What are Red Spider Mite?

Spider Mites are less than 1mm in size and difficult to see without a lens or microscope unless you have very sharp eyes. They often live underneath leaves, and are only active when it is warm. So can be around all year in houseplant collections.  Outside in winter they hibernate either as eggs, or inactive newborns which you can often spot as tiny cream, red or orange shiny dots.

These tiny, highly destructive pests are common in sunny greenhouses and houseplants, they can also be found on outdoor plants during the warmer summer months. In the greenhouse look out for them on citrus, tomatoes, cucumbers, melons, vines, carnations and chrysanthemums. Outdoors, you may find them on daylilies, gladioli, conifers and many tender plants.  Unfortunately for houseplants they don't seem to discriminate.

What does spider mite damage look like?  The symptoms

Spider mites can be spotted more easily by looking for the damage than looking for the culprits. They pierce the leaf cells with their mouthparts and suck the plant juices resulting in discolouration of the leaves and sickly looking growth, and in worst cases the death of the plant. The leaf damage initially results in a fine speckling or mottling effect on leaves where the cells have died. The pattern of the mottling varies from plant to plant, so on strawberries you will see brown spots on the underside, and in citrus these develop into yellow patches throughout the leaf. On some plants with tougher leaves the spider mite eats young growth and flower buds so may be even more difficult to spot.

A very sick lily

 How do you stop Red Spider Mite?

Depending on your growing conditions, it is a good idea to inspect vulnerable plants every week and deal with the first signs of mite infestation immediately. Where possible, remove infested leaves, buds and stems because this will initially reduce numbers. If there is any part of the plant which is covered in cobwebs then regrettably it will need to be sacrificed as it will not recover. Spider mites prefer hot dry environments, so spraying the infested areas of a plant with cold water and, in greenhouses, damping the floor areas will raise the humidity and hopefully slow the infestation rate.