How To Get Rid Of Fungus Gnats In Soil In 11 Ways That Work

The soil beds of your houseplants and garden are breeding grounds of fungus gnats. 

These nuisance pests will lay their eggs on them. And their larvae can cause significant damages to the plants and seedlings. 

If you don’t eliminate fungus gnats on the soil beds, then the infestation spikes up, leading to further harm to your plants.

This guide will reveal how to get rid of fungus gnats in soil beds. 

You’ll find out both the natural home remedies and chemical options to end the fungus gnats problem on the soil.

Keep reading. 

What Are Fungus Gnats?

Fungus gnats are tiny black flies that look like fruit flies.

They infest damp soils, decaying organic matter in compost bins, recycle bins, and garbage cans where they lay their eggs.

Fungus gnats are tiny moisture bugs that are heavily reliant on moisture for their survival.

The molds and fungi that form on the damp soil and decaying organic matter are their food sources.

Adult fungus gnats grow between ⅛ and ⅙ inches in size. They’ve got Y-shaped wings, a pair of antennae, slender long legs, and they’ve got a zig zag flying pattern. 

When fungus gnats’ eggs hatch, little white legless worms, which are the fungus gnat larvae, emerge. They have a tiny black dot at the top which is their head. 

The larvae are harmful for both indoor and outdoor houseplants, especially for the seedlings.

The fungus gnat larvae will feed on the roots of the plants. Too many of them can cause the plants to wither and die. 

Fungus gnats in houseplants are also a common problem. They’ll lay their eggs on the soil beds of potted houseplants and in greenhouses. 

Fungus gnats in the house can lay eggs in the choked drains of sinks in the kitchen and bathroom. 

They will also target the appliances like dishwashers and coffeemakers to lay eggs. 

Adult fungus gnats are attracted to light from the light bulbs.

So, you may notice them flocking near the windows during the evening hours trying to make their way inside the house.

The entire fungus gnats life cycle is short. But it doesn’t take long for their numbers to spike up within a week or two. 

Fungus Gnats Life Cycle

Fungus gnats life cycle begins when the adult fungus gnats lay their eggs in the soil and in other areas like damp and decaying organic matter.

A single female fungus gnat can lay up to 300 eggs. The fungus gnat eggs are tiny, white, transparent, and they hatch within 4 to 6 days.

The fungus gnats larvae that hatch out of the eggs are tiny legless whitish worms with a tiny shiny black head that appears as a black dot. 

These larvae are harmful for the plants because they target the plant’s roots to feed. 

If there are too many of them, then they’ll certainly harm the plant’s roots, making the plant lose its vitality.

The fungus gnat larvae is also responsible for the death of seedlings.

The larvae take 10 days to turn into pupae. Pupae are the life stage when the larvae lock themselves in a cocoon. 

The larvae remain in the pupae stage for 4 days before they emerge out as adult fungus gnats with wings.

The adults are sexually mature and active from day one after emerging out from the pupae stage. 

And they’ll start to breed and lay more eggs on the soil. That causes the infestation to worsen. 

Too many fungus gnats in the indoor houseplants soon turn into a nuisance. 

And they start to show up in places like bedrooms and living rooms where there’s no decaying organic matter, food source, and potted plants.

So, getting rid of fungus gnats in the soil beds of both indoor and outdoor plants is vital to eliminate them and to stop them from coming back. 

Let’s find out how you can do it, without fail and without harming the plants.

11 Ways To Get Rid Of Fungus Gnats In Soil

Hydrogen Peroxide Spray For Fungus Gnats

Mix equal parts of 3% hydrogen peroxide and water in a spray bottle. Stir the mixture well. And spray it on the soil of indoor potted plants and in outdoor plants.

Hydrogen peroxide will kill any fungus gnats eggs and larvae that are active on the soil.

Hydrogen peroxide kills the fungus gnat larvae by producing radicals that contain hydroxyl. These radicals attack the membrane lipids and other cellular components in the larvae. 

Hydrogen peroxide is also helpful for plant’s growth if you spray it on the soil. 

It kills all the molds and fungi that form on the soil beds. These molds and fungi prevent the plants from extracting nutrients from the soil and oxygen from the air. 

You can also spray the hydrogen peroxide mixture on the plant’s leaves and stems to kill any active fungus gnats and other plant pests like spider mites. 

Don’t Water Your Plants For A Week

Overwatering the plants makes the soil beds wet. And that makes the soils of potted plants and garden plants attractive for fungus gnats. 

So, refrain from overwatering your indoor plants and outdoor plants. If the soil is damp, then it’ll be best to not water the plants for a week. 

Fungus gnats and their larvae depend heavily on moisture for their survival. And they can’t survive for long in the dry soil beds. 

Pour Gravel And Sand On The Top Of The Soil

Pour dry sand or gravel on the soil of the plant pots and soil beds of your garden. It’ll soak the excessive moisture in the soil beds.

As fungus gnat larvae and adult gnats are heavily dependent on the moist soil, they won’t be able to survive and get food if the soil bed covered with sand or gravel. 

