Issue With Sugar Leaf Curl

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smbobeast

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Hello,


I wanted to get in touch here because we’ve been dealing with a problem for about a year now. After almost every combination of trying to find a solution, we can’t figure this one out. We are a team of veterans (each of us having at least 15 years of experience cultivating), but this one constantly is a problem for us and the problem is very scattered and random. There are plants in the exact same conditions that are fine, while others that are not. Yet for others, things are even more confusing as half the plant is fine, yet the other half is not. And still, for others, half the branch is fine, when the other half isn’t. It’s all very mad, but I’ve tried my best below to give you the proper variables we go by. I also am including a picture to get a better visual.



For the last year, we’ve been dealing with an issue of sugar leaves curling down right around during the Week 3 mark (sometime always between the 14th-21st day). Now, this only happens on the sugar leaves! I will further add that the day before the problem exists, there wasn’t a problem leading up to this! What I mean is, there isn’t a situation where it’s gradually getting worse. The next day comes, and we’re hit with the picture below. Trees don’t show any discoloration, lockout, and/or nutrient burn. Everything seems beautiful, except for the actual problem.



At first glance, you would think it’s a N toxicity problem, but why would ALL the fan leaves be perfect and not show the “claw”?! This “claw” only exists on the sugar leaves. We have gone through dialing down nutrients, to changing entire lines of nutrients (3-4 nutrient lines), to come to the conclusion that this doesn't seem like a nutrient line problem. At first, we thought to ourselves maybe these “newer” nutrients (HGV, Athena, etc), just had a higher N concentration than we’re used to. Even the older lines and recipes showed the same signs.



Secondly, even though the plants overall seemed very happy, we thought a safe bet would be to decrease our input EC. Even at levels 50% of nutrient lines, we’re still hitting this snag. Again, the plants weren’t necessarily telling us they needed less nutrients. Our runoff ECs along with our runoff PH is telling us everything is kosher, but we thought it was worth the experiment since nothing really is adding up. Another thing to add is that we did see some correlation between plants with higher runoff and plants that did have the problem. So this is why we assumed these strains were not liking certain EC inputs.



Thirdly, we started asking ourselves if it’s an overwatering issue. But this is ruled out since the rest of the plant is fine. Leaves aren’t drooping down like an overwatering situation and we know we’re not overwatering, since the plants are drinking quite nicely.



In all of our years, although we don’t have personal experience of seeing this, we have heard of PGRs causing slightly similar things. However, we don’t haven’t run PGRs in 10 years, so this can’t be it. I’m just stating this just in case someone thinks PGRs are the culprit when they can’t be.



Next on our list was growing medium. We experimented with both rockwools and cocos, and the same problem exists. We also ended up ruling this out.

Finally, shortly before this issue had started, we had switched things over to drip irrigation. Although we had a couple of stellar runs before, we were stretching at this point trying to figure out if this might be the culprit. At this point we had already gone crazy and were thinking if it’s possible that the channels the drippers had created in the rockwools were somehow to blame? Meaning, was the rockwool medium’s EC high everywhere else BUT the channels where the drippers went down? We thought that maybe when we were flushing out the medium, we actually weren’t and we were just flushing out only those same channels and not the rest of the rockwool block? This is also something that was ruled out since substrate EC readers were used and they showed nothing to be alarmed about.



Now, getting to probably the last piece of the puzzle that we are about to experiment with is NOT foliaring with the recommended weekly Stack + IPM + Silicate foliar. Throughout all of these other experiments AND nutrient lines, we have always sprayed with this recommended mix. Is it possible that this could be the culprit? Is it possible that this mix shouldn't be used past week 2?



I've attached one picture of what the problem looks like. You see the green arrows showing normal signs. Most of the time, the nodes closer to the light seem less effected. The red arrows show the problems.



Conditions:

We keep a close grip on running our environments with proper VPD. Some more information is given below at what things are looking like around the time the problem pops up:

Running LED lights

Growing Medium: Rockwool

Leaf Temp: 82 degrees F

Room Temp: 85-86 degrees F

Room RH – 75%

CO2 Levels – 1250-1500ppm

Athena Blended Nutrients, Athena Pro Nutrients, HGV Nutrients, Heavy 16 Nutrients were all given a run. All showed the same issue, right around the same time frame.

Input EC / PH – We’ve tried everything from recommended levels of each nutrient line to dropping things down to about ~1.8 EC / 5.8 PH

Output EC / PH – Again, we’ve tried everything from recommended levels of each nutrient line to dropping thing down to about ~2.0 EC / 6.2



Any help is appreciated here. At this point, we are all just stumped and would love to get past this problem.
 
Issue with sugar leaf curl
BryanOconner

BryanOconner

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great advice above. What lighting above ? Why i ask to see i can help with the yield .
 
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smbobeast

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this phenotype doesn't like too high nitrogen it seems, i'm seeing nitrogen toxicity.
Thanks for the reply.

The reason we dropped nutrient strength is because we thought that if this was a N toxicity issue, the only way to drop the N on these was lower the nutes since Athena and HGV are 2 part dry powders. It's hard to think of going higher on the EC when it shows what it might be getting on the lower EC is already too much.

With that said, if it was indeed a N toxicity, why would the fan leaves or the top of the plants not show the same curl? When we've seen true N toxicity, we see a dark forest green color on the leaves and the claw everywhere. In this case, it's only on the sugar leaves and the leaves aren't even dark like that. Thoughts?
 
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Trichome.valley

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Hey broski, have you figured this out yet? I have literally the EXACT same issue. I’ve tried different nutes, pretty much most of what you did too and did not figure it out. I’m in coco, hand watering, co2 injection from a tank, sealed room, running 1000w de hps. Always day 15-21 too. It’s been like this religiously for over a year now where I never would have it before. I even set up a plant in my basement where it’s cooler, less transpiration, watering everyday no matter the wetness and I don’t have this happening. And I literally took the same feed from my rez and brought it home to feed with. So it shouldn’t be the nutes, the watering, the lighting. The only thing I’ve been told from the guys on the aroya podcast which I can’t say if it’s true or not but humidity spiking at night. I know my room when lights go off humidity gets to 70% for a few hrs. How is your humidity at night?
 
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Gmix

Gmix

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serious stretching going on and the plants are very stressed you can see that quite easily.

Very Sparse bud sites sry to say as well most lightly due to the stretching

What light are you using and how far away and is it set to 100% would be my questions as that’s way to stretchy however it also looks stressed and I am wondering what’s causing it if it’s not due to excess food. ( definitely toxic levels of n you got there bud )
 
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SnappyJack

SnappyJack

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smbobeast.. just noticed how long ago... oh well...

First off ... I've have little experience growing weed... but 35 years exp with gardening and plants in general... my first impressions are the lights are 2 far away because the plant look like their are stretching to the point of torture... I'm thinking for a room grow that temperature is to hot and hum is to high.. I've been flowering at 72F with a humidity of 45-52.. and I keep my lights 2" away... if my hand can stand it (think getting a suntan) so can my girl... not my recommendation ...just a thought to take with a grain of salt... or something like that
 
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Trichome.valley

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What about mine? I'm at 77f/ 55-60% humidity during day. PPFD at canopy is around 800. Big leaves look pretty good its just mainly the sugar leaves. And this is happening now.
 
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