Pythium infection on lettuce root

Author: Scott  


Pythium infection on lettuce root

Hi Scott, I would like to know if I can use 50% hydrogen pyroxide to eliminate pythium on lettuce root in a NFT system.

Which dose (ml/100 l) can I use ? How it’ll be added to the tank solution ? Thanks for your response.


Hydrogen peroxide will oxidize root rot fungal infections.
There are 2 problems for you to understand.
1st. The Hydrogen peroxide (H2O2) breaks down into H2O and releases oxygen ions to bond with other molecules and/or release as O2 Gas when it comes into contact with the infection. Because of this, the H2O2 is destroyed in the process of cleaning your system. If you add a specific dose to the root zone and it does very little, then you have a bigger infection than the dose you used. It could be the other way, that you clean the system, and have a residual level of H2O2 in the solution. This may be ideal, but I wouldn’t want a bleaching agent around the roots too often in too high a residual or you may oxidize some healthy tissue in the root zone. In reality, this almost never happens, because we use a safe dosage and add it, say daily, until the problem improves, then say weekly, to keep anything from building up again.

20ml per litre is a relatively high dose, and I’d use that as a weekly shock dose. 100ml per litre seems to be good to add daily until the condition improves.

Be careful handling it. I am one of those who is fairly slack with safety, but this stuff at 50% really burns. But I use 6% H2O2 with silver ions to brush my teeth, (knowing Fluoride and Chlorine are very deadly poisons) and the H2O2 at that level is quite safe. The silver makes a big difference to the longevity of the effect, and pure H2O2 may be gone in minutes after being added, H2O2 with silver ions (not Colloidal! silver) has a much longer effect.

2nd. H2O2 will not penetrate into a solid mass like a decaying roots. So if the infection was inside say a big glob of dead roots, then the outside of the roots would be sterilised. If the root broke down into smaller bits, the infection may be released again. Using enzymes to break down old roots has been effective in preventing root rot because it robs the infection of a place to live. Although enzymes can be expensive, commercial growers using even small amounts below recommended levels have seen sick plants recover, and healthy plants thrive. Enzymes are capable of removing dead roots and freeing up airspace in the root zone, allowing healthy roots more room to air and water. At $50 a litre and adding a low level of 10ml/100litres, it is still very expensive. When using H2O2 you may find infections return very quickly.

Local Commercial growers have installed large Ozone units (Under $1000 usually) to add O3 gas to the tank, which breaks down into O2 and O- the same as H2O2 without the ongoing costs. The advantage here is that for the cost of $120 per lamp and some electricity, you should get long periods of cheap Oxygen ions in your tank.
As for how to add H2O2, we just pour it into the main tank in one dose every day until the problem is under control, and then use a shock dose once a week or so, to keep it there.

Hope that is helpful

Scott Andrew
Nerang Hydroponic Centre 4/50 Spencer Road Nerang QLD 4211 Australia

Phone (07) 5527 4155
email checked morning and afternoon minimumon week days only


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