The little flies like to colonize the soil in the flower pots of our plants. We reveal how to fight fungus gnats and their larvae naturally and get rid of them permanently.
Many plant lovers know and fear them: the little flies that suddenly climb out of the potting soil and multiply at breakneck speed. Fungus gnats occur again and again, especially in potted plants with a planter in living rooms. We will show you how an infestation occurs and how you can combat fungus gnats and prevent another infestation.
Mourning Gnats: Wanted Poster
The family of fungus gnats (Sciaridae), colloquially also known as mourning flies, occur in nature primarily in damp habitats such as forests, moors and wet meadows. The adult black flies are up to seven millimeters long and lay their eggs in moist soil. Outdoors this happens in May to June, but in houses or greenhouses all year round. A female can lay up to 200 transparent eggs. The fungus gnat larvae, which hatched about a week after the eggs were laid, live in the ground and decompose organic material such as leaves, fungal threads or roots. It is precisely these larvae that become problematic in the soil of indoor plants. In the absence of sufficient dead plant matter and fungal mycelium, the hungry larvae encroach on living plant roots, damaging our beloved green fellow residents. In addition, the black mosquitoes in the potting soil are perceived as annoying and disgusting - especially when they appear in large numbers.
Note: All hobby mushroom growers should be told that the larvae of the fungus gnat particularly love the mycelium of mushrooms as a food source. It is not for nothing that the mosquito is called “fungus gnat” in English.
How to recognize fungus gnats(larvae)
The small black flies in the potting soil are clearly visible to the naked eye. They usually stay close to the ground, run around on the soil and the pot and fly around, tumbling slightly when you see the infested onewatering the plant or moving the pot.
In order to recognize an infestation by fungus gnats before mass reproduction takes place, we recommend yellow charts such as those from our Plantura Shop, which are conveniently delivered to your home. Yellow boards are coated with glue so that the adult flies stick to the boards. Incidentally, in order to catch and discover fungus gnats as effectively as possible, the yellow boards are best attached directly above the surface of the potting soil, for example with small wooden skewers. If you discover the first fungus gnats, you should start fighting them quickly.
After hatching, the larvae of the fungus gnat stay in the ground and can only be seen when repotting. The fungus gnat larvae are worm-shaped, white in color and up to five millimeters long.
In young plants in particular, an infestation can quickly lead to wilting or the death of the plant, even though there is a good water supply. This also indicates an infestation by fungus gnats.
Tip: Fungus gnats are often confused with fruit flies. However, fruit flies need fruit or vegetables as a food source and will not be in or near houseplants, making the distinction easy.
Fighting fungus gnats: how to get rid of them
You have noticed an infestation with fungus gnats and are now considering whether and how you can combat it? The first thing to decide is whether fighting it makes sense at all. In the garden and on the balcony, the small black flies almost never multiply to large populations, which is why there is usually no need to fight them. If fungus gnats have nested in the soil of your indoor plants, the situation is different: in a warm house and in the wonderfully water-storing potting soil, the problem is guaranteed to grow without your intervention, instead of going away on its own.
What to do if you notice a mild to moderate infestation:
As long as you can observe the "mushroom flies" especially in the pot and in the immediate vicinity of the plant, the infestation is not very severe. To prevent a severe infestation, you should nevertheless take action against the "fungus flies" as soon as possible with biological pesticides. Fighting fungus gnats with home remedies is also possible with a light to medium infestation. Our Plantura BioFungus gnat-free neem can provide very good service with a light to medium infestation and protects your plants and their roots with natural active ingredients from the neem tree. We describe the application in more detail below.
What to do if you notice a heavy infestation:
When is it actually a severe infestation? If you already encounter the stumbling black flies in other areas of the apartment, then their breeding ground is already "too small" for the existing population and many individuals are looking for a new home - a clear sign of a heavy infestation. Yellow boards, which you can use to monitor an infestation in the house and greenhouse, provide another clear indication. If the adhesive panels are already overflowing with the small black flies after 2 to 3 days, there is a severe infestation. In addition to the use of biological pesticides, a heavy infestation also requires a number of other measures, since the preparations alone can hardly achieve complete control.
In the event of a severe infestation, proceed as follows:
- Repot infested plants, free roots from soil as much as possible, if necessary under running, lukewarm water; As a precaution, treat freshly potted plants once with a remedy against fungus gnats.
