Two-spotted spider mite

Tetranychus urticae

1. Identification

• Common name: Two‑spotted spider mite, yellow mite
• Scientific name: Tetranychus urticae Koch
• Order: Trombidiformes
• Family: Tetranychidae

2. Pest description

• Adults: Oval body, very small (≈ 0.4–0.6 mm); variable coloration (yellowish‑green to reddish); two typical lateral dark spots; presence of fine webs on the underside of the leaves.
• Nymphs and larvae: Similar to adults, but smaller; lighter coloration.
• Eggs: Spherical, translucent to yellowish, laid on the underside of the leaves.

3. Main hosts

• Vegetable crops (tomato, bean, cucumber, melon, pepper).
• Fruit trees (apple, pear, citrus).
• Grapevine.
• Ornamentals and numerous spontaneous plants.
• Highly polyphagous species, with hundreds of known hosts.

4. Symptoms and damage

• Chlorotic stippling on the upper side of the leaves.
• Yellowing, bronzing and progressive drying of the blade.
• Reduction of photosynthesis and vegetative vigour.
• Premature leaf drop in severe attacks.
• Presence of fine webs that protect colonies and eggs.
• Significant production losses in sensitive crops, especially in hot and dry conditions.

5. Biological cycle

• Rapid cycle, which can be completed in 7–10 days in hot conditions.
• High number of annual generations.
• Development favoured by high temperatures and low relative humidity.
• Winter spent as a fertilised female in shelters of the plant or in the soil.
• Populations increase rapidly in greenhouses and during periods of heat.

6. Monitoring

• Observation of the underside of the leaves with a magnifying glass.
• Assessment of the presence of webs, eggs and mobile forms.
• Counting of individuals per leaf to support decision‑making.
• Intensive monitoring during hot and dry periods or in greenhouses.

7. Management measures

• Cultural: Removal of heavily infested leaves; avoid water stress; promote ventilation; avoid excess nitrogen.
• Biological: Conservation and/or introduction of predatory mites (e.g.: Phytoseiulus persimilis, Amblyseius swirskii, Neoseiulus californicus).
• Integrated protection: Intervention only when population levels justify it; rotation of active substances to avoid resistance; preference for selective products compatible with beneficials.

Bibliographic references

• EPPO Global Database – Tetranychus urticae.
• CABI Invasive Species Compendium – Tetranychus urticae.
• van Leeuwen, T. et al. (2010). The spider mite Tetranychus urticae: a model organism for acaricide resistance. Pesticide Biochemistry and Physiology.
• Helle, W., & Sabelis, M. W. (1985). Spider Mites: Their Biology, Natural Enemies and Control. Elsevier.
• Bolland, H. R., Gutierrez, J., & Flechtmann, C. H. (1998). World Catalogue of the Spider Mite Family (Tetranychidae). Brill.