Class: Arachnids
Size: 0.25 to 0.8mm
Weight: Variable
Appearance: Yellowish, greenish, orange or red coloured
Food: Plant sap
Distribution: Worldwide, 1’200 species
Original location: Unknown
Habitat: Open field, greenhouse, indoor culture
Natural enemies: Gall midge larvae
Threatened with extinction: No

• There is one common reason for the occurrence of spider mites: dry indoor air. For this reason, they mainly appear in the autumn and winter months, when the indoor air becomes noticeably drier due to heating. These tiny plant pests feel particularly at home in a dry indoor climate.
• Spider mites normally live under the leaves of plants, where they spin fine webs for protection and feed on the sap of the plant. As they penetrate the epidermal cells of leaves to feed, they can damage plants. Hundreds of plant species are known to be infested by spider mites.
• Certain spider mite species are pests of great economic damage, such as the red spider mite (Panonychus ulmi), the common spider mite (Tetranychus urticae) or the lime spider mite (Eotetranychus tiliarum).
• The spider mite gets its name from the fine webs that most species use to wrap the leaves and stems of infected plants. Other signs of pest infestation are slight discolouration of the leaves and small silvery or yellowish leaf spots. Due to damage, the leaves eventually curl up and die. However, there are some species of spider mites that hardly form webs, such as the fruit tree spider mite.
• Another characteristic of spider mite infestation is the many tiny bright spots on the leaves, which can appear outdoors from spring to autumn, even in houseplants or greenhouses all year round.
• Since spider mites like dry and warm climates, they have the best breeding conditions in warm greenhouses. Spider mites occur on outdoor, greenhouse or indoor plants.
• Female spider mites overwinter in protected places and as colonies, e.g. under the bark of wooden host plants or under foliage. They can easily survive for weeks at temperatures as low as minus 15°C.