Get Rid of Fungus Gnats For Good Using Mosquito Dunks

Treetroit City

Moderately Super
Hi Folks,
Just my pennies worth. In the UK we pay £20 for small bottle of Gnat Off from Ebay, more from your hydro shop. It contains Bacillus Thuringiensis, the same active bacteria as Thuricide. Only Thuricide is £6.58 for an 8oz bottle - no brainer!

Bonide Thuricide (BT) 8oz
Bonide's Thuricide is a liquid formulation of bacteria, Bacillus Thuringiensis (Bt), which is specific to leaf eating caterpillars. Controls loopers, cabbageworms, tomato hornworms, leaf rollers, gypsy moths and many others. The insects stop feeding and die within 2-3 days of ingestion. There is no residue problem, and being exempt from tolerance requirements, this product may be applied at recommended amounts up to the day of harvest. Will not harm beneficial insects. One 8 oz. bottle treats over 5,000 sq. ft.
Directions for use:
Mix 1-4 tsp. per gallon of water and apply at first sign of infestation.
Repeat at weekly intervals as needed to maintain control.
May be applied by hose or pressurized sprayers.
Apply thoroughly to upper and lower leaf surfaces, but not to the point of excessive run-off.

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Stay safe :tiphat:

While I won't say that Thuricide won't work, it is not the ideal strain of Bacillus Thuringiensis for this application. Thuricide contains the strain kurstaki.

For gnats we want to use Bacillus Thuringiensis israelensis.

I have found the best deal to be Microbe Lift BMC.


Treetroit City

Moderately Super
Take one Mosquito dunk break in half put in bowl and crush into powder. Just put powder on top of soil (my mother plants) water in. Never seen a white fly or gnat for all the years I been using them unless one sneaks in from outside and even then they won't colonize.You can put a dunk into your hydro rez too.:tiphat:

Good prevention idea, however, I would recommend putting the dunk in a stocking or cheesecloth or similar as they tend to make a mess.


Nil Illegitimus Carburundum
ICMag Donor
Hi Folks,
I've just sprayed all the surfaces of my growroom with Fendona. It's a contact pesticide that has high residual qualities. So it dries leaving a film of crystals that kill all insects on contact.
I think it may be restricted to Pest Control professionals in some countries but its not hard to get hold of. Its even safe in food prep areas but extremely harmful to aquatic life!

Kind of 'belt-and-braces' I know but for those continually pestered by flying critters it may be the answer. my pal is an exterminator so it was free & I did it myself!
Stay safe :tiphat:


Active member
I used a half a dunk crushed up and put over the medium... Seems to have worked a little bit but my sticky traps are still being covered within 3-4 days. Any problem in crushing up another half a dunk and spreading it over the medium? They are 7&10gal smart pots so they are pretty large in surface area.


Active member
^ Anyone got input on this? Can you over due it with the dunks do the point it will cause any damage to the plant? I was thinking about crushing up a whole dunk per plant and re-applying...

Storm Shadow

Well-known member
Dunks work awsome...they just need to be given sometime to work... I take a whole pack of Dunks..crush them up and toss em in a 300 gallon rez... after a couple of weeks Gnats are all Gone ..

Enstar2 works pretty insane as well...


Active member
For soil Mosquito Bits are easier to use - same manufacturer and material as Dunks, just small pieces in a shaker container.

I tried to eradicate an infestation with Dunks/Bits and couldn't do it. Beat them back but not enough. Took three consecutive drenches with 2 teaspoons of Gnatrol per gallon of water to wipe them out. Also tried nematodes and AzaMax with similarly incomplete results.

Been months since I've seen one (knock wood) and I''m still adding Bits and doing 1 teaspoon per gallon of water Gnatrol drenches every time new soil comes into my grow. Also hgave a quarter inch of sand and a half inch of pea gravel on top of all soil as a barrier.


Could somebody confirm if these are flying root aphids or fungus knats or..?

