Fungus gnats are a common pest that can plague carnivorous plants. They are small and dark in color and can often be seen flying near the surface of damp soil. While adult fungus gnats aren’t harmful to carnivorous plants (and may even be a free source of food!), the larvae can cause severe damage.

Fungus gnat larva feed on fungi and organic matter in soil, but they also feed on plant root, stems, and leaves. The larvae have also been known to spread pathogenic fungi. Infested carnivorous plants may become unhealthy and slow their growth while seedlings and Butterworts can be lost altogether, yikes!

Fungus Gnat Larvae

Fungus Gnat Larvae

Fungus Gnat Prevention

There are a several of ways to combat fungus gnats, the best of which is to prevent them taking up residence in the first place. Preventative measures include:

  • Ensuring there is adequate airflow around plants to discourage fungal growth. This creates an unattractive location for fungus gnats to lay eggs.
  • Covering soil with at least 1/4 of an inch of coarse sand or gravel to create a physical barrier between the gnats and the soil.
  • Allowing the soil to dry out between waterings. Caution: Only use this method for plants like Mexican Butterworts that can tolerate dryer conditions.
  • Isolating infested containers to keep uncontaminated plants from becoming infested.

 

An adult Fungus Gnat preparing to lay eggs in damp soil

An adult fungus gnat preparing to lay eggs in damp soil

 

How to Fight an Infestation

If preventative measures have failed, there are several ways to combat an infestation:

 

CheckmarkPhysical removal

One way is to replace the soil in the pot. Remove the plant from the pot and discard the contaminated soil. Rinse the roots and container with clean water to knock off remaining larvae. Also try to kill any adult gnats. After removing all of the contaminated soil and clearing the area of adult gnats, repot the plant with fresh soil and then follow ongoing preventative measures.

 

CheckmarkOrganic pesticides

If repotting isn’t an option, natural pesticides are another way to manage infestations. Products that target larvae systemically like Cold Pressed Neem soil drenches or biological larvicides like Gnatrol or Mosquito Dunks are all options known to be safe for many carnivorous plants.