manganese toxicity or what?

Hi all,

I noticed some spots on my seedlings' leaves yesterday, today they're much more pronounced, want to nip this in the bud ASAP so I'll have some healthy plants. Went through all the "plant problem" threads and the best guess I've got it manganese toxicity. I'm only seeing it on 2 of 7 plants, so I guess it's possible that these are just weak plants, although they look fine to me compared to the others-- not stunted or spindly. The strain is Nirvana's Blue Mystic.

Leaves are looking dry and wrinkly/curly. Yellow/orange spots and necrosis where these spots are at. Stems have a not too pronounced red/purple hue.

Plants are in a DWC hydro setup, TDS is currently at 930ppm. I'm using tapwater that's 170ppm to start, so there's currently 760 of actual 'nutes' in the solution. I'm using the "Lucas Method" for nutrients-- General Hydro Micro and Bloom at and 1:2 ratio, nothing else. PH is currently at 5.2-- I let it ride up and down between 5.2 and 5.8 before adjusting. Temps are a little high, usually between 80-90f, but I try to keep it under 87. Temps drop to as low as 65-75 at night if it's cold outside. Plants are under a 400watt HPS bulb at a distance of about 2.5 feet. 18 hours of light/ day. My DWC tank is not light-proof and there's a fair bit of algae growing in the solution, not sure if that would be the cause, but am just trying to rattle off all the factors that could possibly contribute. Nute solution was changed out 11 days ago.

Sorry for the crummy pictures, obvious the HPS is on and washing everything out, and my digital camera is like 10 years old. Any thoughts? Again, I've looked through the nute problem threads and am just not sure. Thanks for your time for looking at this.

Take pics with the light off, throw a cfl in there and take the pic

Looks like you could possibly have spidermites too

lower the res temp to 68* no higher, cover those damn net pots and cloning cubes the alge growth is killing your shit, your tap water is a probibly on the hard side due to high ppm at start. throw that GH shit in the trash go spend a few bucks on DM gold nutrients it has ph buffers to prevent ph float/drift and as young as the plants are you should be sitting @ 750ppm not 750 of nutes and 170 of hard ass water thats loaded with all kinds of crap, hell running it through a brita water filter would make a different, you need to add some good mico's to your res and it will take care of 98% of your issues like subculture-m

Hi all, thanks for your input. I've posted better pics. Someone PM'd me and asked about my PH meter. The PH meter is good, brand new and I have a 2nd that's high end lab equipment, both have been calibrated in the past week. I've been worried that I've been taking the PH too low at 5.2. It does come up over the course of a few days to 5.6-5.8, and I always add water every couple days to top off, which brings the PH up also as my tap water is 7.5.

I don't think I have spider mites. No evidence of webbing, eggs or bugs (I've went over them with a loupe just a minute ago).

These plants are putting out their 4th sets of true leaves, and the problem leaves are at the bottom, working their way up.

Not convinced that Gen Hydro brand products are the problem either. I had some good grows with them last year and many people use them to great results. I've grow with Dutch Master before and don't have any complaints against the company, but haven't seen any better yields with it than Gen Hydro in my experience. If I were almost out of nutes I'd consider switching, but that's not the case.

Reservoir temp is almost 80 degrees. Not sure how to bring that down with my current setup, though. My reservoir is only 2-3 gallons in size so there's not much thermal mass to keep temps down with. I just built a wooden reservoir which should hold about 20 gallons, but can't put that into use quite yet (hopefully will have it set up in a week or 2 after some of my other plants have finished ripening seeds). Hopefully the larger res will mean cooler water temps, and at least that res will be big enough to throw frozen water bottles into if need be.

I ran some water though my brita filter and measured it with my TDS meter, same ppm as straight unfiltered tap water. 170 ppm from the tap, 170 ppm after filtration (and yes my meter is calibrated). I think I'd need a R.O. setup or buy distilled water to get 'clean' water.

I'll try taping up my reservoir box to prevent the algae. It always looks awful covered in tape and it never lasts, but it's probably about time to build a new setup anyway. I'll change out my nutes, too. I can put a foam puck over my rockwool plugs to minimize light hitting the rockwool. I don't think this would be an issue as I've grown with lots of algae-coated rockwool before and not had problems, but I'm certainly willing to try. I also have beneficial microbes I can put into the tank, I usually save that for later in the grow but it looks like these gals need help now. Funny thing is a friend just gave me a couple bottles of Subculture-M, I was just reading the label on it this morning. Should I try to kill off the algae on the roots with peroxide before adding the good microbes, or just go straight to the microbes?

