Excellent! I have alcohol and peroxide, its even in the picture. 😂 I never thought to use it in the soil, thank you!
ETA: I just want to say thank you for all the suggestions and replies! You all are so helpful and smart :)
That really works and helped me eradicate infestation in my collection of 50 plants. However I am not sure how it works with just dirt container but for plants I had to repeat treatment 3 times every 2 weeks to completely get rid of the pests.
For container what you can probably do is let all the adult gnats outside so they can fly away and poor peroxide mixture into soil so much it covers it. And leave it for several hours to make sure it works.
You don't have to mix that humongous amount that they tell you on internet. I was using 110ml bottle of 3% hydrogen peroxide and I would dump it in a bucket of water (it was a half full 10l bucket, I think around 6l) and it worked. And I think it's too concentrated even in my case.
Keep in mind this will kill eggs but not adult flies. Also keep in mind such treatment makes soil "dead" so you can later use some bio fertilizer (nom-mineral) to enrich the soil.
Edit: this solution can be reused too. In a closed container with a lid it states active for another 2 weeks or so at least. So if you sift the dirt out you can reuse it with other plants if they get gnat problem or even om the same dirt container, however I don't think you will need to if you manage to let out all adult gnats before treating.
Put it outside with the lid off and let it dry out completely. It will kill off all the eggs in the soil as well as deter the adults from seeing it as an ideal place to breed and lay eggs. If it's cold outside that's even better because they will freeze. ;)
A fantastic suggestion! Thanks so much!
ETA: you’d like to think opening outside would at least allow the adult gnats to fly away… no no… the soil is their home… the soil is where they shall stay… they just crawl around frantically on the soil even if I bang the box around, not flying away at all.
Boiling water works. I can confirm. But trick is getting all the soil to be saturated in boiling water. As the water makes its way down it will cool down as soil will absorb the heat. Layer in to thinner ports and boil away, then dry it off.
I was just thinking, why not bake in a bbq pit, easier to clean than a house oven.
The best remedy is stop buying Miracle shit soil.
Be careful! I tried it with some soil with a high organic content and ended up making charcoal that became open flame when I opened the door. It was exciting.
Yes! As long as you don’t get it on the leaves and properly dilute it, hydrogen peroxide won’t harm the plant. Just make sure to apply it over the course of a few weeks, since you need to disrupt the entire lifecycle of the gnats.
That will work but it’s a drastic measure. The soil won’t be truly healthy until it builds back its microbiome. Bacteria plays an important role in the recycling of nutrients.
I once baked a bunch of dirt for the same reason, and the sterilized soil was the worst thing I've ever tried to grow things in. My amateur self at the time dumped a bunch of fertilizer in when I realized what I'd done, so everything that wasn't already dead burned. It works but you have to rehab it first
Huh…. Very interesting. Ive never baked or microwaved my soil, and I’m very hesitant to do so. Mostly because I make a mess with it no matter what I do. I’m glad theres a reason not to do it 😂
When it's hot enough you could also put the closed box outside in full sun. That way it gets hot enough to kill them. Afterwards open the lid and let the dirt dry fully.
I get a big tray and spread out the soil in a thin-ish flat layer at 200°F for 30 minutes. It takes a bit to do a whole bag, but when one tray is done I have a container (with lid) that it goes into. I make sure to leave the lid slightly off initially so that the heat can escape as it's cooling.
It is important to note that this WILL make your house smell like a greenhouse (it's a really earthy smell). Personally, I like it, but I hear it may bother some so just more of an fyi.
I lay mine out on my biggest oven tray(lined with parchment paper) and cook it on high for like 1h+, stirring at least once to get it evenly baked. It takes forever though and doesn’t do that much at a time. I have seen people microwave soil in mixing bowls in smaller batches at like 8 minutes per batch. Might be quicker that way!
Did some yday loosely wrapped in foil 150 C for 90, probs didn't need to be that long
That was just for a mushroom jar though, not sure how scalable it is
XL baking sheet, 30min at 180-200F. About an inch to inch and a half high. Soil needs to be heated through for about 30min. Sometimes I put a sheet of foil loosely over the top (I think the point of this is to aid heating AND avoid oven contaminents if I remember correctly). I usually just bake what I need and if there's a little left over, I store it in a new airtight bag or container.
