How to kill fruit flies in potted plants

Have you seen little bugs fluttering up from your houseplants' pots whenever you water? Known as fungus gnats, they're actually tiny flies, about 1/8-inch long, drawn to moist potting soil and decaying leaves on the surface of the soil around your plants. If you spot one up close, you'll notice that they look a little like tiny mosquitoes, but they don't bite. Fungus gnats also don't cause much harm to plants, but they can be annoying to have around. Luckily, there are ways you can make your houseplants less welcoming for them in the first place. And if they've already moved in, there are methods you can try to get rid of fungus gnats.

shelf of houseplants in front of window

Fungus gnats love to lay their eggs in damp potting soil. The eggs become larvae, which feed on fungi in the soil (hence their name). The larvae are around 1/4-inch long with a shiny black head and an elongated, white-ish transparent body. In addition to fungi, they also like organic matter and will sometimes eat plant roots or seedlings. A slime trail that looks like traces of slugs or snails across the top of the soil is another telltale sign of fungus gnats in your houseplants. These insects also like light, so you may notice them on your windows, especially if houseplants are nearby.

Take action as soon as you spot gnats in your houseplants. While it may be tempting to spray the adult fungus gnats, that's usually just a short-term fix because more adults will appear from the larvae in the soil. A better approach is to target the larval stage of their life cycle. Because gnats lay their eggs in the moist soil around houseplants, reducing excess moisture is key to getting rid of them. Avoid overwatering your houseplants and make sure they have good drainage. Allow the soil to dry between regular watering, not to the point that your plant begins wilting but enough that the soil isn't always moist. The eggs and larvae usually die in dry soil. Remember to drain any excess water that accumulates in saucers, too.

If drying out the soil doesn't help, it might be time to try a product such as BioCare Gnat Stix Traps ($10, Amazon), which are sticky yellow traps. Place one sticky paper near your plants to trap the adults and reduce the number of eggs the fungus gnats lay. Be careful not to touch the plant leaves with the trap. Check them every few days and replace them with new traps when they become covered with gnats. Eventually, you'll eliminate all the gnats.

Fungus gnats are usually more noticeable in the fall. Some might hitchhike on houseplants when you bring them inside for the winter. Before taking plants inside, check them to make sure they're free of insects. When you're looking to buy new plants, examine them to make sure there are no insect infestations. And always use the fresh potting mix when planting or repotting.

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What are fruit flies, and where do they come from on your indoor plants?

Before addressing the issue, let us understand what fruit flies are and how they reach your indoor plants.

Fruit flies are common household pests. They are primarily seen during the late summers and fall months. They have red eyes, brown bodies, and are very small in size. If growing conditions are ideal, fruit flies will live up to 40 to 50 days.

They are found chiefly near overripened or rotten fruits, fermented vegetables, and moist areas.

They like to feed on the decaying organic matter in the potting soil. Moreover, if the potting soil remains moist most of the time, it becomes another advantage for fruit flies.

If you have kept any ripened and rotten fruits near your indoor plants, that can also be why fruit flies surround your plant.

Some of us confuse fruit flies with fungus gnats. Fungus gnats, too, are the flies that like loitering near the indoor plants. Gnats look like mosquitoes, black in color, but fruit flies have brown bodies. 

Also read: How To Get Rid Of Gnats In Indoor Plants? (Identification, Causes & Solution)

Why do you need to remove fruit flies?

Fruit flies do not cause any harm to your houseplants. They only come to the indoor plant soil to feed on the decaying matter.

When they approach your plants and find conditions ideal for their stay, they will lay eggs on the surface of the soil.

Fruit flies can lay up to at least 500 eggs at a time. Although fruit flies do not harm the plants, they are health hazards. That is why it is better to remove them.

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How to get rid of fruit flies?

Fruit flies are not much attracted to indoor plants.

They enter our home because they get attracted more to fermented fruits and vegetables or overripe and rotten fruits, dustbins, etc.

Before you take steps to remove fruit flies from the plant, remove the items attracting the fruit flies.

Taking the garbage bins outside and keeping fruits covered or in refrigerators will help eliminate fruit flies from the house.

Also, clean the refrigerators where fruits are kept. Fruit flies don’t have a problem staying in cold areas. Clean the areas where you prepare food to keep them away. Fruit flies won’t come near clean places.

If your kitchen has bins to discard scraps or compost heaps, make sure they are sealed well. This can also be an attraction for fruit flies.

Now, coming to indoor plants, if your house’s surroundings are kept clean, the fruit flies won’t be able to infest your plant much, the decaying organic matter in the potting soil is exceptional.

Still, if they are infesting your plant, your plant or potting soil has something which attracts them. Now, let us how to get rid of fruit flies from the indoor plants:

Disturb the soil

Fruit flies will infest your potting soil for two reasons. First is, they will feed on the decaying organic materials present in the soil.

Secondly, if the indoor plant soil and plant crevices have fungus, the presence of fruit flies should not be surprising.

