What can you do about fungus gnats in houseplants?
In short
Start by checking the insect and the pot. Fungus gnats are associated with damp growing mix, but not every small fly is one. Review watering, monitor adults, and keep the plant’s moisture needs in view rather than drying every pot indiscriminately.
In this guide
Check the insect before choosing a response
Minnesota Extension describes fungus gnats as small, slender, dark flies associated with houseplants and damp, organic growing media. Look at where you see them and take a close photo if possible. Flies elsewhere in the home need not have the same source, so a pot nearby is not proof.
Review a constantly wet growing mix
The RHS advises avoiding overwatering and allowing mix to dry only as far as the plant can tolerate. Established plants are usually not damaged, while seedlings and soft cuttings deserve closer attention. Check your actual growing method before applying advice meant for a conventional pot of compost.
Source: RHS: Fungus gnats
Use sticky traps to monitor adults
Wisconsin Extension recommends yellow sticky cards to catch adults and track their numbers. They do not remove the developing stages in the mix, so a trap is not the whole solution. Its guidance also distinguishes fungus gnats from fruit flies; vinegar traps used for fruit flies are not a reliable monitoring method here.
Source: University of Wisconsin Extension: Fungus gnats on houseplants
Keep observations tied to the affected pot
Name the pot and location, note the date, and photograph both the insect and plant when possible. Record moisture checks and what you changed. When comparing trap catches, keep the trap position and observation period consistent; a new card and an old card are not a useful direct comparison.
If plant condition worsens or the insect remains unidentified, take those photos and notes to a local plant adviser. Do not stack unrelated treatments because a first guess was uncertain. Keep this guide’s monitoring steps separate from any treatment instructions you receive for a confirmed problem.
Your checklist
Tick off what you have already checked. Nothing is saved.
Frequently asked questions
Will one sticky trap remove the whole infestation?
No. It catches adults, not all stages developing in the growing mix. Review conditions and monitor the result instead of treating the trap as a complete fix.
Must I throw away a plant when I see fungus gnats?
Usually not. Established plants are generally not damaged, but young plants and cuttings need closer attention. Check both the insect and the plant condition.
Keep the pest observation with the plant
Use the Plantly journal for dated photos, moisture notes, and actions taken. A shared household can see which pot you are monitoring and what has already been done. The journal keeps evidence together; it does not confirm an insect identification.
Explore the related Plantly feature
Sources
- University of Minnesota Extension: Fungus gnatsapps.extension.umn.edu
- RHS: Fungus gnatsrhs.org.uk
- University of Wisconsin Extension: Fungus gnats on houseplantshort.extension.wisc.edu
Checked on 12 October 2026. This guide does not replace advice for your individual plant.
