Mold on Rapid Rooters

CBrittJanuary 7, 2014

Hi all~

I've got nine, 3 week old plants (tomatoes, habaneros, and beans) in an ebb- and- grow system in a 4x4x6.5 greenhouse. I started them in rapid rooter plugs and then transplanted the plugs into net pot bucket lids with water- wicking rocks as growing medium. There is ample airflow, and the humidity stays around 50%

I have now noticed some gray and light green mold on the rapid rooters, especially affecting the tomato plants. (They seem to be dying.) I have heard that adding 3% hydrogen peroxide to the reservoir should help kill the mold, but I want to be sure it wont harm the plants, and if not, how much should I use??

Any other troubleshooting suggestions are welcome as well.


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PupillaCharites(FL 9a)

Not sure if I can add to what you seem to already know, but here's a try. On small plants if mold gets out of control it is almost always a lost cause and spreads further spores around your system and house. The best bet for an aggresive mold and and a marginal young plant is immediate disposal, and disinfection of the entire system.

If it is not so aggressive and things are otherwise looking up it's a judgement call as to where to draw the line.

Just spraying H2O2 or adding it might work for a mature system if you wanted to get some decent production out of it, even regular flushes in cycles and faster nutrient changes. But if thing are still to get rolling and the plants are dropping under good conditions, I would definitely start over after using bleach to disinfect everything from plug trays to res, etc.

A few things to watch. Rapid rooters are excellent growth media for more than roots. If they sit around unprotected, warm, even in light, they can go bad in the sense of have a tendency to express the mold problem. So storage and fresh product are both considerations.

You mention you have humidity covered. Still you are indoors I assume and this is winter, so an actual fan over it all might help for the next cycle, even if you think there is some air movement. Plants appreciate a light breeze and mold hates it, and it evaporates water in the crevaces where mold errupts out.

Another consideration is temperature, look up your optimal temperature range and see if you are close to it, neither too warm or too cold, and a little more aeration of the water (bubbler or flow) might help since everything adds up.

And all you can tell so far is that everything added up to give the mold a happier home than the plants. Anything that upsets the balance back in your favor, including checking if anything is too waterlogged and levels should be lower, etc., is worth checking, including temperature range you grow under.

When you do it again, be sure your hands are sterilized and maybe the seeds to. We really don't know where that mold came from. Using hydrogenperoxide or any bleach will destroy the beneficial microbes of the rapid rooter and whatever other microbial flora that's there, and if the mold is tough, might just invite further spreading by clearing those niches. So you might experiment just a little is there is still promise, but remembering that more spores are being blown around your growing area the longer you go.

Best of luck with it.

    Bookmark   January 7, 2014 at 3:05PM
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PupillaCharites(FL 9a)

One more thing. If I were in this situation and wanted to mess around, but weren't able to get any real hard facts besides the typical guidelines, I would [edit out pH comment, it was a bad suggestion] put in the real slight breeze fan, and cover my media with foil cutouts. That's because I don't think you have a green mold, but rather the common gray mold only, mixed up with some algal growth which is carving out an undesireable system of its own. I if I were almost ready to write it off, I might spray a light 10:1 rainwater:3%hydrogen peroxide (in other words like a 0.25% to 0.27% net) over upper exposed greenish surfaces only., but avoiding much penetration to the roots, this just to smack the odious algae with a 1-2 punch (peroxide damage (1) and blocked light (2). But given the state of my plants I would keep it off them since it would likely also finish off weak plants if I weren't careful. The thing with using H2O2 to fight gray mold is, I believe, that the plant is more vulnerable than the mold (unlike algae). I believe this because surprisingly the mold actually creates some H2O2 of its own to digest the plant tissue it attacks. On the other hand, it can't do the same with a bleach solution. If spraying that instead, use about 250:1 of 5% store bleach like regular strength Clorox, applied in the same way.

Finally, potassium silicate products are helpful in preventing mold, but once you have it bad, it would be probably using good money to chase bad, if you used the silicate. An experimental hobby treatment I'll pull out of left field in this moment, untested, would be to sprinkle a very small amount of baking soda on the moldy area, keeping in mind it will also effect the root zone pH, mineral absorption ability and critical maximum sodium concentration, and a heavy hand would be bad news for the plants. But a small dusting as a surface treatment might help raise the mold pH and effectively hold it at bay. The mold can't putrify at pH's around 7.75 and up easily, and while you do that consider that air temp of 77F-80F would be just about the best you could do to make the mold uncomfortable without inconveniencing the plant. Finally the biggest thing to watch and the real reason for the fan is that with low transpiration rates at low temperatures even where the leaves are open, a film of water can develop like dew and it is precisely that which you need to eliminate from happening since it is from where the mold initially breaks out.

This post was edited by PupillaCharites on Tue, Jan 7, 14 at 16:36

    Bookmark   January 7, 2014 at 3:43PM
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I agree with Pupilla Charites he really knows what he is taking about. I have had spider mites on my Brandy wine tomatos, I have had white flies laying their grubs and I have had fruit flies all having a go, but by general hygiene and insect solutions I have overcome all . I have found Google a very good source of indentifying the problem by looking at the images to determine what bugs our mould etc and attacking the problem in the early stages before it goes haywire. People like Pupilla Charites have a lot of information and knowledge that will guide you in the right direction , but I still believe in the old adage if in aint broken it dont need fixen. I have just harvested some Brandy Wine tomatos that are growing in a single tray , but I also have 5 other trays where the nutrient needs are different, These are growing outside under the roof eaves , where they get blazing sun , torrential rain downpours and have had all he problems I have mentioned above , but they are doing well now and a further crop is about 2 weeks away.

    Bookmark   January 8, 2014 at 2:31AM
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