Fruit flies will also lay eggs below the soil’s surface if the condition is ideal for them.

The larvae will start growing on the micro-organisms which live in the dark and moist soil. If your potting soil is healthy, the fruit fly larvae will get all their needs from your potting soil.

Disturbing the soil will disturb the breeding process of the fruit flies. For this, turn over the surface soil and expose the eggs or the larvae towards the light and dry air surrounding your plant.

You can create an obstacle between the soil and the air by placing a thick layer of course gravel.

Another way of disturbing the eggs or larvae of the fruit flies is to allow the topsoil to dry out completely. But for this, you need to know whether your plants will be able to tolerate drought.

If the flies still don’t go away from the soil, you might have to opt for re-potting the plant. Collect and place the larvae in a sealed container and discard them far away.

Dispose of the infested soil much away from your home. Wash and disinfect the pot for further usage.

Remove the food source

Most potting soil has decaying organic components, a good food source of fruit flies, for example, peat moss.

But peat moss is very beneficial for indoor plants, and it might not be possible to remove it. You can also use perlite in your potting soil. It is lightweight compared to peat moss.

Another good food source for fruit flies is a fungus. The quicker you remove fungus from the plant, the fewer fruit flies will wander near your indoor plant.

Prevent fungus and fruit flies by decreasing the humidity around your indoor plant. The fruit flies breed mainly in damp and moist areas. But, before reducing humidity, make sure that your plant can tolerate the situation.

You can use dish wash soap for spraying or rubbing alcohol to wipe out all sorts of fungus and pests from your plant. This will prevent any further appearance of fruit flies.

Clean all surfaces

Always try to keep the sink drains free from all sorts of food particles and residue. These damp spots are the best place for the fruit flies to stay and lay eggs.

If you keep wet clothes or rags in rooms where you have placed your indoor plants, move away either the wet clothes and rags or the plants away. Keep your plants away from such damp environments to avoid fruit fly infestation.

Throw away the over-ripe or rotting fruits away

For keeping the indoor plants free from fruit flies, you will need to keep your house clean.

If you are growing fruit plants indoors, you should pinch off the ripening fruits from them as soon as possible. Keeping ripen or rotten fruits away from the plant will help keep fruit flies at bay to some extent.

Set traps

DIY FLY Trap to Get Rid of Flies and Fruit Fly

Fruit flies can be lured by vinegar, wine, or yeast as they are attracted to them.

Mix apple cider vinegar and dish wash liquid soap with water and pour it into a bowl. Cover the container with a wrapper.

Make holes over it big enough for the fruit flies to get into it. Now place the container near the infested plant. They will enter into that bowl through these holes but won’t be able to come out.

Take an old wine or beer bottle and place it near the infested indoor plant. They will be attracted by that old, stale smell and enter the bottle. The narrow-necked bottle will make it difficult for them to come out of it.

You can also buy flytraps from the market. These will not only trap them but also stop them from further breeding.

These are disposable fly traps entrapped with a non-toxic lure. This will be able to catch at least 2,000 fruit flies. The product will last at least one month. 

Growing indoor plants that can repel insects

Plants like mint, basil, sage, lemongrass, lavender, marigolds, and many more are popular houseplants that repel insects.

The flies cannot stand the presence of some insecticidal components in them and their strong odor. Thus, the fruit flies will stay away from the indoor plants.

Another plant that can keep flies away is carnivorous plants, such as venus flytraps or pitchers. These kinds of plants will eat up the fruit flies once they land in their mouth. They, too, are one kind of trap for them.

Use insecticide

Now, if all the above methods are not working and whatever you do, fruit flies are still wandering near your plant or the potting soil, it is time to try commercial ones.

But as commercial insecticides contain chemicals, you should be careful while using them.

Read all the instructions given in the labels very carefully before applying. Go through the ingredients, the directions for use, and the caution and warning points. Also, consult with the buyer or experts about the best way to use them.

Don’t allow them inside.

You can close the windows and doors in the room where the indoor plants are kept. This might not be possible as plants will need air and sunlight to thrive. 

You can organize nets or any screen as a barrier to prevent the fruit flies from entering the room.

Also read: How To Get Rid Of Bugs On Indoor Plants? (Identification+Remedy)

Final words

Fruits flies are a common and annoying problem in houseplants. Even though they don’t harm the plants, they are a health hazard.

Moreover, their infestation can increase in no time that will give your plant a dull look. So, it is better to remove them as soon as possible.

Try all the methods alternately to remove them. First, try the natural ways and if it fails, go for the chemical treatments, but be careful. Always keep the surroundings of your indoor plants neat and clean.

Fruit flies don’t like neat places. Clean places will keep them away from your plants and even from your home. Take good care of your plants to keep the fruit flies away.

Source: University of Illinois, Growing Indoor Plants with Success, Agriculture, and Natural Resources, University of California, Missouri Botanical Garden.