Eliminating Fungus Gnats from Houseplants Naturally

I have annoying flies on my three living room plants—maybe fruit flies? How do I get rid of them without harming my plants? I'm not a green thumb but have kept these alive for 8 months.

Expert Advice

They look like fruit flies but are actually fungus gnats. Adults are annoying but harmless; each lives about 5 days. The key is eliminating the next generation—larvae in the top soil layer that feed on decaying organic matter (pine bark in potting mix, decaying roots).

Effective Controls

• Dry the soil: Keep soil as dry as possible. Remove loose surface soil and add a light layer of coarse coir, sand, or diatomaceous earth—their sharp edges damage larvae. Fine peat moss also deters them.
• Potato traps: Place ½-inch raw potato slices on the soil surface to attract larvae. Discard after a day with larvae inside. Repeat until no larvae appear.
• Biological controls: "Knock-Out Gnats" (Gardens Alive, ~$20) or "Gnat Not" (parasitic nematodes on a sponge, rinsed into water and applied to soil).

Detection & Prevention

Detection: Add a little water and watch closely for tiny larvae swimming in pooled water on the soil surface.

Prevention: Use sterile, bark-free potting mixes with ample perlite for drainage. Fungus gnats almost always trace back to overwatering and/or poor soil quality.

Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC
wcreed@HorticulturalHelp.com