While gnats aren’t the worst pest for your plants, they are the most annoying. Learn how to get rid of fungus gnats in houseplants once and for all.
Small dark flies that look like fruit flies and mosquitoes had a baby are a true nuisance. Adult gnats won’t really harm your plants much – but they will annoy you if nothing else because of their mosquito-like sounds and their need to fly right in your face.
While adults are harmless for your plants, the larvae are not. Larvae feed on the roots of your plants, and although they might not hurt larger plants, they can kill smaller ones pretty fast.
As these buggers fly, they easily spread from plant to plant so a small number can quickly multiply and your home will be overrun with this pest. A few flies can turn into a couple of thousand pretty fast.
How to get rid of fungus gnats in houseplants
There are many ways you can go about eliminating, controlling or preventing fungus gnats in houseplants. Depending on the size of the infestation and types of plants in your home, as well as your preference to “chemical” vs “natural” approach, there are many options for you to choose from when dealing with this issue.
If you already have a large population you will need to use more than one ways to get rid of gnats, use as many options as possible or you feel comfortable with.
We’re listing many possibilities that will show you how to get rid of fungus gnats in houseplants, with pros and cons for each as well as how effective they are.
Choose a combination that works best for you. We’ll also share the combinations that work best in our opinion.
Before you get started
Assume all plants are infested.
Treat all plants at the same time. If you treat plants in batches, you are giving gnats the time to reproduce.
Patience is key.
Not all methods work for everyone. Not all gnats are the same. If someone had success with one method and you aren’t seeing the same results, don’t despair. Try a different tactic.
Once you get on top of the issue, work on prevention, as fungus gnats can be easily reintroduced to your home.
1. Controlling the Population with Sticky Traps
Yellow sticky traps are great for controlling smaller populations of fungus gnats as adults gnats will get caught on them.
If you are extremely, extremely lucky, you might even stop the spread with just these. However, it’s more likely that you will need to take further action to get rid of fungus gnats in houseplants.
Combined with other methods that also work on the larvae and eggs in the soil, these are really effective in quickly getting rid of the issue.
Pros: it’s hassle-free (set and forget), it’s inexpensive and it works for keeping the population of gnats under control.
Cons: usually not enough alone to get rid of fungus gnats, doesn’t look the best
2. Vinegar, Sugar and Soap Traps
A homemade alternative to yellow sticky traps, vinegar and soap traps do the same job, albeit a little less effectively.
Pour the vinegar, water, a spoon of sugar, and a few drops of dish soap into a glass and place it next to the plants. This mixture attracts fungus gnats, and they should fly right into it. Works for fruit flies as well. You can try different rations in different glasses as not all fungus gnats like the same thing.
Using wine instead of vinegar works too.
We’ve had some success with homemade lemonade as well (unintentionally).
This is a great method to start your battle, as you can most likely do it right now without leaving your home.
Pros: inexpensive, you most likely have all you need at home
Cons: smells bad, not enough to get rid of the fungus gnat population entirely
3. Letting the Soil Dry Between Watering / Bottom Water
Gnats need moist soil to reproduce. Dry soil isn’t ideal for them. If the soil isn’t ideal, the fungus gnats usually won’t reproduce. Sadly this isn’t really an option for most tropical plants, and gnats do love those. And even with plants that prefer drier soil, they need to be watered at times, and the fungus gnat life cycle is pretty fast.
If you have plants that can tolerate dry soil between watering, take advantage of that.
Bottom watering the plants can help too.
Pros: easy
Cons: not all plants tolerate dry soil. Most plants susceptible to fungus gnats require moist soil.
4. Insecticide / Systemic Insecticide
If you are comfortable with using insecticides and aren’t set on getting rid of fungus gnats the natural way, using insecticide can be a fast and effective way to help you with the problem you are facing.
Sadly not all insecticides are made the same, and not all gnats react the same way either. The brand that works for some might not work for others.
The insecticide spray might not be effective with eggs and larvae in the soil, so you will need to repeat the treatment for several weeks (use it as frequently as instructed on the box – some are used weekly, others biweekly or monthly). You can get the “drench” types that get poured in the soil; those will be more effective with dealing with the whole population than the spray ones.
Many, not all, insecticides are also toxic for pets and dangerous for children, so this isn’t a solution for every plant parent. Be extra careful when purchasing, making sure you get one that you can use in your home.
If you decide to go this route, make sure you read the instructions for the specific pesticide and choose the one that can be used in your home safely. Carefully follow the instructions. We can’t stress this enough.
Some plants don’t tolerate chemicals and might react to insecticide – leaves getting spots or getting burned. This too is something you should keep in mind too.
Pros: can be extremely effective
Cons: you might need to try different brands, can be toxic to pets and children, some plants react negatively
5. Neem Oil
Neem oil is a natural insecticide, and plants generally tolerate it well. You can also drench the soil with neem oil – taking care of larvae and eggs, too – to some extent. If you have a large infestation and want to deal with it only using neem oil, it will probably take a while.
Dilute neem oil as per instructions on the box/bottle, spray the plants, the soil, and drench the soil with it too if it’s time for watering. Repeat as per manufacturer’s instructions.
Neem oil is a bit better as a preventive measure than it is a fix of the problem.
Pros: less aggressive alternative to insecticides, easy to use, plants tolerate it, great to use as pest deterrent / prevention, natural fertilizer
Cons: less effective than “chemical” insecticide
6. Hydrogen Peroxide
Drench the soil with diluted hydrogen peroxide, for getting rid of fungus gnat larvae and eggs.
