After a bad outbrake of fungus gnats I have learned many things about them, to help you identafy these pest and the symptoms that accompany them, I want to list what I noticed, and please anyone with insight on these pest, please enlighten the rest of us, I want to create culmination of benificial information on these pest and how we can most efectivly fight them.

1. visually seeing small blackish gnats flying and landing on your plants, or crawling on the soil.

2. you notice leaves dieing and leaf damage that appears like something is eating away at the leaves but actually the leaves are dieing due to the roots supplying these leaves are being eatin by the varva soil dwelling babys of the fungus gnats .

3. your leaves appear dry, not wilted but dry, crumbly feeling, some may yellow on you with brown spots noticable before they fall off compleatly.

4. 1 fungus gnat has the ability to reproduce and destroy your whole garden, even if your plants are 5 feet tall, and they do it from the soil, the gnat itself doesn't really cause the damage, but they lay eggs in your soil and with a little moisture they hatch becoming larva that eat on fungus and the tender roots of your plants, roots die below, plant dies above.


I have here 1 very good idea suggested by sickboy to compleatly illiminate these past, after reading, again if you have something to add, methods, insectasides, whatever might help people reading this control these pest.

also need to cover your pots so no adult fungus nats can get in or out of the soil. if they cant get out or back in they cant lay eggs and reproduce. i have found that this is the only way to kill them 100%  heres the steps i take.i drench the soil with azamax and then right after i cover each pot with panda plastic,white side up and i make sure that theres no way for adult gnats to enter drain holes. i use tape around the stalks so there is no little holes for any to escape. then i will spraythe leaves w azamax. when i need to water i will take each plant out one by one, out of my grow room, and water individually, so if any adults come flying out they are not stuck in my room, i do it outdoors, then i will put the panda back on making sure no little holes. my water and nutes have had an airstone in it for at least 12 hours so roots get good oxygenated water. i left panda plastic on for three weeks. the life cycle is said to be about two weeks from hatch to death,thats why i do make sure that all eggs have hatched and gnats have died. my experience just doing the drench and sprays just controls them and doesnt fully eliminate. you will end up thinking they are gone and a month later you will get a bad break out again. hope this is helpful, letme know your outcome

6 Answers


GrowDaddyGrow Points4997
Go hydro and use h2o2 and never have a fungus problem again...

As for beneficial bugs.....ladybugs

superdaddy6 commented May 1, 2012

that would be a dream to go hydro,but only after i master soil first.i have read that hydro is very unforgiven.if one thing is out of wack kiss your crop good bye.i tryed it once with a 5 gallon bubble bucket.but i had no idear what i was doing.but the smoke was to die shit i smoked in 10 years.and i had prob.with heat.


airplane Points17605


superdaddy6 Points46
i just seen one that  came out of one of my plants i mixed up some dish soap in a spray bottle and sparyed all leves top and under and then socked soil with same soapie water.and i hope this works.i have no money to buy if anyone knows of anything that would be in the house that will kill these little fuckers please lit me know.because i just spent my last $200.on seeds from nivia.i will be pissed off if they kill my girls,all seeds are feminized.Bubbleicious,snow white,purple kush,white widow,AK48,swiss cheese,PPP,northern lights,and one unknow bag i hope all nine make it all are just two weeks from seed.and look good.but the bag seed at about three and a half weeks dose have some yellowing spots on some big fan leaves but it looks ok now.and i,am not useing ferts i,am open to anything at this point.

superdaddy6 commented May 3, 2012

thanks.i,am still trying too find it on the internet chepper then my local hydro store.but dvs247 said that 3%peroxide will kill laviar and tabco kills the flys and laviar,so i used them both so i mixed 1cup of 3% to half a litier of tabco tea added water to fill bottle and socked two other plants.will wait and see if any any of three,over the next two now to find somewere that has Beneficail nematodes,for $25 shipping inclued.i,am going to cheek EBAY had great luck finding stuff there.

dvs247 commented May 3, 2012

this is great info, please update how your peroxide tobacco tea works please, no idea if you can dilute the peroxide and it still be effective, but I did put a bottle straight into my soil and my plant is still alive, over a week ago so as far as I know it won't harm your plant,,,, I think the  beneficial nematodes is probably the best solution, my only thought now is how long I will need to wait after soaking my soil with the Azatrol  mixture in order for the beneficial nematodes live? I'm going to order in the next few weeks after I see how my soak treatment worked, even if it kills  all the gnats, I still want to add the beneficial nematodes for the future, I never wish to have these fungus gnats break out again, besides the damage to my bigger plants they have all but stunted my clones, but they are starting to grow since the Azotrol treatment. Anyone use lady bugs? I'd like to get completely away from any pesticides but remain in soil.

