When you discover small black flies, those affected will notice that fungus gnats have found their way into your home unnoticed. The flying pests hide in the potting soil of houseplants and multiply quickly. The entire life cycle of the fungus gnat is only about three to four weeks, but the rapid reproduction of the animals keeps those affected busy in the long term. An infestation must always be treated because the plant pests do not disappear on their own. You can find out here how you can fight fungus gnats and get rid of them in the long term.

In nature, the fungus gnat – especially the larvae – is one of the most important leaf-decomposing organisms and therefore one of the useful animals. The flying pests are only considered a pest if they attack houseplants. A fungus gnat infestation is particularly common in the winter months, when dozens of the small animals often sit on the plants’ potting soil. This is because people tend to overwater their houseplants in winter due to the dry heating air. However, fungus gnats love to lay their eggs in moist soil, where the larvae develop, which feed on the soil and roots and harm the plants. That’s why potting soil that’s constantly kept too wet is the ideal habitat for black flies. Fungus gnats are one to seven millimeters long and have a black body with long legs and black wings. The larvae are grayish white and six to seven millimeters long.

Most people recognize a fungus gnat infestation when there are more small black flies buzzing through the air. The small pests are often confused with fruit flies, so it takes some time until the fungus gnat infestation is identified. But once you get to know fungus gnats, you will be able to easily distinguish them from fruit flies in the future. The mosquitoes fly up when you water the plants or when you move the plants. Fungus gnat larvae live in large groups on the moist plant roots. A look into the soil of the affected plant is enough and you can see the larvae with the naked eye. As soon as a plant is affected, you should also check the other plants for an infestation, because the fungus gnats multiply quickly. It is best to isolate the infected plants from the rest until the infestation is controlled.

Tip: If the plant soil is already too badly affected, you should repot the plant and implement the following tips to permanently combat fungus gnats.

Moisture is the most important requirement for fungus gnats or for the survival of the larvae, so the first step you should take is not to water the affected plants for some time. Of course, you need to monitor the plants to prevent them from drying out, but in the short term this drying out can help against the fungus gnats. The following measures can also be effective in combating fungus gnats:


Fungus gnats can be effectively controlled with so-called yellow traps. You stick the yellow stickers directly into the affected potting soil and the small insects stick to them.

Fighting fungus gnats with carnivorous plants

You can even fight the pests with plants. The butterwort is suitable for this, a carnivorous plant that can trap fungus gnats with sticky leaves. Place the butterwort near the affected plant and the flies should stick to it.

Nematodes or predatory mites

In professionally managed garden businesses, nematode and predatory mite species are also used to combat or prevent fungus gnat larvae. Nematodes, for example, are beneficial insects for the sustainable and effective control of fungus gnats and their larvae. You can add them to the plant soil as a spray or watering agent using a spray bottle or watering can.

Home remedies for fungus gnats

A good home remedy for combating fungus gnats and their larvae is to cover potting soil with a layer of quartz sand approximately one to two centimeters thick. This prevents the adult flies from laying their eggs in the moist soil.

Fungus gnats are harmless to humans, but they are very annoying. The flying pests are actually only harmful to houseplants. However, in some cases the increased moisture in the potting soil can lead to mold forming on the soil. This should be removed quickly as its fumes are not good for the human respiratory system.

Fungus gnats often find their way into many households during the winter months. This is because houseplants are often not cared for correctly. Therefore, a short excursion into plant care makes sense in order to prevent pests such as fungus gnats in the long term. In winter, plants indoors get less daylight and are usually kept in heated rooms, making them more susceptible to pests. The following tips can help keep plants healthy.

Source: Federal Environment Agency

You might also be interested in:

This article contains so-called affiliate links. Further information are available here.