Where do Houseplant Flies come from and how to Get Rid of Them


We all like house guests, especially those who are as fond of our houseplants as we are. However there is one house guest which is extremely unwelcome and can damage our plants, houseplant flies or fungus gnats.

What every single grower asks when they see little flies around their houseplants is “where did they come from?!”. It may seem like a mystery, you didn’t bring any thing in, you didn’t intend to have flies in your house but yet here they are. In this article we’ll explore where houseplant flies come from, what they actually are, how to prevent them from becoming a problem in the first place and if you do have houseplant flies, we’ll tell you how to get rid of them.

What are houseplant flies?

The first question that needs to be answered, is what are houseplant flies? Those tiny, black, mosquito like bugs that fly around your plants are called fungal gnats and they can become extremely destructive if you’re not careful. Not only are fungal gnats annoying as they buzz around but they can become an eyesore and also damage your houseplants.

It isn’t the flies which damage your houseplants but rather their larvae which lives beneath the soil. These larvae have tremendous appetites and will eat through roots, stems, and anything beneath or near soil level. The life cycle of a fungal gnat is around 3 weeks however females can lay 100-300 eggs at one time. This ability to mass produce combined with a big appetite means that if you get an infestation it can snowball and become an issue for all of your houseplants.

So where do houseplant flies come from?

Houseplant flies are most commonly brought in by the grower themselves. Now I know you didn’t mean to, but it happens. When you bring in new plants, new potting mix or any organic matter at all there may be the chance that it is carrying fungal gnats or just the larvae.

Once in your home and given time, colonies will begin to grow if not tended to quick enough. You need to be careful when bringing any organic matter into your home to ensure that you’re not bringing this pest in.

How can you tell if a plant has fungal gnats?

It is always good practice to check if what you’re bringing into your home or greenhouse has fungal gnats and there are some simple ways of doing this.

The first sign to look for is if there are any of the little flies buzzing around. If you do notice them, especially if they are around or sitting on the plant or potting soil you’re looking at purchasing, there is very good chance that you may be bringing fungal gnats into your home if you do go ahead with that purchase.

Another test is to gently turn over the soil around the base of the plant, at least a few inches deep, this is where fungal gnat larvae will most likely live. This larvae if present will be shiny, clear and about the size of a maggot. If you see anything matching this description, it would be wise to give this plant a miss.

If you suspect that a plant has fungal gnats but you cant see any of these signs there is a test you can run. Cut a few slices of potato and put it on top of the soil. Leave the potato overnight and when you check in the morning, if fungal gnats are present you will be able to see the larvae all over the potato slices, they absolutely love the starchy treat and will not be able to resist. Now obviously you cant go around your local garden centre putting slices of potato everywhere so this test would be more suited to you at home checking if you have fungal gnats.

How to prevent getting fungal gnats?

The easiest way to prevent getting fungal gnats is to not bring them into your house in the first place. By using the tricks explained above about identifying if something is carrying fungal gnats you will be able to prevent this.

There are some things you can do with your current plants to prevent them from developing fungal gnats, the most important of which is to not overwater your houseplants. Fungal gnats love a moist environment, but more concerning is that if you are overwatering your plants this excess water may begin to pool and stagnate which can lead to algae growth. This algae can be a food source for fungal gnats leading them right to your home.

How to get rid of fungal gnats?

The next thing you’re probably asking yourself is how to get rid of these houseplant flies? there is some really good news when it comes to this and that is that it isn’t hard at all to get rid of houseplant flies.

The first thing you should do is to let the top 4-6 inches of soil try out. As mentioned before fungal gnats love a moist environment and without that they will either move on or die off. By letting the top soil of your plants dry out you are not only taking away their home but you’re also making it so they cannot get to their food source. This may only affect the larvae, but if they are no allowed to grow to become flies, then they cannot reproduce which will get rid of your problem.

The other way to get rid of fungal gnats is to apply a soil drench containing gnat loving nematodes. A nematode is a small type of worm, but these in particular absolutely love gnats and will get rid of your problem in not time. The best part is that they wont harm your plant, pets or any of the good bugs and bacteria in your pot.

To get rid of the flies buzzing around in the air you can use sticky traps. The large yellow sticky sheets will attract the flies as it smells like delicious food to them but once they land they will become stuck to the sheet, not being able to move they will eventually die and you can get rid of them easily.

So now you know where houseplant flies come from, what they actually are, how to prevent getting them and how to get rid of them if they do become a problem. You should have no issue in the future with this pest and can go on to enjoy your indoor garden.

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