superdaddy6 commented May 4, 2012

i will,so now i,am going order Beneficial Nematodes from Ebay found it for $14.00/$5.00 shiping they say it will be here in two days.(i hope)ok to recap what i did.4 plants treated the big one was done with just the tabco tea.and the other three were done with the tea&peroxied,so thats 1 cup of peroxied too a half litier of tabco tea topped off to fill the when the nematodes get here i will use on all other plants.then i will flush the first 4.and give them some just too be on the safe could just be me but i sweare its like they stoped growing.and i,am realy scared i dont want to lose not one.i know that sounds bad.with all the seeds i have.OH JUST AN F-Y-I i,am not buying my soil from home depot or lowes any more.this is the sceond time i got my soil from them and had this happen.first lowes and now home depot.but lowes was much worse and i mean real bad they were all over the place.i was shocked that the plants made it.until the update.peace and happy growing all.

dvs247 commented May 8, 2012

I am going to top dress all my plant containers with a mixture of vermiculite/peat-moss and Beneficial Nematodes, will add to the soil in my larger containers before transplanting my clones as well as top dressing them,,, 7 million Beneficial Nematodes  is 1 pint and mixes with 5 quarts of vermiculite to top dress 200 plants in 4 inch pots. I pray this works.

superdaddy6 commented May 9, 2012

ok just an update the mix i made worked a little.Beneficial Nematodes came so mixed it up have three 1gallon bottels in frige waiting for my soil too dry out some before aplying.hope these little buggers work.


TwistedEvil Points880
Mosquito dunks will kill/prevent the gnat larva. If you have a water bucket, drop a dunk (about 1 dunk per gallon of water)  in it and let it float for at least 24hours then water your babies :)  I put a few dunks in a baggie and take a hammer to crush them up then sprinkle them on top of my soil then water them in. I also have some fly tape up just because even though the adult gnats are not doing direct damage...they are a pain in the rear!  It is easier than covering, uncovering etc etc in my opinion...and very effective.

Also agree with lady bugs and I use dawn dish soap mixed with water as a cheap and effective pest killer to spray the babies with :)


inanear Points131
The easiest and cheapest way to deal with gnats is to cover the soil with sand - (builders sand is the best but well washed sand works too), around an inch thick. This is enough to prevent any adult from reaching the soil to lay their eggs; the larva needs wet soil to live. Sand laid right up to the stem of the plant will not hurt the plant in any way.

Watering the plant from the top can easily cuts right through the sand and the soil and sand will mix together; to prevent this I lay a sheet of paper on the sand and pour my water on the paper so it disperses rather than digging holes in the sand. Often I use the plastic cut from a milk jug instead of paper.... anything so the soil does not get exposed.

If water is sitting around in the dishes under the plants, the adults will live much longer than otherwise. Dump those saucers. And if an adult is flying around,  just vacuum it up; just remember to spray the inside of the vaccuum hose with Raid or something, otherwise a gnat is liable to re-enter your room.

Like others have attested to, gnats come in your room via the soil you buy and they also tend to enter on the hair of dogs. Dogs that like to dig will also bring larva in on their paws.

ZRocket commented Jan 7, 2013

boy i got this prob bad think im going to lowes and get dunks and thin thik ill take some sifted sand and put over my soil..purdy cheap freaking im almost 20 days into flowering...lots of killer info here keep it up ...

inanear commented Jan 7, 2013

Good luck ZRocket, enjoy your flowers filling out.

ZRocket commented Jan 7, 2013

ok so for next grow i dont want this is there a soil that is suitable for growing and dosent give you these nasty bstards...

ZRocket commented Jan 7, 2013

Most hydroponics gardeners are familiar with the usual pests that can attack your hydroponic indoor garden and turn your hydroponics plants into sick or dying plants.

These little insect criminals include thrips, whiteflies, and spider mites, but there’s an increasing hydroponics gardening problem from an upstart pest called fungus gnats.

These grayish-black little bugs are unique among hydroponics insect pests in that they live mostly in the root zone, and especially at the top of your root zone.

Why are they called fungus gnats? I guess I could say it’s obvious - they’re gnats that like to eat natural fungi that live in most root zones.

What happens is that flying adult fungus gnats lay eggs that become fungus gnat larvae in your hydroponics root zone.

The larvae eat fungi and organic materials, and they also eat your plants’ roots. As they mature, they buzz around, and they lay more eggs. Pretty soon, you’ll be seeing a thriving fungus gnat colony in your upper root zone.

Other signs of fungus gnat damage include your hydroponics plants growing or maturing slowly, their leaves are yellowing, brown or curling, and their overall vigor is reduced.

There are three biological controls for fungus gnats available.I haven’t seen any fungus gnat infestations where the pests have eaten a hydroponic plant’s entire root ball, but fungus gnats can cause plant death because they’re vectors for root zone diseases including the notorious Pythium root rot.

