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Fungus Gnats are a common problem on houseplants. In this article we will look at the root cause of fungus gnats and how to treat them.

| What Are They | What They Do | Why are they on my plant || Identify |Treat | Prevent |

What are Fungus Gnats?

Fungus Gnats are small winged insects that have dark bodies and measure in between 2-3mm. They thrive in moist conditions and the larvae feed on decaying organic matter. Adult females can produce 100-150 eggs throughout their life. They can complete their life cycle in 3-4 weeks depending on the temperature.

Fungus Gnat Life Cycle


What do Fungus Gnats do?

Luckily for us, Gnats don’t pose much of a risk to our houseplants. The larvae feed on organic matter found in potting soil.  They can occasionally feed on the roots of the plants so it is still a good idea to get rid of them ASAP!

Why are they on my plant?

Gnats live in the potting soil of plants. They love warm moist conditions and thrive in potting soil where the surface of the soil remains wet for extended periods of time. They commonly appear where plants are over watered. 

How to Identify Fungus Gnats

They can be seen flying around and above the potting soil of the affected plants pot. If you look closely at the soil, you may also see them crawling around. They resemble fruit flies but aren’t very good fliers so they will tend to run away rather than fly away if you approach them! They also tend to group around the area where the larvae are feeding and where they are laying eggs. 

Fungus Gnat on leaf

Dark-winged fungus gnat, Sciaridae.

How to treat Fungus Gnats

There are many ways to treat them.

  • Yellow sticky traps are a great way to get rid of gnats. 
  • Neem Oil Soil Drench Make a neem solution combining castille or dish soap. To one liter of water add 1tsp of neem and 1tsp of castille soap. Water your plant thoroughly with the solution, ensuring to saturate all of the soil.
  • Change the Top Soil Gnats eggs and larvae live in the top 2-3 inches of soil. Changing out the top 2-3inches of topsoil can get rid of the gnats for good.

How to prevent Fungus Gnats

Preventing Fungus Gnats is as simple as letting the soil dry out between waterings. Many of our plants love consistently moist soil (ferns, calatheas) We can still allow the top inch of soil to dry out between watering with no ill effect on the plant. This will keep gnats at bay. Having soil that is consistently moist or wet on the surface is also a sign of overwatering and can lead to other problems like root rot. 


Happy gardening!


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