Andre CampbellLarge populations of fungus gnat larvae can damage seedlings, young plants, and weakened houseplants by feeding on their roots. Fungus gnats are small, gray to black flies that primarily affect indoor houseplants.
Adult gnats do not damage plants; however, they can be annoying, as they tend to fly around potted houseplants during watering.
These pests are destructive at the larval stage [1].
How to Get Rid of Fungus Gnats Naturally
Below are some of the most common home remedies and natural control methods for controlling these pests.
1. Sticky Traps
Fungus gnats deposit their eggs in the soil. Sticky traps help reduce adult populations and can catch many females before they lay eggs.
These mosquito-like insects are attracted to yellow, so they will easily get caught in yellow sticky traps. You can also hang the traps near plants in nurseries or indoors to trap new adult gnats flying in.
2. Diatomaceous Earth
This product is excellent for getting rid of fungus gnats in the house. Food-grade diatomaceous earth works best when dry, so reapply after watering.
Diatomaceous earth damages insects’ outer cuticle, causing them to dehydrate. Therefore, mix it into the potting soil or sprinkle it evenly over the top layer of the soil of your potted plants.
3. Vinegar
You can use vinegar to help control fruit flies and adult gnats.
Pour some apple cider or white vinegar into a shallow bowl and add a little liquid dish soap. Next, place the bowl near the affected plant.
The pests love the smell of vinegar and will enter the bowl for it. But thanks to the dish soap, they’ll fall in and drown.
This vinegar treatment is an excellent home remedy for fungus gnats in houseplants. Continue using it until the infestation is under control.
This method primarily targets flying adult gnats rather than soil larvae.
4. Bacillus thuringiensis israelensis (Bti)
Bti is a bacterium that naturally occurs in soil [2]. Once ingested by larvae, Bti produces proteins that are lethal to certain pests, such as gnats and mosquitoes.
Follow the product instructions and water the soil with the solution to kill fungus gnat larvae. You can also use it to get rid of mosquito larvae.
5. Beneficial Nematodes
You can also purchase beneficial nematodes and apply them. They will hunt down and parasitize fungus gnat larvae in the soil.
6. Raw Potato
You can also use sliced potatoes to control fungus gnats by removing their larvae.
Slice raw potatoes into chunks and place them on the soil surface. Fungus gnat larvae may gather under the potato pieces, making them easier to remove.
After a few days, dispose of the infested potato chunks. Repeat the process with fresh potato chunks.
7. Hydrogen Peroxide
Hydrogen peroxide is valuable because it can kill fungus gnat larvae on contact. It is mainly effective against soil-dwelling larvae and may also help reduce eggs in the soil.
Mix one part hydrogen peroxide (3%) with four parts water. Let the soil dry a little, then use the solution to water your plants. This diluted solution is usually safe for most plants when used occasionally.
8. Cinnamon
Cinnamon is a unique home remedy for plant gnats. It may help reduce fungal growth in the soil, making the environment less attractive to these pests.
To use cinnamon for fungus gnats, spread a thick layer of the powder over the soil surface. Repeat every few weeks.
9. Sand
Fungus gnats like damp soil to lay their eggs. However, a layer of sand on the soil surface helps it dry out faster.
It will discourage soil gnats from laying their eggs there.
10. Soapy Water
Soapy water may help kill adult gnats on contact and can reduce some larvae near the soil surface.
Therefore, combine one tablespoon of liquid soap with a quart of water to make a homemade spray for fungus gnats.
Spray this soapy water solution on the plants and soil.
11. Keep the Soil Dry
One way to fight these pests is to make their environment inhospitable. This way, they won’t have what they need to survive.
So, keep the top level of the soil dry. Doing so will deter the adult gnats from laying their eggs there.
Preventing the soil from becoming overly moist is always helpful in controlling these pests.
12. Molt-X
This commercial product is a botanical pesticide that contains azadirachtin.
Molt-X works by preventing insect molting and inhibiting feeding. It also acts as a pest repellent.
Apply this treatment as a foliar spray to kill fungus gnats, or use it as a soil drench.
13. Azera Gardening
This product is another organic insecticide containing azadirachtin from neem seeds.
It also includes pyrethrins derived from some chrysanthemum flowers. These two ingredients are potent, plant-based pesticides that help control fungus gnats and other soft-bodied pests.
Apply Azera Gardening to your plants according to the product’s application instructions.
14. Bug Buster-O
Monterey Bug Buster-O is an organic insecticide that quickly kills fungus gnats and other pests. Dilute according to the product instructions and spray at the first sign of plant gnats.
Aim the spray at the flying adult gnats. Spray around plants and seedlings to kill others and destroy larvae.
However, be careful not to spray near bees outside because it is toxic.
15. Bottom Watering
Bottom watering can help reduce fungus gnat infestations by keeping the top layer of soil drier. Since adult fungus gnats prefer moist soil for laying eggs, this method makes the environment less favorable for them.
To bottom water, place the plant pot in a shallow tray of water for about 15 to 30 minutes. Doing so allows the soil to absorb moisture through the drainage holes.
Remove the pot afterward and let the excess water drain away. Regularly using this watering method can help discourage fungus gnats.
16. Organocide
Organocide is a 3-in-1 spray that is effective against many soft-bodied insects.
Be sure to also treat the soil surface, where fungus gnat larvae develop. It is suitable for both indoor and outdoor use.
17. Neem Oil
Neem oil is a powerful organic solution for controlling many garden pests.
To use neem oil to control fungus gnats, combine 1 teaspoon of organic liquid soap with 1 tablespoon of neem oil and 1 liter of warm water. Shake well.
Finally, soak the soil and spray your plants with the solution. Repeat as necessary.
Fungus Gnat Prevention Tips:
- Avoid overwatering.
- Use well-draining soil.
- Remove dead plant material.
- Quarantine new plants.
- Ensure pots have drainage holes.
Takeaway
Fungus gnats, known as sciarid or mushroom flies, attack plants such as geraniums, African violets, poinsettias, and carnations. However, many other indoor and greenhouse plants can also be affected.
Allowing the top layer of soil to dry between waterings is one of the most effective ways to prevent fungus gnats. Adding one or more natural remedies above will help eliminate the problem.
Sasha Campbell
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