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Deficiency? Toxicity? Lettuce plants no bueno. Can anybody help?

Hello fellow aquapons.  Gotta quick question for you very knowledgeable folks out there.

The lettuce in our system has had a few problems as of late, and I'm not sure what is going on.  

It seems that only the older leaves are affected, and it starts with a general interveinal chlorosis, then the tips burn, then a bronzing / leathery thing happens.  They are very quick to wilt when it's hot, the roots are somewhat stunted and some of them tear easily when I harvest.  Some of them are kinda brown above the water line (they are grown in NFT channels). 

Pictures are worth a thousand words, so before I say any more, here are some pictures.  If you know what's going on, please help!  Thanks everybody. 

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Hmm...there might be more than one thing going on there...But I'm willing to bet that if you take one or two of the worst looking plants and carefully inspect all around the crown area (where the roots meet the stem at the base of the stalk/leaves)...you will in all likelihood see a slight brownish red discoloration on one side or another. (If so, in a few weeks time it will be more than just 'slight'...might get kind of mushy and fuzzy down there even...at which point some of the lettuces will look look the garden gnomes sat on them)...

I'm trying to learn how to diagnose nutrient imbalances so take this with a grain of salt.

I got this from ENH1098: Nutrient Deficiency Symptoms of Woody Ornamental Plants in...

"P deficiency, in combination with K deficiency, results in diffuse reddish spotting on the oldest leaves (Fig. 4)."

Hey Vlad.  After some much closer inspection down there, you were pretty much right on the money.  Some of the older leaves at the base of the crown have brown sections that have become translucent - like when lettuce goes bad in the fridge.  The parts of the leaves that touch the NFT channels seem to be more affected than those that are elevated.  The red oak seems to just be discolored like the pictures (although that was the worst one, most just look slightly "off"), but the butterhead gets these black spots near the crown, on the inside of the stems, that extends about 1" from the base. 

The ones that are the most affected, after examining more thoroughly, have stunted and "sludgy" roots.  Could those spots be mold?  They seem slimy, but I can't wipe them off.  There's also a ton of dead aphid bodies (the white shells after I killed those bastards with insecticidal soap) near those black spots.

There were only a few leaves that looked liked the garden gnomes sat on them - they were cinched and there was a grey fuzzy filament on them (not a spiderweb), kind of like grey cotton candy.

What does this mean? Do we have brown rot or something horrible like that?  

Any ideas for how to fix?  


Vlad Jovanovic said:

Hmm...there might be more than one thing going on there...But I'm willing to bet that if you take one or two of the worst looking plants and carefully inspect all around the crown area (where the roots meet the stem at the base of the stalk/leaves)...you will in all likelihood see a slight brownish red discoloration on one side or another. (If so, in a few weeks time it will be more than just 'slight'...might get kind of mushy and fuzzy down there even...at which point some of the lettuces will look look the garden gnomes sat on them)...

Yeah, I've got a couple ideas that might help some. What size system are we talking about here? i.e about how many heads of lettuce do you have going on in your NFT sub-system (a real, real brief description of your AP system would be cool too...you know, volumes sizes, components blabla)...Since what might be a fine and dandy remedy in a system with 20 or 40 plants...might be a phenomenal pain in the butt strategy in a system with 2000 or 40000 plants and vice versa...

Aphids huh? Bummer. I was thinking thrips. Check for thrips too. They are super hard to see sometimes, since they're so darn tiny...they're pretty fast too and like to hang out in the moist darkness. They don't seem to really do a heck of a lot of damage themselves (unless there's a ton of 'em maybe), but they do spread around a lot of disease and infection

Yes, those spots could be mold, but could also be bacterial in nature.

The grey fuzzy filaments and brownish-red mush is are both very likely caused by an oomycete (many of which are still mistakenly classified as fungi in literature).

Yikes!  So you are thinking that this isn't a nutrient thing then?  This is more scary than I thought.