- Either repot plants in the immediate vicinity of the heavily infested plants or treat them with a pesticide against fungus gnats.
- With every plant in the apartment, without exception, cover the surface of the potting soil at least 0.5 cm thick with a dry material, for example crushed expanded clay, expanded clay balls, lava chippings or decorative gravel.
- Equip each pot in the apartment with a yellow board; the yellow board should be positioned close to the surface of the earth to directly intercept flies emerging from the earth.
- Find fungus gnats on the yellow boards, use a pesticide again.
Fighting fungus gnats naturally
If home remedies against fungus gnats and prevention have failed or you want to be on the safe side, you should use real pesticides. However, we recommend not using synthetic pesticides, especially in living rooms or the house garden, so that you as a user, playing children or pets are not exposed to a disproportionate risk. Instead, we advise against biological meansFungus Gnats.
A highly effective and natural method of fighting fungus gnats is the use of neem preparations. The seed oil of the neem tree contains the active ingredient azadirachtin, which acts on the sciarid larvae in the soil. Our Plantura organic sciarid-free neem is based on this neem oil and offers you a reliable and organically certified method of getting rid of sciarids. You can use organic sciarid-free neem both indoors and outdoors.
Our organic fungus gnat-free is not dangerous to bees and ensures that the plant-damaging larvae of the fungus gnat stop eating quickly. The ease of use allows you to accurately dose for an optimal effect. For ornamental plants in your home, 15 milliliters mixed with three liters of water is sufficient to treat an area of around 1 m2. Simply pour the emulsion onto the soil of the affected plant. When using our organic pest-free neem, please pay attention to the application recommendations in the package leaflet.
Fighting fungus gnats with nematodes
An effective, safe and simple control method is the use of insect-damaging nematodes. They really do not pose any danger to other plants, insects or even pets.
An example of this is our Plantura SF nematodes against fungus gnats, codling moths & ants. The predatory nematodes of the species Steinernema feltiae infest the larvae of fungus gnats after application and multiply in them, which leads to the death of the larvae. The first larvae die off after about 3 days and since the nematodes continue to multiply in the larvae, the success of the treatment increases until the nematodes can no longer find any larvae. Incidentally, the tiny threadworms are very easy to distribute with the irrigation water. They are harmless to humans and animals - they specialize solely in the larvae of some pests and have been used successfully in organic farming for many years.
Tip: When using SF nematodes, it should be noted that the substrate should be at least 12 °C warm and direct sunlight should be avoided during application, as the nematodes are very are sensitive to UV radiation.
Prevention of flies in potting soil
Fungus gnats only become a problem when the flies find permanently wet soil. The best prevention is therefore a suitable oneWatering behavior: Always let the surface of the soil dry slightly before watering again. Firstly, the sciarid fly larvae need moist soil to live, and secondly, the eggs are laid directly on the soil's surface. If the substrate is too dry, the larvae will die immediately after hatching.
You can also apply a 0.5 centimeter layer of sand, lava chippings or broken expanded clay to the soil as a preventive measure. This means that the surface is always dry and therefore unattractive to fungus gnats. To use this method effectively, houseplants should only be watered from below over the saucer or planter.
You can also get fungus gnat eggs from potting soil. Under favorable breeding conditions, the fungus gnats can penetrate through small ventilation holes into earth sacs and lay their eggs while the sacs are still being stored. This often happens with the unprotected stored earth in hardware stores. Unfortunately, an infestation with fungus gnats cannot be ruled out during transport and storage at home, even with high-quality soil such as our Plantura potting soil.
If you buy new potted plants, we recommend that you put them directly into a repot unaffected soil, which will also ensure vigorous growth of your new plant.
Tip: If your potting soil is infested with fungus gnats, you can use the moistened soil in the microwave (highest level for seven minutes) or sterilize in the oven (200 °C for 20 minutes).
Summary: Preventing Fungus Gnats
- Always let the soil dry out before the next watering
- Spread a layer of sand, lava grit or broken expanded clay on the potting soil
- Water plants over planter and saucer
- Check potting soil and sterilize in microwave or oven if necessary
- Always repot potted plants after purchase
You can find helpful tips on how to repot popular indoor plants in our special article.