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How to Prevent Flies from Indoor Plants

In a separate post, I’ve gone over how to get rid of those pesky fruit flies. While those methods are certainly effective, it’s much better if you never actually have to deal with them in the first place. That’s why it’s a good idea to learn how to prevent flies from indoor plants.

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The first step you should take is repotting your new plants in fresh soil. Soil or potting mix that’s been sitting for a while could already have flies or what are often referred to as fungus gnats, and you certainly don’t want them to spread.

how to prevent flies from indoor plants

Prevention is critical, as infestations can be pretty annoying to get rid of. Still, it’s easy enough to prevent these issues from happening in the first place, so keep reading to learn some of the the best preventative measures you can take.

If You Don’t Know How to Prevent Flies from Indoor Plants…

how to prevent flies from indoor plants

All plant and garden projects can be at risk of getting flies, making it essential to learn how to prevent flies from indoor plants. Knowing how to prevent them is only part of the battle, though. It’s important to understand why they can survive and even thrive for so long in your beloved plants.

With that knowledge, I think you’ll find basic preventative measures much easier to understand and implement effectively.

They Need Organic Matter

Staghorn Fern Mounting Prep Roots

Organic matter is essential to the survival of fungus gnat larvae. While adult fungus gnats only need liquids to survive, their larvae feed on roots and other ​plant material as they grow. As you might expect, this can cause quite an issue, particularly if your plant is already struggling from root rot.

This makes your favorite plant(s) excellent targets for these flies.

They Require Wet Soil

Soil treatments how to prevent flies from indoor plants

Soil with excess moisture is the ideal breeding ground for flies. The moist soil promotes fungi and algae growth, but lots of moisture on the top of the soil can also indicate root rot below. In turn, this gives the flies plenty to feed on as they can eat the rotting plant roots for sustenance.

As such, you should shoot for dry soil as much as possible. Avoid overwatering to prevent wet soil and reduce the attractiveness of the area.

They Prefer Light

hanging plants that do not need sunlight

Although not explicitly required, adult gnats tend to prefer bright light sources. If these lights are placed near your plants then an infestation becomes more likely. While knowing this isn’t necessarily part of knowing how to prevent flies from indoor plants, it can be helpful when trying to find out if you have an infestation issue.

How to Prevent Flies from Indoor Plants: The Best Prevention Methods

How Often to Water Snake Plants Indoor Plants

Now you know what flies prefer when trying to find indoor plants to infest, so what’s the best way to prevent them from moving in? Well, the first thing to do—as mentioned above—is repotting the plants.

There are a few more things you can do, but the good news is it’s not complicated! I promise. The best pest control methods are very easy to implement when dealing with flies, and taking the time to do things right will definitely be worth the effort in the long run.

Perfect Your Watering Schedule

Making sure you perfect your watering schedule is one of the best ways to help prevent a fungus gnat infestation. I can’t tell you exactly how much water to give your plants in this how to prevent flies from indoor plants guide, of course. 

That varies from plant to plant. Whereas a small houseplant may require more frequent watering, a larger plant may only need an occasional splash to thrive. Regardless, you should leave some time for the surface of the soil to dry before watering the plant again. This will help keep the gnats away.

Minimize Water Usage

how to prevent flies from indoor plants watering

It might take a bit of trial and error, but eventually, you’ll be able to figure out exactly how much water your specific plant needs. Determine this amount and stick to it. Going overboard can result in higher moisture levels, encouraging root rot and increasing the likelihood of an infestation.

It’s also a good idea to ensure that your plant pot has good drainage, as this will help prevent excess moisture from building up.

Try Bottom Watering

Instead of watering your plants from above as normal, consider bottom watering instead. The process is actually quite simple. All you need is a pot with superior drainage.

Fill a tub with water then place the pot inside. The soil will absorb the water through the drainage holes. This approach is great because it gives the plant adequate water without leaving the top of the soil wet. In doing so, the dry topsoil can help ward off flies.

Treat the Water

While I wouldn’t necessarily recommend doing this for propagation projects, treating the water you’re using is an excellent way to prevent infestations in currently potted plants. You can simply dissolve mosquito dunks in the water you’re using before watering the plants.

Water from the top using this method, as the BTI (Bacillus thuringiensis israelensis) from the mosquito bits will kill any larvae present in the damp soil. Alternatively, you can achieve similar results using a 4:1 water/hydrogen peroxide solution.

Treat the Soil

Soil Seddling

You will also want to learn how to prevent flies from indoor plants by treating the soil. Some people have had luck treating the soil with lavender oil, but there are a few other things I’d probably recommend trying first.

Just grab your spray bottle and give one of these a try!

Neem Oil

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This natural pesticide works great at preventing and treating fly infestations. You can buy it as a premade spray, or mix it with a cup of water using a ratio provided by the manufacturer.

The best part about Neem oil is that it’s safe for pets, plants, and people. While you definitely shouldn’t eat it or rub it in your eyes, you can confidently use it around your family without worry.

