Thrips
Orius + Amblyseius swirskii systems.
Thrips damage flowers and foliage. Swirskii + Orius provide season-long suppression...
About Thrips
Thrips are small, fast-moving pests that feed by rasping and sucking plant tissue. In UK horticulture the main species of concern are the western flower thrips (Frankliniella occidentalis) and onion thrips (Thrips tabaci). These pests cause silvery scarring, distorted growth and can transmit plant viruses such as TSV and INSV, making early detection and biological control essential.
Symptoms of Thrips Damage
- Silvery scarring on leaves, flowers or fruits
- Small black faecal spots (“tar spots”)
- Distorted growth and flecking on young tissue
- Flower deformation and poor fruit set
- Presence of tiny, slender insects when tapping foliage
Why Biological Control Works
Thrips have vulnerable larval stages that spend time on the plant surface or drop to the compost, making them ideal targets for predators and soil-dwelling beneficials. Two of the most effective agents are Orius laevigatus, a robust predatory bug that feeds on all thrips stages including adults, and Amblyseius swirskii or Amblyseius cucumeris, which target first-instar larvae.
Common UK Thrips Species
- Frankliniella occidentalis — Western flower thrips (WFT)
- Thrips tabaci — Onion thrips
- Chaetanaphothrips signipennis — Banana thrips (occasionally encountered)
IPM Recommendations
- Introduce Amblyseius predators early, before thrips adults establish
- Use Orius for control of adults and to clean up flower hotspots
- Place blue sticky traps to monitor incoming thrips pressure
- Improve hygiene and remove old flowers where larvae hide
- Mist lightly or raise humidity to disrupt thrips development
- Maintain a preventative population of predators through the whole season
Preventative vs Curative Strategy
Preventative: Slow-release sachets of Amblyseius cucumeris or Amblyseius swirskii should be placed early in the crop, especially in propagation and young plants.
Curative: When adult thrips are abundant or when flower damage is visible, introduce Orius laevigatus for fast knockdown. Orius is particularly valuable in summer crops where thrips pressure spikes.
Environmental Notes
- Amblyseius cucumeris performs well in cooler UK conditions
- Amblyseius swirskii excels in warm summer crops and heated glass
- Orius requires higher light levels to thrive—early introductions help
- Low humidity and high temperatures accelerate thrips reproduction
Biological Controls for Thrips
The options below are examples of beneficial insects and biological products commonly used against thrips. Always refer to supplier guidance and product labels for crop safety and local registration status.
Amblyseius cucumeris
Product: Amblyline
Environment: glasshouse
Temperature Range: 18.0 – 32.0°C
Rate: 50–100 mites/m² or 1–2 sachets/m²
Frequency: Top up every 3–4 weeks
Preventative control of WFT and other thrips; introduce early.
Amblyseius montdorensis
Product: Montyline
Environment: glasshouse
Temperature Range: 20.0 – 32.0°C
Rate: 50–100 mites/m²
Frequency: Repeat after 2–3 weeks in high pressure
Warm-season predator for thrips larvae.
Orius laevigatus
Product: Oriline
Environment: glasshouse
Temperature Range: 20.0 – 32.0°C
Rate: 0.5–2 bugs/m²
Frequency: Re-release after 2–3 weeks
Predator of adult and larval thrips; requires flowers.
Amblyseius cucumeris
Product: Amblyline
Environment: tunnel
Temperature Range: 18.0 – 32.0°C
Rate: 50–100 mites/m²
Frequency: Monthly top-ups during season
Useful in tunnels with suitable humidity.
Steinernema feltiae
Product: Exhibitline Sf
Environment: glasshouse
Temperature Range: 12.0 – 28.0°C
Rate: 250k–500k nematodes/m² (media drench)
Frequency: Repeat every 2–4 weeks
Targets thrips pupae in the substrate.
Amblyseius cucumeris
Product: Amblyline
Environment: glasshouse
Temperature Range: 18.0 – 32.0°C
Rate: 50–100 mites/m² or 1–2 sachets/m²
Frequency: Top up every 3–4 weeks
Background control of larvae on foliage; combine with hygiene and monitoring.
Amblyseius cucumeris
Product: Amblyline
Environment: glasshouse
Temperature Range: 18.0 – 32.0°C
Rate: 50–100 mites/m²
Frequency: Monthly top-ups while risk remains
Useful in protected onions, leeks and alliums; combine with Exhibitline Sf drench where pupation occurs in soil.
Amblyseius cucumeris + Orius laevigatus
Product: Amblyline + Oriline
Environment: glasshouse
Temperature Range: 18.0 – 32.0°C
Rate: Amblyline 50–100 mites/m²; Oriline 0.5–2 bugs/m²
Frequency: Introduce mites preventatively; add Orius once flowers appear
IPM combination for thrips in peppers and chillies; support with sticky traps and careful chemical choice.
Amblyseius montdorensis + Orius laevigatus
Product: Montyline + Oriline
Environment: glasshouse
Temperature Range: 20.0 – 32.0°C
Rate: Montyline 50–100 mites/m²; Oriline 1–2 bugs/m² in hotspots
Frequency: Re-introduce after 2–3 weeks where pressure is high
Warm-season thrips predator combination; early introductions essential with T. parvispinus.
Amblyseius cucumeris + Orius laevigatus
Product: Amblyline + Oriline
Environment: glasshouse
Temperature Range: 18.0 – 32.0°C
Rate: Amblyline 50–100 mites/m²; Oriline 0.5–2 bugs/m²
Frequency: Mites preventatively; Orius top-ups every 3–4 weeks
Standard biocontrol programme for WFT in many protected crops; support with sanitation and compatible chemistry.
Related Biological Solutions
Growers dealing with thrips often also monitor these pests as part of a complete IPM programme: