Fungus gnats/ sciarid flys. What should I do

Hgrow4

Active Member
I have 2 grow tents and every day I go in there is a sciarid fly about.
I have those yellow sticky pads in both tents and they have about 2-3 flys on them.
Is this something I should act on now and be worries about or is it normal.
If a problem what is the best/most effective way to help.
My plants are fairly young (a few weeks) so could do with a less harsh method.
 

simpleleaf

Well-Known Member
I have 2 grow tents and every day I go in there is a sciarid fly about.
I have those yellow sticky pads in both tents and they have about 2-3 flys on them.
Is this something I should act on now and be worries about or is it normal.
If a problem what is the best/most effective way to help.
My plants are fairly young (a few weeks) so could do with a less harsh method.
In the 1970s we used to be able to purchase steam-sterilized potting mix! No more. :( I treat my potting mix with boiling water before planting, problem solved, but it's a PITA.

Gnatrol works well. Food-grade DE seems to help reduce populations, as does H2O2.

Neem oil soil drench also seems to work.
 

Hgrow4

Active Member
In the 1970s we used to be able to purchase steam-sterilized potting mix! No more. :( I treat my potting mix with boiling water before planting, problem solved, but it's a PITA.

Gnatrol works well. Food-grade DE seems to help reduce populations, as does H2O2.

Neem oil soil drench also seems to work.
Thank you for the insight , I'll look into it :)
 

speedwell68

Well-Known Member
Bottom water if you can, it allows the surface of the medium to dry out and they aren't keen on that. After that treat the soil with Nematodes. After repeated fungus gnat infestations I have taken to buying my soil direct from Amazon. They keep it indoors and dry, so it doesn't become a breeding ground for fungus gnats.
 

DrDukePHD

Well-Known Member
I grow a few autos in happy frog on my deck every year and every time I get fungus gnats! Here's what I use to completely get rid of them I use microbe lift bmc 2-3 drops in a gallon of water and water with it every time I water in till they go away it works for me 100% of the time for me.
Yea Microbe-Lift BMC is by far the easiest & most effective bti product I've used.
 

TaoRich

Well-Known Member
A vinegar trap helped me out when those buggers were attacking my psilocybin grow.
The most popular option is a vinegar trap, which is simple and cost-effective to create. Simply place a few tablespoons of apple cider vinegar, a few drops of dish soap, and a tablespoon of sugar in a bowl and stir. Set your bowl in an area where gnats are prevalent, such as your kitchen or bathroom. The sugar and apple cider vinegar combination will attract gnats, and the dish soap traps the gnats and eventually causes them to drown.
I used apple cider vinegar and fresh orange juice.

Obviously, try to deal with the root cause, but this works well to catch and kill the flying adults.
 

PhernPhan

Member
I had a bad gnat problem stemming from (un)happy frog last spring. It manifested slowly through veg, and got real bad just before I wanted to flip to flower. I tried a number of things, and eventually used a multi pronged approach to knock them back. It was a war, and very frustrating, but it worked - over time. I refused to use bt toxin or toxic pesticides of any kind.

Plants were in 5gal felt bags. I started by drying the soil out thoroughly (about 7-8 days without water), I then used the shop-vac to remove all the loose soil from the top and sides of the containers, right down to the root ball. I fully topped the containers with fresh soil mix (rice hulls and Stonington), and worked it down the sides of the pots as best I could. The top dressing was about 2 1/2 " when I finished. I watered it in with a strong water / neem oil solution (I think it was 6tbl concentrate : 1 gal water - it was in the pamphlet on the side of the concentrate bottle).

I set up a yellow sticky trap in each pot, and hung a couple of fly strips in my tent. (Vinegar traps will catch a few, but nothing compared to the sticky traps, and they stink too). After two days, I watered with a hydrogen peroxide solution (3 water : 1 Peroxide), and sprayed the top of the soil with neem oil solution - smaller ratio of neem oil in the spray). BTW, the plants LOVED the peroxide soak and it really aerates the soil!

Then I alternated feeding waterings and peroxide soaks for the next two weeks (3 total peroxide soaks), ALWAYS spraying the soil surface and base of the trunks with neem oil solution after every watering, trying to deter the adult bugs from entering the soil. I've heard that a little peppermint oil can be added to the neem oil solution too, but I didn't have any.

This method assaulted the infestation in five ways. 1) It took out a majority of the nesters and larva in the loose soil when I got rid of the loose stuff. 2) It put a major deterrent (neem oil) through the soil and all over the root ball in the initial soak. 3) The peroxide soaks worked on killing the larva without toxins (over time). 4) The neem oil sprays deterred re-entry of adults flying around. 5) the sticky traps catch the flyers over time, reducing the number of egg-layers getting to the soil.

I eventually destroyed them, but it took even longer than the initial two week treatment to knock them out. They are really hard to get rid of once established. Prior to this, I tried several of these things, and others, individually, with no success. I firmly believe it took the full combination of methods to truly do the trick. Good luck!

PS - I never buy Fox Farm anymore.
 

ALPHA.GanjaGuy

Well-Known Member
Most likely it wasn't fox farms fault but the place you bought it. They likely didn't have it stored properly.

Just to mention it, I often say it but I think most people think it couldn't work but Cinnamon scratch through and topping will eradicate even the worst fungus gnat issues and your roots will enjoy it also.
 

PhernPhan

Member
Most likely it wasn't fox farms fault but the place you bought it. They likely didn't have it stored properly.

