Hydrogen peroxide for fungus gnats

[Judi]

There has been a lot of discussion about hydrogen peroxide, but has anyone used it as a soil drench to kill fungus gnats? While at my favorite nursery, I was talking with a nurseryman who said they use a drench of 1 part hudrogen peroxide to 2 parts water on all their houseplants to controll fungus gnats. She said that she heard it is actually good for the roots. She never used it on orchids because they don't carry too many and they sell fast. So, my question is has anyone tried this and do you think it is safe for orchids? How about actually being good for plants? Do you think it would also kill roller bugs?

[Donald]

Greetings. Never heard of it for treating gnats. It's usually used for treating crown rot although I did read somewhere that it's used at a 5% strength to kill insect eggs. I'm sure someone with a little more knowledge than I will "pipe in" with more info.
Good Luck

[camille1585]

The standard hydrogen peroxide (3% I think) is really useful for crown rot or other types of rot. The effect of H2O2 is very short as it quickly decomposes into H2O and 02. When you pour some into a crown it will fizzle a bit, and after that, all you have left is water. It works on rot because it is a powerful oxydizer. What’s interesting to know is that plants actually produce H202 very locally to combat pathogens. If a plant recognizes that a pathogen has entered a cell, the cells initiated a hypersensitive response where H2O2 and other compounds will destroy the cell and invading microbe. It’s very effective.So all we do by applying it externally is mimic something the plant already does on a smaller scale.

As for using it for insects, I’ve never heard of it. I have heard of it being used as a drench to stimulate root growth (from the extra 02) and I know it's very effective in killing pathogens in the medium.