If you’re here, then chances are you already have fungus gnats and are desperately trying to get rid of them. If you’ve been keeping houseplants for a while, you will inevitably come across these little demons. Read on to find out how I got rid of them forever.

What are fungus gnats?

Fungus gnats are little insects that resemble fruit flies but rather than fly around the produce in your kitchen, they tend to congregate and swarm around the soil in your potted plants. As far as I can tell, the adults don’t harm your plants other than being a nuisance to people. Unfortunately, they lay their eggs in the soil. Fungus gnats go through a larva stage in the soil before they transform into their adult form. This larva stage is harmful to young plants and soft roots and they’ve murdered several of my seedlings and cuttings before. So how do you get rid of them?

Step 1: Spray them to death

First, we attack the adults. Using an indoor houseplant insecticide like this one (I personally use Endall), spray as many fungus gnats as you can around your plants and the top of the soil. This should get rid of the current ones almost instantly. Repeat Step 1 whenever you see more of them appear.

If you want an organic approach, you can use Neem Oil. Combine about a tablespoon of dish soap, a few squeezes of neem oil using the dropper (I use around 2-3 squeezes) with a litre (around 2 pints) of water in a spray bottle. Shake well and spray on the fungus gnats and on the soil. You can also use both methods above and alternate sprays each day. Just make sure that they are killing the adults. (I noticed that just dish soap and water can also have a similar effect if you are trying to save some money). If you are planning to spray the leaves, test on a small area first.

Step 2 : Place yellow sticky traps

Using some sticky traps like these, peel the stickers and place the sticks in the soil. Fungus gnats seem to be attracted to them and in no time, you will start seeing them stuck to the traps. Whatever adults you miss in Step 1 will end up getting caught on these traps. You might be wondering if you’ve sprayed all the adults then why do you need the traps? Remember those larvae in the soil? Well they will become adults soon so we want to make sure any larvae that make it past Step 3 get taken care of.

Step 3: Biowarfare.

Finally, I used these Mosquito Dunks to get rid of the larvae and prevent the next generation of fungus gnats. So mosquitoes, like fungus gnats, also go through a larval stage. Mosquito dunks is a product with BTI, a bacteria toxic only to mosquito larvae that will completely eradicate the larvae in your soil. The best part is that it is completely harmless to other lifeforms. I tested this on my plants and despite it being advertised for Mosquitoes, it worked equally well for fungus gnats larvae as well. All you need to do is break off a chunk and put it in your watering can (use gloves or wash your hands properly after just in case). Then simply water your plants as usual. Try to cover every inch of soil to ensure the product saturates the soil.

Step 4: The hardest part - Patience!

And that’s pretty much it. After a few days, you should see a significant decrease in the amount of fungus gnats and after a few weeks they should be completely gone! As a precaution, I left some of the sticky traps in the soil. I also occasionally add a little bit of mosquito dunk in my watering can because I am paranoid that they will make a comeback and so far I’ve been fungus gnats-free for 3 years. Now if only I could figure out a way to get rid of thrips!!

No, hydrogen peroxide does not work.

Despite so many blogs I’ve read online pushing for hydrogen peroxide, I have personally tested it by applying it directly to the larva and unlike the claims that hydrogen peroxide kills them on contact, it is simply not true. The larvae just carry on. They do seem to have a seizure if you spray them with the Endall’s insecticide which is why I recommended spraying your soil with it as well.

Perlite

In an effort to cover up the soil to prevent the fungus gnats from laying their eggs in it, I applied Perlite to the top of all my pots. It did not seem to help much, I found the fungus gnats simply walking their way through the gaps. It did give my houseplants an artificial look though but overall I would not recommend. I’ve heard of some people trying the same approach using sand.