Brown Spots on Older Leaves of Otherwise Vigorous Plant - 4 Pics

chizarium · Oct 19, 2009

Sup everybody, I have this problem that's boggling my mind.

Brown spots appearing on the older fan leaves of an otherwise healthy fast-growing plant, pics shown below.

These spots started appearing about 2 weeks into flowering and keep multiplying in numbers as time goes by, but the plant keeps growing and looks great otherwise.

This only affects the older growth, everything that is new looks perfect with no spots.

And I do not have an ozone generator or ion generator anywhere in my house, so it can't be that.

Here are the setup details:

Strain: El Nino

Hydro: 2-Gal DWC bucket (expanded clay pellets as medium in 6" net pot)

Nutrients: GH Flora, Lucas formula (~950ppm max during full bloom)

Water: 130ppm Tap water (left to sit out for 24 hours before use)

pH: Checked daily and kept between 5.5-6.0

Temps: ~75 during day, ~65 at night

Humidity: ~40-55%

Lighting: 225 watts total CFL (2700k and 5000k bulbs)

My thoughts are that it shouldn't be a nutrient deficiency because the Lucas formula accounts for everything the plant needs. I thought maybe it could be chlorine toxicity from my tap water but its a fairly low ppm and I let it sit out for 24 hours in an open bucket before use.

Anybody have any ideas??

Any help is greatly appreciated, thanks

fatigues · Oct 19, 2009

Older leaves showing problems; newer leaves ok. This tell you it is likely a mobile deficiency - NPK Mg or Zn.

In this case, given the brown spots, you have a magnesium deficiency - probably caused by a Ph lockout (below 5.5) - or it may well be that your EC is too high.

Have you calibrated your testing equipment? I suggest you do so.

Also - if you are going to use Lucas ratio, you really should be using RO water.

Check your testing gear first please. Be certain.

chizarium · Oct 19, 2009

Thanks fatigues for the great info, I really appreciate it

I'm going to test my equipment to make sure they're calibrated right

If a pH below 5.5 would cause this that could very well be the problem, my meter could be off

Thanks again

fatigues · Oct 19, 2009

Could well be your TDS you know and your EC is little high. Is your meter measuring at .5 or .7?

If you are running Lucas full strength at 950, I'm guessing your TDS meter is using .5?

Given the problem has happened as you've switched over to bloom nutes and you've switched over to 8/16 strength, that plus the tap water may be pushing your TDS over the point where you plant is drawing magnesium properly.

If your pH is fine, do a rez change and back off on your nute strength and see if it recovers. If it does, increase nute strength a bit at a time.

If you have to, Cal+Mag or some epsom salts can be used to make sure the magnesium is in the water. It's been growing fine so far though, so I think it's a matter of your Mg getting locked out by pH or, just as likely, too high a TDS.

chizarium · Oct 19, 2009

I'm not sure if my meter measures at .5 or .7, I have a Control Wizard Accurate PPM 2.5 Digital Meter

I checked GreenHouseSeeds' grow video for this strain and they recommend a 1.9 EC at peak flowering, do you know what this translates to in ppm?

I have a 1.5 Gal res and what I do is add 10ml of Micro and 20ml Bloom to get to the ~950ppm

I check my pH meter and it seems like may have been off 0.1 or 0.2, which means when I adjusted my solution to 5.5 it was actually 5.4 or 5.3, is that bad enough to cause this you think?

Thanks again

fatigues · Oct 19, 2009

chizarium said:
I check my pH meter and it seems like may have been off 0.1 or 0.2, which means when I adjusted my solution to 5.5 it was actually 5.4 or 5.3, is that bad enough to cause this you think?

Thanks again

Yes. Below 5.5, Magnesium uptake tails off significantly. Jorge Cervantes' Indoor Growers' Bible recommends making sure pH is 5.5 or higher to avoid Mg lockout. So at 5.3 and this particular strain you are growing? Might well be the cause.

By the way, your TDS meter calibrates with a 1382 solution, so it's a .50 factor scale meter. Do keep that in mind in the future.

chizarium · Oct 19, 2009

Awesome thanks man, your advice helped me find the answer

you should be the one writing a book! =)

fatigues · Oct 19, 2009

chizarium said:
you should be the one writing a book! =)

Please. I'm a hydro newb. Almost everybody who posts here knows more about this crap than I do.

I may well be qualified to write a few books; but not on hydroponic MJ growing

That said, I do read books fairly well.

