Fungus gnats in rez

Redoctober

Redoctober

Well-Known Member
Never had any problem like this but when I opened the lid of the rez, there were literally hundreds upon hundreds of fungus gnats both dead in the water and flying around on the underside of the lid. I have no idea how they got there. The system has no media whatsoever (no rockwool, perlite, hydroton, nothing) and is aeroponic.

Firstly, are they hatching from the nutrient solution itself? Is that a thing? Contaminated nutes?

Secondly, what can I do about it?
 
TheFuture

TheFuture

Well-Known Member
They are probably in the root mass as larvae. Sterilize your reservoir with 17% hydrogen peroxide. This will kill bacteria, fungus, as well as larvae. Then, after waiting two days, replenish your system with Orca or other beneficial mycorrhyzae and add a nematode product such as Gnatrol available in some grow stores. It is a live cake of predatory nematodes that eat those gnat larvae.
 
Redoctober

Redoctober

Well-Known Member
TheFuture said:
They are probably in the root mass as larvae. Sterilize your reservoir with 17% hydrogen peroxide. This will kill bacteria, fungus, as well as larvae. Then, after waiting two days, replenish your system with Orca or other beneficial mycorrhyzae and add a nematode product such as Gnatrol available in some grow stores. It is a live cake of predatory nematodes that eat those gnat larvae.
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Thanks Future! I am going to do just that after this grow. I wish I used bennies but I used tap water instead of RO this time which has chloramine in it. Next time, RO with bennies for sure!

Giving them a quick blast of plain tap water pH adjusted with 4-5% H202 for a day or two before resuming light nutrients (~600ppm) to finish flower
 
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TheFuture

TheFuture

Well-Known Member
Ew if they are root aphids. If you look at them and they look kinda rounded and tear shaped with two tailpipes at the ass end, congratulations it is indeed Aphids. the previously mentioned fix would knock their population down, but you would also need to add in some Bacillus Thuringiensis (Safer Brand Thuricide) to finish them off and reduce future populations. In addition if it were aphids, reduce temperatures and lower Nitrogen inputs temporarily as N makes aphid populations explode. If they have wings, it is because population has become unsustainable and they are looking for home elsewhere.
 
Cl@rksville

Cl@rksville

Well-Known Member
Redoctober said:
Never had any problem like this but when I opened the lid of the rez, there were literally hundreds upon hundreds of fungus gnats both dead in the water and flying around on the underside of the lid. I have no idea how they got there. The system has no media whatsoever (no rockwool, perlite, hydroton, nothing) and is aeroponic.

Firstly, are they hatching from the nutrient solution itself? Is that a thing? Contaminated nutes?

Secondly, what can I do about it?
Click to expand...
Could I ask how long you are looking to be growing theses plants that have the gnats, aphids etc? As in when is your harvest?
Also have you seen any 'weird growth' 'magnesium defs' 'Necrosis' 'Yellow dots/mottled foliage' 'Curling/Twisted Leaves' or basically any signs that resemble a P overdose, maybe a K def? Do you have any yellow pest strips that are empty or just the odd little black fly? I am very interested in what your outcome is but if you have an infestation thats quite bad I would be looking to a suitable solution immediately. Organic preferences don't kill them off easily ime, I use a chemical from a UK supplier that has them wiped in a week but a bacterium based solution needs 2-3 months of application from the start of a crop to be effective imho?
 
Redoctober

Redoctober

Well-Known Member
Cl@rksville said:
Could I ask how long you are looking to be growing theses plants that have the gnats, aphids etc? As in when is your harvest?
Also have you seen any 'weird growth' 'magnesium defs' 'Necrosis' 'Yellow dots/mottled foliage' 'Curling/Twisted Leaves' or basically any signs that resemble a P overdose, maybe a K def? Do you have any yellow pest strips that are empty or just the odd little black fly? I am very interested in what your outcome is but if you have an infestation thats quite bad I would be looking to a suitable solution immediately. Organic preferences don't kill them off easily ime, I use a chemical from a UK supplier that has them wiped in a week but a bacterium based solution needs 2-3 months of application from the start of a crop to be effective imho?
Click to expand...

