Western flower thrips

Frankliniella occidentalis

1. Identification

• Common name: Western flower thrips
• Scientific name: Frankliniella occidentalis Pergande
• Order: Thysanoptera
• Family: Thripidae

2. Pest description

• Very small insect (1–1.5 mm), with a narrow body and yellowish to brownish coloration.
• Narrow wings with long fringes, typical of thrips.
• Nymphs of pale coloration, generally found on young leaves and flowers.
• Highly polyphagous species and one of the most important agricultural pests worldwide.
• Efficient virus vector, especially of the Tomato Spotted Wilt Virus (TSWV).

3. Main hosts

• Vegetables (tomato, pepper, cucumber, bean, lettuce).
• Ornamentals (chrysanthemum, gerbera, rose).
• Fruit crops (strawberry, grapevine).
• A great diversity of spontaneous plants that act as a reservoir.

4. Symptoms and damage

• Silvering of the leaves due to the rasping of the epidermal tissues.
• Black spots (excrement) on the leaf surface.
• Deformations in young leaves, flowers and fruits.
• Scars and blemishes on fruits, reducing their commercial value.
• Transmission of viruses, with a high economic impact.

5. Biological cycle

• Eggs inserted into the plant tissues.
• Nymphs feed actively on the leaves and flowers.
• Pre‑pupa and pupa in the soil or in plant debris.
• Very rapid cycle in hot, dry conditions, favouring population outbreaks.
• High capacity for reproduction and dispersal, especially in greenhouses.

6. Monitoring

• Blue or yellow sticky traps for detection and counting.
• Direct observation of symptoms and insects on young leaves and flowers.
• Regular sampling in greenhouses and sensitive crops.
• Reinforced monitoring during hot, dry periods.

7. Management measures

• Cultural: removal of infested plants; control of spontaneous plants; adequate ventilation in greenhouses.
• Preventive: use of pest‑free plants; insect‑proof nets; strict cultural hygiene.
• Biological: release of predatory mites (Amblyseius swirskii, A. cucumeris) and predatory bugs (Orius spp.).
• Integrated protection: judicious application of authorised insecticides; rotation of modes of action; integration with biological control.

Bibliographic references

• EPPO Global Database – Frankliniella occidentalis
• CABI – Invasive Species Compendium – Frankliniella occidentalis
• Kirk, W. D. J. (1997). Feeding behaviour and nutritional requirements of thrips. In: Thrips as Crop Pests.
• Reitz, S. R. (2009). Biology and ecology of the western flower thrips. Annual Review of Entomology.
• Mound, L. A. & Teulon, D. A. J. (1995). Thysanoptera as phytophagous pests. Annual Review of Entomology.