Common houseplant pests: fungus gnats, spider mites, mealybugs, scale and thrips

Start with identification, not a spray

Many problems that look like pests are not. Yellow leaves, brown tips and leaf drop also come from watering, light and temperature. Iowa State suggests checking that growing conditions suit the plant before blaming insects, and acting early while numbers are still low. Iowa State University Extension: insect pests of houseplants

We have not added photographs here. Pest identification needs accurate, close-up images; use the pictures on the institutional pages linked in each section, or ask a local extension service or garden advice service.

Fungus gnats

What you see: small, dark grey-brown flies, mostly 3–4 mm long, running over the mix or flying slowly around pots. Their larvae are pale with black heads and live in the mix.

What they do: the adults do not damage plants; they are a nuisance. Larvae feed mainly on fungi and decaying matter, though they can occasionally damage seedlings and young cuttings. They are associated with damp compost. RHS: fungus gnats

Least harmful steps: let the mix dry to the level that suits the plant before watering again, and empty saucers. Yellow sticky traps catch adults and show whether numbers are falling. University of Minnesota Extension: houseplant pests If gnats keep returning, check whether the pot drains properly; see overwatered or underwatered?

Spider mites

What you see: fine speckling or dull, bronzed leaves and, in heavier infestations, fine webbing. The mites themselves are tiny. To check, tap a leaf over a sheet of white paper and look for small moving specks. University of Minnesota Extension: houseplant pests

What they do: they feed on leaf cells, so leaves lose colour and vigour.

Least harmful steps: isolate the plant and rinse foliage, including the undersides, with lukewarm water where the plant tolerates it. Remove badly affected leaves. Insecticidal soaps and horticultural oils are options for indoor use when used according to the label. University of Minnesota Extension: houseplant pests

Mealybugs

What you see: small insects covered in white, cotton-like wax, gathered in leaf joints, leaf sheaths and between twining stems. Sticky honeydew and black sooty mould may follow. RHS: indoor plants, sap-feeding insects

What they do: they suck sap and weaken the plant. They are hard to eliminate because they hide in tight places and their wax protects them.

Least harmful steps: for a small infestation, Michigan State University Extension suggests dabbing individual insects with a cotton bud dipped in rubbing alcohol, touching the insect rather than the leaf. Test on one small area first, keep the plant isolated and check again regularly. Michigan State University Extension: mealybugs Heavily infested plants are often better discarded. Iowa State University Extension: insect pests of houseplants

Scale insects

What you see: small, raised, brown or grey bumps that do not move, often along the midrib and main veins on the underside of leaves and on stems. Sticky honeydew is a common clue. RHS: indoor plants, sap-feeding insects

What they do: they feed on sap and can cause yellowing and dieback. University of Maryland Extension: indoor plant insects

Least harmful steps: pick or gently scrub off small numbers and prune heavily infested shoots. Recheck every week or two, because young scale crawlers are hard to see.

Thrips

What you see: silvery or pale speckled patches on leaves, sometimes with tiny dark spots, and distorted new growth. The insects are slender and very small, generally more numerous on leaf undersides. RHS: indoor plants, sap-feeding insects

Least harmful steps: isolate the plant, remove badly marked leaves or flowers, and use sticky traps to monitor. Thrips are easier to detect by their damage than by sight, so confirm with a magnifying glass before you act. UC IPM: houseplant problems

Prevention and follow-up

1. Isolate new plants for one to two weeks so any pests have time to show. University of Minnesota Extension: houseplant pests
2. Look under leaves whenever you check or water.
3. Keep a note of the date, the pest, what you did and what you saw a week later.
4. Repeat checks: one round rarely clears a pest completely.

Products, their active ingredients and their legal use differ by country. We do not give doses: the label on the product you buy is the only reliable instruction. Keep products away from children and pets, and if anyone swallows one, contact a doctor or veterinarian; in Türkiye, people can call the poison line 114 (UZEM). This is general information, not veterinary or medical advice.

If a plant also has yellow leaves, work through yellow houseplant leaves as well. Plants brought indoors after summer need extra checks; see an autumn reset for houseplants.

If you share your home with cats or dogs, also read houseplants and pets before choosing new plants.

Common questions

Do fungus gnats mean I'm overwatering?

Often the mix is staying wet too long, but not always. Check the mix and drainage before changing anything else.

Is neem oil or washing-up liquid safe to use?

Homemade mixes have no standard strength, and some can damage leaves. A product labelled for houseplants comes with tested instructions; follow them.

Should I throw the plant away?

If a pest is widespread and keeps returning, discarding one plant can protect the others. Decide after a careful look, not in the first panic.