How to get rid of fungus gnats

Safety tip: Always wear the appropriate safety equipment (safety glasses, gloves, and a mask, for example) and always follow the instructions for the product or equipment. Always wear gloves and a mask when handling potting mix, mulch and compost, and store products out of the reach of children and pets.  

What are fungus gnats? 

Fungus gnats are small flying insects that often infest potting mix and soil, and they can cause great damage to potted plants if they’re allowed to spread and multiply. Their larvae feed off fungus and other decaying matter, which is where their name derives from. The larvae also chew on plant roots, stunting growth and weakening the health of the plant. 

Fungus gnats must be controlled during this larval lifecycle stage; they are almost impossible to control once they have matured into their adult flying form. Adult fungus gnats don’t bite humans or damage plants, but they are annoying, and they will go on to infect other plants by laying eggs in other pots if they are not controlled, prolonging the infestation. They are also known to spread plant diseases such as Pythium and Fusarium. 

How do I identify fungus gnats? 

Adult fungus gnats basically look like small, delicate mosquitoes. They are small (3 to 4mm in length) and predominately black, with long legs and segmented antennae. They have a single set of clear, highly veined wings – look for the ‘Y’ pattern in the veins at the end of the wings. Fungus gnats are not good fliers – they tend to stay close to where they were born.  

The larval gnats are translucent / white worms 5mm to 8mm in length, with a small, shiny black head. They can be found in potting mix or soil. 

How do I control fungus gnats? 

Be vigilant! That’s the key to breaking their lifecycle. The adult flying gnats are difficult to eradicate, so begin treatment as soon as you spot them. Regularly inspect your plants for pests and disease. The quicker start treatment, the easier it will be.

Watering: Allow pots to dry out in between watering; do not over-water your plants. 

Apply insecticide: Apply Eco Neem as a soil drench. This will control the larval form in pots. (More than one application may be required.)

Place a barrier: Place a 6mm to 10mm layer of gnat barrier, sand or gravel on top of the pot. This prevents the adults from laying eggs in the pot, breaking the lifecycle.

Quarantine: Isolate infected plants so that they don’t cross-contaminate other plants. Keep plants isolated until the control is complete.

Lay a trap: Sticky traps can be placed in the pots of affected plants to capture flying fungus gnats.

Control insects around the home 

Check out our guide to controlling insects in and around the home.