Spider mites overview
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 (also commonly called red spider mite)
- 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 control of spider mites
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.
A strategy for managing spider mites in susceptible crops
Californicus and Persimilis predatory mites can both do a good job to help manage spider mite problems in a wide range of crop environments. They are quite different species and do offer pros and cons depending on the crop, the nature of the infestation and environmental conditions. As a general rule we suggest regular releases of Californicus predatory mites in susceptible crops for use in a preventative way. If monitoring indicates that the problem persists (or is getting worse) then release of Persimilis mites may be warranted. Do not wait until your spider mite problem is severe before initiating releases of beneficial mites.
Spider mite chemical control considerations
If chemical support is necessary, choose selective products that will cause minimal disruption to predatory mites and other biocontrol agents. Use the Biobest Side Effects App to access information about the effects of pesticides on biocontrol agents.
Many spider mite problems can be traced back to the negative effect of pesticides. We urge you to take great care and to understand the potential implications before applying any pesticide.
