Spider mites are a group of over 1,000 species of plant feeding mites belonging to the family Tetranychidae. Adult mites are less than 1mm in size and vary in colour depending on the species and their food source. They have very small spherical eggs and they produce silk webbing that may help to protect the colony from predators or can be used to enable wind dispersal.
Spider mites are major pests in a wide range of indoor and outdoor fruit, vegetable and ornamental crops worldwide. Significant pest species include:
- Two-spotted spider mite Tetranychus urticae
- Bean red spider mite Tetranychus ludeni
- Carmine mite Tetranychus cinnabarinus
Spider mites colonise the underside of leaves, where they puncture plant cells to feed on the contents. Feeding damage first appears as white or yellow speckles (stippling) visible on the upper surface of the leaf. Extreme feeding damage causes leaves to lose all their colour and dry up. Heavily infested plants can become completely covered with the fine silken webbing produced by the mites.
Spider mites thrive under hot and dry conditions and populations can increase very rapidly in the absence of suitable biological, cultural and or chemical controls. Their short life cycle and high reproductive rate have enabled them to rapidly develop resistance to miticide products.
Biological and cultural control
Spider mites have several biological control agents including lacewings, tiny mite feeding ladybirds (Stethorus spp.), predatory gall-midges (Feltiella spp.) and a variety of predatory mites (including Phytoseiulus persimilis and Neoseiulus californicus).
It is possible to achieve excellent results using predators to control spider mites. Sustainable control is best achieved using a combination of biological and cultural controls. Cultural practices such as increasing humidity in the crop microclimate during extremely hot or dry periods can favour predators and disadvantage the pest.
If chemical support is necessary, choose selective products that will cause minimal disruption to predatory mites and other biocontrol agents. See the Koppert Chemical Side Effects database for more information on the effects of pesticides on biocontrol agents.