Again, thanks for the help. Let me know if you see something real obvious in the new pics. I'll try the above measures and report back.

Hey guys
I have same prb 2 weeks ago
Its mag def and its locked by your acidic water so
use epsom salt or cal mag and ph around 8.90
I will put the chart tomorrow but u can easy search it on other threads

Bro the ph is out of whack. Far too low causing multiple deficiencys. Get it to 6.5 or growth will stop(it has already slowed up) and calibrate your meter. Ok i just realised its hydro make it 5.8 and im sure that your meter is out, calibrate it.

he is in hydro

@op.... What makes you think its a magnesium toxicity?

manganese toxicity (not magnesium) is the only thing I saw that caused orange/yellow spots on the leaves. I thought that sounded weird though, as I'm using what I'd consider very 'normal' nutes, which is why I posted to the forums asking.

Gotta say don't thats your problem

oooooooooooooooooooooooooooooo sorry thought you said magnesium.. read it twice and still didn't notice lol

You could always try some micro nutes and see if that helps..

check the effected leaves just for the hell of it and see if you see any little black dots on the undersides of the leaves

Alright, covered my DWC reservoir tub with enough foil tape to make it look like something out of the Sputnik space program and put foam plugs over my rockwool to keep light from hitting the rockwool, should eliminate any problems caused by algae. I changed out the nute solution and added some botanicare aquashield to promote some beneficial microbes. New TDS is 910ppm and PH is 5.56, and I'm expecting it to creep up, it always does. I used filtered water this time, even though I'm not seeing a drop in TDS between filtered and non-filtered. Just trying whatever I can. Thanks everyone for the help, keep it coming if anyone has any other ideas. I'll post back in a day or two with the results of what's happened so far.

no black spots under the leaves, most of the damage appears to be on the top of the leaves. Some spots have gone all the way through the leaves, so there's some necrotic spots on the underside, but definitely not black.

magnesium / manganese, why did they make two elements sound so much alike in the 1st place??

carl, manganese tox is exceedingly rare.
I went over the conditions in the first post, and imo your ppm are very high. Also since your water starts at 170 ppm, almost entirely calcium ... I imagine you are experiencing nute lockout combined with nute burn. I had very similar problems with a Nirvana White Widow, a similarly nute-sensitive strain.
I've also noticed that the water in my region contains over 2 ppm chloramine, which does not degrade/evaporate by letting the water sit. This is probably stressing your plants if present ... it did mine.
Two immediate recommendations:
1) remove any chloramine.
2) use nutes designed for hard water.
Ideally skip 1) and 2) and get a RO water source!
This plus dropping TOTAL ppm BELOW say 450 should make a world of difference.
your hydroponic polar bear, cn

wow, 450 ppm, I'm already at twice that, and was shooting for more. I do keep stumbling across the advice to "use half or 1/3 stength nutes than what the bottle recommends" but then hear people on these forums vegging at 1200ppm. I'm gonna cut my nutes back to 600 and see what happens for a few days. And I'm saving up for a RO setup.

carl1078lewis said:

wow, 450 ppm, I'm already at twice that, and was shooting for more. I do keep stumbling across the advice to "use half or 1/3 stength nutes than what the bottle recommends" but then hear people on these forums vegging at 1200ppm. I'm gonna cut my nutes back to 600 and see what happens for a few days. And I'm saving up for a RO setup.

Click to expand...

carl: It's dependent on strain. My first hydro grow I ran at 1200ppm throughout veg ... it was Cinderella 99 and in retrospect it was a lucky strain choice. I was poisoning my White Widow at 550 ppm!
A am re-entering growing after a decade's hiatus, and I too thought "the low ppm for young planys seems overly cautious". Whaddya know; it made me learn something about strains and how different they are.
Try running at low ppm, say 400 cumulative ... see how they respond ... you can always ramp up from there. At the minimum, your overfed dearies need a time to chew all that cud. cn