Spider Mites

Spider mites (Tetranychidae) are among the garden pests. Two species in particular cause most of the damage:

the two-spotted spider mite (Tetranychus urticae)

the fruit tree red spider mite (Panonychus ulmi)

These creatures are very small - about 0.5mm in body length - and are barely visible to the naked eye. Depending on their developmental stage and feeding, spider mites turn yellowish, greenish or reddish. They occur in colonies and are usually found on the underside of leaves, where fine webbing can be spotted within a very short time. They are leaf suckers, meaning they suck out the contents of the leaf cells, so that a pale, silvery, translucent stippled pattern appears on the upper side, until the leaves eventually wilt.
Dry air and high temperatures encourage the spread of spider mites, which mainly threaten cucumbers and beans. Among fruit, they readily attack raspberries, gooseberries, blackcurrants and blackberries as well as nectarines, apricots and peaches. The following flowers should be checked regularly for these tiny sap-suckers, as they are frequently used as host plants: hydrangeas, dahlias, mallows, roses and chrysanthemums.

In the greenhouse, good ventilation and adequate humidity should be provided as a preventive measure, and in the case of heavy infestation, predatory mites can be introduced as beneficial insects.

As a rule, healthy, well-tended plants are naturally more resilient. This can be achieved by trying to avoid over-fertilising and instead feeding plants a "balanced" diet, as well as making sure they do not dry out. Affected plants can be strengthened with nettle manure, rock dust or seaweed preparations. Diseased leaves should be removed and destroyed. For control, spraying with horsetail decoction, garlic and onion decoction or neem preparations is recommended.

Natural enemies of spider mites include: predatory mites, predatory bugs, parasitic wasps, lacewings, gall midges, spiders, ladybirds and predatory beetles. Encouraging beneficial insects in the garden is always worthwhile and, in the form of an insect hotel, also very decorative.