This discoloration appeared within the past 12 hours on a Northern Lights and an Acapulco Gold. Both are photo/fem, germinated Nov. 13, growing in soil (sphagnum peat moss, perlite, buffered coir, tiny bit of composted cow manure), in a tent. I’m using Jack’s Part A and B and Epsom salts.
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When you look it up it goes to nutrient deficiency.
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Here is what I found.
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I was going to compare the photos to a picture chart of common problems but thought I would ask the forum first for more expertise.
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I’ll flush them tomorrow. That site also said light burn might be the issue, but the other three plants don’t have that discoloration. Yet.
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I flushed each one with 15 gallons of de-chloramined water. I don’t have RO water. I trimmed off all bad leaves (about 8 per plant) and removed the barley straw top cover.
I don’t know if this will fix it but it’s all I can do. I thought Jack’s nutrients were ok for non-hydroponic grows but that’s not what I’m reading now. But it’s all I have.
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Looking at the really deep green of the upper leaves, it looks to have great nitrogen content. May I suggest just watering with straight water with just a little cal/mag for a little bit and see if the potassium uptake is being inhibited by the abundance of the nitrogen?
EDIT: don’t lose hope, they look pretty good!
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Thanks. So the abundance of N makesit difficult for the plant to use K? I have a bottle of liquid CalMag, so I’ll do what you suggest; just water with CalMag for a while. The three other plants in the tent; another Acapulco Gold and Northern Lights both germinated Dec 13, and an Acapulco Gold germinated Nov 30, don’t have the discoloration. Should I continue feeding them with the nutrients, or just the water + CalMag? I was planning on flipping the lights to 12/12 in a week or two, but does that change now with this feeding change?
Here are those other three plants:
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I would let them dry a little.
then reassess.
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Yep potassium.
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Even after 15 gallons of flushing the other day and no feeding since then, this is on one of those same plants this morning.
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That is Alternaria. Pluck the infected leaves and spray them down with Hypochlorous Acid at lights out. Increase your air flow and check humidity levels.
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Will diluted hydrogen peroxide be an ok substitute? I don’t have hypochlorous acid.
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According to AI, Yes, diluted hydrogen peroxide can be used to treat Alternaria, a type of fungal disease, on plants. It works by killing the fungi when applied correctly, typically using a 3% solution mixed with water. You need enough to spray the tent also.
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I just noticed there are numerous small mold spots on the inside top of the tent. I stopped using the humidifier about 5 days ago. I guess I have to take the plants out and spray the inside with bleach.
When Bob was still on here he said use 3% H2O2 straight. But don’t let it sit, in dead air. Put it on with enough time to let it dry before lights off.
And Art this post the leaves do not look anything like your original post, the necrosis is totally different.
Marty
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Why people confuse it with nutrient burn
Nutrient burn:
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Leaf tips turn yellow or brown first
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Damage starts at the edges or tips
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Usually affects many leaves evenly
Alternaria:
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Damage appears as spots, not just tips
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Looks patchy and uneven
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Can spread from leaf to leaf
So if you see spots with patterns, it’s more likely Alternaria than nutrients.
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I took all 5 plants out of the tent and set them in an open area and removed the few problem leafs. Per a search, I put 3 tablespoons of 3% hydrogen peroxide in 32oz spray bottle and misted each plant including the underside of the leaves. While they dried, I sprayed the entire inside if the tent with full strength bleach and then wiped it down. I turned the small fan off and sprayed its blades. After everything was dry, I put the plants back in and got the fans going to really circulate the air. The room smells lime a sterile lab room now, but hopefully I won’t have that stuff come back. I’m wondering how badly this has affected the plants. Only time will tell. Thanks for the identification of that mold.
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Well I apologize for the straight 3% h2o2, too strong, but yours is too weak it is a 3-1 ratio. you used three tablespoons in a quart of water, too weak. And Art Alternaria can be systemic it is actually in the tissue of and travels through the vascular system of a plant, the brown spots are the symptoms, the actual fungus can be internal in the plant, removing the leaves and spraying the plants may get rid of it but it also may not.
Marty
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I’ll just have to watch them because there’s nothing more I know of to do at this point. I’ll add more peroxide to the spray solution and apply again if I see more spots.