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 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.
How to Fight an Infestation
If preventative measures have failed, there are several ways to combat an infestation:
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.