I am just about in flush getting ready to finish. I have some burn on the leaves but that was because of nutrient burn, too much phosphorus. No other leaf symptoms. I do have gnats in the root chambers....not tons, but some. No yellow strips. If it were earlier in the grow I might attempt more aggressive action however since I am so close to being done, I think I'll just sterilize the whole system and use bennies next time.
 
Cl@rksville

Cl@rksville

Well-Known Member
Redoctober said:
I am just about in flush getting ready to finish. I have some burn on the leaves but that was because of nutrient burn, too much phosphorus. No other leaf symptoms. I do have gnats in the root chambers....not tons, but some. No yellow strips. If it were earlier in the grow I might attempt more aggressive action however since I am so close to being done, I think I'll just sterilize the whole system and use bennies next time.
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Hmmm interesting, let me add my experience as a resource/reference. I have never used an aeroponics system for my MJ but I do grow herbs in an aerosystem, so I know a little bit about what it does. During a lot of years of growing MJ using DWC, NFT and Flood Drain with no soil I have only once had a P overload or Zinc, Iron, Mag deficiency affect my plants, or so I thought... Nutrient overdosing was too unlikely, I'm too careful or tight fisted for that lol. Plus I was working for a nutrient company at the time and felt clued up, notice I say 'thought' but after doing all the amendments with some success I was still unhappy. So further down the line, say 7 days? I found I had some winged flies in my room and the fuckers avoided everything including my yellow strips like the plague! They then appeared in my reservoir in quite large numbers, I wiped them out in a swipe using some aphid killer 2 weeks off harvest. Interestingly my plants went another 4 weeks and grew like another 30% on the buds, I would put a little question mark against a P overdose unless you really went overboard with a slip of MKP of course. it could well be the flies in your soup and their toxins in the foliage, eggs in roots and decomposed poops thats fucking with your mojo?
 
Dr.Pecker

Dr.Pecker

Well-Known Member
Redoctober said:
I am just about in flush getting ready to finish. I have some burn on the leaves but that was because of nutrient burn, too much phosphorus. No other leaf symptoms. I do have gnats in the root chambers....not tons, but some. No yellow strips. If it were earlier in the grow I might attempt more aggressive action however since I am so close to being done, I think I'll just sterilize the whole system and use bennies next time.
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aphids
fungus gnat
The fungus gnat has a pointed abdomen. The aphid has two points at the end of the abdomen, legs are longer, the antennae are different.
 
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Cl@rksville

Cl@rksville

Well-Known Member
Dr.Pecker said:
aphids
fungus gnat
The fungus g
nat has a pointed abdomen. The aphid has two points at the end of the abdomen, legs are longer, the antennae are different.
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I'd probably struggle on the I.D as they whizzed past Pecker lol but its good information.
 
Redoctober

Redoctober

Well-Known Member
Cl@rksville said:
Hmmm interesting, let me add my experience as a resource/reference. I have never used an aeroponics system for my MJ but I do grow herbs in an aerosystem, so I know a little bit about what it does. During a lot of years of growing MJ using DWC, NFT and Flood Drain with no soil I have only once had a P overload or Zinc, Iron, Mag deficiency affect my plants, or so I thought... Nutrient overdosing was too unlikely, I'm too careful or tight fisted for that lol. Plus I was working for a nutrient company at the time and felt clued up, notice I say 'thought' but after doing all the amendments with some success I was still unhappy. So further down the line, say 7 days? I found I had some winged flies in my room and the fuckers avoided everything including my yellow strips like the plague! They then appeared in my reservoir in quite large numbers, I wiped them out in a swipe using some aphid killer 2 weeks off harvest. Interestingly my plants went another 4 weeks and grew like another 30% on the buds, I would put a little question mark against a P overdose unless you really went overboard with a slip of MKP of course. it could well be the flies in your soup and their toxins in the foliage, eggs in roots and decomposed poops thats fucking with your mojo?
Click to expand...

