An infestation of fungus gnats can cause plants to show signs of wilting, slow growth, and yellowing of the leaves.
Fungus gnats are small, dark flies that mostly affect indoor houseplants. The adults are non-biting and do not cause damage to plants; however, they can be annoying as they tend to fly up when watering houseplants.
These pests are destructive at the larval stage [1]. The larvae feed primarily on fungi and decaying plant material, as well as plant roots. Below is a picture of fungus gnat eggs in the soil and a larva.
How to Get Rid of Fungus Gnats Naturally
These are some of the most common home remedies and natural control methods for controlling these critters.
1. Sticky Traps (Yellow)
Fungus gnats infest the soil. Therefore, to catch the adults before they lay eggs, put the traps on the soil surface. This will mess up their life cycle.
These mosquito-like insects like yellow, so they get caught easily on yellow sticky traps. You can also hang the traps vertically close to plants in nurseries or indoors to catch new adult gnats flying in.
2. Diatomaceous Earth
This is a great natural pesticide for getting rid of fungus gnats in the house. Diatomaceous earth will cut through the larvae and adult pests, dehydrating and killing them.
Therefore, mix it in with potting soil or sprinkle it onto the top layer of the soil.
3. Vinegar
You can use vinegar to help control fruit flies as well as adult gnats.
Pour some vinegar into a shallow bowl and add a little liquid dish soap. Next, place the bowl near the affected plant.
The critters love the smell of vinegar. As a result, they’ll fall in and drown, thanks to the dish soap.
Continue this home remedy until the infestation is under control.
4. Bacillus thuringiensis israelensis (Bti)
This is a bacterium naturally occurring in the soil [2]. BTi produces a protein that is toxic to gnat worms, mosquitoes, and certain other pests once ingested.
Following the product instructions, 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
Purchase beneficial nematodes and work them into the soil, where they will hunt down and parasitize fungus gnat larvae in the soil.
They produce bacteria that destroy the larvae from the inside out. Purchase them online or at various organic farm store centers.
6. Potato Slices
A rather unpleasant but easy and inexpensive way of controlling fungus gnats is by removing the larvae.
Slice raw potatoes into one-inch pieces and place them on the soil surface to attract gnat larvae. After a few hours, you will find the larvae underneath the slices.
Look for whitish-to-clear worms with shiny black heads. Remove the top layer of soil, larvae, and potatoes. Repeat until free of the problem.
7. Hydrogen Peroxide
The value of this common household chemical is that it kills fungus gnat larvae on contact. Moreover, it can eliminate the pest at all stages of its life cycle—eggs and adults too.
To use hydrogen peroxide for fungus gnats, mix one part hydrogen peroxide (3%) with four parts water. Leave the soil to dry out a little, then use the solution to water your plants.
Also, lightly spray the leaves and stems of plants. This DIY gnat spray will not harm your plants.
8. Cinnamon
This fungus gnat home remedy is unique because it kills the fungus that the gnats rely on.
To use cinnamon for fungus gnats, spread a thick layer of the powder over the soil and repeat every few weeks.
9. Sand
Soil gnats like damp soil in order to lay their eggs. As a result, a layer of sand on the soil surface will dry it out quickly. This discourages them from laying eggs there.
10. Soapy Water
Make a homemade spray for fungus gnats by combining one tablespoon of liquid soap with a quart of water.
Spray this soapy water solution on plants and soil. Repeat once or twice to ensure all larvae in the soil are killed.
11. Keep the Soil Dry
One of the first lines of attack against these pests is to create an inhospitable environment so they lack what they need to thrive.
Therefore, keep the top level of the soil dry to deter adults from laying eggs. Preventing the soil from getting excess moisture is always helpful in controlling these indoor 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. You can also use it to drench the soil.
13. Azera
Azera is another organic insecticide containing Azadirachtin from neem seeds. It also contains pyrethrins derived from some chrysanthemum flowers.
These two ingredients act as powerful botanical pesticides that help control a wide variety of pests, including garden gnats. Apply as a spray solution as per the product directions onto the plant and on the soil.
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 to them.
15. Melissa Oil
This is also known as lemon balm oil. It is very attractive to these critters as well as other insect pests.
A few drops of Melissa oil added to sticky traps will invite a cloud of adult flies to your trap. Remove this homemade fungus gnat trap and set a new one frequently, adding some oil each time.
16. Organocide
Organocide is a 3-in-1 spray that is effective against many soft-bodied insects.
You can use it as a fungus gnat treatment to spray the leaves and stems of your plants. It is also great for indoor and outdoor use.
17. Neem Oil
Neem oil is a powerful organic solution used to control many garden pests.
To use neem oil for fungus gnats, combine one teaspoon of organic liquid soap with one tablespoon of neem oil. Add a liter of warm water. Shake well.
Finally, drench the soil and spray your plants with the solution. Repeat as necessary.
Takeaway
Plants particularly susceptible to attack by fungus gnats include geraniums, African violets, poinsettias, and carnations. However, many indoor or greenhouse plants are also vulnerable.
The most important action to take to keep these pests at bay is to keep the soil dry to slow down or stop an infestation. Additionally, adding one or more of the above natural remedies will help eliminate the problem.
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