I noticed this problem a couple weeks ago, when some of my bigger fan leafs just started falling off or would very easily fall if agitated. And now at 1 month into flowering it looks like my ladies are having a major deficiency problem. Does this look like root aphid/fungus knat symptoms to some of you pros?

All my ladies went into flower with nice green fat leaves, and now it looks like they've taken a major turn just one month in and idk what else it could be...I haven't fed them anything other than ro water with cal mag. Its fox farms ocean forest soil mixed with dry fruit and flower. I never had this problem before but I recently moved to a much warmer climate and it seems like my last grow this same thing happened and I thought it was an actual deficiency but now Im not so sure...Thank you guys so much for your time and help.


I've noticed that the more cheaper the dirt i get, the more problems with bugs ,and wayward plants growing in the soil. esp when the stock is kept outdoors


Lots of soil drenches out there. Have had good results with Azatrol as both a foliar and a drench. Root aphids, fungus gnats etc.


Well-known member
For some reason mosquito dunks have never eliminated gnats. A bugbomb at the onset of flower + careful watering seems to be the best method, sand/perlite+diotomites work pretty well too.
can you overdo it with these things? like crushing them up and putting them on top of pure there a such thing as too much? can it hurt the plants at all? can it cause ph or ec issues in the coco?
Does "Gnat off" have the same ingredients?

I use it and it works, but only if you remember to stay on top of a schedule, otherwise there's always a few coming back.

I use 1.5 cups of the Mosquito Bits to a 50 gal rez. I toss it all in a stocking and let it steep for about 10 mins, i move it around a lot. You will see all the stuff coming off of it and it clouds your rez pretty good.

Then water. Within 48hrs you will have no more larvae. Just keep sticky traps out to catch the rest of the adults.

Stop overwatering.
just thought i'd throw my bud's experience with Diatomaceous Earth

for the record, i'm a newbie watching a bud's grow, figuring i'd learn the "trade" so to speak. My bud is also computer "shy" so i've been doing the research on a couple of aspects, one was the fungus gnats.

A few posters in this thread recommend DE, with a few of those indicating to put a 1" layer on top of the soil, so the gnats would have to crawl thru it to burrow into the soil. Well, my bud did exactly that and sure enough the gnats did, and started dying.

The problem started when my bud watered the plants a few days later and the DE turned to clay (or clay like) and when it did dry, it was a solid block of hardened clay (when still damp it was like greasy play dough).

After about three weeks, just before transplanting before flowering he pulled or scraped all of the DE out that he could. Three to four weeks later, leaves started turning yellow, and the run-off pH was nose diving. He found root rot was the cause and details of that are in another thread.

Point here is i don't think layering DE on the soil is the way to go. Interestingly, he tried the #0000 steel wool route and that seemed to help, but the gnats were finding gaps and using those as pathways to the soil. Plus after awhile the steel wool on the lower side of the "apron" was a rusty wet brown mass. Messy to deal with and it gave some concern about creating an iron abundance.

What did work, the DE was the Safer Brand, and they claim their DE contains "bait" to draw insects in. I noticed the dusting he'd put down on the tables around the runoff trays was drawing the damn gnats and while some would hesitate to land, others wouldn't and others would run into it (and turn around haul ass out). but once they'd touch'd the stuff, they seem to go into a spiral toward death. It wasn't a couple of weeks without steel wool that the population was way down and now is next to nothing.

I did contact Safer Brand as i had some concern about the smokability (or ingestion by humans) and they would not tell me what the "bait" compound was, only stating the DE was "22% not silica dioxide but that they would not reveal the propietary compounds" or words to that effect. So i don't know if the turning into clay was natural for silica dioxide or if the "22%" propietary compounds were the cause.

BTW I've since learned there is "food grade" DE available. And his gnat infestation came in with a new bag of FoxFarms happy frog soil.

If / when i get a grow room going, think i'll use the safer brand DE on the tables etc, but not on the soil. Maybe some fine river sand layered on the soil but that'll be it