Get Rid Of Black Fly On Plants (Updated 2024)

Last Updated on April 15, 2024 by Real Men Sow

Are small black flies in your compost and hovering over your house plants? These are the fungus gnats also known as sciarid flies or house plant flies.

After my 2012 post, it’s only fair if I write an updated blog on how to get rid of black flies.— Because their annoying buzzing deserves another post!

Are Black Flies Harmful In The Garden

Although they are generally harmless, adult gnats can cause minimal or no damage to plants. However, they can be a nuisance in your home. The larvae are tiny, worm-like and live in the top 5 to 8 cm of compost. They feed on plant roots, fungi, algae, and fungi. This minor root damage is usually not harmful to healthy houseplants, but it can cause injury to seedlings and weak plants.

How To Identify Black Fly (Fungus Gnats)

Fungus gnats, small black flies, are found around houseplants. They live in compost and fly around the house. They may look like fruit flies, but they are likely to be Sciarid flies.

How To Get Rid Of Black Fly (Fungus Gnats)

It is much easier to get rid of fungus-gnats than you may think. You can stop fungus gnats from breeding in your compost by using gravel mulch and watering less frequently. There are many other methods. Below are four methods to eliminate fungus gnats.


  • House plants
  • Yellow sticky traps
  • Grit mulch
  • Biological control for fungus gnats

Step-By-Step To Get Rid Of Black Flies In Your Garden

Step 1 – Water Less Often

The larvae of fungus gnats require damp compost in order to survive. This is because it is where the algae and fungi thrive and on which the larvae feed. Allow the compost to dry between waterings and you will greatly reduce the number of fungus gnats.

Step 2 – Use a Gravel Mulch

Commercially available composts are sterilized so that they don’t have fungus-gnat larvae. The compost can be covered with 1 cm thick mulch of gravel, grit, or ornamental glass beads to stop houseplant flies laying eggs. You should avoid using garden compost made at home indoors as it can attract fungus gnats.

Step 3 – Use Sticky Traps

The yellow sticky traps trap the adult fungus larvae and end their life cycle. You can either hang a trap close to the plants or attach it with a bamboo stick. The trap should be kept at soil level as gnats are unlikely to fly too far from the compost. You can also put hanging traps outside can trap hoverflies and butterflies.

Step 4 – Use Biological Control

It may be worthwhile to apply a biological control if you have many houseplants. Use the nematode Steinernema feltiae, predatory mites, or rove beetle larvae to combat fungus gnats. These can be purchased online, just follow the instructions on the pack.

Although nematodes are safe to use in your home, beetle larvae and mites should be kept in a closed conservatory or greenhouse. A sundew (Drosera), a sticky carnivorous plant, can be grown nearby if you only have a few plants. Also, they are excellent at trapping fungus and gnats.

Real Men Sow
Real Men Sow

Hello, I’m Pete and I’m currently based in the west of Scotland, in a small place called Rosneath, where I’m exploring my garden adventures. I personally started gardening around 6 years ago and initially, I started out by growing my favorite fruits and berries, such as strawberries, Raspberries & Gooseberries. Since then I’ve added a lot of vegetables and working closely with my neighbor, it’s been a lot of fun.