Red Spider Mite

Tetranychus urticae

Red Spider Mite, Two Spotted Spider Mite , Glasshouse Red Spider Mite

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Tetranychus urticae (4884149094) by Gilles San Martin (CC BY-SA 2.0)
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Tetranychus urticae (4884149094) by Gilles San Martin (CC BY-SA 2.0)
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Tetranychus urticae, or Red Spider Mite, is a tiny 8-legged arachnid. They belong to a family called Tetranychidae which contains many other sap-sucking mites considered serious plant pests. They're barely visible with the naked eye, so they can be difficult to identify at the species level. The Red Spider Mite is by far one of the most common species. A tip to see if they are present on plants is to look for tiny, dusty cobwebs. In front of a light, they are easier to spot. Leaf mottling is also another common symptom associated with these pests. They're common in glasshouses, where temperatures are warm. They're a frequent pest of houseplants, too. They have a broad host range, feeding on anything to vegetables, fruits and ornamental plants such as roses.


Sucks plant cells from plants, resulting in yellow mottling and reduced photosynthesis.


Adult: They're extremely small, yellowish-green or red-brown mites that you can barely see with the naked eye, hence they're fairly tricky to diagnose. The key is to monitor the plant symptoms. They measure below 0.4mm in length.


Fine, dusty webbing on foliage. Yellow mottling on leaves. Leaf yellowing. Dried up leaves. Premature leaf fall. Loss of vigour.












Biological treatment

Try to keep glasshouses clear of debris over the winter, as this provides great hiding spots for Spider Mite. Likewise, try to keep gardening tools clean and disinfect them at the end of each season. If a Spider Mite infestation is suspected, plants should be treated as soon as possible. Try to remove the parts of the plants infested, if possible. Spider Mite thrive in dry conditions, so increasing humidity in the glasshouse can make conditions unfavourable. Spritzing leaves and stems with water indoors can help, too. Natural plant oil and extract containing products can help tackle Spider Mite. Using surfactants can help to control mite numbers, too. Within a heated glasshouse, year-round the predatory mite Phytoseiulus persimilis may be used as a form of biological control. It is effective at consuming spider mites at each stage of their life cycle. Predatory ladybugs or lacewing love to eat spider mites. If you see any in your garden, help them out and pop them on your infested greenhouse plants.

Chemical treatment

Insecticidal soaps or products containing pyrethroids should be used as a last resort as they can negatively affect other beneficial insects. If a chemical option is sought, check with your local garden centre and please take care to follow the manufacturers' instructions. Check with your local regulating body for guidance on active ingredients and their authorisation for use. Avoid spraying flowers and stick to spraying in the mornings and evenings.


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