❚ All products chosen independently by our writers. We may receive commission via affiliate links. See affiliates FAQs.

How to get rid of house plant flies (fungus gnats)

Published: Friday, 6 September 2024 at 9:00 pm

We show you how to tackle house plant flies, also known as fungus gnats or sciarid flies, with advice from house plant expert Jane Perrone

JanFebMarAprMayJunJulAugSepOctNovDecTo Doyesyesyesyesyesyesyesyesyesyesyes**yes

Save

Do you have small black flies living in your house plant compost? Or hovering around your house plants? These are fungus gnats, also known as house plant flies and sciarid flies. They're mostly harmless – adult gnats cause little or no harm to plants, but they can become a nuisance in the home. Their tiny worm-like larvae live in the top 5-8cm of compost, where they feed on algae, fungi and plant roots. Healthy house plants usually tolerate this minor root damage, but the larvae can harm seedlings or weak plants.

Ad

How to identify fungus gnats

Fungus gnats are small black flies that fly around house plants and live in house plant compost. You may mistake them for fruit flies – but if they're in and around your house plants, they're likely to be sciarid flies.

How to get rid of fungus gnats

Getting rid of fungus gnats is easier than you might think. Simply by watering less often and using a gravel mulch you can break the fungus gnat lifecycle and stop them breeding in your house plant compost. But there are other ways, too. We list four ways to get rid of fungus gnats, below.

Want to see this content?

This page contains content provided by Squirrel. We ask for your permission before anything is loaded, as Squirrel may use cookies and other technologies. To view this content, choose 'Accept and continue' to allow Squirrel and its required purposes.

Accept and continue

Passionate about your indoor jungle? Find a gorgeous new plant container with our carefully curated collection of the 10 best indoor plant pots, or create an eye-catching display with one these stylish indoor plant stands. Alternatively, you might find our selection of the best indoor greenhouses just what you need to nurture tender specimens?

You Will Need

Step 1: Water less often

Watering the compost

Watering the compost

Fungus gnat larvae need damp compost to live, as this is where algae and fungi thrive, on which the larvae feed. Simply by allowing the compost dry out between waterings, you’ll greatly reduce the fungus gnat population.

Step 2: Use a gravel mulch

Covering the compost with gravel

Covering the compost with gravel

Most commercially available composts have been sterilised, so they don’t contain fungus gnat larvae. If you cover the surface of the compost with a 1cm-thick mulch of gravel, grit or ornamental glass pebbles, this will stop house plant flies from being able to lay their eggs. Avoid using home-made garden compost indoors, as this can be a source of fungus gnats.

Want to see this content?

This page contains content provided by Squirrel. We ask for your permission before anything is loaded, as Squirrel may use cookies and other technologies. To view this content, choose 'Accept and continue' to allow Squirrel and its required purposes.

Accept and continue

Step 3: Use sticky traps

Yellow sticky trap

Yellow sticky trap

Yellow sticky traps work by trapping the adult fungus gnats and breaking their lifecycle. Simply hang up a trap near affected plants, or attach it to a bamboo cane inserted into the compost. Keep the trap near soil level, as gnats rarely fly far from the compost. Avoid hanging the traps outside as you'll also trap butterflies and hoverflies.

Want to see this content?

This page contains content provided by Squirrel. We ask for your permission before anything is loaded, as Squirrel may use cookies and other technologies. To view this content, choose 'Accept and continue' to allow Squirrel and its required purposes.

Accept and continue

Step 4: Use biological control

Carnivorous sundew plant

Carnivorous sundew plant

If you have lots of house plants, it may be worth applying a biological control. To tackle fungus gnats use the nematode Steinernema feltiae, predatory mites or rove beetle larvae, and apply according to the pack instructions. These are available from online suppliers. While nematodes can be used in the home, the mites and beetle larvae are best used only in the contained environment of a greenhouse or sealed conservatory. If you’ve only got a few house plants, try growing a sundew (Drosera) nearby, as these sticky carnivorous plants are very good at trapping fungus gnats.

Want to see this content?

This page contains content provided by Squirrel. We ask for your permission before anything is loaded, as Squirrel may use cookies and other technologies. To view this content, choose 'Accept and continue' to allow Squirrel and its required purposes.

Accept and continue

Ad

Want to see this content?

This page contains content provided by Google reCAPTCHA. We ask for your permission before anything is loaded, as Google reCAPTCHA may use cookies and other technologies. To view this content, choose 'Accept and continue' to allow Google reCAPTCHA and its required purposes.

Accept and continue

Loading...

Ad

Ad

Don't miss out this Winter

Enjoy expert advice on what to plant and grow this winter, and how to prepare your plot for the year ahead. Enjoy, 6 months for just £31.99

Subscribe now

Email signup promotion with bold text “Your garden deserves a great deal” and a smartphone displaying a Gardeners’ World offers email about a free allium bumper collection, over a soft-focus purple floral background.

Great gardening savings - straight to your inbox

Sign up to the BBC Gardeners’ World offers newsletter for exclusive deals, seasonal savings, and early access to special promotions.

Sign up now

Loading...

Ad

Loading...

Loading...