ICMag is a great resource for growing. The best resource there is, perhaps. But then it comes to diagnosing problems, I turn first to Cervantes' Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible. It's a far better tool to use to diagnose deficiencies/toxicities and pest problems on your own. Turn to ICmag's Cannabis Infirmary when, after Cervantes is of no help, you still need a second opinion.

thoughtcollapse · Oct 19, 2009

I would agree with it being a EC problem. 950ppm is rather high especially at the beginning of flower imo. Anyways, report back?

fatigues · Oct 19, 2009

chizarium said:
I have a 1.5 Gal res and what I do is add 10ml of Micro and 20ml Bloom to get to the ~950ppm

BTW, if you are in bloom, for a 1.5 gall res, you should be adding 12 micro and 24 bloom per 1.5 gallon in flower for full strength nutes when using GH micro/bloom in Lucas ratio using RO water, not 10ml and 20ml.

Are you screwing with Lucas ratio because you are using tap water? (I'm not saying you are wrong to do so given your water. I don't know what's in your tap water, of course.)

The small adjustment to your nutes is probably not the cause of your current problem. I'm just drawing this to your attention. Might be that picking up 5 gallons of RO (distilled water would also be fine) from the local grocery store will allow you to better control your grow. The size of your rez is modest, so the cost of buying Distilled water is not cost prohibitive for you.

Buying a RO unit off of ebay for $80-$100 is a better investment, of course.

OC80 · Oct 19, 2009

i had this problem from my nutes splashing on lower leaves...

jmansweed · Oct 19, 2009

Potassium - potassium - potassium

2fast4u2 · Oct 19, 2009

fatigues said:
Yes. Below 5.5, Magnesium uptake tails off significantly. Jorge Cervantes' Indoor Growers' Bible recommends making sure pH is 5.5 or higher to avoid Mg lockout. So at 5.3 and this particular strain you are growing? Might well be the cause.

By the way, your TDS meter calibrates with a 1382 solution, so it's a .50 factor scale meter. Do keep that in mind in the future.

Jorge Cervantes' books is better as a source of heat from a fire than reference material for growing pot, lol.

seriously, not the best info. just sayin, not for nothin.

fatigues · Oct 19, 2009

jmansweed said:
Potassium - potassium - potassium

Disagree. Potassium deficiency starts at the tips and edges of the leaf and yellows - not brown spots in the interior of the leaf like he has. There is also no curling at the edge. Not potassium def.

chizarium · Nov 5, 2009

Hey guys, so I have an update, and not a good one LOL

I re-calibrated my meter (even bought a second one) and confirmed that my pH is in the correct zone every day (5.7-6.0)

However, 2 weeks ago I had a plant in veg, using a 5-5-5 ratio (in mL) of G-M-B, and it was perfectly green and healthy (no spots on leaves after 3 weeks of veg growth)

So 2 weeks ago it was ready to switch to flowering so I mixed up a new res of the Lucas formula (a lighter one for the first week of flowering), I mixed 0-8-16 (mL) into 1.5 Gals of my 130ppm tap water and ended up between 700-750ppm, i figured this was ok since my plant was used to being at 600ppm in veg

After about 10 days of flowering (fresh res change every 4 days) this plant started developing the brown spots on the older, lower leaves as well

So, seems to be happening when I switch to the Lucas formula and stop using the Grow bottle

Could it be that some strains just do not like the Lucas formula? I'm seriously doing the exact same things I did when i grew my last strain (NL99) and it didnt have these problems

I don't know what else to do so today I decided to ditch the Lucas formula and do whatever it says on the bottle (a 1-2-3 ratio of G-M-B)

It's obviously too soon to tell if it's working cus i just did it today, but I'll def report back what happens

Does anybody think it could just be the strain im growing not liking the Lucas ratios?

MIGHTYMITE · Nov 6, 2009

seems to me the plant wants more cal /mag..
but what do i know

squirrelfooker · Nov 6, 2009

bendoslendo · Nov 6, 2009

chizarium said:
Does anybody think it could just be the strain im growing not liking the Lucas ratios?

I doubt many people here would say that's possible.

I, however had a very similar problem. I had a successful grow in DWC with Supergirl using Highgrades formula (basically 1/3 strength GH label with epsom salts added).

Next grow (using clones of the first) I switched to Lucas and had several different problems (possibly none of them related to the lucas ratio). One of them being exactly what's in your picture. I also had some issues with ph being too low, but even aftert that was corrected, the brown spots persisted.

RebelGrow · Nov 6, 2009

a little addition of cal/mag is probably in order. my purple urkle does exactly what yours is doing in the first two weeks of flower if i don't add it. i run flood and drain buckets with 5 different strains, urkle is the only one that does it. cheers friend, good luck

chizarium · Nov 6, 2009

thanks a lot for the tips fellas

any recommendations on how much CalMag to add?

I have a 1.5 gallon rez

Brown Spots on Older Leaves of Otherwise Vigorous Plant - 4 Pics

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