If you find maggot-like larvae in a plant pot, identify them before adding any treatment. Fungus gnat larvae, crop-specific root maggots and flies feeding on decaying material are different problems. Wilting or yellow leaves alone do not prove that larvae are damaging roots.
Look at the larvae and the adult insects
Photograph a specimen beside a ruler and note where you found it: on decaying debris, in the growing mix or inside a damaged root. Record the plant species and whether the pot is indoors or outside. Avoid repeatedly uprooting an otherwise healthy plant just to search.
Fungus gnat larvae are small, slender and translucent, with a dark head capsule. Adults are tiny gnat-like flies commonly associated with damp potting mix. Larger pale larvae without that appearance may need a different diagnosis. Use a local extension service if you cannot identify them from clear photographs.
If the organism is segmented like an earthworm or has obvious legs, start with the broader worm-like organisms in pots guide. A treatment for one fly larva will not necessarily control another organism.
Check growing conditions before assuming root attack
Inspect drainage, standing water in an outer cover pot and decaying material on the surface. A plant wilting in wet mix may have unhealthy roots for several reasons. Larvae present nearby are not enough to establish the cause.
Remove fallen debris and sources of decay without stripping healthy roots. Adjust watering to the particular plant, allowing the surface to dry between waterings where appropriate. Do not severely dry a moisture-loving plant just to make its pot less attractive to insects.
For confirmed fungus gnats, target the right stage
Yellow sticky cards can help monitor adult activity. Keep them where they will not contact leaves, pets or people. Fewer trapped adults are encouraging, but adult traps alone do not establish that all larvae in the mix are gone.
Maryland Extension describes Bti products labeled for indoor plants and fungus gnat larvae. Use only a product whose label covers your plant, setting, pest and application. Follow its rate and repeat-treatment directions rather than using a generic homemade drench recipe.
UC IPM also describes the beneficial nematode Steinernema feltiae for fungus gnats. Living products have storage and application requirements. That does not mean every product sold as beneficial nematodes controls every maggot.
For suspected root-feeding maggots, get a crop-specific diagnosis
Note the host plant and actual root damage. Some root maggots affect particular vegetable crops, so advice for a cabbage seedling is not automatically suitable for a houseplant. Ask a diagnostic service about management for the identified pest and location.
Keep affected pots separate where practical while investigating, and avoid moving infested mix into other containers. If roots are badly damaged or the medium has failed, discuss whether careful repotting or discarding the plant is appropriate. Repotting every healthy plant after seeing one fly can cause unnecessary disturbance.
Avoid broad household remedies
Do not pour boiling water, salt or vinegar into a living plant’s root zone. These are not a suitable general treatment plan for a potted plant. Likewise, do not turn a foliar insecticide into a soil drench unless its label permits that use.
“Natural” does not mean harmless, and a layer of diatomaceous earth is not a dependable answer to every larva in damp mix. Start with identification and conditions, then select a permitted targeted option if needed.
Check whether the response is working
Keep dated notes on adult catches, visible larvae and new plant growth. Old yellow leaves may not recover, so assess the trend rather than expecting immediate cosmetic improvement. Persistent decline despite corrected care deserves diagnosis, not repeated combinations of unrelated treatments.
