Thrips — identification and control

How to identify thrips

Look for these symptoms on susceptible plants:

• Silvery or bronze rasping marks on upper leaf surfaces
• Tiny black faecal specks scattered on leaves and petals
• Distorted, scarred fruit and flower petals
• Streaks or rings on tomato or pepper fruit (TSWV symptoms)
• Slender adults that scurry when leaves are shaken over white paper

Egg-to-adult in 2-3 weeks. Pupation happens in soil, which is why a multi-tactic approach (foliar spray plus soil drench plus sticky traps) outperforms any single intervention.

Crops affected by thrips

Thrips are documented on the following host crops in authoritative extension sources. Click any crop for the full per-crop protocol, including symptoms specific to that host and the recommended biological control.

• Thrips on tomatoeshigh

  Silvery rasping marks and black faecal specks on upper leaves and fruit; concentric ring spots or necrotic streaks on fruit indicate tomato spotted wilt virus (TSWV).

  Severity: High — act quickly · Western flower thrips and tobacco thrips arrive on transplants or migrate from weedy field edges — manage them BEFORE planting. Once TSWV is in a plant, there is no cure.

• Thrips on peppershigh

  Western flower thrips on pepper flowers and young fruit; silvery scars on fruit, distorted blossoms, and TSWV streak symptoms on leaves and fruit in heavy infestations. Chilli thrips can defoliate younger plants.

  Severity: High — act quickly · From the first flowers onwards — thrips concentrate in pepper flowers because of the pollen.

• Thrips on rosesmoderate

  Streaks of brown discoloration on rose petals, especially light-coloured varieties; deformed buds that fail to open cleanly; silvery scarring on young foliage.

  Severity: Moderate — monitor closely · Through the summer flowering period — thrips are drawn to pale, fragrant cultivars in particular.

• Thrips on cucumbersmoderate

  Silvery scars on cucumber leaves; melon thrips (Thrips palmi) and western flower thrips on leaf undersides; reduced fruit set in heavy infestations.

  Severity: Moderate — monitor closely · Under glass from the first true leaves; outdoors from mid-summer.

Non-chemical controls

Start with the lowest-impact options before any spray. These work for the vast majority of home garden cases.

• Blue or yellow sticky traps at canopy height
• Remove weedy field edges and bridge crops that harbour thrips before transplanting
• Use thrips- and virus-free transplants — inspect every seedling
• Reflective mulch to disrupt incoming flights
• Maintain consistent watering; drought-stressed plants suffer more

Biological controls

For greenhouse, polytunnel, and indoor production, biological controls give long-term suppression without the residue or pollinator harm of synthetic sprays.

• Orius insidiosus (minute pirate bug) — single adult eats up to 40 western flower thrips per day; the gold standard for pepper banker-plant systems
• Amblyseius swirskii — predatory mite, effective on chilli thrips in peppers
• Neoseiulus cucumeris — predatory mite for cucumber and ornamental greenhouse use
• Steinernema feltiae nematodes — soil drench targets thrips pupae

Organic and chemical spray options

Spinosad gives strong thrips control while being relatively soft on Orius populations — apply at dusk to protect bees. Cyantraniliprole and spirotetramat are systemic options compatible with Orius but require label-dosing care. Pyrethrin is a knockdown option for severe outbreaks.

How to build a thrips control protocol

1. Identify first. Snap a photo and confirm the species before treating — different pests respond to different protocols, and one wrong call wastes weeks. Open Growli for instant species ID.
2. Start with non-chemical control. Water blast, sticky traps, manual removal, reflective mulch, or quarantine — these alone clear roughly 60-70 percent of home cases.
3. Add biological control if you have a long-cycle crop. Greenhouse tomatoes, cucumbers, peppers, and indoor citrus all justify a single release of the right predator or parasitoid.
4. Layer in insecticidal soap or horticultural oil. Apply to thorough wetness on both leaf surfaces; repeat every 5-7 days for three weeks to catch successive hatches.
5. Reserve stronger sprays for outbreaks. Spinosad, pyrethrin, and species-specific options like Bti should be your second-line response, not your first.
6. Monitor weekly. Thrips populations rebound from any single intervention. Two or three weeks of follow-up checks separate a fixed problem from a recurrence.

Common mistakes

• One-and-done spraying. Thrips go through staggered hatches; a single spray misses everything that hatches afterwards. Always plan a 3-week protocol.
• Treating without confirming species. Insecticidal soap clears aphids but is wasted on slugs; Bti clears fungus gnat larvae but does nothing for spider mites. Wrong protocol equals wasted weeks.
• Spraying in hot sun. Soap and oil sprays burn leaves above 30 degC and on drought-stressed plants. Apply at dawn or dusk.
• Mixing biological control with broad-spectrum sprays. Pyrethroids and neonicotinoids wipe out predator releases. Use one strategy at a time, or stagger them by at least a week.

Frequently asked questions

How do I get rid of thrips?

Thrips are slender 1-2 mm insects that rasp leaf surfaces and suck the released sap, leaving silvery scars and black faecal specks. Western flower thrips also vector tomato spotted wilt virus. Blue sticky traps catch adults, weekly insecticidal soap or spinosad targets larvae, and Orius insidiosus (minute pirate bug) or Amblyseius swirskii are the standard biocontrols.

What does thrips damage look like?

Look for: Silvery or bronze rasping marks on upper leaf surfaces; Tiny black faecal specks scattered on leaves and petals; Distorted, scarred fruit and flower petals; Streaks or rings on tomato or pepper fruit (TSWV symptoms). Each host crop shows slightly different symptoms — see the per-crop pages linked above for details.

What is the best biological control for thrips?

Orius insidiosus (minute pirate bug) — single adult eats up to 40 western flower thrips per day; the gold standard for pepper banker-plant systems. Several other biocontrols are documented for specific conditions and host crops; see the full list above.

When during the season do thrips appear?

Late spring through late summer; year-round in greenhouses. Egg-to-adult in 2-3 weeks. Pupation happens in soil, which is why a multi-tactic approach (foliar spray plus soil drench plus sticky traps) outperforms any single intervention.

Are thrips harmful to pets and people?

Thrips themselves are not directly toxic to pets or people. The risk is from chemical sprays used to control them — use insecticidal soap, horticultural oil, or biological control wherever possible. Always check the product label for re-entry and harvest interval guidance, and confirm the active ingredient is currently approved via the UK HSE register or US EPA.

What plants do thrips not affect?

Thrips most commonly affect tomatoes, peppers, roses, cucumbers. Plants with thick, waxy, or hairy foliage typically resist this pest better than soft-leafed crops. For pet-safe houseplant alternatives that resist most common pests, see our pet-safe houseplants guide.

Can I use the same protocol indoors and outdoors?

The biological-control choices change (indoor releases of ladybirds rarely work; predatory mites and parasitoid wasps do), but the spray protocols (insecticidal soap, horticultural oil, neem) translate directly. Outdoor cases benefit from reflective mulches and companion planting; indoor cases benefit from quarantine and routine wipe-downs.

Sources

Identification and control guidance sourced from US Cooperative Extension publications (UC IPM, NC State, UMD, UMN, Penn State, CSU, UF/IFAS EDIS), Clemson HGIC fact sheets, Royal Horticultural Society guidance, and Cornell NYS IPM Biocontrol fact sheets. Reviewed by the Growli editorial team in May 2026.

Keep going

• All 8 garden pests covered in this guide
• Garden pest identification — complete article
• Companion planting chart (pest-deterrent pairings)
• Common houseplant diseases