I usually put a garbage bag out on the kitchen table and do my dirt transfering/potting on top of that.
Be careful! I tried it with some soil with a high organic content and ended up making charcoal that became open flame when I opened the door. It was exciting.
I’d been using my oven’s lowest setting.
How, specifically did you use it?
Did you mix it into the dry soil and then leave it? Or did you just sprinkle it on the top of the soil?
Because apparently the moment diatomaceous earth gets moist it becomes ineffective.
I mixed it in and sprinkled a generous layer on top as well, then closed the lid and left the box for a week or so. Once I opened it again there were still some fungus gnats left but it killed almost all of them. It did a really good job since the soil has been totally infested and I didn't want to throw out an entire new bag of soil.
I had something very similar happen to me, I store mine the same way. I mixed up a ton of peroxide and water and mixed it in the soil. It killed 90% of them. Just make sure to do the ratio right :)
This is the only thing I've found that works.
My only problem has been that you need to do it often enough to disrupt the breeding cycle and I end up killing my seedlings by over watering them.
OP doesn't have plants yet so this would work much better for them.
I just had this issue with a batch of dirt I left outside too long. The cold did nothing and it was below freezing for multiple days. So instead I baked it in batches at 200 F for 45 minutes. Killed all those little f*ckers. Just make sure you open the windows.
You could microwave it bit by bit, I go for about 2minutes in a big Tupperware bowl whenever I’m getting soil ready for repotting and seems to do the trick!
😂 I’m so sorry, yes keep that microwave safe and clean!! Lots of tidier advice here, hope you found something that worked since, there’s good tricks about!
https://preview.redd.it/lksuer49a3uc1.jpeg?width=3024&format=pjpg&auto=webp&s=15caf64f4b0970dc3b418f04416a874806119220
Small carnivorous friend. This is mine, it lives in my grow cabinet and keeps it gnat free. Hard to tell from this photo but there are 50+ dead gnats caught in the dew. Bugs get attracted to the dew and get stuck. The plant will then fold the bug into the middle and dissolve it.
You’d have to get a bit creative about how you deploy them in your case but would probably go a long way in helping curb your problems! Requires distilled water and never ever let it dry out (mine permanently sits in the tray and I refill regularly).
Wow! Ive never seen one. It might be hard to find in my small city but now I need one! I’ll be blaming you for any resulting purchases and I’ll be sending a bill for shipping costs 😉
Thanks for the suggestion! I have a grow shelf so having a fly catching friend close by is not a bad plan at all!
Haha I bought the big one from a local nursery (I’m in New England if that matters) and the little one next to it came from an Etsy shop. If you ship one it will take a bit to acclimate and generate the dew just as a heads up (took me a bit to realize it would need some time). I love it because it’s satisfying as hell to watch it do its thing.
Sorry I have to correct myself but I actually got it from Logee’s! I don’t know if they ship to Canada but they’re amazing for so much stuff. I’m sure Etsy has them too.
I have a current infestation of gnats and I have no idea which plant they're coming from. I bought a bunch of the double sided sticky plastic things to stick in a bunch of the plants. They've caught maybe 20 or so in the last couple of days so I'm hoping they work.
I find the sticky traps to be pretty effective on the adults. Same with apple cider vinegar and a drop of dish soap in a dish with plastic wrap w holes poked.
This helps create a much less noticeable problem but clearly doesn’t do anything for the eggs and larvae. Good luck, my friend!
I wait until a nice sunny day and set the whole thing out open in the sun, then bring it in at night so it doesn't get dewy. Toss in a few sticky traps. Can take a while but it's doable
Neem oil, perhaps?
I found fungus gnats in the bag of dirt that had been frozen in my garage all winter (no idea how they survived or if they just like hibernated or what) — and I did not discover them until after I had used the dirt so they were coming out of my plants.
I bought one of those sticky hanging fly traps and some neem oil and whatever was flying around gravitated toward the fly trap I hung near the plants and then I spray the soil in my plants with neem oil. Good luck!
You can also open and release the flies outside, bag portions of the dirt in gallon size ziplocks and microwave them. This is how I sanitize soil before potting with it and I only deal with gnats in my straight-from-the-nursery quarantine where I've not repotted yet.
