How to Get Rid of Fungus Gnats in the House

You’ve bought your plants, set them up in a nice cosy area and everything is going well. Then, one day you’re enjoying a meal or watching your favourite show and you’re interrupted by a tiny insect fluttering near your face. You swat it away, only for another one to appear a short time later. You look more closely around your house and notice there are more of these little flies hanging around your plants.  

I’ve been driven crazy by these pests too but don’t fear, I’ve got some solutions to get rid of them quickly and effectively. 

This is a comprehensive guide for easy and effective ways to get rid of fungus gnats and prevent future infestations in your house. Drawing from my own experience with these annoying pests, this guide has the methods I used to successfully get rid of them. 

What are Fungus Gnats?

Fungus gnats are small, short-lived insects that look like mosquitoes. They thrive in warm conditions but can also survive in colder environments. Unlike mosquitoes, they are not good fliers and tend to crawl around on the soil surface. Their larvae feed on the fungus present in the soil.

While harmless to people, pets and healthy plants, fungus gnats can pose a threat to seedlings, and their buzzing around can be incredibly annoying.

You can usually spot the adults flying around your plants or crawling on the soil.

Controlling a Fungus Gnat Infestation: Effective Strategies

In order to get successfully manage fungus gnats we first need to understand their life cycle. Once we understand each stage of the cycle we can use different strategies that target that stage.

The Lifecycle of Fungus Gnats

1. The eggs are laid in moist soil and will hatch after 5-6 days.
2. They then become larva which eat the fungus and other decomposing matter. After 10-14 days they will become Pupa.
3. The pupa take 5-6 to days until they finally hatch into adults.
4. The adults will live for around 10 days. During this time they can potentially lay hundreds of eggs in the soil and complete the cycle.

Now that we know about Fungus Gnats and their lifecycle, it’s time to take action. In my experience, there’s no one-size-fits-all solution; eradicating an infestation might lead to another if good practices aren’t followed. You’ll find the most success by using a holistic approach to manage them. With that in mind, let’s explore the following strategies that I’ve found effective.

Proper Watering Practices

You will tend to find certain plants are infested while others have little or no presence. There in lies one of the clues to controlling them. Their presence usually indicates an issue with overwatering house plants. As we now know, they like moist soil to lay their eggs, making a damp pot the perfect breeding ground.

Using well-draining potting mix is crucial to prevent the conditions fungus gnats thrive in. If you’re unsure about the quality of your potting mix, or if you’re interested in creating your own, check out our guide on How to Make the Best Potting Soil for Indoor Plants.

With all that in mind, keeping the top layer of soil dry can help prevent infestations, this means watering your plants less often. You may also consider bottom watering rather than watering from the top.

If you’re dealing with a plant suffering from fungus gnats, allowing the soil to dry out as much as the plant can tolerate will help reduce their numbers by destroying eggs and larvae.

Isolate the Infected Plant

If you notice fungus gnats early enough consider moving the affected plant outside to prevent the spread of the infestation to other plants. This will also expose the gnats to potential predators who might deal with the problem for you.

On a related note, it is good practice when buying a plant to inspect it for pests before bringing it home. Once it’s home you could isolate it for observation also but I know you are eager to get it in the perfect spot and I don’t blame you!

Using Sticky Traps for Fungus Gnat Control

The adults naturally feed on the nectar of plants, making them attracted to yellow sticky traps. This method helps reduce the number of eggs being laid and is an effective step in breaking the cycle.

However, even if you manage to eliminate all the adults (which is unlikely), there may still be eggs and larvae present in the soil.

Sticky traps are also very useful for monitoring your plants. They will allow you to detect fungus gnats and treat the problem before their numbers increase and they infest your other plants.

I recommend buying them online in bulk and using both for monitoring and whenever you need to place more in strategic areas to catch adults.

