I'm specifically talking about orchid seedlings, more specifically, plants that are newly removed from flask and are in a community pot situation etc. These seedlings will have been used to 100% humidity and will have received all their nutrients from the agar media. Once out of the flask, the seedlings get exposed to fluctuating temps and humidities and no longer have the agar for nutrients. They tend to lose the roots that had grown into the media and during the transition stage before they grow new roots and 'harden off' they are VERY sensitive to fungus and bacteria. Thus, it is often recommended that they be treated with peroxide and fungicides.

I understand (basically) how fungicides work and why they're recommended. I do know that peroxide is used both as a preventative treatment and as a treatment for existing problems. I'd like to know why it works. What effect does it have on the plant tissue? Does it kill the bacteria or strengthen the plant or both? Does it only kill anaerobic bacteria? What about concentrations? I have 3% and have sprayed it diluted by about half. Is that too strong? etc. etc.

Any words of wisdom on the topic are appreciated.
MB

Since H2O2 is an unstable molecule, it breaks down easily. When it does, a single O- atom and a molecule of water is released. This O- atom is extremely reactive and will quickly attach itself to either another O- atom forming stable O2, or attack the nearest organic molecule.

Many disease causing organisms and spores are killed by O, the free O H2O2 releases is extremely effective at this. H2O2 can help eliminate existing infections and help prevent future ones. The free O atom can destroy dead organic material (i.e, leaves roots) that are rotting and spreading diseases.

Reduced O levels and high temperatures encourage both anaerobic bacteria and fungi. When plants growing in soil are treated with H2O2 it will break down and release O into the area around the roots. This helps stop the O from being depleted in the water filled air soil air spaces until air can get back into them. High O levels at the roots will encourage rapid healthy root growth and discourage unwanted bacteria/fungi.

I know it comes in several different strengths. I'm thinking 3%, 5%, 8% and 35% solutions. Cheapest is 35% which you dilute (to 3%) by mixing 1:11 with water. Plastic or glass is best to store it in, & the container should be opaque to prevent light degradation. If three-liter pop bottles are available in your area they are ideal for mixing and storing H2O2. Once you have it mixed at 3% (or start with 3%) mix it at the rate of 1-1/2 tsp/gallon of water as a cutting dip & up to 2-1/2 tsp/gallon to water containers with on a regular basis. Start at the lower concentration and increase concentrations gradually over a few weeks.

H2O2 in high concentration is a powerful oxidant & will bleach skin white & oxidize almost anything it contacts - quickly, so be careful with it if you use it. A solution that's too strong can kill any organic molecule it contacts.

Al