The most common cause of fungus gnats in plants is overwatering, so be sure to let your soil dry out in between waterings as often as possible.
Get rid of gnats in houseplants with vinegar
You can simply fill a small shallow bowl with vinegar and add a few drops of dish soap. Refresh every few days as it fills up with dead gnats.
Adult fungus gnats don't damage plants or bite people; their presence is primarily considered a nuisance. Larvae, however, when present in large numbers, can damage roots and stunt plant growth, particularly in seedlings and young plants.
Pests like fruit flies and gnats are comfortable in damp dirt; eggs and larvae can't survive without constant moist surroundings. Chances are, your plant can handle less water than you're giving it, so try testing the soil with your finger and only watering when it's completely dry at least 2 inches down.
One of the main reasons fungus gnats are attracted to houseplants is that lay their eggs in moist soil. Once the eggs have hatched they will dine out on roots, algae fungi's, and other organic material such as potting soil. While adult fungus gnats are fairly harmless, the larvae can cause damage to your houseplants.
Fungus gnats only lay their eggs in the top inch of soil.
Replacing that top inch with sand or gravel creates a dry environment and robs them of nutrient-rich fungus to munch on. Without their needed source of food available, they won't want to lay their eggs.
Fortunately, it's possible to keep these pests at bay with some common kitchen ingredients like cinnamon sticks, which can be placed in the soil of houseplants or even sprinkled on top of the soil in indoor plant containers if gnats are already present.
It is perfectly safe for plants when properly diluted and used in moderation. Adding hydrogen peroxide to water promotes better growth in plants and boosts roots ability to absorb nutrients from the soil. Diluted 3% peroxide adds needed aeration to the soil of plants and helps control fungus in the soil.
Diatomaceous Earth works best when there's a layer of sand on the top of your plant's soil. Additionally, it's a good idea to mix it right into your potting soil to prevent insects. There are many brands of Diatomaceous earth available, as it helps control many types of pests, in the garden and the home.
Mix four parts water with one part hydrogen peroxide and soak your soil with the solution. Neem oil can also be diluted with water and applied to the soil to kill larvae. You can also use neem oil as a spray to kill adult flies on contact.
“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.”
Repotting is an effective way of getting rid of the gnat larvae. Clean the pot thoroughly and place the plant in new, clean potting soil. The rotting roots, plant remains and damp soil that fungus gnats love so much will be completely gone.
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.
Vinegar itself does not get rid of gnats, but it is a good luring tactic to attract gnats into a trap. Vinegar smells sweet, so gnats will fly into a trap to get a drink. Using another substance like liquid dish soap helps to trap the gnats, that way they end up dying in the vinegar mixture.
Or, you can switch up your favorite scent with something they don't like. Try Lighting citronella candles, using lemon or vanilla sprays. While gnats are a fan of sweet-smelling fruit, they can't seem to stand vanilla, lemon, or even lavender. A little spritz can at least keep them at bay.
Reapply the hydrogen peroxide solution once a week until you see that the fungus gnats are gone. Place yellow sticky traps near the infested plant. These 3-by-5-inch (7.6-by-12.7-centimeter) adhesive-based traps attract and kill many, though not all.
I would only use it as often as is necessary, but wouldn't recommend using it more than twice a week. What is this? If I'm treating a plant for pests or root rot, I'll either spray the leaves or the soil with a hydrogen peroxide solution once a week until the issue has been resolved.
Step 1: Mix one part of hydrogen peroxide and four parts of water in a spray bottle. Step 2: Lightly spray the plant leaves and stems where the adult fungus gnats are visible. Step 3: Repeat as needed until the adults are no longer visible.
Making DIY gnat traps
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.
Mix with water and spray onto plant stems
'Another option is to mix cinnamon with water to create a spray that can then be applied directly to the leaves and stems of your plants,' Diana explains. This can help distribute the cinnamon more evenly and will be the best method if you want to target pests.
Try cinnamon to kill the larvae.
Cinnamon is a natural fungicide. It will kill the fungus that the larvae feed on, essentially starving them to death. Simply sprinkle cinnamon on the surface of the soil in your potted plants or garden beds.
Hydrogen Peroxide
A peroxide solution apparently kills larvae and eggs on contact, effectively killing off all infant gnats and disrupting the lifecycle. You should be able to buy hydrogen peroxide from any high street pharmacy or online. Mix 1 part 9% hydrogen peroxide with 6 parts water.