powder fungicide might work better . maybe use a fan on the pot for a hour or whatever it takes to dry out the fungus and not the cactus.

After using H₂O₂, how long do you wait to see if it's effective? In the past I've used Daconil, but there seems to be some anecdotal evidence that it's use may inhibit further new germination.

Tom in Tucson wrote: ↑Sun Nov 19, 2023 2:18 am After using H₂O₂, how long do you wait to see if it's effective? In the past I've used Daconil, but there seems to be some anecdotal evidence that it's use may inhibit further new germination.

Most important property of H₂O₂ is that it's totally harmless (actually it might be beneficial) to seedlings. With some types of fungi/mold I had excellent results, while some varieties required consistent repeated treatment in combination with regular ventilation.
Best policy, of course, is to attempt avoiding infestation at all which requires rigorous preparation. For very small and slow growing seedlings (e.g. Aztekium, Blossfeldia or Strombocactus) this is the only way to ensure any success.

Jangaudi wrote: ↑Sat Nov 18, 2023 10:09 am I'd lower the water a bit anyway, looks very wet, good for seed germination but seedlings don't need it to survive. Mostly it's gonna be the empty seed pods that start the mold and keep it growing. You could use tweezers, and take them out. Also a top layer of sand works well to keep the mold at bay, but I'd remove the seed pods first, that's the main cause.

Removing those moldy parts should be a good idea, I am currently working on it. I hope it works

Nino_G wrote: ↑Sat Nov 18, 2023 1:59 pm I agree with Jangaudi's advice. Also, you may apply 3% hydrogen peroxide (H2O2) with an eyedropper, which might help.
What species are the seedlings?

The variety of these seedlings is: aztekium

I have also prepared a hydrogen peroxide disinfectant because there are three pots in this batch of seeds that have this situation. I'm going to take a basin for testing

Steve Johnson wrote: ↑Sat Nov 18, 2023 4:40 am Definitely mold. Although I don't have any experience growing cacti from seed, this may provide y'all with a few ideas:

https://www.thespruce.com/white-fuzzy-m ... gs-3972289

Other ideas from Craig Fry of C and D Plants:

viewtopic.php?t=34225

Craig recommends Chinosol fungicide, and I think that could take care of your mold problem.

Thank you for your suggestion.

The main reason is that the variety of this batch of seedlings is Aztekium valdezii

I started using a friend's suggestion last year to use bags and seed in a sealed state.

This method indeed sprouts more than before. But it brings a new problem, which is this bacteria.

Sometimes ventilation and moisture retention cannot be achieved simultaneously. This seems to be a bit contradictory. I'm trying to figure out a way

If you use the baggy method, the whole pot needs to be sterile before sealing
otherwise it's haven for fungus growth

You need to sterilize the soil first, then sow the seeds, then sterilize the seeds

After using H₂O₂, how long do you wait to see if it's effective?" a day and it often doesn't work the plants will die by then. Best to avoid fungus if possible I tried strombocactus in a baggie and they all rotted , I don't use baggies much anymore . Will try again in the spring no baggie and I should have used H2O2 on the seeds then rinse them that's often where the fungus starts. Dry air helps BUT the seedlings really slow down if they are cactus seedlings no effect on Mesembs as far as I can tell.