Garden pests

Thrips

Frankliniella occidentalis, Thrips tabaci and related species · Insect

Also called thunder flies (UK).

Illustration

Onions, leeks, peas, gladioli, roses, tomatoes, capsicum and indoor plantsTiny sap-feeding insectSpreads by flying adults and infested plants

Tiny, slender insects that rasp leaves and petals, leaving silvery patches dotted with black specks and flecked, distorted flowers. Some spread tomato spotted wilt virus. Established plants usually cope; traps and predators help.

How to spot it

Tiny, slender, cigar-shaped insects up to 2 mm, yellowish to dark brown, with fringed wings; the young are paler and wingless.
Silvery or dull, mottled patches on leaves, dotted with tiny black specks of excrement.
White flecks on coloured petals, and buds that fail to open or open distorted.
Scabby, scarred patches on fruit.

Easily confused with

Spider mites

Fine pale speckling with silk webbing and no black specks; the mites are tiny eight-legged dots under the leaves.

Leafhoppers

Coarser pale spots, insects that jump when disturbed, and white cast skins stuck under the leaves.

Where it's a problem

Worldwide: Many species damage flowers, vegetables and fruit, and some spread plant viruses such as tomato spotted wilt.
Australia: Western flower thrips, onion thrips, melon thrips and yellow tomato thrips spread tomato spotted wilt and related viruses to tomatoes, capsicum, lettuce and flowers such as dahlias. Melon thrips is established in parts of Queensland, and Biosecurity Queensland asks you to report signs of it on 13 25 23.
United Kingdom: Onion, pea and gladiolus thrips are common outdoors, and western flower thrips on houseplants and in greenhouses. Glasshouse thrips now also damages Viburnum tinus hedges in southern England.

What to do

Shake a flower or shoot over white paper to confirm thrips before acting; by the time damage shows they have often moved on, and established plants usually cope.
Hang blue or yellow sticky traps to spot flying thrips, especially in greenhouses.
Prune off damaged shoots and flowers, and keep nearby weeds down.
Keep plants growing strongly, and go easy on nitrogen fertiliser.
Encourage predators such as pirate bugs, lacewings and ladybirds; predatory mites are sold as a greenhouse biological control.
Pull out tomatoes, capsicums or lettuces with spotted wilt virus, as infected plants can't be cured.

If you use an insecticide, choose one labelled for thrips and follow the label and local rules. Sources say sprays won't repair damage already done, can kill the thrips' natural enemies, and western flower thrips resists many chemical groups.

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Sources

Facts checked Sunday 27 September 2026. General guidance only: follow your local council, agency and product label.