Guides
What are these tiny flies around my houseplants?
Several small insects get called gnats, but they need different treatment. Watch where they sit and what happens when you disturb the pot or the leaves.
Watch where they come from
Tap the pot and then the leaves. Dark flies that walk over the compost are usually fungus gnats, and control starts with watering less. White flies that lift from leaf undersides are whitefly, and treatment is on the plant. Small brown flies near fruit, bins or drains are usually fruit flies, not a plant problem.
Work down the list
Fungus gnats
- What you would see
- Dark grey-black flies a few millimetres long, running over the compost surface and flying up in a short weak flight when the pot is moved.
- The check
- Push a finger into the compost. Fungus gnat larvae live in damp compost with organic matter in it. Letting the top few centimetres dry between waterings ends most infestations on its own.
Whitefly
- What you would see
- Tiny white moth-like insects clinging to the undersides of leaves and rising in a cloud when the plant is knocked, with sticky leaves beneath them.
- The check
- Turn a leaf over. Whitefly stay on the plant and do not walk on the compost. Sticky leaves help separate them from harmless flies.
Fruit flies from the kitchen
- What you would see
- Small tan or brown flies with red eyes, hovering around fruit bowls, bins, drains and recycling instead of around the plants.
- The check
- Move the fruit bowl for two days. Fruit flies breed on fermenting material, not compost. They leave when the food source goes.
Thrips
- What you would see
- Slender dark specks a millimetre or two long that dart rather than fly, on leaves that are turning silvery and stippled with dark varnish spots.
- The check
- Tap a leaf over a sheet of white paper. Thin dark slivers that run rather than fly are thrips. The silvery leaf damage separates them from harmless flies.
Shore flies
- What you would see
- Stockier dark flies with clear spots on the wings, on the compost of plants that stand permanently wet, often alongside a film of algae.
- The check
- Look at the compost surface for green algal slime. Shore flies feed on algae rather than roots. They do not harm the plant, and drying the surface removes them.
Flies from fresh compost
- What you would see
- A short-lived burst of flies from a plant potted on within the last few weeks, fading without treatment.
- The check
- Note the date. An open bag of compost stored damp breeds gnats, and a fresh sealed bag prevents the next round. Store what is left dry and closed.
Still not sure which one it is? Photograph the leaf and compare it against the full library.