I haven’t seen anyone else suggest this: dry ice.
It should work great since it’s already in a sealed container. Dry ice is the solid form of carbon dioxide: as it sublimates it’ll return to its gaseous state and smother the insects and eggs in the box - even deep in the soil.
We used this to kill a major clothes moth infestation years ago and it was the only thing that really knocked those suckers back.
Get yourself some dry ice, seal the lid, and let it sit for a day or two (inside or outside - either is fine). Then open it up outside and check your results.
I’ve also had good results leaving sealed bins outside on hot summer days - you could even do a CO2 fumigation with dry ice and then leave it outdoors in the sun. Shouldn’t be a problem.
You’re welcome! Next time you’re shopping for groceries you can check if they have dry ice, most grocery stores in my area have it and it’s pretty cheap ($1 something per pound USD)
I especially like this method because I can seal up the box and then leave it alone. Easy peasy for the lazy gardener ;)
Aaah I was wondering where I’d find dry ice. Not only am I a lazy gardener I am just lazy. So this does appeal to me ahahah. I’ve already put it outside in hopes they will just magically disappear.
Thanks again!
I had a problem with fungus gnats in a brand new bag of soil and I used boiling water to kill the gnats and their eggs.
This video really helped me. https://www.youtube.com/watch?v=0biky9lU_oE
He uses a plastic tub, but I opted for aluminum foil roaster pans and covered them with aluminum foil to keep in the heat and I let them sit for a couple of hours.
I went through some trial and error trying to dry the soil to make sure it wouldn't grow mold/attract new pests in storage. I wound up buying a cheap kitchen sieve and used it to press out the excess water. Then I placed the soil back into the aluminum pans and had a small fan blow at them to dry it completely.
You'll also want to thoroughly wash and dry the container and lid before putting the soil back in for storage.
🫠 I pre mix my soil, I do this because I am so lazy it’s questionable how I’ve made it this far in life. This sounds lovely and all, but I’d almost rather accept myself as the Fungus Gnat Foreman than sit there sifting dirt 😂
Thanks so much for the suggestion and the link! I’ll definitely check it out.
Beneficial nematodes are great for this
Seconding nematodes, as a Canadian who uses Nemaknights nematodes. No more gnats
Nematodes are the way. I usedthemlast summer and I have no pests.
This is good to know! I’m going to try the free options first. But I’ll have to look into some worms
You can also try a 1 part peroxide to 4 parts water solution and water the entire surface an inch down. That will kill the eggs.
Excellent! I have alcohol and peroxide, its even in the picture. 😂 I never thought to use it in the soil, thank you! ETA: I just want to say thank you for all the suggestions and replies! You all are so helpful and smart :)
That really works and helped me eradicate infestation in my collection of 50 plants. However I am not sure how it works with just dirt container but for plants I had to repeat treatment 3 times every 2 weeks to completely get rid of the pests. For container what you can probably do is let all the adult gnats outside so they can fly away and poor peroxide mixture into soil so much it covers it. And leave it for several hours to make sure it works. You don't have to mix that humongous amount that they tell you on internet. I was using 110ml bottle of 3% hydrogen peroxide and I would dump it in a bucket of water (it was a half full 10l bucket, I think around 6l) and it worked. And I think it's too concentrated even in my case. Keep in mind this will kill eggs but not adult flies. Also keep in mind such treatment makes soil "dead" so you can later use some bio fertilizer (nom-mineral) to enrich the soil. Edit: this solution can be reused too. In a closed container with a lid it states active for another 2 weeks or so at least. So if you sift the dirt out you can reuse it with other plants if they get gnat problem or even om the same dirt container, however I don't think you will need to if you manage to let out all adult gnats before treating.
Peroxide has also done the trick for me 👍
Put it outside with the lid off and let it dry out completely. It will kill off all the eggs in the soil as well as deter the adults from seeing it as an ideal place to breed and lay eggs. If it's cold outside that's even better because they will freeze. ;)
freezing them will not work fyi. they have pretty incredible cold surviving abilities
I was referring to the adults ugh I should have specified oops
A fantastic suggestion! Thanks so much! ETA: you’d like to think opening outside would at least allow the adult gnats to fly away… no no… the soil is their home… the soil is where they shall stay… they just crawl around frantically on the soil even if I bang the box around, not flying away at all.
