Looking for a way to kill fungus gnats naturally? Sooner or later you will have to deal with fungus gnats infesting your houseplants. Fungus gnats are the tiny flying pests that can swarm like an annoying black cloud whenever an infested houseplant or outdoor potted plant is moved.
Fungus gnats (Bradysia species) are small, mosquito-like insects that commonly infest the soil or growing medium of potted plants. When outdoor plants are brought indoors for the colder months, fungus gnats in the potting mix are brought indoors. That’s when they can quickly infest the soil of other houseplants.
Fungus gnats thrive in moist potting soil, where they lay their eggs. After the eggs hatch, fungus gnat larvae live in the top two to three inches of the potting soil. Fungus gnat larvae can cause plant damage by eating plant roots. After about two or three weeks, the fungus gnat larvae pupate in the potting soil. Then they become the tiny black adult gnats that fly erratically when a potted plant is moved.
Let the potting soil dry out between plant waterings. This will help control fungus gnats. But sometimes more aggressive measures are needed to kill these insect pests. Fortunately, there are now natural, non-chemical ways to naturally kill fungus gnats and control fungus gnat infestations.
Naturally Kill Fungus Gnat Larvae with BTI
To kill fungus gnats naturally, use BTI. Fungus gnats are closely related to mosquitoes, so fungus gnat larvae are effectively killed by BTI. (BTI is a naturally occurring bacterium that is deadly to mosquito larvae AND fungus gnat larvae.)
BTI, which is short for Bacillus thuringiensis israelensis, is deadly to mosquito larvae and fungus gnat larvae but harmless to other living things. The bacterium is nature’s way of keeping fungus gnat and mosquito populations down. But fortunately, BTI has no effect on other insects (such as bees and butterflies). Nor does it harm animals, fish, birds, plants, pets or people.
BTI is the active ingredient in top-selling Mosquito Bits®, which is approved for the control of fungus gnats. To kill fungus gnat larvae, simply shake the granular Mosquito Bits® onto the potting soil in houseplants. Also use it on other container-grown plants—including vegetables and herbs.
Soak Mosquito Bits in Water
Here’s another easy way to kill fungus gnats naturally with BTI. Make Mosquito Bits tea! Just mix 4 tablespoons of Mosquito Bits® in 1 gallon of water. Let the Bits soak for 30 minutes to remove the BTI, then skim off the floating granules. (You can also place the Bits in a nylon stocking prior to immersing them in water. That makes it easier to remove the granules, which can be composted or discarded.)
Now stir or shake the water to make sure the BTI is thoroughly mixed in. Then use the “BTI tea” to water the soil or potting mix of houseplants and container plants. This treatment controls fungus gnat larvae present in the soil at the time of application. For best results, use your Mosquito Bits/BTI tea solution within 48 hours.
Repeat this process weekly for three weeks. If fungus gnats reappear at a later time, simply repeat this treatment again. Buy Mosquito Bits here.
Because fungus gnats can be an ongoing problem, keep a container of Mosquito Bits on your Potting Table with your other gardening supplies.
Kill Adult Fungus Gnats with Horticultural Oil
There is also an environmentally friendly, organic way to kill fungus gnats after they become adults. Summit® Year-Round® Spray Oil is a lightweight horticultural oil that controls a wide variety of insect pests including fungus gnats. Summit® Year-Round® Spray Oil is OMRI Listed® by the Organic Materials Review Institute and approved for use in certified organic production, and it’s perfect for indoor use.
Unlike many other pesticides that kill insects with toxic chemicals, Summit® Year-Round® Spray Oil literally smothers insects to death. The oil spray blocks an insect’s breathing holes (called spiracles), causing insects to die from asphyxiation.
Summit Year Round Spray Oil can be used any time during the year to kill fungus gnats because it won’t harm tender plant buds, shoots or leaves. This lightweight oil has no odor, and it will effectively control pests on even sensitive plants such as tropical houseplants, roses, impatiens, citrus trees, and ferns. Summit® Year-Round® Spray Oil naturally kills fungus gnats. It also kills a wide variety of insect pests including aphids, whiteflies, spider mites, mealybugs, scale, thrips, lace bugs and more. Unlike chemical pesticides which can become less effective after repeated use, there is no known build-up of insect resistance to horticultural oil sprays.
Mosquito Bits® and Summit® Year-Round® Spray Oil are available at home centers, hardware stores, garden centers and at www.SummitResponsibleSolutions.com.
Can BTI Be Used to Control Mosquitoes?
The short answer is Yes! In fact, BTI has been used to kill mosquitoes for more than 30 years. Bacillus thuringiensis israelensis (BTI) has been called “Mother Nature’s mosquito control” because this bacterium kills mosquito larvae and virtually nothing else. BTI also kills fungus gnats, because fungus gnats are genetically very closely related to mosquitoes.
The best-selling BTI product in the world is called Mosquito Dunks. Just place the handy donut-shaped Dunks in birdbaths, rainbarrels, ponds and anywhere that water collects. The BTI in the Mosquito Dunks will kill mosquito larvae for 30 days or longer. For more information, read Use BTI to Kill Mosquitoes. To check the price and availability of Mosquito Dunks, click here.
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