Arghh!! 600 seedlings wiped out - what is going on?

[Salsacharley]

Put some air on your seedlings with a fan to help keep them from damping off.

[ScottinAtlanta]

Yes, a germination mix.

[seaeagle]

Originally Posted by clspie

I use h2o2 for my seedlings always, to prevent damp off. A very weak solution. One and one half teaspoons of 3% h2o2 for one cup of water. 50% is way too much.

I am glad you posted the exact measurement you use because it confirms the research report from the high school student with real life application almost exactly.His measurements were :

A. One cup of water. Label this bowl as None.
B. One cup of water and one teaspoon of hydrogen peroxide. Label this bowl as Low.
C. One cup of water and three teaspoons of hydrogen peroxide. Label this bowl as Medium.
D. One cup of water and five teaspoons of hydrogen peroxide. Label this bowl as high

Results
The hydrogen peroxide had a positive effect on the plants. The ones with a low concentration of hydrogen
peroxide grew the fastest, then the medium, then the high, and lastly came the ones with only water in
their cup (dependant variable). Since the hydrogen peroxide contains oxygen, the plant roots grew faster.
The roots need oxygen, and it was always readily available in this way. As the concentration of it got
higher, the acidity of the hydrogen peroxide began to affect the seeds and made them grow slower.


https://csef.usc.edu/History/2013/Projects/J1717.pdf


Also fish emulsion has been proven to control damping off

https://garden.org/learn/articles/view/2267/

http://tomatoville.com/showthread.php?t=44486

[MissS]

I am so very sorry for that big loss. On the other hand, count your blessings that you had enough seed to start again and that this happened so early. It would be far worse if all of those seedlings were ready to or had been set out.

It definitely was a burn from the hydrogen peroxide.

[simmran1]

[A post from an .edu I use every year] - When planting seeds in cells - one method to help eliminate damping off is - after they have sprouted and you see the cotyledon, is to water your new little plants with a *weak solution of chamomile tea, after it has cooled. Chamomile tea naturally contains sulfur, which has anti-fungal properties. *Three parts water to one part tea. Even if you just see fuzzy-like places on the soil surface, this chamomile tea solution will eliminate it with one spray.

So providing good air circulation is important, and a weak (3:1) solution of chamomile tea spritzed on the sol surface also reduces damping off.