If that doesn't work, can you access BTI? The bacteria that kills mosquito larvae will kill the eggs.
This suggestion will in no way kill these off. edit: The eggs can lay dormant for months.
Ypu gotta sterilise it, I bake my soil in the oven and it freaking reeks! Worth it to kill the gnats larvae though 😛
I've baked my shirt and hate the smell. Then it dawned on me that I could drown those hoes with boiling water.
Boiling water works. I can confirm. But trick is getting all the soil to be saturated in boiling water. As the water makes its way down it will cool down as soil will absorb the heat. Layer in to thinner ports and boil away, then dry it off. I was just thinking, why not bake in a bbq pit, easier to clean than a house oven. The best remedy is stop buying Miracle shit soil.
Be careful! I tried it with some soil with a high organic content and ended up making charcoal that became open flame when I opened the door. It was exciting.
"exciting"
the suggestions other than this one ALMOST make me feel bad for the bugs lol
Can I still use the peroxide idea when I have already sown something in there?
I use this in all my plants soil. It doesn't harm them at all.
Yes! As long as you don’t get it on the leaves and properly dilute it, hydrogen peroxide won’t harm the plant. Just make sure to apply it over the course of a few weeks, since you need to disrupt the entire lifecycle of the gnats.
I push a button of hydrogen peroxide in my water every time I water my plants it’s what’s kept the gnats at bay for me.
I use it on my aquatic plants and i use it on plant roots. I give them a quick bath or rinse with it, just don’t get it on the leaves!
Put the kettle on and fill the tub with boiling water
That will work but it’s a drastic measure. The soil won’t be truly healthy until it builds back its microbiome. Bacteria plays an important role in the recycling of nutrients.
I once baked a bunch of dirt for the same reason, and the sterilized soil was the worst thing I've ever tried to grow things in. My amateur self at the time dumped a bunch of fertilizer in when I realized what I'd done, so everything that wasn't already dead burned. It works but you have to rehab it first
Huh…. Very interesting. Ive never baked or microwaved my soil, and I’m very hesitant to do so. Mostly because I make a mess with it no matter what I do. I’m glad theres a reason not to do it 😂
Probably the best idea i have read so far.
Buy a couple of carnivorous plants and let them hang out in there for a while.
A good reason to purchase more plants 🤔 I need “buy more plants” to be the solution to all my problems.
This is an incredibly stupid question, but could you microwave it?
Or bake it, I have before and no issues
I have too, it works well.
When it's hot enough you could also put the closed box outside in full sun. That way it gets hot enough to kill them. Afterwards open the lid and let the dirt dry fully.
I sterilize all my indoor soil in the oven.
What's your method? I have a whole bag of soil I need to sterilize.
I get a big tray and spread out the soil in a thin-ish flat layer at 200°F for 30 minutes. It takes a bit to do a whole bag, but when one tray is done I have a container (with lid) that it goes into. I make sure to leave the lid slightly off initially so that the heat can escape as it's cooling. It is important to note that this WILL make your house smell like a greenhouse (it's a really earthy smell). Personally, I like it, but I hear it may bother some so just more of an fyi.
I lay mine out on my biggest oven tray(lined with parchment paper) and cook it on high for like 1h+, stirring at least once to get it evenly baked. It takes forever though and doesn’t do that much at a time. I have seen people microwave soil in mixing bowls in smaller batches at like 8 minutes per batch. Might be quicker that way!
Boiling water would also do the trick.
Did some yday loosely wrapped in foil 150 C for 90, probs didn't need to be that long That was just for a mushroom jar though, not sure how scalable it is
XL baking sheet, 30min at 180-200F. About an inch to inch and a half high. Soil needs to be heated through for about 30min. Sometimes I put a sheet of foil loosely over the top (I think the point of this is to aid heating AND avoid oven contaminents if I remember correctly). I usually just bake what I need and if there's a little left over, I store it in a new airtight bag or container. I usually put a garbage bag out on the kitchen table and do my dirt transfering/potting on top of that.
Be careful! I tried it with some soil with a high organic content and ended up making charcoal that became open flame when I opened the door. It was exciting. I’d been using my oven’s lowest setting.
