How To Use Mosquito Dunks for Fungus Gnats

Mosquito dunks are not only great at getting rid of Mosquitoes – they’ll work on killing off fungus gnats too! Dunks will not harm your plants so long as you prepare them properly – so, read on to learn how to use mosquito dunks in potted plants, and how you can manage them over time.

What is a mosquito dunk?

A mosquito dunk is a cake-shaped mound which needs to be dissolved in water – and then applied to soil or compost to kill off fungus gnats and other pests. 

How do I prepare and apply a mosquito dunk?

You will need one Dunk broken into several pieces, ready to soak overnight – they should be ready for use the following day.

Surplus fluid can be used later depending on how many plants you are treating, or, you can also share any leftover solution with other plants as a preventative measure.

To kill off fungus gnats, simply apply the solution to the surface of the growth medium and let magic commence.

How do mosquito dunks work?

 mosquito dunks

Mosquito dunk solution will trickle down through the growth medium and kill off fungus gnat larvae. Fungus gnats are particularly partial to moist areas – which means they often thrive on roots deep in moisture. 

Mosquito dunk solution will not harm leaves, stems or the roots of your plants. It’s a nice, quick way to stop gnats from breeding constantly in your soil.

How often should I apply mosquito dunk solution to kill fungus gnats?

That depends on how large your target plant is, and how many plants you have around it. Larger plants will require a bigger dose of the solution simply because they have larger containers and provide homes for larger numbers of eggs, larvae and pupae! 

If you have several plants, it’s possible more than one is infected – it’s wise to treat several plants that may be in close proximity. As an extra precaution, you may decide to treat them all in one go!

I recommend that once you begin this treatment, you continue for several weeks or perhaps even two to three months. This really does depend on how prevalent the fungus gnats are, too, as well as how many plants you have. They reproduce wildly and pop up again before you know it!

How often do fungus gnats reproduce?

Fungus gnats produce an average ten eggs per lay, which then hatch after around five days. They can reproduce several times per year. Adult gnats lay eggs in shallow damp soil or other types of growth medium.

Once hatched, after approximately five days pass, the larvae develop white bodies and black heads. They begin eating the roots of plants and can work their way through the interior of stems. The destruction of plants is often noticeable before any sighting of these greedy pests is discovered! 

What are the main signs of a fungus gnat infestation?

Aside from actually spotting the pests, any given plant may begin to look unwell. For example, structural damage to the stems can first cause discolouration, usually yellowing. 

As the integrity of stems receives damage, the plant may begin to lean or flop over. This is exacerbated by root damage. Left untreated, fungus gnats can devour a whole root system, so your plant or plants stand little chance of recovery. 

Can I take cuttings from plants treated with mosquito dunk solution?

Yes! If you are unsure how badly damaged your plant is, you may decide to propagate part of it to ensure it lives on elsewhere. Don’t worry if you have begun to treat your plant(s) with mosquito dunk solution. 

If the plant looks structurally sound, you can take a cutting and treat this as normal. Simply pot it up in fresh growth medium and apply a dose of mosquito dunk solution.

Even if fungus gnats are persisting, and your plant may not have suffered too much structurally, to be on the safe side, it may still be wise to take a leaf cutting. Or, alternatively, you can take a stem cutting and root it in water, where you can see the roots are clean.

How long should I use mosquito dunk solution on a plant cutting?

If you are rooting cuttings in water, I recommend using the diluted solution immediately after surgery, separating the cutting from its parent. 

Continue on this basis for up to two weeks. During this time, you will need to change the water regularly and check root development. 

If you see pieces of rotting root floating around or if the cutting is not developing in a healthy fashion, examine the stems and other roots. 

Are mosquito dunks the best option for killing fungus gnats?

Mosquito dunk solution is great at killing off gnat larvae before they can start causing serious problems. However, it may also be worth investing in fly traps or even a handful of carnivorous plants.

Fungus gnats, for all they are small and cause us no harm, are frequent pains in the neck for indoor horticulturists. They can propagate and spread before you know it, with damage already accruing beneath the soil.

However, as you can see, there are a few ways you can fight back against these invasive pests. If you don’t feel mosquito dunks are right for you, or you’d like to try a different solution first, take a look at our rundown of ways to kill fungus gnats before you get started.