Thrips are some of the hardest houseplant pests to see and to stop. Adults are only 1–2 mm long, they hide in buds and leaf folds, and part of their life cycle happens inside the leaf and down in the potting mix. You usually notice the damage before you notice the insects.

This page covers identification, the life cycle, damage, sticky cards and control from least toxic up. For a side-by-side view of all the common pests, see our houseplant pest overview.

How to identify thrips

Maryland Extension describes thrips as slender, rice-shaped insects about 1–2 mm (1/16 in) long, tapered at both ends. Adults are usually yellow, brownish or glossy black. Nymphs look similar but are wingless and often near-white or yellow. The RHS says adults have two pairs of narrow wings fringed with hairs, folded back along the body at rest.

You will rarely identify the species yourself. UC IPM says thrips can be positively identified to species only by an expert, and colour does not reliably separate them. Most respond to the same controls.

Two quick tests:

  1. White-paper test. Shake or tap a leaf or flower over white paper and watch for tiny moving slivers (UC IPM, RHS). A hand lens helps.
  2. Breath test. Clemson says blowing lightly into blooms and leaves makes thrips move, which makes them easier to spot.

Western flower thrips and other indoor species

UC IPM says western flower thrips (Frankliniella occidentalis) adults have thick, bristle-like hairs at the tip of the abdomen and vary greatly in colour. The RHS lists it on many indoor and greenhouse plants, including African violet, streptocarpus, cyclamen and fuchsia. It can spread impatiens necrotic spot virus and tomato spotted wilt virus (UC IPM, Colorado State).

The RHS also describes banded palm thrips, a blackish-brown thrips with banded wings. It feeds all year on tough-leaved houseplants such as ficus, dracaena, citrus, monstera, schefflera and palms. Greenhouse thrips, UC IPM says, are sluggish, feed in groups on leaf undersides and are easier to control.

Look-alikes

Maryland lists several small creatures mistaken for thrips:

Look-alikeHow to tellSource
SpringtailsStay in damp soil; rarely on leaves; jump but cannot flyMaryland
Armored scale juvenilesNever move when prodded; thrips run or jumpMaryland
Whitefly nymphsFlat, oval and stuck to the leafMaryland
Spider mite damageFiner stippling, sometimes webbing; Colorado State says thrips wounds are larger and more silveryColorado State

If you see webbing, read spider mites on houseplants. Thickened, brittle new growth without visible insects may instead be cyclamen mites.

Life cycle

UC IPM says thrips develop from egg through two feeding larval stages, then two non-feeding stages called prepupa and pupa, before becoming adults.

  • Eggs are inserted into leaves, buds or other soft tissue (UC IPM, Maryland).
  • Larvae feed alongside the adults.
  • Prepupae and pupae of most species drop to the soil or leaf litter, or lodge in plant crevices (UC IPM). The RHS says these stages take place in the soil or in sheltered spots on the plant.

Speed depends on temperature. Maryland says egg to adult takes about a month at around 16 °C (60 °F) and two weeks or less at around 29 °C (85 °F). Adults may live about a month. The RHS gives 24–35 days under ideal conditions, with breeding all year under glass.

Maryland notes most thrips on a plant are female and can reproduce without mating, one reason populations rise fast.

Why thrips are hard to control

  • Protected eggs. Eggs sit inside plant tissue (Colorado State).
  • Soil stages. Prepupae and pupae develop in the mix, out of reach of sprays (Colorado State).
  • Hiding. UC IPM says most pest thrips feed hidden in buds, shoot tips and folds.
  • Mobility. Adults fly, and Colorado State says they slip through most screening.
  • Resistance. Colorado State says many strains resist insecticides.
  • Lagging damage. UC IPM says injury often appears only after the leaf expands, by which time the thrips may be gone.

Which houseplants get thrips

Maryland lists African violets and other gesneriads, tradescantia, aroids such as alocasia, philodendron and anthurium, orchids, peperomia, poinsettia, ficus, palms, miniature roses and herbs. See our pothos thrips guide and croton pests guide.

Damage signs

  • Silvery or bleached patches. The RHS says leaves turn dull green, then silvery-white. Maryland says stippling can turn yellow, then bronze, and dry out.
  • Black specks. Small, dark, tar-like spots of excrement near the damage (Maryland). UC IPM calls them varnish-like.
  • Distorted new growth. Young leaves fed on while expanding can stay stunted, crinkled or curled (Maryland).
  • Flower damage. Streaked petals, and buds that die without opening (Clemson, Maryland).
  • Yellowing and leaf drop in heavy infestations (UC IPM).

Damaged leaves will not regain their green colour, even once the thrips are gone (RHS). Judge progress by new growth.

Sticky cards

UC IPM recommends blue or bright yellow sticky traps to detect flying thrips. Colorado State says adults are attracted to yellow or pale blue. The RHS says blue sticky traps hung among plants can trap thrips and help monitor and reduce numbers.

Hang cards above or among the plants, as the RHS suggests, and check them regularly to see whether numbers are falling. Traps catch only adults; eggs in leaves and pupae in the mix are untouched.

Control, least toxic first

1. Isolate the plant

UC IPM’s houseplant note says to isolate an infested plant immediately. Maryland notes adults fly, so keep it well away from your other plants.

2. Rinse and prune

Wash thrips off with water (UC IPM, Clemson). Maryland suggests a strong jet of water on both sides of the leaves, or rubbing soft-bodied juveniles off with your fingers. Trim disfigured leaves and infested flowers that hide thrips inside.

3. Refresh the potting mix

Maryland says repotting into fresh mix may remove pupae in the soil, though it will not touch thrips elsewhere on the plant. Remove all the old mix when you do it. Maryland also advises against potting mixes very high in organic matter such as compost.

4. Insecticidal soap or horticultural oil

Colorado State says exposed stages are controlled with soaps or oils. UC IPM says contact sprays must thoroughly cover buds, shoot tips and other spots where thrips feed. Maryland says to repeat applications, because missed thrips reproduce quickly.

Use a product labeled for indoor plants. Maryland warns against home remedies such as household soap or detergent. See our neem oil guide and neem oil vs insecticidal soap comparison.

5. Spinosad and systemics

UC IPM says spinosad is generally more effective against thrips than soaps and oils, because it moves a short way into sprayed leaves. It is toxic to bees for about a day after spraying, and UC IPM says not to apply it to flowering plants. Check that the product is labeled for indoor use.

Extension advice on systemics differs. Clemson lists imidacloprid granules as effective for houseplant thrips. UC IPM says imidacloprid commonly fails against thrips and is generally not recommended. If you try a systemic, choose one labeled for indoor plants.

When to discard the plant

Maryland says plants heavily infested with thrips are best removed and discarded, because it is simpler and generally cheaper than treatment. Discard the potting mix too, since pupae may be in it.

Prevention and quarantine

  • Check flowers when buying. The RHS advises avoiding plants with thrips or pale flecking on the petals.
  • Quarantine new plants. Colorado State suggests at least three weeks; Clemson suggests six weeks with weekly checks.
  • Avoid overwatering and excess nitrogen. UC IPM says both can increase thrips populations.
  • Keep a blue or yellow card near susceptible plants as an early warning (RHS, UC IPM).

References