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Notebook · Guide 1 October 2026 · houseplants

Houseplant pests: how to identify them and what actually works

Fungus gnats, red spider mite, mealybugs, scale, aphids and thrips — how to spot each one, the simple fixes that work, the biological controls, and when to bin the plant.

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A natural-history study sheet of houseplant pests at enlarged matched scale on cream: a fungus gnat, a red spider mite, a mealybug with white waxy coating, a scale insect, a green aphid and a thrips.
1Fungus gnat, red spider mite, mealybug, scale insect, aphid and thrips.

Most houseplant pests arrive on a new plant, or move in because conditions favour them — wet compost for fungus gnats, warm dry air for spider mites. So the best control is usually the cheapest: inspect new plants, quarantine them, and change the conditions that let pests thrive. Here's how to tell what you've got.

In pictures

  1. A leaf of a houseplant showing fine pale stippling/mottling on its upper surface and fine silk webbing between leaf and stem.
    2Red spider mite: fine mottling on the leaves and silk webbing.
  2. Fluffy white mealybugs clustered in the leaf joints of a houseplant, being wiped away with a damp cloth.
    3Wipe mealybugs off with a damp cloth.
  3. A yellow sticky trap on a stick in a houseplant pot with a few small dark flies stuck to it, compost surface dry.
    4Yellow sticky traps catch adult fungus gnats.

01Fungus gnats (sciarid flies)

  • What you see: small dark flies, 3–4mm, flitting around the compost.
  • Do they matter? The adult flies don't damage plants. The larvae mostly eat decaying matter, and only harm seedlings and soft cuttings.
  • Why: constantly wet compost.
  • Fix: let the compost dry out more between waterings; use yellow sticky traps for the adults; top the compost with grit. Biological controls include the nematode Steinernema feltiae and predatory mites. See overwatering.

02Red spider mite

  • What you see: fine pale mottling on the upper side of leaves; fine silk webbing in bad infestations.
  • Why: warm, dry air. They're worst from March to October.
  • Fix: misting helps but won't control them on its own. The predatory mite Phytoseiulus persimilis is very effective — release it early, before numbers build.

03Mealybugs

  • What you see: fluffy white wax in the leaf joints, sticky honeydew, black sooty mould.
  • Fix: wipe off small colonies. The ladybird Cryptolaemus montrouzieri and parasitic wasps control them, but need warmth (most effective May to September). For a heavily infested plant, the RHS notes binning it can be easier than treating it.

04Scale insects

  • What you see: small shell-like bumps on stems and under leaves, plus sticky honeydew.
  • Fix: scrape them off by hand; light infestations can be tolerated.

05Aphids

  • What you see: clusters of small green or black insects on shoot tips; curled leaves; white cast skins.
  • Fix: squash or wipe off colonies by hand.

06Thrips

  • What you see: dull or silvery leaves with tiny dark, varnish-like spots.
  • Fix: biological controls such as predatory mites and the bug Orius laevigatus.

07Prevention

  1. Check new plants carefully, including under the leaves.
  2. Quarantine them for a few weeks, so any eggs or young pests have time to show up before they spread.
  3. Check every plant when you water.
  4. Don't mix biological controls with pesticides — the pesticide kills the predators.
Save your money
The RHS doesn't recommend pesticides for houseplants. A damp cloth, a sticky trap and drier compost fix most problems.
Sometimes binning is cheaper. A badly infested, inexpensive plant isn't worth treating for months.

How we checked this

Every care and safety claim on this page is verified against horticultural and veterinary sources.

Sources: RHS — Indoor plants: sap-feeding insects · RHS — Fungus gnats (sciarid flies) · RHS — Glasshouse red spider mite · RHS — Mealybug

Checked 1 October 2026. If our advice ever conflicts with the RHS, believe them and tell us.