Fungus on seedlings, again

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Shane
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Fungus on seedlings, again

Post by Shane »

I have orange fungus on some seedlings, again. The last time this happened I tried sulfur and I'm not super happy with the results. Also it's hard to apply to seedling pots, and requires repeated application, which isn't ideal

So I'm looking for some ideas for other fungicides I can try. What do you use?

Also thinking about prevention. I heat my soil to about 90 C to sterilize (in the microwave), but I don't think that's hot enough to destroy some kinds of fungus spores. So I guess my options are add fungicide to the mix or find a way to heat the soil to a higher temp. Any suggestions there?
Los Angeles, California (USA)
Zone 10b (yearly minimum temperature 1-5° C)

Fishhook cacti are like cats, they only like to be petted in one direction
Sarraceniacrazy
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Re: Fungus on seedlings, again

Post by Sarraceniacrazy »

I mix water and peroxide in a liter water bottle and spray my seedlings with it. Fill with water and add 3 or 4 caps full of peroxide. Doesnt kill some stuff but keeps it controlled.
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Aiko
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Re: Fungus on seedlings, again

Post by Aiko »

Shane wrote: Sun Feb 23, 2020 8:40 pm Also thinking about prevention. I heat my soil to about 90 C to sterilize (in the microwave), but I don't think that's hot enough to destroy some kinds of fungus spores.
Is the soil wet? Why don't you just cook wet (!) soil in an old pan on your stoove for ten minutes? That will kill everything at 100C.
Are the pots in an air sealed container right after you sowed the seeds?
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7george
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Re: Fungus on seedlings, again

Post by 7george »

Shane wrote: Sun Feb 23, 2020 8:40 pm Also thinking about prevention. I heat my soil to about 90 C to sterilize (in the microwave), but I don't think that's hot enough to destroy some kinds of fungus spores. So I guess my options are add fungicide to the mix or find a way to heat the soil to a higher temp. Any suggestions there?
I agree with at least 15 min. steaming at 100 C of the mix. Also sterilizing of pots, seeds, plastic baggies and even water used for watering. If the mix is 100% mineral getting fungus is less likely. Usually fungicides don't help much. If seedlings look more or less grown up better open the baggies and transfer the remaining ones to drier regime gradually.
If your cacti mess in your job just forget about the job.
°C = (°F - 32)/1.8
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Shane
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Re: Fungus on seedlings, again

Post by Shane »

Aiko wrote: Sun Feb 23, 2020 10:55 pm Is the soil wet? Why don't you just cook wet (!) soil in an old pan on your stoove for ten minutes? That will kill everything at 100C.
Are the pots in an air sealed container right after you sowed the seeds?
I do seal the pots in bags after sowing. I also sterilize the pots and any tools and surfaces I use in the sowing process beforehand (with alcohol). I learned today that alcohol is ineffective at killing fungus spores, so that's one area I could improve

Some kinds of fungal spores can survive temperatures greater than 100 C. I'm not sure if any fungus we care about can survive those temperatures though. I've thought about putting the soil in the oven dry at maybe 150-200 C / 300-400 F. Though I think I'll hold off for now. There's enough cross contamination between mixing soil batches that there should be fungus in everything if the soil was the vector. I'm guessing maybe poor growing practices caused the fungus :oops: (formerly I had groups of pots in a single bag, and have also had to open bags at different times). Possibly combined with not sterilizing the seeds. Which I haven't been doing out of forgetting that was something I was going to do :oops:
Los Angeles, California (USA)
Zone 10b (yearly minimum temperature 1-5° C)

Fishhook cacti are like cats, they only like to be petted in one direction
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supergodzilla
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Re: Fungus on seedlings, again

Post by supergodzilla »

When you’re careful with sterilising soil and other components, I find that the only real source of fungal infection comes from the seed coats themselves. Since you can’t just nuke seeds in the microwave, you’ve got to get a bit creative with sterilisation. Ive done a bit of research and quite a few tests and found that cacti seeds are surprisingly hardy when given some tough love. My process, therefore, is as such:

Seeds are soaked in dilute bleach for an hour, dried on paper towel and sown on soil mix that has been microwaved for five minutes. I almost never see any sorts of fungal outbreaks with this process.

Don’t try this with other succulent seed though - I’ve killed a few Pachypodium seeds with bleach, a costly mistake.
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mmcavall
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Re: Fungus on seedlings, again

Post by mmcavall »

Sarraceniacrazy wrote: Sun Feb 23, 2020 10:33 pm I mix water and peroxide in a liter water bottle and spray my seedlings with it. Fill with water and add 3 or 4 caps full of peroxide. Doesnt kill some stuff but keeps it controlled.
What is the final concentration of H2O2 to be sprayed on the seedlings?
I want to try it on my newly sprouted seedlings but I'm concerned with some kind of negative effect...

Thank you
Pereskiopsisdotcom
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Re: Fungus on seedlings, again

Post by Pereskiopsisdotcom »

As far as prevention is concerned some of it starts with the quality of the soil components. I have never had problems with rust or fungus on seedlings until one of my latest 1020 trays in which I cheaped out on the soil and used some more affordable store bought soil (in addition to my mix of DE, granite grit, and perlite. My latest batch of Gymnocalycium and Turbinicarpus look exactly like your Astrophytum photo in your previous thread. I also ended up with weed seeds germinating which I never had before.

