Predatory mites
Overview
Predatory mites are one of the most important groups of beneficial organisms used in biological pest control. They are small, mobile predators used against thrips, spider mites, whitefly, broad mite, sciarid flies and some soil-dwelling pests.
Different predatory mite species occupy different parts of the crop. Some live mainly on leaves and flowers, while others live in the growing media. This makes predatory mites useful as both preventative and curative tools in IPM programmes.
Main groups
Foliar predatory mites
Foliar predatory mites live on leaves, flowers and growing points.
They are commonly used against:
- Thrips larvae
- Spider mites
- Whitefly eggs
- Broad mite
- Other small arthropod pests
Examples include:
- Amblyseius swirskii
- Amblyseius cucumeris
- Amblyseius montdorensis
- Phytoseiulus persimilis
- Amblydromalus andersoni
Soil and substrate predatory mites
Soil predatory mites live in growing media, capillary matting, benches and the upper substrate layer.
They are commonly used against:
- Sciarid fly larvae
- Shore fly larvae
- Soil-dwelling thrips stages
- Small soft-bodied organisms in the substrate
Examples include:
Why predatory mites are important
Predatory mites are often used as the foundation of a biological control programme because they can be introduced early, before pests become damaging.
They are especially useful where growers want to reduce reliance on pesticides and maintain continuous background suppression.
Strengths
- Useful preventatively
- Can establish before pest pressure is high
- Good fit for protected crops
- Compatible with many other beneficial insects
- Useful in residue-sensitive crops
- Can be applied by sachet, loose material or broadcast release
Limitations
- Species choice matters
- Some species are highly pest-specific
- Poor distribution can cause gaps in control
- Very dry conditions can reduce establishment
- Pesticide residues can disrupt populations
- Heavy pest outbreaks may require additional control measures
Environmental requirements
Temperature
Different species have different temperature preferences.
Warm conditions favour species such as Amblyseius swirskii, while Phytoseiulus persimilis is especially important in active spider mite outbreaks under suitable humidity.
Humidity
Many predatory mites perform better when the crop is not excessively dry.
Very hot, dry conditions can reduce egg hatch, survival and movement.
Crop structure
Dense crops can provide shelter and humidity, but they can also make even distribution harder.
Practical IPM strategy
Predatory mites are usually strongest when used as part of a layered programme:
- Identify the main pest risk.
- Choose the correct predatory mite species.
- Introduce early where possible.
- Maintain even distribution through the crop.
- Monitor pest hotspots.
- Add specialist predators or parasitoids where needed.
- Avoid disruptive pesticides.
Common mistakes
Using the wrong species
A mite used for thrips may not control spider mite effectively, and a spider mite specialist may not control thrips.
Releasing too late
Predatory mites work best when pest pressure is low to moderate.
Ignoring climate
Dry, hot or unstable conditions can reduce performance.
Poor application technique
Uneven release can leave parts of the crop unprotected.