Hi there, OK well, I am a newcomer to the art of horticulture, and I am coming to the end of my first grow. Overall it was ok, but I lost a quarter of my plants to some sort of stem/root problem, which I haven't seen much of on forums.
My choice was snow white from seed, all successfully germinated in root riot cubes, transferred to rockwool cubes for potting on. Roots developed although at different rates, and the first issue I wonder about is that perhaps some of them were transferred into the deep water system too early, i.e. not a good enough root structure then.
The system is an ebb and flow, medium, clay pebbles, floods every 3 hours for 2 mins, all under 3 600w HPS lights, humidity good temp in the high 70,s or just over 80. I suspect that as the plants grew as they grew at different rates, some overshadowed others, and their light wasn't as good. Fed on aqua veg for 2 weeks, then into flower stage, aqua flores.

As the plants grew, and were coming into the 5th week of flower, I noticed some had narrowing stems, just above ground level. The stem at this part was slippy, and a bit mushy, I was worried, as well I should have been, as soon, a couple of days these plants wilted, and died. On removing them from the system, i found the root ball was stunted, and very poor. Some discolouration there as well.

Several others went the same way, (see pics) In the main these plants were the smaller ones, underdeveloped. However, just yesterday i found one of the bigger ones is withering, although as we are in the 7th week flower, I think I can salvage the buds of this one. The others are big, strong, and with good bud.

Now, further points. As they were getting too tall for my ceiling, I used the new superbud to halt the vertical growth, and direct the growth to the buds, it works well. I had noticed the narrowing of the stems before this.

When I realised we had a disease on the go, I suspected rhizoctonia, I added a relevant dose of liquid oxygen to the tank. I also added to the tank, root re gen, and wiltguard from canadian express to try and halt the damage, and the spread. I also added a good aeration pump to the tank, bear in mind this was my first grow, and an "expert" had told me, no you won't need aeration, as the tank is constantly drainng and refilling. Now I don't believe that one bit.

On searching for clues as to what happened I found a thing called "girdling" more often happens in trees, the roots wrap around each other and strangle the growth, bad planting in the first place, then root rot sets in like pythium, or rhizoctonia. Ah, btw, the "expert" told me it was ok to put 2 plants into one bucket in the system, I wonder now if that was a bad idea, maybe one plant dominated the other, and deprived the roots of the weaker one of nutrients, and space?

I am due to flush next week,then harvest the following. Next grow planned is going to be a cheese strain. and I want to avoid this happening again.

Sorry for the long post, wanted to give all info I could. What I would like to know is, does anyone have experience of this, and what do you think, or know this problem?

The pics, are of a couple of plants that were the first to go, you can see the damage easily, and the narrowing affect.
Thanks for any advice, or ideas.

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Eeeew, sorry I have no idea how to help you, but that looks nasty.

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Eyes to glazed, I'm being slayed from the potency, toxicated commodity, my property.

It's called "scale" They have a hard outer surface and pierce the stem and suck it dry.

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...out
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You haven't countered nothing, because the points you made are not valid, you are basing your counter on information you don't understand, regardless the accuracy of the information, because it does not state what you are saying.. (Brazko)

Hey Crackerjax Scale? Is that those light brown lumpy looking growths on the stems? And what is scale exactly, a fungus? Any idea where it is likely to have come from?

I looked around on line etc. Scale are indeed insect thingies, the problem here is that apparently you can fairly easily scrape them off the stem or leaf, those brown lumps on the stem are solid, part of the stem, maybe they are normal growth? Plus scale will produce a sooty type of residue, which isn't present. I doubt in truth if it is scale, but I am a newbie after all.

It's an insect...here's a good link to learn more about them. They are truly one of the top pests.

http://entnemdept.ufl.edu/fasulo/woodypest/scales.htm

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...out
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You haven't countered nothing, because the points you made are not valid, you are basing your counter on information you don't understand, regardless the accuracy of the information, because it does not state what you are saying.. (Brazko)