Fungus gnats, how to get rid of them

How do you recognise fungus gnats?

At first glance, mourning flies look a lot like fruit flies. They are both small, black in colour and above all annoying, if you have them around the house. Mourning flies are actually a type of mosquito, also known as Varenrouw mosquito. The Varenrouw mosquitoes are about 2 to 3 mm in size and are recognizable by their black head and dark wings. If you look closely, you will see a “V-sign” on these wings, which you can use to distinguish the creature from fruit flies. Mourning flies mainly occur at the beginning and end of the summer. Even though they only live for a short time, only 1 to 2 days, the bugs are good at reproducing. They lay up to 200 eggs at a time, from which new larvae can emerge. In addition to these characteristics, you can also recognize the mourning flies by the place where they prefer to hang out; your plants!

What’s the risk of having fungus gnats?

Fungus gnats live on plant material and can therefore cause damage to your plants. The larvae spend their time in the potting soil, where they can attack the roots of the plant. Because the eggs and larvae are hidden in the soil, the adult flies are often only discovered when you water or move/touch the plant. Because the eggs hatch after a few days and after 3 weeks have grown into an adult fungus gnats, there is a good chance that a plague will develop. Do your plants no longer look so beautiful? And are there small black flies circling around the plant? Then it is high time to fight the bugs as soon as possible! Damaged roots are less resistant and therefore more prey to bacteria and fungi. Young plants and plants that are no longer as fit are especially sensitive to the larvae of the fungus gnats.

Photo: Unsplash – Giulia Bertelli

Help, how do I fight fungus gnats?

There are a number of home-garden-and-kitchen ways to get rid of mourning flies:


  • Quarantine your plant! The last thing you want is for the flies to find a nice place with the other plants in your house.
  • Have a glass of wine. And put it next to the plant;) The bugs will be attracted to the wine and stay away from your plants. You will also be able to catch them with this.
  • Dry out your plants (temporarily). Wet and foggy soil is attractive for the mourning fly to lay its eggs.
    When the soil has dried considerably, you can replace the soil. Make sure you also clean the pot well.
  • Cover (new) potting soil with a layer of sand, where the mourning flies cannot lay eggs. Please note, this makes it more difficult to estimate when your plant needs water.
    Sprinkling cinnamon powder on the soil or mixing it with the water used to water the plants can also help.

Do you need some heavier guns? There are also various pesticides that you can use to help your plants get rid of the flies. From real plant cures to the use of nematodes.


Sources: Pokon, MaxVandaag, Mooiwatplantendoen, Sprinklr

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