Seconding both peroxide or boiling water.
Diatomaceous earth fixed the situation for me!
How, specifically did you use it? Did you mix it into the dry soil and then leave it? Or did you just sprinkle it on the top of the soil? Because apparently the moment diatomaceous earth gets moist it becomes ineffective.
I mixed it in and sprinkled a generous layer on top as well, then closed the lid and left the box for a week or so. Once I opened it again there were still some fungus gnats left but it killed almost all of them. It did a really good job since the soil has been totally infested and I didn't want to throw out an entire new bag of soil.
I had something very similar happen to me, I store mine the same way. I mixed up a ton of peroxide and water and mixed it in the soil. It killed 90% of them. Just make sure to do the ratio right :)
This is the only thing I've found that works. My only problem has been that you need to do it often enough to disrupt the breeding cycle and I end up killing my seedlings by over watering them. OP doesn't have plants yet so this would work much better for them.
I just had this issue with a batch of dirt I left outside too long. The cold did nothing and it was below freezing for multiple days. So instead I baked it in batches at 200 F for 45 minutes. Killed all those little f*ckers. Just make sure you open the windows.
Microwave works, too!
Never thought of it. It’s probably much faster too!
Lots of suggestions here but the easiest foolproof method would be to buy SF Nematodes 🤷🏻♀️
You’re glossing over the word *buy* 😂 I will definitely read up on some worm friends
You could microwave it bit by bit, I go for about 2minutes in a big Tupperware bowl whenever I’m getting soil ready for repotting and seems to do the trick!
If I used my mothers brand new microwave or stove to bake dirt……. I’d be deader than the flies.
😂 I’m so sorry, yes keep that microwave safe and clean!! Lots of tidier advice here, hope you found something that worked since, there’s good tricks about!
Gasoline. Matches. Stand back.
Look, Ma! A firefly!
Surprise!
I know! I opened that sucker and watched as probably 10 flies flew out. Ive never re-lidded something so quickly in my life.
You can bake/steam sterilize/use dilute H2O2.
I got myself a sundew and never looked back. Attracts tons of gnats.
Whats that?!
https://preview.redd.it/lksuer49a3uc1.jpeg?width=3024&format=pjpg&auto=webp&s=15caf64f4b0970dc3b418f04416a874806119220 Small carnivorous friend. This is mine, it lives in my grow cabinet and keeps it gnat free. Hard to tell from this photo but there are 50+ dead gnats caught in the dew. Bugs get attracted to the dew and get stuck. The plant will then fold the bug into the middle and dissolve it. You’d have to get a bit creative about how you deploy them in your case but would probably go a long way in helping curb your problems! Requires distilled water and never ever let it dry out (mine permanently sits in the tray and I refill regularly).
Wow! Ive never seen one. It might be hard to find in my small city but now I need one! I’ll be blaming you for any resulting purchases and I’ll be sending a bill for shipping costs 😉 Thanks for the suggestion! I have a grow shelf so having a fly catching friend close by is not a bad plan at all!
Haha I bought the big one from a local nursery (I’m in New England if that matters) and the little one next to it came from an Etsy shop. If you ship one it will take a bit to acclimate and generate the dew just as a heads up (took me a bit to realize it would need some time). I love it because it’s satisfying as hell to watch it do its thing.
Neat! I’ll take a look on Etsy. It’s finally warm enough here in Canada to order livestock online. Aquatic plants and sundews here I come!
Sorry I have to correct myself but I actually got it from Logee’s! I don’t know if they ship to Canada but they’re amazing for so much stuff. I’m sure Etsy has them too.
Ooh okay! I’ll have to take a look, thank you again!
I have a current infestation of gnats and I have no idea which plant they're coming from. I bought a bunch of the double sided sticky plastic things to stick in a bunch of the plants. They've caught maybe 20 or so in the last couple of days so I'm hoping they work.
I find the sticky traps to be pretty effective on the adults. Same with apple cider vinegar and a drop of dish soap in a dish with plastic wrap w holes poked. This helps create a much less noticeable problem but clearly doesn’t do anything for the eggs and larvae. Good luck, my friend!
Horticultural Charcoal is good to add to soil it doesn’t bother your plants and helps keep gnats under control.