Get a 3% hydrogen peroxide (3% is the most commonly sold one) and mix it 1 part hydrogen peroxide and 4 parts water. Drench the soil. If you can’t get the 3% solution, other percentages are also fine – however, you should mix with water accordingly – if you get the 6%, you should mix it 1 part hydrogen peroxide 8 parts water.
This solution kills larvae and eggs on contact, so it is very effective in dealing with fungus gnats, combined with other methods. Repeat as needed. Use a combination of sticky traps or other methods that get rid of the adult gnat population.
As you pour the solution down the soil, you might hear a sizzling sound. This is completely normal, nothing to worry about. The hydrogen peroxide won’t harm your plant’s roots. It can damage smaller roots but shouldn’t do much harm to the plant in general – be careful not to get it on the leaves, though.
Pros: deals with egg and larvae population, effectively eliminating them
Cons: it’s an instant fix, not a long-term solution, adult gnats will be able to lay more eggs after treatment
7. Diatomaceous Earth (not necessarily pet and child-safe)
Diatomaceous earth should not be inhaled (at all) as it can cause damage – if you have kids or pets, you need to consider this. Food grade diatomaceous earth is safer than non-food grade; however, it should still be handled with care – avoiding inhalation.
Adding a top layer of diatomaceous earth (DE) in your pots will keep the gnats away. The entire soil has to be covered generously. The gnats that do attempt to go through the layer of DE will get killed (mostly).
If you opt for this method, keep in mind that the diatomaceous earth is only effective when it’s dry and not clumped together. If it gets wet, it loses its effectiveness. You should either bottom water your plants when you use this method or top up the diatomaceous earth layer after you water from the top.
Pros: if used correctly it is very effective in eliminating fungus gnats, even as a sole means of fighting them
Cons: can get messy, potentially dangerous if inhaled
8. Sand
Will a layer of sand kill fungus gnats? Adding a thick top layer of clean sand (without organic matter) / decorative sand makes a dry barrier which is unappealing to fungus gnats. Not the most effective solution, but since fungus gnats lay their eggs in the first inch of soil – if that soil is replaced with sand they will avoid it.
Bottom water your plants if using this method, keeping the top inch of sand dry and fungus free.
Pros: cheap, can be visually appealing
Cons: messy, can mess up your watering routing
9. Cinnamon
Cinnamon isn’t used to get rid of fungus gnats in houseplants directly. What it does is kill of the fungus that the gnats, well their larvae, thrive on.
We find cinnamon to be handy for smaller plants (baby plants) where many other means of getting rid of fungus gnats are harder to apply.
Apply a generous (visible) layer of cinnamon on the soil.
Pros: you probably have it at home, gets rid of fungus on soil
Cons: cinnamon alone won’t stop your problem
10. Mosquito Dunks / Mosquito Granules
Please check the manufacturer instruction on pet and child safety. There are various similar products and not all of them are necessarily safe. Even if safe, we advise to keep them away from pets and children.
These are used to kill the egg and larval population (larvacide). While they are made to fight mosquito populations, they are really effective when it comes to fungus gnats as well. If you are using this method alone, you will need to keep on using it until all the adult population dies off. No larva should reach adult stage with this method.
These are usually used outdoors, in large water quantities (ponds, pools…) so you will need to dilute them accordingly. Pop them in water you will use for watering and let the water sit for a day or two before you use it.
Pros: deals with larval population
Cons: doesn’t deal with adult population
11. Repot Plants
If you are unwilling to do any of the methods that gets rid of the larvae and eggs you can opt for repotting your plants.
While this isn’t the most effective method, and you won’t remove all the larvae from soil / roots by repotting, it will decrease the population and can make it easier to manage.
Make sure you clean the pot too as you repot.
Pros: great if you planned on repotting anyway
Cons: not really effective, and you can’t repeat it often enough for it to have a long term effect
12. Nematodes
Beneficial nematodes combat various pests, fungus gnats larvae included. There are many different species of nematodes, so if you decide to go this route make sure you purchase those that are suitable for dealing with gnats.
Mix nematodes into a watering can and drench the soil. Although they don’t take long to deal with larval population (usually within a day or two), you will need to repeat the treatment.
Pros: natural way to combat fungus gnats
Cons: doesn’t deal with adult population
Don’t forget the drains!
When dealing with fungus gnats, don’t assume they are only hiding in your flower pots and soil. These troublemakers can make their home and even breeding ground in sinks and drains too. They like to keep close to windows too.
So keep any suspicious areas in mind as you get rid of fungus gnats in houseplants too and treat them accordingly.
How to get rid of fungus gnats in houseplants? Combinations we recommend
We always recommend using yellow sticky traps
No mater what method or combination of methods you choose we recommend using yellow sticky traps. They will help with dealing with the adult population of fungus gnats, but more importantly you will see your progress with them.
A ton of fungus gnats could get caught at the beginning of your battle, but you should see less and less as you near victory.
Good natural pesticide + hydrogen peroxide
When we say natural, we mean store bought natural. A pesticide that is safer to use – a pet safe and child safe one. These are usually less harsh and won’t harm the plants. Used in combination with hydrogen peroxide you should be managing both larval and adult population of fungus gnats and getting rid of them.
Bottom watering, sand or DE, neem oil
While bottom watering and DE will be enough to get the issue under control, we do recommend adding neem oil (or pesticide) if you will be using sand.
Mosquito dunks, sticky traps
Prevent larvae to develop into adults and catch adults on sticky traps.
Just might want to explain what bottom watering is, and how to do it, cause I haven’t the foggiest idea how to do that, lol!
Yes, 🙂 bottom watering just means getting the water to the plant from the bottom as opposed to watering the plant/soil from the top. Bottom watering would be either pouring water in the saucer or placing the flower pot in water, so that the water enters the pot from the bottom.