Common Plant Problems: Fungus Gnats 

What’s that swarming around your pothos? Ugh, not the gnats again!

Fungus gnats are one of the most persistent house plant pests, and most plant parents will have to deal with them at one time or another. Adult gnats like to lay their eggs in damp potting soil, where their larvae can find fungi or fallen plant matter to snack on. Plants that like to have wet soil, or those that have been overwatered (oops) are the most at-risk of a fungus gnat infestation.

What to Look for

Wondering if you have fungus gnats? They don’t cause the plants themselves any harm, but check in and around them for any signs.

• Small gray or black flying insects near the infested plant
• Gnats near windows, lamps or other light sources

Treat Your Indoor Plant

To get rid of fungus gnats, you’ve got to serve an eviction notice to the adults (the ones that fly) and their larvae (which are hidden in the soil).

• Place sticky paper traps on top of the soil, or on stakes just above it, around the infested plant. Opt for yellow paper traps, if possible, which will attract them better than other colors.
• Use mosquito dunks containing Bacillus thuringiensis subspecies isrealensis, a bacterium known to infect fungus gnat larvae. Allow a dunk to soak in water overnight and water the affected plants to treat the soil.

Practice Fungus Gnat Prevention

Plants that need moist soil 24/7 may need more monitoring for fungus gnats, and having these tricks in mind will help you check for gnats before they become a full-on infestation.

• Water plants from the bottom by sitting their planters in standing water, which gets moisture to the roots but keeps the surface dry.
• Layer a fine gravel or coarse shell/sand on top of the plant’s soil, about one inch thick, so fungus gnats can’t lay eggs there.
• Use sticky paper traps on stakes in your planter to catch adult gnats as they fly off the soil. This captures some of the pests while also alerting you to their presence.

The good news about fungus gnats is that, unlike other pests, they won’t damage your plant one bit during their stay. And though they can be annoying to see flitting about your indoor garden, with some easy treatments and preventive measures, your plants can be gnat-free in no time.