Adult fungus gnat (Johnny N. Dell, Bugwood.org)
Adult fungus gnat (Whitney Cranshaw, Colorado State University, Bugwood.org)
Fungus gnat larvae (Whitney Cranshaw, Colorado State University, Bugwood.org)
- smaller, dark, delicate-looking flies similar in appearance to mosquitoes
- light gray to clear wings
- long, slender legs
- segmented antennae
- eggs and larvae nest in soil/moist organic material
- usually originate from soil in potted plants
- can develop in soil or mulch outside of building
- attracted to light (e.g., windows and exterior lighting)
- larvae feed on fungi in soil, potting mix, mulch, etc.
- flies inside are a nuisance
- when present in large numbers, larvae can damage roots and stunt growth of seedlings and young plants
- Locate breeding susbstrate and remove or alter.
- Do not overwater plants.
- Let soil in potted plants dry out between watering.
- Keep exterior doors closed, install screen doors, or install automatic door closers.
- Exclude fly entry via caulking, weather stripping, door sweeps, screens, etc., especially around windows and doors.
- If flies are coming from outside, consider changing exterior lighting to sodium vapor lighting.
- Use nematode-based insecticides (e.g., Gnatrol) on soil of affected potted plants.
Fungus Gnats in the Home fact sheet
IPM for Flies: Integrated Pest Management in Sensitive Environments (University of Nebraska-Lincoln Extension)