Red Spider Mite
Pest · Commonly affects: Cucumbers, Tomatoes, Aubergines, French beans, Sweet peppers, Fuchsias, Roses, Strawberries
Red spider mite is a tiny sap-feeding mite that is particularly troublesome in warm, dry glasshouses. Despite its name, it may appear greenish, yellowish or red. Populations can build rapidly on stressed plants, and the resulting leaf damage reduces vigour, crop quality and the ornamental value of affected plants.
How to identify it
The mites are usually less than 1 mm long, so their signs are easier to spot than the creatures themselves. Examine leaf undersides with a hand lens for tiny moving dots, pale cast skins and fine silk webbing. Upper leaf surfaces develop pale speckling, then become mottled, greyish or bronzed. Shake a suspect leaf over white paper to see mites moving. Webbing is most apparent when infestations are advanced.
Damage
Mites pierce leaf cells and remove their contents, producing pale stippling that spreads across the foliage. Leaves may turn grey, bronze or brown, dry at the edges and fall early. Fine webbing can cover shoots and fruit trusses. In glasshouse crops, heavy infestations reduce flowering, fruiting and overall plant strength, especially during hot dry weather.
Prevention
Keep glasshouse plants evenly watered and well ventilated, as drought-stressed plants are especially vulnerable. Raise humidity by dampening paths and benches in the morning, taking care not to leave plants wet overnight. Remove old leaves and plant debris, clean the glasshouse between crops and avoid overcrowding. Inspect leaf undersides weekly in warm weather, particularly on cucumbers and tomatoes. Avoid bringing infested plants into the glasshouse and choose healthy young plants.
How to manage it
Isolate affected plants where possible and remove heavily damaged leaves before mites spread. Rinse sturdy foliage with water, concentrating on leaf undersides, and repeat several times to reduce numbers. Improve humidity by dampening the glasshouse floor and maintain consistent watering. The predatory mite Phytoseiulus can be introduced under glass when conditions are suitable. Continue close inspections, because new colonies can develop quickly in hot, dry conditions.
Red Spider Mite: frequently asked questions
How do I identify red spider mite?
The mites are usually less than 1 mm long, so their signs are easier to spot than the creatures themselves.
How do I prevent red spider mite?
Keep glasshouse plants evenly watered and well ventilated, as drought-stressed plants are especially vulnerable.
How do I get rid of red spider mite?
Isolate affected plants where possible and remove heavily damaged leaves before mites spread.
General guidance for UK home gardens and allotments, focused on prevention and non-chemical control. For a confirmed diagnosis, the RHS or a local garden centre can help. Page updated 19 Sep 2026.