It’s also possible to make your own sticky traps solutions, mix something sweet like apple cyder vinegar with dish soap in a bowl or container. The gnats are attracted to the sweet smell and will become stuck when they touch the soap.

Soil Drench Solutions

To directly target the eggs and larvae, you can use a soil drench with some sort of insecticide. This involves mixing the insecticide with water and watering your plants with it, giving the soil a good soaking.

A cost-effective option would be hydrogen peroxide. You can use a ratio of 2 parts water to 1 part hydrogen peroxide. Be careful not to get the mix on the plant’s foliage as this can damage them. You will see and hear the mix sizzling away.

Mosquito bits or dunks are another excellent option. Follow the instructions as directed on the packaging, but generally, it’s the same concept: mix some bits with water and apply to the soil.

If you are looking for a more organic approach, I find neem oil to be an effective natural insecticide. A good ratio I’ve found is 10ml of oil per 1 litre of water. It can be quite smelly so make sure you open some windows.

Whichever method you use to soak the soil, it’s unlikely you will kill all the eggs and larvae in one shot. Therefore, repeat the application once a week for 3-4 weeks to ensure you break the cycle and eliminate all the eggs and larvae.

Placing Physical Barriers

Adult fungus gnats lay their eggs in the top layer of the soil. Replacing this top layer of soil with grainy textures like sand or small gravel will work as a protective barrier preventing adults from laying their eggs and larvae from breaking out.

It can also look pretty nice as an added bonus. But It can make watering more difficult depending on how you do it as the sand or gravel might get mixed with the soil. It also can make monitoring moisture levels more difficult as you can’t judge it easily from looking at it and it makes poking your finger in the soil potentially harder.

Ideally you would use this method on every plant because any that are not protected are left open to a potential infestation.

Change the Potting Soil

If all other methods have been tried without success, you may need to replace the soil completely. Here’s how to do it effectively:

1. Remove the Plant: Gently take the plant out of its pot. Clean the dirt off the roots to remove any remaining larvae or eggs. For detailed guidance on repotting a plant without damaging it, I’ve got an article on how to repot a plant successfully.
2. Clean the Pot: Rinse the pot thoroughly to eliminate any stragglers hiding away.
3. Dispose of the Contaminated Soil: Leave the soil out in the sun to dry out. The heat and lack of moisture will kill off any remaining larvae. Once dried, the soil can be safely added to compost, used in a raised garden bed, or as organic material when repotting other plants.
4. Prepare New Potting Soil: Use a fresh, high-quality potting mix. Consider adding perlite or other light materials to improve drainage. This helps prevent waterlogged soil, which is conducive to fungus gnat infestations.
5. Soil Drench Treatment: Before planting, treat the new soil with a soil drench using hydrogen peroxide, neem oil, or mosquito bits to ensure any eggs or larvae present in the new mix are killed off.

Replacing the potting soil not only helps to eliminate the current infestation but also provides an opportunity to enhance the potting mix for better drainage and healthier plant growth.

Can I Use Fly Spray for Fungus Gnats?

Using fly spray to control fungus gnats is not an effective long-term solution. While fly spray will kill the adult gnats, it won’t affect the larvae in the soil, so the problem won’t be solved.

Additionally, the chemicals in fly spray can accumulate in the soil, potentially harming your plants and creating an unhealthy environment for you. Therefore, I don’t recommend using fly spray as a control method for fungus gnats.

Conclusion

In conclusion, effectively managing fungus gnat infestations in your houseplants requires a combination of strategies. By implementing proper watering practices, isolating infected plants, using soil drench treatments, employing sticky traps, using grainy soil barriers, and considering potting soil changes when necessary, you can successfully control and prevent fungus gnat infestations in your home.

Remember to be consistent in your efforts, as breaking the gnat’s lifecycle may take time and persistence. With these strategies, you can enjoy healthy, thriving plants without the nuisance of fungus gnats buzzing around.

If you have any tips or tricks of your own for dealing with fungus gnats let us know in the comments!