Stems of seedlings have bottlenecks. Is this damping off / fungus ?

[HaHend]

Hi,

my plants are around six weeks old after they germinated from seed and are now in 1.5" rockwool cubes under a 55W 9000Lumen PL-L.

Humidity is between 40-50%, air temperature is between 24-27° C / 75 - 80 F. The surface of the leaves has the same temperature (measured with a laser thermometer) so not too close to the light.

I started to feed them just formulex 19 days ago. Gradually increasing nutrients from 1/4 dosage and I feed them now double the dosage.

They should be ready for proper nutrients as they have five or more real sets of leaves. Formulex is only NPK 2.4:0,9:3,4, so very mild and I didn't bought proper hydro nutrients yet which have three times the NPK usually.

Within the last week their stem started to thicken up a lot and I noticed a few days ago that 60% of my seedlings have some kind of bottleneck in their stem (pictures attached).

The stems are also in the process to shed a layer of transparent/purplish skin. I assume this is due to the stem growth? They used to have a purplish looking tiny stem before.

Furthermore two days ago three plants broke at their bottleneck as I shaked the rockwool cubes too much after watering to get excesss water out of them.

I attached these plants to a stick and they seem not to bother for now.

I was checking regarding the bottleneck thing and it appears to me that this is "damping off / fungus", can you confirm this please? If so is there a way to try get rid off it?

The roots of the plants are not bright white as they used to be but have a very, very light brown touch to them (see pictures). But they still look more white than brownish.

If this is "damping off" I am surprised how this could happen because I always let the rockwool cubes get nearly dried out before watering again.

I water them from the bottom by holding the lower half into water for max 2-3 seconds.

I used to have a humidity dome on for the first two weeks but removed it after I read it is no good for seedlings.

But the dome was never attached properly to the tray anyway so humidty could escape from the sides and not only the top.

Germination happened via the papertowel method.


Furthermore the lower smaller leaves of most of my plants start to yellow now (plants without bottleneck affected too) but the top leaves are looking good.

Is this because the top leaves are sucking out nutrient from the lower ones or do my plants have any deficiencies?

I also have to note that the lower leaves barely get any light as the plants got bushy and there is not much place for them.

Hence I will repot them into 4" rockwool cubes in the next days and move them to a larger area with more light.

After a couple of weeks in these 4" rockwool cubes I intend to move them in a ebb and flow system with 5 gallon buckets.

I hope you guys can help me out.

 

[HaHend]

Thanks for all the feedback and your support so far.


Update:

I now checked the PH and the EC of my tap water after I just received my EC & PH meter. Previously I was adjusting PH via coloring.

My tapwater has not only a high ~8.0 PH but also a high 0.8 EC to begin with.

I prepared a pot of water with a normal dosage of formulex (10ml on 1l) like I used to for watering just to check the EC.

The EC rose to 2.5 which is way too high.

I prepared another pot of ph 5.5 adjusted water to test flush three plants and the readings of the run off were between 5.6-5.7ph and EC 1.6 - 1.7.

Hence I assume that I overfed the plants. Therefore I flushed all plants with ph 5.5 and EC 1.0 water (including a small amount of formulex).

Lesson learned: Don't rely on what the bottle says regarding the mixture as you might have a high tapwater EC to begin with as I do. A better way is obviously to measure the EC before watering but I didn't had the opportunity to do so.

I think this might explain the yellowing of the leaves but not the bottleneck.

I flushed 24h ago and most Seedlings of mine seem to recover although 20% of them have leaves hanging down and have strange spots on their leaves (see pictures).

However there are also plants without a bottleneck which have the same problem, hence I think that the bottleneck is not contributing to any problems at the moment but this might change in the future.

I will repot the plants in larger 4x4 rockwool cubes today. Do you think I should care repotting the 20% of my seedlings which look like the ones on the pictures? Do you think they might recover?

 

[yttocs1010]

They look good i am gonna try it

 

[yttocs1010]

When do you take clones b4 flower?

 

[HaHend]

Update:

I transplanted all of my seedlings seven days ago in larger 4x4" rockwool cubes.

Before that I used H2O2 (3ml 35% per gallon) to treat the fungus and I am still mixing H2O2 with water when I feed nutrients at EC 1.2.

I also sprinkled a bit of water with mixed H2O2 (12ml 35% per gallon) on the bottleneck affected part of the stem with a syringe.

The 20% of my seedlings which looked bad prior transplanting didn't recovered and died.

The rest looks ok but not great especially as the leaves of most but not all plants are pale green.

The stems are purple and the leaf tips are slightly burned.

The roots are looking great however, bright white and they are shooting out of the new rockwool cube already (check pictures).

It also looks like the stems are trying to heal themself as some light brown colored fibers are growing over the bottleneck affected spots (check pictures).

The growth is now less vertical but more horizontal as you can see in the picture as small sets of leaves start develop all over the old parts of the stem.

I still use formulex but will switch to proper vegetative nutrients shortly.

Do you have any idea what kind of deficiencies the plants have? I checked the abuse chart and it looks like a Sulfur or Zinc deficiency to me.

Do you think the plants (20cm / 8" tall by now) got out of the nutrient lock by now and proper nutrients will get rid of the deficiencies?

The plants are now six weeks old and are probably around two weeks behind due to all the stress.

Still asking myself if it is worth to continue or if I should take cuttings from the seedlings and continue with these?


Temperatures during lights off are 20°C and during lights on 24° now as I switched from 24h to 18/6. Humidity between 40-50%.

Plants are under two Secret Jardin Tneon 2x55W although I only have one 55W lamp per reflector installed now so 110W (9000 lumen) total.

Do you think I need to introduce more light? I could install one more bulb per Tneon reflector (so 220W or 18000 lumen total) or use one 400W MH but the MH would probably be overkill?


I also supported the bottleneck affected plants with wooden sticks (see pictures). Do you think it is overkill in this way and if so do you recommend me supporting the plants in another way and if so which way?

I also noticed some white looking stuff on the wooden sticks above the rockwool surface. What is this, is this bad and do I need to get rid of the wooden sticks?

Furthermore a few rockwool cubes have green algae, how should I get rid of it? I will cut some covers out of aluminium soon to cover the rockwool cubes and prevent algae from growing.