I could definitely see how pests could manifest symptoms that are similar to nutrient imbalances in plants, and they could very well be doing that in this case as well. I did in fact go way overboard accidentally with nutrients a few weeks ago though, so the burn I saw is most likely due to that. I included some new additives that I've never used before and was unsure how many ppm's they would contribute. My meter kept reading 800 every time I would test so I thought it was okay but something seemed off so I cleaned the prongs thoroughly and did a calibration and it turned out to be about 1500ppm instead of 800 :(

I knew something was wrong because the plants weren't drinking much at all (solution too salty). When I did a rez change and gave plain tap water for a day, then dilute solution ~500 - 600ppm, they started drinking voraciously again.

The thing I like (or thought I liked) about aero is that there is no medium, which is one less vector for pests. Plants sit in empty net cups held in place by neoprene discs and pvc supports. Roots hang into empty tubs with a drain in the corner. Very simple. Apparently those little gnat bastards found some way to infest anyway. Maybe some weak or dead roots, or maybe some contaminated nutrients.
 
Cl@rksville

Cl@rksville

Well-Known Member
Redoctober said:
I could definitely see how pests could manifest symptoms that are similar to nutrient imbalances in plants, and they could very well be doing that in this case as well. I did in fact go way overboard accidentally with nutrients a few weeks ago though, so the burn I saw is most likely due to that. I included some new additives that I've never used before and was unsure how many ppm's they would contribute. My meter kept reading 800 every time I would test so I thought it was okay but something seemed off so I cleaned the prongs thoroughly and did a calibration and it turned out to be about 1500ppm instead of 800 :(

I knew something was wrong because the plants weren't drinking much at all (solution too salty). When I did a rez change and gave plain tap water for a day, then dilute solution ~500 - 600ppm, they started drinking voraciously again.

The thing I like (or thought I liked) about aero is that there is no medium, which is one less vector for pests. Plants sit in empty net cups held in place by neoprene discs and pvc supports. Roots hang into empty tubs with a drain in the corner. Very simple. Apparently those little gnat bastards found some way to infest anyway. Maybe some weak or dead roots, or maybe some contaminated nutrients.
Click to expand...
It would be amazing if you could get a picture for us, I am by no means an expert but have an interest in plant bugs... :sleep:
 
Redoctober

Redoctober

Well-Known Member
Dr.Pecker said:
Looks like a fungus gnat to me. You'll have to kill off the food source and the larva. Why would they be in your rez tank though? I had them in my soil and got rid of them with hydrogen peroxide and water 1 part h202 2 parts water that kills the larva. Shop-vac helped a little for adults.
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I suppose that if one of the root masses is infested with eggs, they could be getting washed into the rez every time the roots are misted.

What is their food source? I was including Botanicare Sweet in the nutrient solution but have since stopped because of the gnats. Now it's just GH flora micro/bloom and nothing else.

Is the H202 you are referencing in your recipe 29% H202? Would that damage the roots at that strength?
 
Dr.Pecker

Dr.Pecker

Well-Known Member
Redoctober said:
I suppose that if one of the root masses is infested with eggs, they could be getting washed into the rez every time the roots are misted.

What is their food source? I was including Botanicare Sweet in the nutrient solution but have since stopped because of the gnats. Now it's just GH flora micro/bloom and nothing else.

Is the H202 you are referencing in your recipe 29% H202? Would that damage the roots at that strength?
Click to expand...
no just the normal 3%stuff I also diluted it.
 
Cl@rksville

Cl@rksville

Well-Known Member
I read a good site or two on this because I am sure I have the start of another small infestation myself. 4 Days of having yellow stickies around the base and tops of my plants have caught 1 gnat!!! A single tiny black gnat, its exactly the same as yours I got it under the trichome microscope to check it over. It was still moving the poor thing so I left it squirming as a warning to others lol :twisted:
 
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