I have definitely seen thrips, so you're certainly on the money there, but we spray weekly with OMRI 2% insecticidal soap so not sure if this is still a problem.  I hope they're not spreading disease before the weekly genocide!  Our cold frame is open to the air, so we have all the typical farm bugs - good ones and bad.  

So brief description of the system:

300 plant site Crop-King NFT system (128 sq ft) retrofitted for Aquaponic 

100 gallon clean sump tank (Fish tank to biofilter to sump)

4-5 sq ft biofilter with combo of lava and river rocks (12 inches deep with no plants, just biofilter) sits underneath channels and has autosiphon - I think capacity is 30 gallons - floods and drains completely every 10 minutes

110 gallon fish tank with 4 Koi fish that total about 4 pounds.

Feeding with AquaOrganic feed at Dr. Lennard's ratio of 13g/sq meter, at 25% since we only use NFT.  Feed is 0.085 pounds per day and is easily handled by biofilter.  No leftovers from fish.

We have a 100 micron filter between clean sump and NFT channels, and use large aquarium filter foam to trap large debris.  Water is crystal clear.  pH between 6.4-7.0.  Also we use Sustane OMRI compost tea with Maxicrop seaweed for foliar spray and dump rest in tank for micronutrients and what I thought would be increased plant health!

So I hope that helps.  Thank you so much for taking the time to help Vlad.  Much appreciated.  Can't wait to hear your ideas on how to fix.  -Ben

Oh god no...definitely not a nutrient deficiency (though for your sake I wish it were as that would be less of a hassle to deal with and an easier 'fix).

What you have going on is one of two things, and quite likely both. Though the 'fix' is the same for both, so either way your course(s) of action would be the same.

1) Botrytis cineria

2) Sclerotinia sclerotiorum

The reason I believe your problems derive from both of these fungal pathogens is because you described the moldy webbines as "grey" (Botrytis), but you also gave a pretty good description of the (black about an inch in length) of the fungal resting body (called sclerotia). Had the 'webby' mold been white, we could have excluded the Botrytis. The often go hand in hand with each other though (but you can double check on the color if you wish). The both will cause exactly the same symptoms, both the ones you described and the brown watery lesions near the crown area that i suggested you check for...and both are a pain. I'm guessing that your weather has been mild to warm and pretty rainy and humid lately?

I'm also gonna guess that you haven't been (since there's probably not been a need to) sterilizing your net pots or inoculating your seedlings (or your system) with beneficial microbes...and that you've probably been running for the better part of a season or more...Well, the honeymoon's over 

The "real" thing to do would be to get rid of your plants, sterilize the affected areas, then inoculate...but I would try to save the plants if I could.

Do you have a way to disconnect the NFT from the rest of your system? (Everything I will be suggesting is 'fish safe', but you still need to be able to disconnect...unless you don't mind getting rid of the plants).

I've got to go out for about 2 hours, but would be glad to advise when I get back. In the mean time let me know about the possibility or not of disconnecting the NFT...

And it would be wise to start to source either

sodium perborate or,

sodium percarbonate

(both are just the solid crystalline/powder form of hydrogen peroxide...IMO it is a much better sterilizing agent to use in a living bio-ponic system...bleach can be ok for some things, but it is a leftover from the mineral hydroponic world. You'll need the H2O2 anyways, it's really handy for all sorts of things. The solid form will keep almost forever (unlike the liquid form), it's easier to store and takes up less space than the liquid form and you can mix up the strength that you need/desire. (Unlike being stuck with a 3% liquid solution that is bulky and will 'go bad' in a few month anyway). It should be pretty cheap to acquire by the pound(s)...

Also, look into ordering some type of Streptomyces lydicus product (like Actinovate). I use a Bacillus subtilis recipe (from a Russian lab...not because I think that it is better, but because I can't acquire a S. lydicus product here...but both are very beneficial microbes to have for a number of reasons. They are both anti-fungal bacteria...And can be used foliar or as a soil/media/substrate/system inoculant. Both are fish safe. However they are to be used either pre-emptively, or after a sterilization event (which still counts as "round two"  preemptive)...

