There are natural insecticides, including pyrethrin and azadirachtin, that effectively treat fungus gnats at various life stages. Other natural ways to get rid of fungus gnats involve setting out sticky traps or a homemade gnat trap using one part apple cider vinegar, one part water, and a few drops of dish soap.
Homemade gnat killer spray: A mixture of half a cup of water, half a cup of isopropyl alcohol, and a teaspoon of dish liquid can be filled in a spray bottle. This mixture can be sprayed on the gnats directly to kill them.
Treating a fungus gnat infestation
Add one tablespoon of washing up liquid or liquid Castille soap per one liter of water. Using a spray bottle, shake well and soak the top layer of soil, trying to not splash the leaves. Repeat every few days until larvae have gone, but be careful not to overwater the plant.
Fungus gnats are persistent and will not go away on their own. These pests lay their eggs and multiply quickly, so infestations will continue to grow. The only way to get rid of fungus gnats is to follow a rigorous cleaning program until the infestation has cleared.
Additionally, hydrogen peroxide acts as an insecticide, killing the fungus gnats on contact. 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.
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.
Steinernema feltiae is more effective against fungus gnats than other commercially available nematode species. Mix Bti or nematodes with water, and apply as a soil drench, or spray onto media using a hand-pump spray bottle or other spray equipment, following label directions.
Attracted to damp soil, fungus gnats usually get into homes by flying inside or from infested houseplants brought inside the house. Fungus gnats infest soil and feed upon decaying or damaged plant roots as well as fungi found in the soil.
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.
Mixing half a cup of isopropyl alcohol with a teaspoon of dish soap in a spray bottle, and spritzing it directly on to the gnats will quickly kill the gnats.
Any household aerosol containing pyrethrins (e.g. Raid) should control the adults. Allowing potting soil to dry out a bit between waterings will usually reduce or possibly eliminate fungus gnat problems coming from houseplants.
Combine equal parts vinegar and soap and then add a few tablespoons of sugar – once you mix it all together you can place the bowl wherever the gnats have been gathering. They will be attracted to the sugar and vinegar and drown in the mixture.
Dryer sheets can also be used to protect houseplants from annoying pests. Since they have been proven to repel fungus gnats, placing several dryer sheets near your houseplants could protect them from these root-eating pests.
“These pests are attracted to moisture, so you may see swarms in areas with damp soils, standing water, or even houseplants that have been overwatered,” Ludwiczak adds. “The breeding habits of gnats are most active during warmer months, which is why they seem to be especially prevalent during summer.”
Fungus gnats and mold mites are two other pests closely associated with mold. Cockroaches, camel crickets , slugs, and millipedes are attracted to mold, too, though not because they feed on it. They're attracted to the organic matter that mold helps break down and decompose.
Fungus gnat adults only live for about a week, but during that time, a single female can lay 100-300 eggs. Gnats prefer to lay their eggs in damp soil filled with decaying organic matter, which is why they love hanging out in greenhouses and around houseplants.
Gnats are black with black eyes. Compared to their small bodies, a black gnat's wings are disproportionately large. Fungus gnats also have large, gangly legs, that resemble those of mosquitoes, giving them the ability to jump and fly quickly.
Garlic cloves contain the sulphurous substance allicin, which can kill fungus gnat larvae. Either cut off the tip of a garlic bulb and stick it into the potting soil, or peel and dice some cloves and spread them over the soil.
Dish soap does not directly kill gnats on its own. Liquids like vinegar need surfactants like dish soap to break their surface tension and drown insects. Due to the fruity scent of this gnat solution, it lures the gnats and causes them to get stuck and die in the solution because of the dish soap.
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. Reapply the hydrogen peroxide solution once a week until you see that the fungus gnats are gone.
It can also be used to get rid of fungus gnats. To make a vinegar trap, add a pool of white vinegar into a transparent dish and cover with a tight layer of Saran Wrap, says Tom Dobrinska, pest control expert and entomologist. You can also add a small spoonful of sugar to make it more appealing.