Before that, for the last 8 years I have never sterilized or cooked my soil components. Though, I have gone to hydroponic stores to buy the high-end (often for cannabis) soil to mix with my grits. For me, I have learned my lesson and will go back to the high quality brands.
http://pereskiopsis.com

Interests include: Rhipsalis, Turbinicarpus, Gymnocalycium, and Lophophora.
grewfresw
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Re: Fungus on seedlings, again

Post by grewfresw »

mmcavall wrote: Wed Mar 04, 2020 3:53 pm
Sarraceniacrazy wrote: Sun Feb 23, 2020 10:33 pm I mix water and peroxide in a liter water bottle and spray my seedlings with it. Fill with water and add 3 or 4 caps full of peroxide. Doesnt kill some stuff but keeps it controlled.
What is the final concentration of H2O2 to be sprayed on the seedlings?
I want to try it on my newly sprouted seedlings but I'm concerned with some kind of negative effect...

Thank you
0.3% for spaying and watering the seedlings. There is no negative effect
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mmcavall
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Re: Fungus on seedlings, again

Post by mmcavall »

grewfresw wrote: Wed Mar 04, 2020 7:01 pm
mmcavall wrote: Wed Mar 04, 2020 3:53 pm
Sarraceniacrazy wrote: Sun Feb 23, 2020 10:33 pm I mix water and peroxide in a liter water bottle and spray my seedlings with it. Fill with water and add 3 or 4 caps full of peroxide. Doesnt kill some stuff but keeps it controlled.
What is the final concentration of H2O2 to be sprayed on the seedlings?
I want to try it on my newly sprouted seedlings but I'm concerned with some kind of negative effect...

Thank you
0.3% for spaying and watering the seedlings. There is no negative effect
Thank you!
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Shane
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Re: Fungus on seedlings, again

Post by Shane »

grewfresw wrote: Wed Mar 04, 2020 7:01 pm 0.3% for spaying and watering the seedlings. There is no negative effect
I've been using 3% H2O2 without any ill effects. But maybe lower is better; I don't want to fry my seedlings. I used to use alcohol, but found out the hard way some cacti (lookin at you Parodia) don't like that.
Los Angeles, California (USA)
Zone 10b (yearly minimum temperature 1-5° C)

Fishhook cacti are like cats, they only like to be petted in one direction
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mmcavall
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Re: Fungus on seedlings, again

Post by mmcavall »

Shane wrote: Thu Mar 05, 2020 4:28 am
grewfresw wrote: Wed Mar 04, 2020 7:01 pm 0.3% for spaying and watering the seedlings. There is no negative effect
I've been using 3% H2O2 without any ill effects. But maybe lower is better; I don't want to fry my seedlings. I used to use alcohol, but found out the hard way some cacti (lookin at you Parodia) don't like that.
Good to know, thank you Shane. I'll try with some concentrations.

My doubt now is how to dilute it correctly, since the H2O2 sold here is classified in "volume". For example, 10, 20 or 30 volumes. Not sure how to obtain 3% from a 20 volumes, for example.
DaveW
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Re: Fungus on seedlings, again

Post by DaveW »

Apparently you can "over sterilise" potting soil by using too high a temperatures. Also never try and sterilise dry soil since it needs the steam the damp soil produces to sterilise it. In any case a microwave works on vibrating the water molecules to produce the heat, therefore dry soil will simply not heat up.

Opinions as to the ideal sterilisation temperatures differ however:-

"Place the tray into an oven and set the oven to a low temperature. The ideal temperature for sterilization is 180 degrees Fahrenheit. Temperatures over 180 degrees Fahrenheit (49 C) may cause burning. Burning the soil will chemically change the composition of the soil. Soil that is burned or overheated will harm plants.

The soil needs to remain in the oven for 30 minutes, while the temperature needs to remain closely around 180 degrees Fahrenheit. Monitor the thermometer and adjust the oven temperature as needed. Paying close attention to temperature fluctuation is a must."


Another different opinion on sterilising soil from the Web:-

"You can’t buy the stuff, but you can sterile it yourself. There are many described processes on the internet. Colorado State University provides information and temperatures for sterilizing soil. You will need a temperature of 212F (100C) for 30 minutes in order to sterilize it.

But ……”Excessive soil heating may also increase chance of phytotoxicity due to soluble salts, manganese toxicity, and toxic organic compounds. Soil mixtures high in readily decompostable organic matter (manure, leaf mold, compost) are most likely to give injury when exposed to excessively high temperatures”.


Sometimes we can be overclean and kill off all the good bugs as well as the bad ones.

Looking on the web for Orange Fungus on soils many seem to think it is because the soil is kept too wet, a condition that can occur in baggies for seed raising.
keith
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Re: Fungus on seedlings, again

Post by keith »

I find that the only real source of fungal infection comes from the seed coats themselves."

yes they need to be rinsed in H2O or something similar. If you look closely ( big seeds at least) you can often find the fungus threads start at the seed coat as it splits and the plants begins to grow and then infects the tiny seedling.
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Edwindwianto
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Re: Fungus on seedlings, again

Post by Edwindwianto »

keith wrote: Fri Mar 06, 2020 9:37 pm yes they need to be rinsed in H2O or something similar
Hi Keith

Could you please explain more, what is something similar with H2O (water)?
Thanks

EDWIN
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