Fungus gnats (a type of sciarid fly) are one of the most commonly encountered pests of indoor plants. In fact, they're one of the bugs Flower Power's plant experts get asked about most often. Seen tiny, black, fly-like insects hovering around your indoor plants? You may have fungus gnats - and if you're wondering how to get rid of fungus gnats, you're in the right place!


Fungus gnats and your indoor plants

The adult flies are the visible part of this insect’s life cycle, and cause plenty of annoyance to plant parents. However, it is the larvae that damage plants and really need to be controlled. Larvae are tiny, clear, worm-like creatures that feed on plant roots in potting mix. They may also burrow into stem tissue.

Heavy feeding by fungus gnat larvae can cause indoor plants to die-back in response to damage to their feeder roots. Young plants can die as a result of this damage.

The presence of fungus gnats is a sign that the potting mix is both too wet and also high in undecomposed organic matter or peat. Keeping potting mix drier – that is, watering and allowing water to drain through the mix before returning the plant to its saucer or cover pot – and not leaving plants sitting in water, makes conditions less favourable for these insects to breed. Less favourable conditions should help to prevent problems arising in the first place.


An adult fungus gnat and its troublemaking, worm-like larvae.


Fungus gnat life cycle

Fungus gnats have a very rapid life cycle, so acting quickly when you spot them helps to reduce their numbers. A female fungus gnat may only live for a few days, but can lay more than 100 eggs in your potting mix in that time. The eggs hatch into larvae, which feed and pupate in the potting mix before emerging as adults. The time from egg to adult is about three weeks, meaning population numbers can build up rapidly.


A yellow sticky trap is a great tool to catch and remove adult fungus gnats - but to truly solve the problem, you need to target the larvae.


Controlling fungus gnat populations

As well as trying to prevent fungus gnat populations building up in indoor potting mixes, there are ways to reduce established numbers. If you've got a visible infestation, here's how to kill fungus gnats. Flower Power do sell sticky traps which will reduce adult gnat numbers, however the larvae will continue to cause damage. To remove the larvae, you should repot any badly infested plants. Gently wash old potting mix from the roots and thoroughly clean the container before re-potting into fresh premium potting mix. A great option recommended by Flower Power is Debco Premium Indoor Potting Mix, which has been formulated to be less prone to fungus gnats. Don't reuse the old mix for other plants, but you can sterilise it (for example, treat with boiling water or expose to sunlight for several days) and spread it in the garden to avoid wastage.

The organic pesticide eco-neem (active ingredient azadirachtin) is now registered as a fungus gnat treatment to be used on infested potting mix. Apply it as a soil drench following the recommended rates on the container. You may need to do this multiple times, several days apart, in order to remove the infestation completely. Check out Flower Power's handy video below on how to perform an eco-neem soil drench.


Found a bug on your indoor plant and need help to identify it? Check out this article, or take a photo and pop in to your local Flower Power Garden Centre for a chat with an expert horticulturist. They'll help you identify the pest and find the right products to treat the problem!