So you have a fly problem, and now you want to get rid of plant flies in potted plants.
It can seem unusual at first, but it’s a common problem for many plant owners. Having a small infestation of flies in your plant pots can be annoying and worrisome.
Have you seen little bugs fluttering up from your houseplants’ pots whenever you water? Known as adult fungus gnats/
Fungus gnats are small black flies that fly around house plants and live in house plant compost. You may mistake them for fruit flies – but if they’re in and around your house plants, they’re likely to be sciarid flies.
Houseplants are beneficial for several reasons, though they attract nuisance flies and fungus gnats.
Not only do flies irritate you in your home, but they can also be quite damaging to your plants.
If you can see a trail, it’s likely that there are gnats in your indoor plants. Gnats also like light, so you may notice them on your windows, particularly if houseplants are nearby.
The larvae are around 1/4-inch long with a shiny black head and an elongated, whiteish 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.
Thankfully, there are a few ways to help eliminate flies in potted plants to ensure your plants remain healthy and your home stays free of pests.
Why Do Flies Flock to Your Potted Plants?
A few different species of flies breed and infest potted plants. For brevity, we will cover the most common fly in potted plants: fungus gnats (Sciaridae).
Fungus gnats are small flies with round wings that are greyish in color. They can resemble mosquitoes in their adult stage of life, though they are much smaller.
Fungus gnats lay eggs in the soil, and these eggs become larvae, which feed on fungi in the soil of plants.
Moist soil draws fungus gnats to the plentiful amounts of organic decomposition. The soil makes potted plants an ideal home for gnats due to the pot’s moisture and organic material. Also, the pot itself offers more protection from other pests.
These flies are inclined to move toward the light, making them quick to identify. If you see small gnats flying around the windows closest to your houseplants. This could indicate fungus gnats.
What Damage Do Flies Cause?
Fungus gnats do not typically damage plants. In large numbers, gnat larvae can cause root rot and can break down the plant.
How? The larvae attach to the roots and stunt plant growth, preventing the root from expanding. This naturally cuts off the plant’s ability to collect water.
Be careful not to touch the plant leaves with the trap. Check them every few days and replace them with new yellow sticky traps when they become covered with gnats.
In the gnats’ early life stages, they may eat the roots for nourishment, speeding up the problem of rotting.
How To Control Flies in Your Potted Plants?
When controlling flies in potted plants, Clemson.edu suggests that the best method of protecting plants from flies is through – prevention.
But, if you already struggle with a fungus gnat problem, there are a few ways to combat the infestation with chemical and natural methods.
How To Get Rid Of Flies in Potted Plants Naturally
Natural remedies work wonders in eliminating fungus gnats from your plants. There are many different solutions. Natural methods often get rid of flies better than chemical insecticide solutions.
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.
Clean the Roots
One of the simplest methods to combat fungus gnats is by clearing out their larvae. An easy way is to pull your plant out of its pot and clean off the soil.
Water less often Fungus gnat larvae need damp compost to live, as this is where algae and fungi thrive, on which the larvae feed.
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.
Clean the roots with water. Be gentle! Do your best to clean all of the larvae and eggs attached to the plant’s roots.
Dump the infested soil and clean out the pot with soap and water. Repot your plant with fresh soil. Watch the plant for a few weeks to see if it needs another cleaning.
Expect some “Transplant Shock”!
Dry Out the Soil
The best time to use this method is in the winter when your plant enters its dormant state.
Fungus gnats need moist soil for their larvae to survive. Allow the soil to dry out for a few days. The lack of moisture will kill off any larvae inside the pot and prevent fungus gnats from viewing your potted plant as the perfect home.
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).
If your plants still face problems with fungus gnats, make a proven insecticidal spray to use on the plant’s roots.
Mix two tablespoons of mild soap (Dawn dish soap or Castile soap) to a gallon of water. Pour the solution into a spray bottle to spray the soil and plants.
Neem Oil Drench
Neem oil is a “natural insecticide” useful in combating various plant insect pests.
Both ground cinnamon and chamomile tea are natural fungicides. Since fungus gnats snack on fungus, killing their food source sends them away.
For more, read our tips on:
- How To Apply Neem Oil to Soil
- Controlling Fungus Gnats with Neem Oil
- Home Remedies For Getting Rid Of Fungus Gnats
- Ladybugs and Fungus Gnats
Fungus gnats are easy to control and get rid of. Chemical solutions are the last resort. But, if you find yourself with a large infestation, there are a few insecticides that work.
Bacillus thuringiensis israelensis (Bti) is a bacterium used in Mosquito Dunks to control the larval stage of mosquitoes, fungus gnats, and black flies.
Bti is safe for use around mammals, birds, fish, and amphibians.
Once ingested, the bacterium produces crystalline toxins disrupting the digestive system of the fungus gnat. This results in stopping development and kills the larvae pest before reaching adulthood.
Steinernema feltiae are parasitic nematodes. These non-segmented, microscopic worms destroy insects in soil-borne stages from the inside out.
These nematodes kill 100’s ground maturing insects before they reach the adult stage. They include:
- Fungus gnats
- Japanese beetles
… and more
When released into the soil, the nematodes enter the pests through various orifices. The bacterium released by the nematodes kills the pests in a day or two.
The nematodes feed on the dead remains and continue to multiply. After exhausting the food supply, they leave and move to another food source.
These nematodes do not prey on beneficial insects such as ladybugs and earthworms. The bacterium they produce is harmless to humans and plants.
This can be a costly option but a useful solution depending on the infestation level. Either way, figuring out how to get rid of flies in potted plants is necessary to keep your home (and foliage) healthy.