H202 directly on the seedlings?

[RichR]

I am running some tests using Hydrogen Peroxide and Physan 20 on seeds when they are sown. So far, Mammillaria heyderi and Echinofossulocactus seeds sprayed with straight 3% peroxide right out of the bottle did not germinate after two weeks, while those that had only distilled water spray at sowing germinated quite well, as in 80-100%. On the other hand, Ferocactus wislizeni and Echinocereus enneacanthus sprayed with 3% peroxide had about a 50% germination rate after 14 days, about the same as seeds sown only with distilled water spray. 3% H2O2 seems to have a negative effect on some seeds, but more testing needs to be done. Perhaps a distilled water rinse after 10 minutes of soaking in 3% H2O2 would have fewer negative effects, particularly on the smaller seeds such as M. heyderi. I have never seen any data on using peroxide at higher dilution rates as far as germicidal and fungicidal efficacy, but I know that a lot of people use it at fairly high dilution rates. 3% peroxide needs to sit for 10 minutes to achieve disinfection, so I wonder-- is it really that effective at high dilution rates?

[A1essandro]

... Perhaps a distilled water rinse after 10 minutes of soaking in 3% H2O2 would have fewer negative effects...

I believe that after 10 minutes most of H2O2 will be broke down (if we are saying about drops, not about liters ). But just for being sure...

[Steve-0]

Hey mmcavall, great thread! Good Intel here for newbies like me.

[Steve-0]

I am running some tests using Hydrogen Peroxide and Physan 20 on seeds when they are sown. So far, Mammillaria heyderi and Echinofossulocactus seeds sprayed with straight 3% peroxide right out of the bottle did not germinate after two weeks, while those that had only distilled water spray at sowing germinated quite well, as in 80-100%. On the other hand, Ferocactus wislizeni and Echinocereus enneacanthus sprayed with 3% peroxide had about a 50% germination rate after 14 days, about the same as seeds sown only with distilled water spray. 3% H2O2 seems to have a negative effect on some seeds, but more testing needs to be done. Perhaps a distilled water rinse after 10 minutes of soaking in 3% H2O2 would have fewer negative effects, particularly on the smaller seeds such as M. heyderi. I have never seen any data on using peroxide at higher dilution rates as far as germicidal and fungicidal efficacy, but I know that a lot of people use it at fairly high dilution rates. 3% peroxide needs to sit for 10 minutes to achieve disinfection, so I wonder-- is it really that effective at high dilution rates?

Please continue to post your results. After reading your remarks, I'm thinking what I did ....two capfuls in a liter dilution....was about as effective as just plain H2O. What surprised me though earlier was the fella in the video I linked who wetted his soil mix for germination with nothing but 3% H2O2...undiluted. He must have had a fairly sterile mix because I saw no foaming reaction like I see when peroxide meets my germy mouth or toothbrush.

[Steve-0]

...

[RichR]

I will post results as they come in. I am interested in long-term disinfection, especially for the baggie technique of sowing. I'm looking for something that will allow me to leave seedlings in bags for up to a year. The best results I have gotten were from using both Chinosol and Physan 20. at sowing--a method used by C&D Cacti and outlined in another thread: "The C&D Seed Growing Method." I'm waiting to see how my seedlings that were sprayed with only 3% H2O2 will do after several months--if there any infections or algae blooms.

[mmcavall]

I'm already doing my tests. Too early to say something. Until now, nothing happened with undiluted H2O2 (seedlings are fine, and algae/mold too).
I'm testing also a solution of Cl (chloride), in separated pots.

[Steve-0]

I'm already doing my tests. Too early to say something. Until now, nothing happened with undiluted H2O2 (seedlings are fine, and algae/mold too).
I'm testing also a solution of Cl (chloride), in separated pots.

What is the Chloride solution? Not bleach, right?

[mmcavall]

What is the Chloride solution? Not bleach, right?

Yes...bleach ...diluted bleach...I like to learn from testing, even if means kill some plants sometimes...if you follow my posts here, you will see I have already tested hot water bath to kill mealybugs (risking cooking some plants), or giving a long dry period to some plants to see how long they can endure. Despite this, I seldom lose a plant. I really hope they can survive the bleach but if they don't I will learn it for life. That's a good way to learn.

[mmcavall]

Nothing happened.
I tested two solutions over different pots of very young seedlings.
Solution 1 was H2O2 straight from the bottle (3%).
Solution 2 was 2,5 ml of bleach (2.5% chloride) diluted in 100 ml of water.

Results:
Nothing happened.
Seedlings are absolutely fine...as well as the algae and mold.

[keith]

Didn't do anything ? I pretty much don't grow under plastic anymore too many years fighting mold which I still get in air but not as much.

[PHcacti]

This is very informative. Thank you all for sharing. Started sowing seeds in the first quarter of 2020. Have some algae growing but did not bother them since they did not envelope the seedlings. I find this very informative as I might need to spray the H2O2 in the future (as needed).

[mmcavall]

This is very informative. Thank you all for sharing. Started sowing seeds in the first quarter of 2020. Have some algae growing but did not bother them since they did not envelope the seedlings. I find this very informative as I might need to spray the H2O2 in the future (as needed).

As I said , H2O2 was not effective and algae/mold still growing. So I'm not sure it is useful.

[Steve-0]

Didn't do anything ? I pretty much don't grow under plastic anymore too many years fighting mold which I still get in air but not as much.

This is my first attempt at growing from seeds and a black mold has attacked my Escobaria vivi.batch. 3 or 4 died in quick succession. Then I opened the lid and left it off a day or two. Fresh air dried it out and slowed or stopped the "black plague". The Echino. tex and Sclero. p's are doing well with a little bit of algae here and there. I just added a fine layer of sand over the algae.

Out of sight, out of mind. Have not used H2O2 lately...just snow melt and rainwater.