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Many indoor plant owners complain of tiny bugs hovering over their plants. These bugs are known as fungus gnats. If left untreated, they can cause damage to your potted treasures.
This guide shares some easy and effective tips on preventing and getting rid of fungus gnats. Let us know if you have any questions. We’d be happy to assist.
What are fungus gnats?
In the adult stage of their lifecycle, fungus gnats are commonly mistaken for fruit flies. They are winged and are usually dark grey or black in colour.
These pests live off decaying organic matter. They reproduce by laying eggs in the soil and can grow from an egg to adult in a span of three weeks. Fungus gnats typically lay around 300 eggs at once, so it’s key to take swift action if you want to protect your plant from an infestation.
While adult fungus gnats can be annoying to deal with, they don’t really harm our plants. It’s the pot-dwelling larvae that cause the real damage. They love feeding on organic matter in pots, including plant roots and seedlings. This can cause growth issues in plants.
How to protect your plants from fungus gnats
It’s key to target both the larvae in the pot and the winged adults if you want to avoid a fungus gnat infestation.
Below are some effective ways to protect your plants from fungus gnats:
Don’t water your plants too frequently
Fungus gnats thrive in damp potting mixes, so try to keep your mix as dry as possible. Dry mix is an inhospitable environment for any existing larvae and it will discourage adults from laying eggs. Try to ensure the top three centimetres of mix are dry.
Allow the potting mix to dry out before watering your plants again, and do not water too frequently. I also recommend emptying any stagnant water sitting in a pot saucer. 
Trap adult fungus gnats
Trapping adult fungus gnats prevents them from laying eggs and causing an infestation.
Fungus gnats are attracted to the colour yellow, so using yellow sticky insect traps is a great method. It may take approximately a month to capture any larvae that hatch to gnats. Don't forget to replace the traps regularly to avoid congestion.
If you decide to move your plants outdoors, use protected traps with cages.
Kill the larvae
For non-edible plants, I recommend drenching your pot with Neem oil to kill any larvae residing in the potting mix. Make sure to read and follow the instructions on the oil bottle before use.
Let the pot dry for over a week before drenching again. Keep applying the oil weekly until the adult flies disappear for at least three to four weeks. 
Repot your plants
Use fresh potting mix suited for indoor plants when repotting. Old potting mix may contain decaying matter like fine Pine bark and compost. Fungal gnat larvae are attracted to this decaying matter.
My guide on How to know when to repot your plants contains more information on potting mixes and when to replace them.
Create a barrier
Add a layer of mulch made from fine gravel or clean horticultural sand across the surface of your pots. You can use specialised gnat barriers to do this. Ensure the layer is no more than three centimetres thick.
These barriers can prevent adult fungus gnats from burrowing into the pot and laying eggs in the potting mix. They can also block the new adults from emerging once the larvae have matured.
Need more help with protecting your plants from fungus gnats?
The Bunnings Workshop community is here to assist if you have any specific questions about preventing or getting rid of fungus gnats. Feel free to start a new discussion and let us know your needs. We're here to help.
