Have you ever noticed those tiny black flies around your houseplants?
Last year, I went to battle against what felt like an ever and fast increasing hoard of little black flies which were having a field day with my beloved house plants. Fungus gnats are a common problem, gathering on your window sills and hanging around your houseplants. You might notice them in your greenhouse too. They may be small, but they are very persistent – and very annoying!
Houseplant love
I love houseplants. They bring a touch of nature to my space, and I find real joy in caring for them and watching them grow. It’s well-documented that being in the presence of plants is good for our wellbeing.
However, if our beloved plants are plagued by pests, it’s not so peaceful. If you are troubled by fungus gnats and wondering how to get rid of them, here are a few options to try.
Understand the problem
Fungus gnats lay their eggs in the soil around your houseplants. The eggs hatch into larvae, which feed on decaying organic matter in the soil including algae and fungi. They can also damage the roots and leaves of your plants.
To get rid of fungus gnats effectively, it’s important to deal with them at all stages of their life cycle:
- the adult flies to stop them laying more eggs
- the eggs to stop them hatching into more larvae,
- the larvae to stop them emerging as more adult flies.
So, a combined approach is best, because one solution is unlikely to be effective against all 3 stages of the fungus gnat lifecycle.
Dry out the soil
Fungus gnats lay their eggs in damp soil, and these are the best conditions for the fungi which the larvae eat. So, allowing the soil around your plants to dry out between waterings could be the simplest solution.
Try covering the top of the pot with a layer of decorative grit or gravel. This makes it difficult for the adult fungus gnats to lay their eggs. Aquarium gravel is ideal.
Avoid over-watering
As fungus gnats thrive in damp conditions, over-watering your plants creates the ideal environment for an infestation. As well as allowing the soil to dry out between waterings, make sure the plant is draining fully. Try watering your plants from the bottom. Stand the pot in water until most of the compost is moist, but the top layer is dry. Lift the pot out of the water and allow it to drain.
Sticky traps
Sticky traps are a great way of dealing with the adults fungus gnats. The flies are attracted to the bright yellow colour, and get stuck to the sticky surface. It’s gruesome, but it works. Shop around for plastic-free options.
Soil treatment
A solution of hydrogen peroxide can be effective in killing the larvae, and won’t harm your plants. Mix 1 part hydrogen peroxide to 4 parts water and water your plants with it. Hydrogen peroxide breaks down to water and oxygen and is used as a green alternative to bleach. Buy if from the pharmacy.
Neem oil
Neem oil comes from the seeds of the neem tree. It is a natural pesticide – it both repels the fungus gnats and interferes with their reproduction. Mix the neem oil with water according to the instructions and drench the soil as well as spraying it onto both sides of the leaves. Neem oil is safe for humans and animals, but be careful around fish.
Nematodes
Nematodes are microscopic creatures which prey on the larvae of other insects. The nematodes are supplied in a powder. Mix with water and apply to your plants according to the instructions. You can buy nematodes at your garden centre or online. Use in combination with traps, to deal with both the larvae and the adult flies.
Repotting
If you have a severe problem with fungus gnats, try repotting the affected plants. Remove as much of the existing compost as possible and repot using sterile houseplant compost. Add a layer of grit to the top of the pot and be sure to clear away dead leaves and debris, to prevent the pesky pests from returning.
Final thoughts
I’m pleased to say, I won the battle. If you’d like to know which of my researched options above worked, just drop me a line in the comments or get in touch via my website. Don’t let fungus gnats come between you and your houseplants. Try a couple of these options, banish the black flies and love your houseplants all over again.