Not only that, when fungus gnats die, they leave behind ugly little carcasses that turn into sludge in your root zone. Not only does this sludge feed more fungus gnats, it can also build up as a kind of filler that impedes oxygen from entering your root zone from the top, as well as interfering with aeration and drainage inside your hydroponics root zone.

Fortunately, there are easy ways to prevent fungus gnats from taking hold in your hydroponics garden and to defeat them if they’ve somehow made it inside.

As with all prevention tactics, your first line of defense is total perimeter control for your hydroponics garden. It’s kind of sad to see growers investing a lot of money and time in their hydroponics plants while allowing lots of vectors so that pests, diseases and other problems can creep into their hydroponic gardens.

You want to put a wall between the outside and the inside of your garden. This can include using filters on any vents, doors or other entryways to your garden. It also includes sterilizing tools and supplies, keeping pets out of your garden, and making sure that any clone or seedling material you bring in is absolutely free of pests and diseases.

You have to look really closely at clones with a magnifying glass or microscope, as well as examine their overall health, before you decide to bring them into your hydroponics grow room.

It’s unlikely that clones may vector fungus gnats, but it’s possible. More often, clones will vector whiteflies, mites, and thrips into your grow room, so be careful.

Another vector comes when you use organic potting soil that hasn’t been properly sterilized.

Fungus gnat larvae are small, translucent to white in color with a distinctive black head capsule.You can prevent fungus gnats by using proper watering and feeding techniques. This is more difficult if you’re using soil as a root zone media, and/or if you’re running an organic feed program that hasn’t been properly implemented or manufactured.

In particular, many growers have had problems with Earth Juice, FoxFarm and Pure Blend “organic” products that may not have been processed or designed properly to work in your hydroponics garden.

Remember- fungus gnats eat organic materials. So if you feed these inferior ferts to your crops, their organic components may accumulate at the top of your root zone where they combine with overwatering to create the kind of rich, damp, organic environment that fungus gnats love.

Avoid overwatering and let your top 2-3 inches of root zone dry out in between waterings. This on its own can kill most or even all fungus gnat larvae.

To kill flying fungus gnat adults, put up those yellow sticky strips that most hydroponics growers are very familiar with (also great for attracting and trapping whiteflies).

Another strategy is to help natural breakdown of organic materials in your root zone by adding hydroponics enzymes that decompose organic matter.

Fungus gnats are those little hopping bugs you see when you water your indoor plants.By combining interdiction, killing adults, and drying out the root zone, you can eliminate 99% of your fungus gnat problems without using harmful chemicals or other tactics.

Some people recommend using a hydrogen peroxide treatment, but this runs the risk of killing beneficial microbes that you want in your hydroponics root zone.

You can also ask your hydroponics store to get you Gnatrol WDG, a granulated material that uses natural means to kill fungus gnat larvae. You can also use a mild anti-gnat solution derived from Neem oil, although this is not as effective as Gnatrol.

The bottom line is that fungus gnats are a persistent problem in some hydroponics grow rooms, and although they aren’t as frequently seen, nor do they create as serious a problem as caused by mites, whiteflies or thrips, they are a sign of poor grow room hygiene and they negatively affect your hydroponics plants.

Do what it takes to keep fungus gnats out of your hydroponics garden, and you’ll enjoy more of the vigorous growth and larger yields that you want from your hydroponics plants.

inanear commented Jan 7, 2013

I do not know of any soil medium that guarantees no gnats. Personally, I use Sunshine Mix #4 and/or Pro Mix. I do not remember having any gnat problem with S Mix #4 but I definitely had some gnat problems when I introduced Pro Mix. The appearance of gnats when using Pro Mix is natural because it has beneficial live components in it; my logic says if a mix is not sterilized to the extent that nothing lives in it, gnat eggs might be present.
In my case, I think it was myself who brought gnats into my grow space by going from my outdoor garden into my grow room without changing my attire. Cleanliness is a must.

ZRocket commented Apr 29, 2013

benificial nematodes is by far the best method ive found...usually just 1 treatment seeds and clones are started in solo cups then from there to my final grow soil...soon as that happens i do my treatment...


roadhog Points318


Purchase an 18-watt Insectalite Fly Trap to kill fungus gnats . This trap uses ultraviolet light and pheromones to attract these pests.



Use a pyrethrin spray or aerosol to knock down and kill fungus gnats. Make sure the label states the product is for "gnats." One example of a product you can use is Garden Safe All Natural Houseplant & Garden Insect Killer.





Use yellow sticky traps to monitor and kill fungus gnats in your home. You can lay these non-toxic traps across potting soil. Or, you can hang them up to catch even more pests besides fungus gnats. One example of a yellow sticky trap can be found at


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