How To Use Mosquito Dunks For Fungus Gnats

House fungus gnats are tiny bugs that can cause significant problems for indoor plants. Although harmless to humans, their larvae can feed on the plant roots of container plants, causing permanent damage.

While any house plant is potentially at risk, fungus gnats are particularly destructive to spider plants, African violets, geraniums, and peace lilies.

Use Mosquito dunks to control Fungus Gnats Pin

Mosquitoes in Africa and other parts of the world may carry malaria, west nile virus, or yellow fever. Mosquitoes do not carry the human immunodeficiency virus.

A pest control gadget called a mosquito dunk is one of many methods to remove fungus gnats from plants.

Mosquito Dunks are approved for organic production and organic gardening under National Organic Program guidelines.

This is a safe, nontoxic way, and quick way to control gnat infestations. But mosquito dunks for fungus gnats require a unique technique for the greatest effectiveness.

The active ingredient in Mosquito Dunks is very target-specific for mosquitoes and does not adversely affect other organisms in the water.

What Are Fungus Gnats?

You’ve likely seen fungus gnats before, as they’re a prevalent indoor pest.

They’re small, black flies drawn to lights and dampness. You’ll find them near windows, lamps, still or standing water, and houseplants.

Fungus gnats have four development stages:

  • Eggs
  • Larvae
  • Pupae
  • Adults

Adults lay about ten eggs at a time, which hatch after about five days. The species of mosquito larvae have shiny, black heads with white bodies.

Furthermore, the Pupae feed voraciously before they emerge as adults. Fungus gnats reproduce quickly, producing many generations every year.

Related: Does Neem Oil Get Rid of Mosquitoes?

Fungus Gnat Damage: What Damage Do Gnats Cause?

It is interesting that adult fungus gnats are harmless. They don’t bother people, pets, or plants.

Yet, fungus gnat larvae are a different issue.

Fungus gnats prefer to deposit their eggs in two to three inches of damp soil. Inside a house, that type of environment is often found in the potting mix of a potted plant.

One female fungus gnat alone can produce several generations of offspring each season. This can inundate your plants with larvae.

Fungus gnat larvae feed on the roots and inside stems of most common houseplants. The resulting damage manifests as plant yellowing and slow, stunted growth.

Additionally, adult gnats can spread pathogens from one plant to another, harming all the plants in your house.

Related: Does Cinnamon Help With Fungus Gnats?

How To Control Fungus Gnats?

A fungus gnat outbreak is difficult to stop. The best strategies are prevention and quick action at the first sign of any fungus gnat infestation.

If an animal eats a Mosquito Dunk or drinks water treated with a Mosquito Dunk, it essentially gets a large dose of protein and calcium.

Fungus gnats in soilPin


By the time you see fungus gnats, you might already have a problem.

Place sticky notes or strips of tape, sticky side up, around your potted plants. If dead gnats start to appear on the sticky notes, it’s time to take further action. Growers use commercial yellow sticky traps.

Each beige donut Mosquito Dunk treats up to 100 square feet of surface water. Using mosquito dunks for houseplants is an effective way of controlling the fungus gnats population.

Place Mosquito Dunks in standing water, water troughs, water gardens, or wherever it accumulates around your home: koi ponds, gardens, flower pots, bird baths, rain barrels, roof gutters, unused swimming pools, tree holes,  rain gutters, planter reservoirs where water collects and remains for periods of time.

Non-Chemical Solutions

First, you’ll want to put a few simple techniques for your plants in a well-ventilated place.

Fungus gnats wish to lay their eggs on the moist soil surface, so reduce the amount of water you give your plant as much as possible.

If the top three soil layers remain dry, fungus gnats cannot lay eggs. In this way, you limit (and cut back) their numbers.

Additionally, cover the drainage holes underneath the flower pots. Although gnats lay most of their eggs near the soil’s top layer, they’ll lay eggs in any soil if necessary.

Block the drainage holes with a synthetic fabric to stop gnats. This still allows water to drain.

More recently, the biodegradable mosquito dunks have been approved for use in Organic Production and Gardening under the National Organic Program guidelines. 

They have been registered by the EPA for use in animal watering troughs and fish habitats. 

They are effective low-impact products on mosquito and blackfly larvae and have been recommended for use in backyard ponds or fountains where fish, frogs, tadpoles, and other aquatic animals live.

Recommended Reading

Using Mosquito Dunks for Fungus Gnats

So, how to use mosquito dunks for fungus gnats?

A biodegradable mosquito dunk is a simple, effective device used to kill female mosquito populations and other pests. Although Mosquito Dunk is a brand, many people refer to all generic equivalents as mosquito dunks, too.

Mosquito dunk for fungus gnatPin
Photo Credit: Instagram @cecc_plants

The Mosquito Dunks® is America’s best-selling home owner mosquito control product. 