Just to mention it, I often say it but I think most people think it couldn't work but Cinnamon scratch through and topping will eradicate even the worst fungus gnat issues and your roots will enjoy it also.
Unfortunately, I never heard of the cinnamon thing when researching eradication methods at the time. I will certainly give it a try if I ever have the problem again. Thanks!
 

laddyd

Well-Known Member
I had fungus gnats, what a pita, I should probably hold my head down and shuffle my feet in shame after that statement. They spread from the tent to the houseplants, boy was the wife pissed. I tried neem oil, mosquito bits DE and finally ground pumice. Oh and sticky traps, lots of sticky traps.
The DE with a layer of pumice on top did the trick. I didn't have much luck with the mosquito bits even after 3 treatments.
Number 1 try and eliminate at the source. No Fox Farms, Miracle Grow or Black Gold. I tried all of these and they all had gnats. I use pro-mix now and have yet to see a gnat in two grow cycles.
Water from the bottom. My latest grow I'm using self watering wicking buckets and the plants are flourishing.
If you already have a gnat farm growing I heartily recommend a layer of garden pumice fine ground with some sticky traps to finish them up.. They can't crawl through it, works like sand but is easier to water over.
 

cougheeesm

Well-Known Member
What you need is to keep Bacillus thuringiensis alive in your soil or coco. This can be found in microbial products like Great White and many more. You can also get a product like Mosiquto Bits which is just BT.
 

effexxess

Well-Known Member
What you need is to keep Bacillus thuringiensis alive in your soil or coco. This can be found in microbial products like Great White and many more. You can also get a product like Mosiquto Bits which is just BT.
p.37.1-bmc_sm.jpg

MICROBE-LIFT/BMC 8% Bacillus thuringiensis israelensis.

Online and at pet stores.
 

Boatguy

Well-Known Member
Most likely it wasn't fox farms fault but the place you bought it. They likely didn't have it stored properly.
I grow indoors in the winter only to avoid bug problems
The only time i got gnats was the one time i used ffof. In 10 years of using promix not a single bug.
I know alot here swear by fox farms soil, but i wont use it again.
The bag was undamaged, and other than some large sticks in it, it seemed fine.
 

Moonmanyyc

Active Member
Will microbe Lift BMC be ok to run with a sterile system? I thought running sterile would keep everything or most at bay but these bastardized gnats were breeding under my felt bags in the elevators you put the bags on to drain. The bottoms of them have holes but they are bevellEd upwards so the end of last grow I drilled them out with 2” holes saw.
 

Marti Masters

New Member
I had a bad gnat problem stemming from (un)happy frog last spring. It manifested slowly through veg, and got real bad just before I wanted to flip to flower. I tried a number of things, and eventually used a multi pronged approach to knock them back. It was a war, and very frustrating, but it worked - over time. I refused to use bt toxin or toxic pesticides of any kind.

Plants were in 5gal felt bags. I started by drying the soil out thoroughly (about 7-8 days without water), I then used the shop-vac to remove all the loose soil from the top and sides of the containers, right down to the root ball. I fully topped the containers with fresh soil mix (rice hulls and Stonington), and worked it down the sides of the pots as best I could. The top dressing was about 2 1/2 " when I finished. I watered it in with a strong water / neem oil solution (I think it was 6tbl concentrate : 1 gal water - it was in the pamphlet on the side of the concentrate bottle).

I set up a yellow sticky trap in each pot, and hung a couple of fly strips in my tent. (Vinegar traps will catch a few, but nothing compared to the sticky traps, and they stink too). After two days, I watered with a hydrogen peroxide solution (3 water : 1 Peroxide), and sprayed the top of the soil with neem oil solution - smaller ratio of neem oil in the spray). BTW, the plants LOVED the peroxide soak and it really aerates the soil!

Then I alternated feeding waterings and peroxide soaks for the next two weeks (3 total peroxide soaks), ALWAYS spraying the soil surface and base of the trunks with neem oil solution after every watering, trying to deter the adult bugs from entering the soil. I've heard that a little peppermint oil can be added to the neem oil solution too, but I didn't have any.

This method assaulted the infestation in five ways. 1) It took out a majority of the nesters and larva in the loose soil when I got rid of the loose stuff. 2) It put a major deterrent (neem oil) through the soil and all over the root ball in the initial soak. 3) The peroxide soaks worked on killing the larva without toxins (over time). 4) The neem oil sprays deterred re-entry of adults flying around. 5) the sticky traps catch the flyers over time, reducing the number of egg-layers getting to the soil.

I eventually destroyed them, but it took even longer than the initial two week treatment to knock them out. They are really hard to get rid of once established. Prior to this, I tried several of these things, and others, individually, with no success. I firmly believe it took the full combination of methods to truly do the trick. Good luck!

PS - I never buy Fox Farm anymore.
What percent hydrogen peroxide did you use?

I tried SF nematodes, which worked pretty well. The problem seemed to be worst in my tradescentia zebrina, so I dumped the entire pot and put the plant in new potting mix. After a couple weeks, I sprinkled cinnamon all over the place in every pot and then I sprayed the transcentia zebrina with a mixture of alcohol, mild dish soap (liquid) and water. That seemed to get stop the gnats and it didn't harm the plant. However, some of my other plants ended up being damaged. Two calathea are down to one leaf, so I'm hoping they will hang on til spring when they come out of domancy. The dracaena marginata is surviving, but I lost the smaller one. All the other tropical plants are fine.

That said, I would like to try using hydrogen peroxide. Next time I'm at the speciality grow store where I live, I'm going to ask the sales person what potting mix they use in the store. There is the biggest, healthest, beautiful monstera I've ever seen and their other plants are also in good shape.
 
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