How to get rid of fungus gnats


So you’ve decided to see if you’ve got the Green Thumb, eh? You read a bunch of articles about how nice it is to have plants in your room, how therapeutic it is to nurture a plant and see it grow something edible. And all of this is true, except after the initial “How hard can it be?” assessment, you realised that looking after plants really isn’t all fun and games.

They don’t like the hot, they don’t like the cold, they’re not getting enough light, they don’t like direct light, you watered too much, you watered too little… Before you know it, your little green baby is wilting before your very eyes and you’ve no idea where you’re going wrong. Then it hits you – maybe it’s just time for a bigger pot?

Like a good plant mummy, you get some lovely organic soil and repot your struggling plant into a new home, in all its fresh soil glory. You pat yourself on the back for a job well done. But within a few days, you get another delightful treat, and this time, it has wings…

Yes, say hello to fungus gnats – because setting up a UV lamp and making your own plant feed just wasn’t fun enough. These little jerks tend to live IN the soil, so by the time you realise they’re there, it tends to be too late. Sadly, your only option is to throw away the sullied soil, get new soil and completely repot the plant – which is no guarantee none of the larva will get through the cracks. Otherwise, there are a few things you can try to get rid of these pesky critters. Just to be clear, they don’t actually harm the plant in any way (unless the infestation gets really bad!), but do you really want a cloud of little flies living in your house? Because the speed with which they multiply is shocking! There are a number of ways to get rid of them, but here are a few I personally put to the test.

  1. Separate the infested plant from your others. 

Fungus gnats very easily hop from one plant to another, so as soon as you notice them on plant-patient zero, immediately move any other potted plants you have as far away as possible.

  1. Sticky traps

These things don’t so much help get rid of the gnats, but they can significantly reduce the numbers. They usually come in visually appealing form (for the gnats, not you of course) of bright yellow flowers or butterflies, to help attract the enemy. Sadly, these things are quite the eye-sore, especially when there are dozens of fly corpses attached to them, but they’ll at least stop them from flying around all over the place. The sticky traps are quite the pain to physically stick into the soil, so I’d recommend wearing gloves and/or handling them with tweezers – the sticky covering takes more than a couple of handwashes to get off your fingers.

  1. Citrus peel

This is quite old school, but the gnats have a very keen sense of smell, which is how they navigate, and there are certain smells that they just can’t stand. Anything citrussy, like lemon, lime or citronella they’ll hate, so it’ll discourage them from laying any more babies in the soil. You can get special sprays, but lemon peels work just as well and are an easier and less chemically solution – just spread a bunch of the peels covering the soil.

  1. Matches 

No, no, I don’t mean smoke ‘em out or give up and give your plant a Viking funeral. The substances used to create the strikable part of the match are phosphorus sulphide or potassium chlorate (plus a bunch of other stuff like glass powder and fillers). These substances are no bueno for the fungus gnats, specifically it kills the larvae – it won’t do any damage to your plant, so don’t worry. Sticking matches into the soil can seriously reduce the gnat numbers, so give it a try. When you combine it with the citrus peel, in a short while, they should be all but gone.

  1. Neem Oil

I personally found neem oil very effective against leaf miners, but not as effective with fungus gnats. They certainly don’t like it, but you’d have to treat your plant very often in order for the neem oil to have any effect. Having said that, the organic stuff will be good at keeping any other nasties at bay and you won’t have to crowd your soil in any of the aforementioned ugliness. Neem oil has a strong scent – it’s not unpleasant necessarily, but I’d recommend using it next to an open window or giving your room a bit of an air out afterwards, so it doesn’t linger or permeate your clothes or furniture. 

Hopefully, these measures should help you eradicate the little critters, but sadly, like zombies, all it takes is to miss one and they’ll wreak havoc yet again. If after a couple of weeks, you see no improvement, the only sensible thing to do would be to repot your plants – and certainly don’t use the infested soil again!