Mosquito Bits

how to prevent flies from indoor plants mosquito bits

While diluting mosquito dunks into the water is a great option, you can also use them to treat the top of the soil. You can spread the granules on top of the soil right after watering to treat it. If you can’t find any at your garden center, there are a ton of online options as well.

Preythrin Spray

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Made from chrysanthemum flower extracts, Preythrin spray is another effective way to treat the surface of the soil for flies. Spraying the soil directly will kill any larvae or adult flies present.

Although generally considered safe, you should take care when using Preythrin spray around cats, as well as fish. Both are considered to be somewhat sensitive to these toxins.

Hydrogen Peroxide

A cheap and effective way to treat the top layer of the soil is by using hydrogen peroxide. First, get a bottle of 3% hydrogen peroxide. Mix one part hydrogen peroxide to four parts water. Then, use this solution to water your plant(s), making sure to water all the way down to the roots.

Although the solution won’t harm your plant, it can help kill larvae and eggs currently residing in the soil itself.

Introducing Nematodes

Lisette Verwoerd YzFKhnTjMcs Unsplash

Introducing even more bugs to your new plants might seem counterintuitive, but trust me, this is an effective way to prevent infestations. Essentially, nematodes are microscopic worms that feed on larvae in the soil. They do require some upkeep, but the upkeep itself is fairly standard for plant maintenance.

This method is especially great if you have hanging plants. While bottom watering your plants every time may be a bit of a pain, introducing nematodes is practically a one-and-done solution. This makes it perfect for harder-to-reach plants.

Implementing Traps

plant pots

So far, I’ve mainly offered ways to treat the plant pots themselves. However, trapping is also an essential thing to learn about when learning how to prevent flies from indoor plants. If any pesky flies are present, this can help get rid of them. If not, it’s a bit of extra work that serves as an excellent preventative measure for the future.

Sticky Traps

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Easy to use and affordably priced, yellow sticky traps are a great way to remove any flies near your plants. Not only are these traps effective at getting rid of fungus gnats, but they can also be useful for eliminating other types of pests (such as houseflies). I use these at the cabin where we have a good amount of bugs – like all the time. They work like a charm.

Vinegar Traps

With a bit of apple cider vinegar and some water, you can make efficient traps yourself. Create a mixture of 50% vinegar and 50% water, then place the mixture near your plants. The scent will attract flies, trapping and drowning them as they come along. 

If you don’t have any apple cider vinegar, mixing a tablespoon of sugar and some dish soap with water can help solve your gnat problem as well.

How to Tell If You Have Gnats

Fungus Gnat

While it’s always best to prevent your first place from being infested in the first place, it’s still good to know the signs that these fungus gnats are around. Fortunately, being able to detect an infestation of these tiny flies isn’t very hard.

You’ll most likely first notice them buzzing around your house plants. While you might not see larvae on top of the soil, you might if you dig into the soil a bit. Look for tiny creatures with black heads and transparent bodies. These are the larvae that damage your plants!

If the infestation is left to prosper then the sign will become more apparent. A sudden lack of growth, wilting, or yellowing of the leaves are all clear indications that something is wrong with your plant. If excess water, a lack of water, a lack of sunlight, or other common problems aren’t present, chances are, you might have fungus gnats.

Life’s Better Once You Know How to Prevent Flies from Indoor Plants

house plants

The easiest way to avoid flies is to only place faux plants in your home. Don’t get me wrong, I do enjoy having some fake plants to go alongside the real ones. Still, there’s nothing quite like having living, vibrant greenery around your home, which is why it’s a good idea to learn how to prevent flies from indoor plants.

Hopefully, this has been helpful. Did you learn anything new? If so—or if you have any helpful hints yourself—then I’d love to hear about them in the comments below.

As always, thanks for reading, y’all. Have a great week!

FAQs About How to Prevent Flies from Indoor Plants


What causes flies around indoor plants?

The moisture, lighting, and food source that your indoor plants can provide make them an attractive option to these tiny flies.

Does coffee grounds keep gnats away?

It can. By spreading the grounds over the top layer of soil, you can prevent gnats from laying eggs in the applied area.

Can I spray my plants with vinegar to get rid of gnats?

You definitely can! Mix white vinegar with water in a 1:1 ratio, then spray this directly onto your plants.

How do I get rid of houseplant gnats naturally?

You have quite a few different options, but repotting, making apple cider vinegar traps, introducing nematodes, and limiting watering frequencies would be my top recommendations.

Does cinnamon deter gnats?

Yes, cinnamon both deters gnats from approaching your plant decor and prevents them from getting the proper nutrients. In fact, thanks to its antifungal properties, cinnamon actually inhibits the fungal growth that the larvae rely on.

How do you put cinnamon on plants?

There are two main methods: using powder or using oil. For the powder, simply sprinkle the cinnamon on the top of the soil to ward away flies. If using oil, mix 10 drops of oil with 30ml of water and spray it directly onto the plants.

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