The bain of every indoor gardener's existence - fungus gnats!

The bain of every indoor gardener's existence - fungus gnats!

If you have indoor plants, chances are you’ve got fungus gnats flying around your home.

Fungus gnats (FGs) are those annoying little insects that buzz in front of your face while you’re trying to watch TV or read or talk to a friend. You swat at them but you can rarely catch them!

Aside from being very annoying, fungus gnats can also damage your indoor plants. The larvae live in the soil and feed on the roots of the plant leading to a “failure to thrive” – you might notice your plant has deformed leaves, isn’t growing new foliage and looks like it’s struggling. Adult gnats (the flying bugs you see) don’t feed on plant foliage but they are very annoying, as we’ve already discussed, and are part of the life cycle so getting rid of them too is an important part of the control process.

So, how do you control fungus gnats? I employ a range of pest management techniques, which I’ll share with you here.

The FG life cycle

To effectively control any pest, it’s important to understand its life cycle. An FG’s life cycle is very quick – around 17 days from the eggs being laid to adults emerging from the soil. As one adult FG can lay up to 150 eggs, getting on top of them can be a challenge.

FGs love a temperature of around 24⁰C (75⁰F) and moist soil, making indoor plants the perfect host.

How I control FGs

As with any Integrated Pest Management program, I use a variety of methods to control FGs.

  • Don’t overwater plants – a dryer soil means less FGs. Most indoor plants are overwatered anyway so this kills two birds with one stone!
  • Quarantine and treat new plants with neem oil drench.
  • Check my potting mix and treat if needed.
  • Use a neem oil drench regularly on my watering schedule.
  • Use FG sticky traps – see below for a recipe.
  • If trying to control an infestation, be patient and treat regularly to get on top of the breeding cycle.

What is neem oil?

A bottle of neem oil

 Neem oil is a botanical insecticide you can use on a range of pests including FGs. I love it and use it in a range of ways to control other pests like aphids and mealy bugs. You can buy neem oil at most nurseries and some hardware stores, or online if you live remotely.

I use neem oil as a drench (diluted with water using the specified ratios) and as a spray (also diluted with water) that I use on the plant’s foliage to kill pests.

When using the drench, I add neem oil to my water while doing my regular scheduled watering around the house. If I have a moderate infestation of FGs, I’ll do neem oil drench fortnightly for around 8 weeks or until I notice I’ve got on top of the issue. I then use a drench every 6-8 weeks after that as maintenance.

Sticky traps

Sticky traps catch and kill the adult insects making them a great addition to your pest-control arsenal. Simply mix together all the ingredients below, pour into little bowls and place them around your plants to catch the little buggers! Change the liquid regularly to ensure it remains effective.

Sticky trap ingredients:

  • ½ cup warm water
  • 2 tbsp apple cider vinegar
  • 1 tbsp sugar
  • About 6 drops liquid dish soap
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