Mix 1 part 9% hydrogen peroxide with 6 parts water. Allow top layer of soil to completely dry out before drenching the soil in the peroxide solution. Did It Work? The peroxide drench was very effective in killing larvae, although it never completely killed off the gnat population within the 3 weeks I used it.
To get rid of fungus gnats, mix a solution of one part hydrogen peroxide with four parts water. Pour the mixture onto the soil around the infested plant.
Mix one part 3% hydrogen peroxide with four parts water. Allow the top layer of your soil to dry, and then water your plants with this solution as you normally would. The soil will fizz for a few minutes after application; this is normal. Contact with hydrogen peroxide will kill fungus gnat larvae on contact.
Water your plant with a mixture of one part hydrogen peroxide and four parts water. The solution will kill the larvae, but is harmless to your plant.
Like our cuts and burns, the soil will begin to fizz and bubble, signaling its decomposition into water and oxygen. Hydrogen peroxide will kill all adult gnats and larvae it touches. It is safe to use this solution once a day for as long as it takes to eradicate the gnats and larvae infesting your house plants.
If you use a higher concentration of hydrogen peroxide on the foliage of the plant you run the risk of burning it. You could burn the roots, but since it's necessary to kill the root rot-causing bacteria, it's a risk worth taking.
The hydrogen peroxide and water mixture will foam and fizz a little when it comes into contact with the growing medium, but that is normal. It will kill fungus gnat larvae on contact. After a few minutes, the fizzing will stop, and the hydrogen peroxide breaks down into harmless oxygen and water molecules.
To make a hydrogen peroxide solution, first be sure you're using the typical 3% household hydrogen peroxide, not the industrial-strength stuff! Dilute it down slightly and mix 1 part 3% hydrogen peroxide to 4 parts water (e.g. 1 cup peroxide and 4 cups water). Allow the soil to dry slightly before application.
Unlike hydrogen peroxide, neem oil solutions kill both larvae and fungus gnats and thereby speed up the process of eliminating the pests for good. To create a neem oil spray, simply mix a teaspoon of dish detergent with a gallon of water and two tablespoons of neem oil.
For planted seedlings: Spray with H2O2 solution of 1 part H2O2 3% to 32 parts water (eg: around 30mls per 1 litre - measuring cup recommended). For established plants: Mix 1:1 ratio of 3% H2O2 and water (eg: 1 cup of each). Bottom or top water as usual (water soil only, do not pour on leaves).
Sprinkle cinnamon powder across the top layer of the soil of your houseplants. Cinnamon is a powerful natural fungicide, which kills off the gnats' primary food source, therefore making the soil inhospitable. You can also use a cinnamon stick, just pop it straight into the soil.
Mix one part of hydrogen peroxide and four parts of water. Use this solution to water your plants. Hydrogen peroxide will kill the gnat larvae and not injure your plant. Keep reapplying weekly until you notice the gnats are gone.
To use hydrogen peroxide on your plants, combine three parts water with one part 3% hydrogen peroxide. Not only will the disinfectant properties of the hydrogen peroxide kill any bugs and their larvae, but also add oxygen to the soil to promote healthy root growth.
Fungus gnat larvae usually are located in the top 2 to 3 inches of the soil, depending on moisture level, and primarily feed on plant roots, fungi, and decaying plant matter. Gnats are not strong fliers and emerge from soil when disturbed.
Make the natural habitat inhospitable. This means drying out the soil they live in because fungus gnat larvae need moist soil. If you let it dry out completely before your next watering, it will get rid of the gnats in the soil and discourage new adults from laying their eggs.
Mosquito bits are little pellets that contain a bacteria that's toxic to fungus gnat and mosquito larvae. You scatter them on top of your soil or let them sit in your full watering can for a few hours or overnight to marinate.
Fungus gnat eggs cannot survive in dry soil for more than 1 or 2 days but thrips can hibernate in the soil as eggs for an entire winter season and the adults can live up to 45 days. If the soil was infested I recommend either discarding the soil outside or sterilizing the soil before using it again.
So, the answer to the question, “Does hydrogen peroxide hurt plants?” is a resolute no, provided the strength is sufficiently diluted. You can purchase hydrogen peroxide in various potencies. The most commonly available is a 3% solution, but they go up to 35%.
Hydrogen peroxide can help to control fungal growth and fungal infection, such as root rot, by preventing the growth of fungi. It can also help kill fungus and bacteria on plant roots.
Spray your plants' foliage once per week if you're using hydrogen peroxide as a preventive. If your garden already has bugs, you may need to use hydrogen peroxide two or three times per week to get rid of them. You should also apply the spray after it rains, as the showers will wash off any spray you have applied.
Make an apple cider vinegar trap
Stir in a few drops of liquid dish soap and place the trap near the base of the affected plant or on top of the soil. You will need to refresh these traps every few days as they attract and kill the adult fungus gnats.