While your surfing or when you have the time you might want to consider looking into an integrated pest management program (IPM)...using soaps and whatnot is fine, but it seems much better to use those sorts of things as "a last resort" type of thing (or second to last resort really). I've been having really good success with a number of different Spinosad A and Spinosad D products I've been using. Spinosad is a bacterial based insecticide that will not harm your fish and is really forgiving on non-target species. Predatory mites are really good to have around, and lady bug larva are free and easy to cultivate...and are eating machines

Bio-diversity really is one of the (major) strengths of these various bio-ponic systems (AP falls into that category). The more beneficial organisms (microbes and all) we cultivate, the less problems we encounter. But they need to be cultivated in the true sense of the word because most pathogens (and many pests) are quite aggressive and will out breed and out compete our nitrifiers for resources and living space. So we can't forever rely on just N. sonoma and N. spira or bacter to keep things running smoothly at all times, during all seasons. There does appear to be sort of a grace period of about a year or two when a system is new, where they will do the trick...but that grace period invariably comes to an end...

Thanks for the system description (hehe... good call on the micron filter, I bet that keeps things nice and free of fines in the Crop-King) sounds like a pretty nifty set up 

Gotta run...



Benjamin Frimmer said:

Yikes!  So you are thinking that this isn't a nutrient thing then?  This is more scary than I thought.

I have definitely seen thrips, so you're certainly on the money there, but we spray weekly with OMRI 2% insecticidal soap so not sure if this is still a problem.  I hope they're not spreading disease before the weekly genocide!  Our cold frame is open to the air, so we have all the typical farm bugs - good ones and bad.  

So brief description of the system:

300 plant site Crop-King NFT system (128 sq ft) retrofitted for Aquaponic 

100 gallon clean sump tank (Fish tank to biofilter to sump)

4-5 sq ft biofilter with combo of lava and river rocks (12 inches deep with no plants, just biofilter) sits underneath channels and has autosiphon - I think capacity is 30 gallons - floods and drains completely every 10 minutes

110 gallon fish tank with 4 Koi fish that total about 4 pounds.

Feeding with AquaOrganic feed at Dr. Lennard's ratio of 13g/sq meter, at 25% since we only use NFT.  Feed is 0.085 pounds per day and is easily handled by biofilter.  No leftovers from fish.

We have a 100 micron filter between clean sump and NFT channels, and use large aquarium filter foam to trap large debris.  Water is crystal clear.  pH between 6.4-7.0.  Also we use Sustane OMRI compost tea with Maxicrop seaweed for foliar spray and dump rest in tank for micronutrients and what I thought would be increased plant health!

So I hope that helps.  Thank you so much for taking the time to help Vlad.  Much appreciated.  Can't wait to hear your ideas on how to fix.  -Ben

Wow Vlad, I'm kind of in shock right now.  I've been Googling pictures of those fungal diseases you mentioned, and....sigh...it looks like you hit the nail right on the head.  Now that you woke us up, we certainly do have Grey Mold and Downey and/or Powdery Mildew.  It has been in the 80-90s and very humid and rainy for the last month, and that's when everything began to turn sour.

I guess on a good note is that only maybe 10-20% of the plants succumb to the mold, and the rest are quite healthy.  So perhaps that's a good sign of a bio-diverse system?  Perhaps that is the work of the seaweed compost tea?  Our plants haven't started looking like the pictures on Google searches, so hopefully we can stem this before it gets out of hand.

So anyways, on to the fix!  As they say, the reason we fall down is so we can learn to pick ourselves up!

We can certainly disconnect the NFT system completely - including the feed and drain.

We would love to save the plants if we can - unless there is a health issue here.  We sell our lettuce to local restaurants, so the last thing I would ever want to do is get someone sick.  If that possibility exists, then we will kill everything and start from scratch.