The key active ingredient is a bacteria called Bacillus thuringiensis subspecies israelensis, or BTI.

BTI isn’t a pesticide product.

Instead, it’s a strain of bacteria that functions as a biological mosquito larvicide. This organism naturally kills a pest but leaves the surrounding environment unharmed. 

While most biological mosquito control agents take days or weeks to show results, BTI is faster. Using bacteria toxic only to mosquito larvae, they kill mosquitoes before they become flying, biting, disease-carrying adults within hours and last 30 days or more.

Dunks dissolve in less water. As they dissolve, they release BTI. It then infects pests, damages them internally, and kills them.

As it slowly dissolves, it releases a bacterium that is toxic only to mosquito larvae in the long term. It’s effective on mosquito larvae and other various flying insects, including fungus gnats, wildlife, and fruit flies. 

This kills the larvae before they can grow up and become biting and disease-spreading adults.

A hand holding a beige, donut-shaped object with potted plants in the background.Pin
Photo Credit: Instagram @chicoguys

When killing mosquitoes, place the doughnut-shaped dunk where the larvae live in bird baths or wherever water collects. Because fungus gnat larvae live in moist potting soil, you need a different approach with the dunk:

  • Break the dunk into a few pieces.
  • Place the pieces into a gallon of water.
  • Let the dunk soak overnight.
  • Remove the dunk from the water container.
  • Pour the water over the potting medium surface area of your houseplants.

Field tests have shown eight-year-old Mosquito Dunks to be nearly as effective at killing mosquito larvae as the new product. 

The BTI-infused water will kill any larvae in the soil. They may also be broken in half to treat smaller areas. 

A portion of a Mosquito Dunk for fungus gnats can be used for less water. You can find a granular form called Mosquito Bits for breeding habitats where the Dunks are impractical.

The effectiveness of mosquito dunks in controlling gnats is not limited to the dunks; mosquito bits for fungus gnats are equally effective.

Mosquito bits are mosquito pellets for plants and come in granular form. They release the same active ingredient as the dunks, Bacillus thuringiensis israelensis (Bti), providing long-lasting protection for indoor plants.

While still watering at minimal levels, use this type of water on all your plants for at least three months. Not only will it remove fungus gnats from your home, but it’s also safe for your plants.

A round, beige object with a hole in the center lying on green grass with clover blossoms.Pin
Photo Credit: Instagram @pluseverteam

Facts About Mosquito Dunks For Gnats

Fact #1: Mosquito Dunks Contain the Naturally Occurring Bacteria – Bacillus thuringiensis israelensis (Bti).

Using mosquito dunks or mosquito cakes for plants is a popular pest control product. They use naturally occurring bacteria to target and kill insect larvae like mosquitoes and fungus gnats. 

Bti is safe for humans, pets, and the environment. It is an eco-friendly option for controlling these pests. [source – EPA]

Fact #2: Mosquito Dunks are Effective Against Fungus Gnat Larvae in the Soil

Fungus gnats lay their eggs in the soil. The larvae feed on plant roots and organic matter.

Mosquito Dunks lets you target and kill fungus gnat larvae before they become adult gnats. This reduces their population and prevents plant damage. [source – CANR]

Fact #3: Mosquito Dunks Can Be Used In A Variety of Settings, including Houseplants, Gardens, and Greenhouses

This versatile pest control product can be used in different settings where fungus gnats may be a problem.

  • Create a solution you can apply to the soil.
  • Break the dunks into smaller pieces and place them in the soil
  • Dissolve them in water. [source]

If you’re wondering how to use mosquito dunks in potted plants, it’s straightforward.

  • Break the dunk into a few pieces, and place the pieces into a gallon of water.
  • Let the dunk soak overnight.
  • Remove the dunk from the container of water and pour the water over the potting medium surface area of your houseplants.
  • Make sure the top 2″ inches of soil remain dry so that fungus gnats cannot lay eggs.

Fact #4: Mosquito Dunks Fungus Gnats: Easy to Use and Have a Long Shelf Life

Using biodegradable mosquito dunks is easy and has long-lasting effectiveness. They can be stored for up to two years without losing their potency against larvae of all species of mosquitoes.

This ensures that you have a reliable solution ready to control fungus gnats and mosquitoes. [source]

Fact #5: Mosquito Dunks Are Non-Toxic and Environmentally Friendly

Are mosquito dunks safe for plants?

Using mosquito dunks to kill fungus gnats have natural bacteria called Bti, so they’re safe and earth-friendly.

They’re great for gardeners and plant lovers who want a harmless way to keep their plants safe from bothersome fungus gnats. [EPA]

JOIN Our FREE Plant Care Newsletter 

By entering your email address you agree to receive a daily email newsletter from Plant Care Today. We'll respect your privacy and unsubscribe at any time.