Fungus Gnats Not a Home’s Best Friend

Talking to my family they would quickly tell you that I have always loved plants. All plants. I would ask about any and every plant I could. Like most plant people I have always had houseplants. If you have houseplants it is more likely than not that you have dealt with or deal with the tiny little squatters known as fungus gnats.

The adult fungus gnat is harmless to people. They may annoy you greatly as they buzz around your face while you sit near your favorite houseplant but they cannot bite you. The adults also are harmless to your plants. It is their tiny little larvae that is the problem.

These small larvae like to consume terrestrial algae in the growth medium, fungus, and your plants’ roots (Cransaw, Cloyd, 2015). The damage they do to your roots can lead to weakened and unhealthy plants. A simple way to determine if you have fungus gnats and not just fruit flies is to place a slice of raw potato on your soil. After a day lift it. They are attracted to the slice of potato and will gather under it.

I am pretty anti-pesticide in most cases. That includes my houseplants. A great method for evicting these little creatures is allowing your soil to dry out (Cransaw, Cloyd, 2015). In the least allow the top one to two inches to dry. This will inhibit the eggs from hatching. It will also make the soil less appealing for the adult female fungus gnats in which to lay her eggs.

Another method is yellow sticky traps to catch the adults (Cransaw, Cloyd, 2015). Personally, these kinds of traps will not work around my house. I have a curious semi-long-haired cat and removing a sticky trap from her fur would be painful for all parties involved. So instead, I bought a few more houseplants, because there is always space for one more houseplant.

The houseplants I am talking about are Sundews (Drosera spp). These small plants form sticky little pads on them that the fungus gnat adults land on. They also catch any fruit flies, flies, and mosquitoes that happen to venture into the house and land on them. The care for them is pretty simple but they must be watered with either distilled water or rainwater (Aloi, 2020). Tap water has too many dissolved minerals in it and they will die. Their growing medium needs to be kept damp but not waterlogged, and that is all you need to know how to care for them. They help break the adult cycle and there is a new and interesting houseplant around.

Another non-pesticide method to control them is the predatory nematode Steinernema feltiae (Cransaw, Cloyd, 2015). These nematodes will hunt down and consume the fungus gnat larvae. The larvae die within three to four days of being infested by the nematode, helping break the cycle in your home.

Whatever method you choose may your houseplants be healthy and your face free of annoying gnats.

References:

Cransaw, W. S., & Cloyd, R. A. (2015, July 27). Fungus Gnats as Houseplant and Indoor Pests - 5.584. Extension.

https://extension.colostate.edu/topic-areas/insects/fungus-gnats-as-houseplant-and-indoor-pests-5-584/

Aloi, P. (2020, November 16). How to Grow Sundew Plants. The Spruce.

https://www.thespruce.com/growing-sundew-plants-5082980