Use Plant-Safe Insecticides 

There are many plant-safe insecticides that you can use to spray on the plants and the soil. 

These insecticides will kill both the adult fungus gnats and fungus gnat larvae on contact. 

However, if you want to use only natural ingredients to kill fungus gnats then you can use a mixture of white vinegar and water as spray. 

Take one part vinegar and one part water and mix it in a spray bottle. And spray the mixture in the soil. 

Prepare A DIY Fungus Gnat Trap Using Dish Soap And Apple Cider Vinegar

The DIY fungus gnat trap works wonders to entrap the adult fungus that are active inside the house. 

And preparing it is easy. 

All you’ve to do is take a plastic water bottle. Cut it in half. And put the nozzle side of the bottle in the bottom half. 

Pour a mixture of apple cider vinegar and dish soap inside the bottle. 

And keep it near your houseplants, on the garden soil beds, or even in places where you’ve noticed fungus gnats activity. 

The fruity smell of the apple cider vinegar attracts the fungus gnats. 

Decaying and ripe fruits and vegetables draw fungus gnats. That’s why you might notice them on fruits and vegetables in your kitchen or on the food wastes in the kitchen trash bins.

The fungus gnats sneak inside the bottle to access the fruity smelling mixture. But the viscous and sticky dish soap entraps them. 

Dispose of the bottle, with adult fungus gnats trapped in it. 

It’ll be best to keep the trap during the morning and keep it for 24 hours. 

Use Yellow Sticky Traps

Keep yellow sticky traps on the soil of your houseplants and on the soil beds in your garden and yard. 

Bright colors like yellow draw fungus gnats and flies like fruit flies.

When the fungus gnats land on the traps, they’ll get stuck. Dispose of the traps the next day. 

Use Beneficial Nematodes That Kill Fungus Gnats Larvae

Nematodes are roundworms that attack the fungus gnats larvae and kill them. These nematodes are safe for plants, humans, and pets. 

And they’re an integral part of biological control of pests that dwell in the soil. 

Steinernema Feltiae, also known as S. Feltiae, are non-segmented parasitic nematodes that enter into the fungus gnat larvae through their orifices like mouth and anus. 

Upon entering, they eat the larvae from the inside.

S. Feltiae has been used for fungus gnat larvae control for many years. And using it is pretty straightforward. 

Scatter the nematodes on the soil. And sprinkle some water on it. That’s it.

These nematodes need some moisture to get activated. When they’re active, they seek out the larvae of the pests on the soil.

However, nematodes are only meant for use on the soil. They’ll not work if you use them on hard surfaces like concrete and furniture. 

Check Potting Mix Or Potting Soil For Any Fungus Gnat Larvae

Many potting mix or soil that are available in the market can contain fungus gnat larvae and larvae of other insects. 

So, check them before buying. 

If you can’t check the packages soil mixes, then there are two things that you can do before you put them on the pots.

First, take the soil mix in a shallow container and scatter cinnamon on it. Or you can also spray neem oil on the soil mix.

If you’re using neem oil, then ensure that you drench at least 2 inches of the top of soil’s layer.

It’ll take care of any larvae in the soil. 

Second, You can also keep the potting mix in freezer, or even inside the oven to kill any larvae that are present in the mixture.

Scatter Diatomaceous Earth

Diatomaceous earth is also a potent fungus gnat larvae killer. It has sharp particles, which are known as diatoms that penetrate the bodies of the larvae and kill them by soaking the bodily fluids.

In other words, it dehydrates the larvae from the inside. 

Scatter diatomaceous earth on the top layer of the soil. And let it do it’s work. 

Diatomaceous earth is also plant-safe and it doesn’t cause harm to humans and pets. 

Keep Drenched Mosquito Dunks On Top Layer Of Soil

Soak one or two mosquito dunks in water and keep it on the soil of potted plants and garden plants. 

The mosquito dunks contain Bti, the beneficial bacteria Bacillus thuringiensis subsp. Israelensis, that they start to release on the soil. 

When fungus gnats and their larvae die when they come in contact with the bacteria.

Scatter Epsom Salt

Epsom salt is one of the most underrated fungus gnat larvae killers.

They contain magnesium sulphate that kills the larvae on contact. 

And they’re safe for plants too. 

Sprinkle Epsom salt on the soil. And let it rest on the soil bed overnight to do it’s work. 

Conclusion

Hydrogen peroxide, Diatomaceous earth,  Epsom salt, and mosquito dunks, and S. Feltiae nematodes kill fungus gnats larvae on the soil. 

All are safe for the plants and humans alike. 

However, there are other methods that you can use in tandem to prevent fungus gnats. 

Things like DIY apple cider vinegar traps and yellow sticky traps work significantly well to eliminate the adult fungus gnats. 

You can use the combination of these prevention methods laid out on the post to get rid of fungus gnats in the soil beds of your indoor plants. 

You can use them in your garden’s soil beds too.