WSU Extension

Hortsense

Predatory Mites
 
Predatory mites 



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Caption: Western predatory mite (Galendromus occidentalis) (Phytoseiidae) with egg (oval) and spider mite egg
Photo by: D.G. James
  
Pedatory Mites : Predatory mites
(revision date: 10/11/2018)


Biology
Predatory mites are among the unseen and invariably unsung heroes of the home garden. A typical garden in the Pacific Northwest not treated with pesticides will be home to dozens of species of predatory mites living on leaves, in trees or on the ground. They prey mainly on plant-feeding pest mites but also consume insect eggs and thrips. A hand lens or microscope is usually needed to have a good look at predatory mites (1/50 inch in length) but most move rapidly thus may be seen by the naked eye as fast moving ‘dots’ on the undersides of leaves. The most important group of predatory mites, known as phytoseiids, are extensively used in biocontrol programs against spider mites in agriculture. A healthy home garden population of phytoseiids will go a long way to ensuring spider mites are not a pest problem on plants. Phytoseiids are excellent predators of a range of plant-feeding mites. If pest mites regularly cause damage in your garden, then you likely have few phytoseiids. Predatory mites may be purchased from biological control suppliers but it is best to attract and conserve locally adapted populations by restricting pesticide use. Plants with leaves that have hairs, chambers or pits on the underside are often favored by predatory mites because they provide shelter.

Prey or Pest Targeted
  • Mites, scale insects, insect eggs, nematodes
     
Attracting and Keeping Natural Enemies & Pollinators in Your Yard
  • Avoid regular use of synthetic, broad-spectrum pesticides. Infrequent use of certain narrow-spectrum pesticides is more compatible with some beneficials but generally the less chemical inputs there are, the greater and more diverse the beneficial insect community will be. Extensive lawns are also not conducive to attracting and retaining a diversity of beneficial insects, mites and spiders. Minimize lawn areas and maximize shrub and bush plantings. Many beneficials reside naturally in riparian and other ‘natural’ areas near to many back yards. Natural dispersion from these refuges ensures that some beneficials will visit back yards but they will not stay unless food, host and shelter resources are available. Native plants have closer affinities with native insects and therefore provide most of these resources. A garden with a good diversity of local native flora in and around back yards, will improve the abundance and diversity of local, beneficial arthropods. Native flora also provides natural overwintering sites for many beneficial insects and it is useful to leave at least a small area of native vegetation undisturbed during fall and winter.
  • Some kinds of beneficial insects (e.g. lady beetles, lacewings, predatory mites) are available for purchase from commercial suppliers. However, benefits from introducing these beneficials are usually limited and short-lived. Upon release, commercially obtained lady beetles and lacewings often disperse and may rapidly leave your backyard despite the presence of prey and suitable nectar resources. Generally, it is more effective and sustainable to create a garden habitat that will be colonized by beneficials naturally.
     

Images

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Caption: Western predatory mite (Galendromus occidentalis) (Phytoseiidae) with egg (oval) and spider mite egg
Photo by: D.G. James