Fast-draining soils with inorganic additives, like perlite,
Miracle-Gro Indoor Potting Soil
This unique mix is made with the right ingredients making it suitable for different container plants, and it is also made to be gnat proof.
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.
Miracle Grow does have fungus gnats. Especially the nature's cure brand. I've used the Black gold organic potting soil a few times, indoor and outdoor, and have never seen a fungus gnat anywhere. Plus it's more like real dirt rather then the soft and unpredictable coco coir base.
Step 1:Make the sand trap Collect all infected houseplants, and remove the top 2 inches of potting mix to dispose of the larvae already laid. Discard the soil immediately, and replace this top layer with sand, which is free of organic matter and dries out quickly—an unappealing medium for fungus-gnat eggs.
Fungus gnats often remain near potted plants and run across (or rest on) growing media, foliage, compost, and wet mulch piles. Females lay tiny eggs in moist organic debris or potting soil.
How to Prevent Fungus Gnats. Neither fungus gnats nor their larvae can survive in dry soil, so let your soil dry out completely between watering as often as possible.
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.
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.
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.
Wet Soil. If you find yourself watering your potted plant frequently and the soil is always wet, that might be the reason you now have fungus gnats flying around. Keeping the soil moist at all times creates the perfect environment for these bugs to survive and reproduce — something we definitely don't want to happen!
Because gnats lay their eggs in the moist soil around houseplants, reducing excess moisture is critical to eliminating them. Avoid overwatering your houseplants, and make sure they have good drainage.
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.
'One method is to sprinkle a small amount of cinnamon directly onto the soil around the base of your plants,' says Diana. This is probably the most simple way to apply the spice, but you'll need to make sure you avoid contaminating the base of particular plants that can be damaged by cinnamon (more on this later).
Alongside its strong aroma, expert Jonny Livingston from Gardeners Dream adds that this spice works as a fungicide to destroy the fungus that larvae feed on in the soil. The trick is simple. You sprinkle cinnamon across the top layer of soil in the plant pot and simply wait for its benefits.
“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.”
Spread a half an inch of coarse horticultural sand on top of the potting mix. When you water, the sand will drain and dry quickly. It is not an attractive place for the adult gnats to lay eggs, and even if they do, the sand makes it difficult for any larvae that hatches to burrow.
If you see fungus gnats in a brand new bag of potting soil, you should not use that soil. If you must, then solar treat it. When the gnats are gone, make a soil cover to prevent gnats from laying eggs.
Food Grade Diatomaceous Earth
Apply a layer of DE to the top of the soil, or mix it into soil mix if you are repotting a plant. Did It Work? DE was very effective in killing off both larvae and gnats, with good results within a week. After around three weeks, the population was all but gone.
Will fungus gnats go away on their own? 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.
But for the curious, here's how you do it: Add soil to a baking pan (3 to 4 inches deep), cover with foil, and bake at 200 degrees F for 30 minutes or when the soil temperature reaches 180 degrees. Anything higher than that can produce toxins. Let cool. Keep covered to remain sterile.