mosquito bits for potted plants

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Mosquito Bits

BTI Against Fungus Gnats

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Fungus gnats are certainly annoying, especially because they are only houseplant pest that comes after you. Yes, the tiny black flies, looking much like fruit flies or midges, tend to flit around your face, drawn to the CO2 in your breath. No, they don’t bite, but who wants to be swatting bitsy flies in their living room? And if you have guests over: oh dear, whatever will they think?

Fungus gnats often come into our homes in peat-based potting soils, on new houseplants, in firewood or in various other objects brought uncleaned from outdoors. They’re very common and almost any gardener who grows plants from seed indoors or houseplants will likely run into them eventually.

Their tiny dark-headed larvae, looking like little translucent worms, live in moist potting soil, right up near the top. They aren’t terribly harmful: they mostly consume decaying plant matter they find in the soil mix as well as small fungi and algae, although they do sometimes nibble on a few root tips. The larvae are the ones to go after, since you know where they live. The adults, scattered here and there all over your house, can really only be quashed (read “squashed”) individually.

Making Them Disappear

There are various treatments you can use to control fungus gnat (more on those here), but one that is particularly successful is to infect them the same disease that kills them in the wild. Yes, use Mother Nature against them!

This natural biological larvicide is called Bacillus thuringensis israelensis (BTI for short), a variant of the ubiquitous soil microorganism BT (Bacillus thuringensis), naturally found all over the world, BTI has long been commercialized as a control for mosquito larvae, but has always worked just as well on fungus gnat larvae as well.

Of course, the disease in question is not deadly to humans (or pets and not even most other insects, like bees and butterflies), but specifically to the larvae of fly species. In fact, commercially they’ve been sold up until recently specifically to control mosquitoes and black flies, with fungus gnats only recently being added officially to the list.

Traditionally, gardeners ground up Mosquito Dunks® for use treating fungus gnats. Photo:

Of course, home gardeners have been grinding up Mosquito Dunks® and using them as a fungus gnat control for years, but that was technically illegal. (When you use a pesticide for a purpose other than that for which it is intended, you’re breaking the law.) But there is now a product that is legally approved for treating fungus gnats: Mosquito Bits®. Yes, the same as good old Mosquito Dunks®, but in the form of granules rather than mini-donuts.

Mosquito Bit® are now officially approved for treating fungus gnats. Photo:

Just sprinkle the little granules on the surface soil, 1 to 2 teaspoons per 15 cm (6 inch) pot and water them in. Or mix them into the potting soil as you pot plants up. Or soak 2 tablespoons in 1 liter (2 quarts) of water for 5 minutes, then water the solution in.

The larvae ingest the bacteria and quickly stop feeding, then die, decomposing in the soil and enriching it in minerals. Repeat the treatment every 3 weeks if needed.

You can find Mosquito Bits® in many hardware stores in the US. Elsewhere, you can buy them online. Or go back to grinding up the much-more-readily-available Mosquito Dunks®. I promise I won’t tell the cops!

Posts about Mosquito Bits written by Laidback Gardener

Kill fungus gnats naturally with BTI

Fungus gnats live in moist potting soil, where they lay their eggs. But all-natural BTI will kill fungus gnats naturally in their larval state–before they can become pesky, flying adults.

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 waterings. That helps control fungus gnats. But sometimes more aggressive measures are needed to kill these 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.

Mosquito Bits contains BTI to kill fungus gnat and mosquito larvae.

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. Mosquito Bits ® can also be mixed with potting soil prior to planting. When the plants are watered, the BTI in the Mosquito Bits ® will be released. After subsequent watering, the BTI is washed below the soil surface. Fungus gnat larvae feed on the BTI and die. Buy Mosquito Bits here .

Because can be an ongoing problem, keep a container of Mosquito Bits on your Cypress Potting Table so you will remember to mix the Bits into the potting soil whenever you re-pot a plant. When the job of potting your indoor plants is done, take a break in your comfortable Victoria Rocking Chair .

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 .

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.

Mosquito Dunks use chemical-free BTI to kill mosquitoes. Just float a Mosquito Dunk in standing water to kill mosquito larvae.

The best-selling BTI product in the world is called Mosquito Dunks. The handy donut-shaped Dunks can be placed 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 .

Kill fungus gnats naturally in potted plants. Use a natural bacterium called BTI to kill fungus gnats naturally without using harsh chemicals.