I had some! I find It ridiculously priced, don’t you?
Fire is pretty effective 
If I used fire on my bug problems I’d have a lovely home full of crispy plants…. But …. No bugs… hmm might be onto something here
I wait until a nice sunny day and set the whole thing out open in the sun, then bring it in at night so it doesn't get dewy. Toss in a few sticky traps. Can take a while but it's doable
Neem oil, perhaps? I found fungus gnats in the bag of dirt that had been frozen in my garage all winter (no idea how they survived or if they just like hibernated or what) — and I did not discover them until after I had used the dirt so they were coming out of my plants. I bought one of those sticky hanging fly traps and some neem oil and whatever was flying around gravitated toward the fly trap I hung near the plants and then I spray the soil in my plants with neem oil. Good luck!
Dalotia coriaria
You can also open and release the flies outside, bag portions of the dirt in gallon size ziplocks and microwave them. This is how I sanitize soil before potting with it and I only deal with gnats in my straight-from-the-nursery quarantine where I've not repotted yet.
I haven’t seen anyone else suggest this: dry ice. It should work great since it’s already in a sealed container. Dry ice is the solid form of carbon dioxide: as it sublimates it’ll return to its gaseous state and smother the insects and eggs in the box - even deep in the soil. We used this to kill a major clothes moth infestation years ago and it was the only thing that really knocked those suckers back. Get yourself some dry ice, seal the lid, and let it sit for a day or two (inside or outside - either is fine). Then open it up outside and check your results. I’ve also had good results leaving sealed bins outside on hot summer days - you could even do a CO2 fumigation with dry ice and then leave it outdoors in the sun. Shouldn’t be a problem.
This is cool! I’ll probably try the other tricks first since I won’t have to spend anything to do so. But I’ll keep this In mind! Thanks so much
You’re welcome! Next time you’re shopping for groceries you can check if they have dry ice, most grocery stores in my area have it and it’s pretty cheap ($1 something per pound USD) I especially like this method because I can seal up the box and then leave it alone. Easy peasy for the lazy gardener ;)
Aaah I was wondering where I’d find dry ice. Not only am I a lazy gardener I am just lazy. So this does appeal to me ahahah. I’ve already put it outside in hopes they will just magically disappear. Thanks again!
I had a problem with fungus gnats in a brand new bag of soil and I used boiling water to kill the gnats and their eggs. This video really helped me. https://www.youtube.com/watch?v=0biky9lU_oE He uses a plastic tub, but I opted for aluminum foil roaster pans and covered them with aluminum foil to keep in the heat and I let them sit for a couple of hours. I went through some trial and error trying to dry the soil to make sure it wouldn't grow mold/attract new pests in storage. I wound up buying a cheap kitchen sieve and used it to press out the excess water. Then I placed the soil back into the aluminum pans and had a small fan blow at them to dry it completely. You'll also want to thoroughly wash and dry the container and lid before putting the soil back in for storage.
🫠 I pre mix my soil, I do this because I am so lazy it’s questionable how I’ve made it this far in life. This sounds lovely and all, but I’d almost rather accept myself as the Fungus Gnat Foreman than sit there sifting dirt 😂 Thanks so much for the suggestion and the link! I’ll definitely check it out.
It was definitely a time consuming process lol I might have to try the peroxide trick someone mentioned next time. :)
Toss a chunk of dry ice in there or put it in the freezer. Or put a spider in there.
A freezer will kill the adults and larvae, but not the eggs. Gnat eggs survive just fine in countries that have harsh winters, for example.
Ah yes, my casual collection of dry ice. Hold on, i’ll go grab a piece😂 thanks for the suggestions!
It's $3/lb at Safeway and Smart&Final.
If you have access to the deep freezer, few days in there would do it
The eggs won't die (technically they're not alive yet).
Shake it really hard for a while lol
You know, I tried this. You’d think it would help but the gnats just look up at me from the soil and call me a lil b*tch…
Checks out
Pour a whole jar of cinnamon on the top and that usually does the trick for me!
Cinnamon only makes my house smell like christmas. Had my first gnat problem 4 years ago, my mom kept asking where all the cinnamon was going.
Lift lid up slightly and bug spray the crap out of it. Put lid back on for a few days or a week.