Yellow Leaf Dots Spreading Completely Over Some Leaves (It's not spider mites)

Hi All,

I'm trying to diagnose this leaf problem. It's currently affecting almost every plant in the room, some significantly (half the leaves), others totally minor. It doesn't seem to have any pattern: the edge plants (least light, least heat) have it no more or no less than the center plants.

I know there are a lot of factors to consider in diagnosing a plant problem, but maybe someone will know what's going on -- once they see the pics and read the post. The pictures show how it progresses from tiny yellow-dot stippling, to more dot stippling, then to stipples growing in size, and finally covering the whole leaf. (It's 100% not spider mites, by the way.) The stipples generally seem to follow alongside the veins, but not exclusively.

On the underside of the leaf, it looks like the stipple is actually a very tiny eaten area, that expands -- both in the number of them and the size. I took an extreme close-up that shows this pretty clearly.

I can see no insects or eggs under multiple magnifications, from 2x to 100x -- and I've looked fairly often. If it's a pest, it's one that is invisible at 100x, and crawling all over my grow room.

The room is going into the latter stages of flowering, but everything will be the same for the next grow -- so I better find out now, before I damage another crop!

Thanks for any help!

~jessie

PS: Links to the HI-RES pictures:
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To supplement the pics, here are the grow details:

MAIN: 15 plants, flowered March 1st, 2010 (after 6 weeks of vegging)
STRAINS: AK-47, White Widow, Ice, Chrystal, LA Woman (all from seed)
GROW ROOM: 6' x 8' SCROG
GROW METHOD: Hybrid Drip/DWC. Six self-contained totes, each its own reservoir.
LIGHT: 2 x 1000w HPS (air-cooled vents)
NUTES: 800-1200ppm, Lucas Method using General Hydroponics, and I don't use any other supplements (when I get more knowledgeable, I'm sure I'll start experimenting . . . ).
TEMP: 70- to 90-degrees
HUMIDITY: Recently upped to 50%, from 30-ish%
PH: Mid 5's, checked regularly.
CO2: None now. Tried for exactly one day: the room is heavily vented. Maybe next grow I'll figure a way that doesn't break the bank.

My main diagnostic theory is HEAT STRESS, possibly compounded by low humidity. The room is really comfy now (mid-seventies, 50% humidity, well-vented), but for a good 4-weeks it was bad (mid- to upper-80's, 30% humidity). My books on growing don't mention heat stress causing dots like this.

My minor theory is some sort of nutrient lockout. I use tap water run through a multi-stage filter, but it's not distillation -- and the tap water here is hard (about 200ppm). The thing is, I've already gone through two grows using this water and nothing like this happened.

I have a similar issue, and it seems I saw somewhere that it is a cal/mag def.......

We use different water, I do not have spider mites, it is not a mold to microscopic exam.

So, I only see in during the last 3 weeks of flower. I am trying Cal/Mag now, but I noticed it really dropped the ph of the water and I had to buffer it first. Next time I give less than the advised I think.

Quote:

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Originally Posted by WashougalWonder

I have a similar issue, and it seems I saw somewhere that it is a cal/mag def.......

We use different water, I do not have spider mites, it is not a mold to microscopic exam.

So, I only see in during the last 3 weeks of flower. I am trying Cal/Mag now, but I noticed it really dropped the ph of the water and I had to buffer it first. Next time I give less than the advised I think.

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Tx for the input! I just wanted to add that the leaves get brittle as this stippling progresses. Still trying to pin this problem down . . . not 100% sure of the cause yet.

I keep looking through the diagnostic pictures in my books (which are pretty extensive), and I'm not seeing a leaf that has this weird stippling. Virus? Aliens? :)

Look here, could be (as already stated) magnesium deficiency or Ozone is also possible.

Marijuana Plant Abuse

Thats not ozone or o3 problems.granted I'm looking at this. On my phone but it looks like the late stages of cal deff.what's the ppm of the water with out nutrients.

Properly fill-out the troubleshooting form, and we can get a better idea of your situation. But with the info provided, looks to me like either nutrient burn or micronutrient burn.

You mentioned not using additives...does this include foliar sprays? How about Superthrive or one of the many bulking agents? Perhaps an iron or magnesium suppliment? Looks like repeated overdosing, but would need more info to confirm or dispell. My guess is magnesium or Superthrive OD. (just a shot-in-the-dark guess)

Then again...I'm not a hydro guy, and it might be something as simple as reservoir temps or nozzle clog. :wtf:

Quote:

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Originally Posted by JessieDiamond

Tx for the input! I just wanted to add that the leaves get brittle as this stippling progresses.

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Same here. Still out to lunch on this one.

It would be nice to know what RustyT thinks it is.

I have the same thing going, but it only effects 1 out of 13 strains in my garden oddly. No Bugs either. For some reason the strain effected has had issues from the very get go so I haven't been too worried, just as long as it doesn't go to other plants :)

Quote:

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Originally Posted by WashougalWonder

It would be nice to know what RustyT thinks it is.

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It could be a limited number of things, but without knowing the exact conditions...I (or we as a community) could possibly recommend the wrong treatment or course of action, and being wrong sucks.

Plus, guessing games cause unnecessary delays that could damage the plant(s) further.

I know it isn't heat stress, unless the roots are being steamed, but I doubt that very much. I live with the heat every summer here in the desert where growroom temps exceed 95 daily. (with A/C running full-bore) That one I can be certain of. :thumbsup:

My inital thought was micronute or steroid abuse. (Superthrive) But perhaps a GH nutrient OD. Hydrogen peroxide mishap? IDK...

Without knowing what is used for ph adjusting, if anything is being sprayed on 'em, (bug sprays, tea's...) or any of the other number of things in the troubleshooting form...the list could go on a whuile.

For faster and more accurate help, fill out the form. It only takes a couple of minutes, and could help this and future grows. There's one form for hydro, one for soil. (the link is in my signature)

Plus...I'm not a hydro guy familiar with common hydro-specific situations, and SOMEBODY is going to need that info, lol.

If I were you, for future reference, I'd leave my tap water sitting out for 3 days (I'd do a week if it's really hard). How often are you feeding them nutes?