I can source all the products you mentioned, and I'm all ears for how to proceed.

Thanks Vlad. -Ben

@Benjamin Frimmer  - Vlad is amazing once again.

This is an interesting topic and I would like to see some pictures of the affected area

Hi guys. (...and thanks Bob :) 

Don't sweat it (but don't be complacent either). It surely can be weird seeing this stuff for the first time, but it's not the end of the world...unless you just sit back doing nothing and hope for the best...in which case it can turn into a nightmare before you know it...

If it's "only" 10-20% It'd be real wise to get rid of at least the worst 10% of the plants out right. Then go through and remove the partially effected roots of the remaining 90% plants. Any roots that come away too easily are suspect and should be tossed (DO NOT compost them...if you guys compost stuff). 

(The idea is to remove as much infected partially rotted root mass as possible. Once that is done, disconnect the NFT and flush it (with the remaining 90% of plants still in it) with a H2O2 solution (sodium percarbonate, perborate or whatever...of the liquid forms of H2O2 the 35% stuff is the most economical). While the plants are out of the NFT hole, spray down the outside and rim of the NFT hole(s) with a 1 to 3% solution of H2O2.

The solution for flushing the inside of the NFT should be mixed to 3% and dosed at a rate of 4ml per gallon (you might be able to get away with a bit more...but it would be risky business, so don't push it too much...maybe 5ml to 6ml per US gallon at 3% strength. The stronger the solution, the more effective BUT you run the risk of damaging healthy roots as well beyond a certain point. Even the 5 to 6ml that I stated is beyond what most people would recommend...so don't go too overboard)...

I would flush-flood the entire NFT tray up to and including the bottom of the lid...net pots media and all. If you can 'cap off' the NFT's outlet all the better. Cap off the outlet and let that H2O2 solution stand for 10 to 20 minutes. Drain (outside of the AP system) and repeat once more. The oxygen released by the H2O2 should chemically eat away any remaining rotted root/slime. Do this again once or twice but at a lower strength (1 to 2 ml per US gallon at 3%strength).

Re-connect the NFT. Spray the crown portion and media/net pots of the lettuce with potassium bicarb (KHCO3) solution (3 grams per litre) and a bacterial anti-fungal produce of your choice (or what ever is available). Follow the manufactures recommendations for solution strength. My B.subtilis is good to go at 0.5 to 1% Actinovate may have a different instruction set. Repeat inoculation either according to manufacturers instructions, or 5 to 7 days later.

The whole point is to lay waste to as many of the pathogenic microbes as possible, and then seed your beneficials right in to hopefully out compete them, since at those H2O2 solution strengths you probably wont be able to kill off many spores. To do that you would have to toss your plants and up the ante (since otherwise you'd likely just totally fry the roots at the strengths needed to kill of spores).

Hopefully you will be able to grow out the crop to harvest size. There is no realistic danger of any adverse human health effects that I am aware of.

I wanted to be as detailed and thorough as I could, but it's now 2am here and I need to be up a 6am again. If there is anything that you need cleared up or that your fuzzy on, just ask. 

Vlad - thank you immensely for that incredible advice.  We are going to tackle that tomorrow and will definitely let you know how it works out.  Hopefully we will be able to bring the system back to the luster it once was!  

I am curious as to how this happened in the first place - I guess our grace period ran out - but I would love to know how to be proactive so that this will never happen again!  I am sure our system is not the only one to have this problem, so hopefully others can learn from my mistakes and your incredible wealth of knowledge! 

Bob - you asked for pictures so here are the worst plants in the system.  I tried to capture the root damage and leaf damage, as well as what I believe are spores or mold directly on the NFT channels.  I can only post 3 pictures at a time, so I'll add more on another post.  Enjoy.

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More pictures.....

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I put this information together so I would be able to find it again.

chicogardens.blogspot.com/2013/06/fungal-diseases.html

I got most of my information from Forest Images

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