i had some papaya seedlings that were over-watered (lots of rain)
and looked about to die.
I had read somewhere that Hydrogen Peroxide would kill the bad fungus etc...
but not hurt the plant.

since i had several, i was willing to try.
i read to use it, even though the roots were soaked,
adding HP would give the roots Oxygen...

i started with %30 HP and the rest water
I actually, gradually increased until it was full strength and it didnt hurt the plant at all. it didnt help a lot, but i think it helped some, i think the plant would have died without it.
ive used it several time since, always full strength, with all my plants now
(only if i think they are not getting enough oxygen to the roots)
compacted type soils etc...

i dont know the strength, that may be a factor,
but just an FYI to all
i think it may be good for fungus problems etc...