In my head my specialist subject would be something quirky or highbrow or pop culture related. In reality it’s probably the life cycle of a fungus gnat.

And yes, this is going to be a boring post, but hopefully it saves one other person a year of their life. Then it’s worth it.

At this point I feel like I’ve read every single comment, post, thread, and article about fungus gnats on plants. I spent two years trying to get rid of them after we bought an infected plant without realising.

After I had tried every single suggestion on the internet (that didn’t seem like it would kill us before it killed them), this is the process we figured out that finally worked to kill all the fungus gnats and break the cycle.

You will need:
– Vinegar
– Spray bottle
– Sand (I just bought some from Amazon, any is fine but you need a lot)
– Sticky fly catching stickers (the ones you stick in pots)
– Some kind of strong insect killing spray (multiple bottles)
– Cling film.

How to kill fungus gnats once and for all

1. Put every single plant in the same room at the same time – one you can shut the door on. Even plants you think are fine. Every single plant has to go in. One missed plant will reinfect the whole lot (yes, we made this mistake because we got lazy about a 5 foot plant).

2. Wrap cling film around the bottom of each pot (this stops the gnats escaping out of the drainage holes in the bottom). You cannot skip this step or think that a decorative plant pot will be enough to keep them in – it won’t! It needs to be cling film pulled tight around the bottom of the pot.

3. Fully cover the soil in the plant pot with a layer of sand. Do it thickly so there’s no gaps at all. This won’t hurt the plant and you can still water it – replacing with fresh sand after if needed. Yes, gnats love water. But so does your plant. Try to water it less if you can, but don’t worry if not.

“Sealing” the top and bottom of the pot means that the gnats hatch, suffocate, and die because they can’t leave the pot.

Now for the adults.

1. Spray the plant leaves and stem with a mix of vinegar and water.
2. Add sticky fly stickers to the pots and replace regularly.
3. Spray the room with strong insect killing spray, shutting the door and leaving.
4. Repeat daily for 3 weeks. Make sure you have multiple days where there are zero flies caught on the sticky fly stickers.

You have to do ALL the above for it to work. This is because you need to kill both the adults and eggs. Be absolutely relentless about following this. You cannot be too obsessive.

Here’s why nothing else works:

– Sticky fly stickers will catch adults but you’ll just be catching adults forever because you’re not breaking the cycle. And they won’t get them all anyway.
– Putting your plant out in the cold doesn’t work because your plant will die before the gnats – they can survive colder temperatures than your plant.
– The various potions and mixtures don’t work because they don’t kill the adults, just the eggs. They are also more work and less effective than covering with sand.
– Insect spray on its own just kills the adults, not the eggs. It doesn’t matter how strong it is, it won’t solve your problem alone.
– Doing it for a few days isn’t enough. It takes more than 14 days to break the cycle and kill everything off fully. One adult can lay 200 eggs, so you can’t afford to let even one pass you by.

And after you’ve done all that…enjoy your gnat-free life!!