Red Spider Mite Pest Solution: Phytoseiulus

Phytoseiulus Description

Phytoseiulus (Pronounced: FY-TOE-SOO-LUS) persimilis is a predatory mite capable of eating large numbers of red spider mites, it moves amongst the plants to find its prey.

It is slightly larger than the red spider mite. With a pear shaped shiny red body, it has long legs and is a quick mover. Young stages are oval and very pale pink.

Phytoseiulus Life Cycle

Each Phytoseiulus can produce 50-60 eggs in 3 weeks. Egg to adult takes about 12 days at 20ºC (68ºF), and half that at 30ºC.

Many hundreds of spider mites will be eaten by a single Phytoseiulus during its life cycle, and it will eat all stages of red spider mite.

Phytoseiulus reproduces at twice the rate of red spider mite at 18ºC (64ºF) and above.

If all the red spider mites are eaten, Phytoseiulus will disperse and die.

Phytoseiulus Usage

  • Phytoseiulus must be introduced at the first sign of red spider mite infestation. If there is a history of this pest in a greenhouse or conservatory it is advisable to check carefully for signs of red spider mite activity early in the spring.
  • The air temperature must be around 20ºC (68ºF) for at least part of the day and humidity should be kept fairly high by damping down or misting. NB. The temperature must not fall below 10ºC (50ºF).
  • Phytoseiulus can be used indoors or outside provided the temperature is sufficient.
  • Phytoseiulus cannot be stored, it needs to be used immediately upon receipt.
  • As a basic rule you should achieve control of red spider mite in about three weeks if the starting ratio of red spider mite to Phytoseiulus is no greater than 20 spider mite to 1 Phytoseiulus.
  • You will know when Phytoseiulus is working as new foliage will not show signs of damage.
  • Like all Defenders biological controls, Phytoseiulus is harmless to children, pets and wildlife.

Biological Red Spider Mite Control Product Details

Defenders supply Phytoseiulus in 3 dose sizes. Each dose is sent out mixed with a sawdust carrier. Phytoseiulus are simply released from the tube they are sent in onto the leaves of affected plants.

Product Code

Area Treated


Phytoseiulus 200

A single dose of 200 to spot treat 1 or 2 specimen plants.
Total red spider mite population should be no greater than 4,000 at the time of releasing Phytoseiulus


Phytoseiulus 1K

The medium dose of 1,000 will treat a greenhouse where red spider mite has been detected but is not yet in high numbers.
Total red spider mite population should be no greater than 20,000 at the time of releasing Phytoseiulus.


Phytoseiulus 2K

The large dose of 2,000 should be used for relatively high infestations or particularly large greenhouses.
Total red spider mite population should be no greater than 40,000 at the time of releasing Phytoseiulus.


All packs of Phytoseiulus are sent with full release instructions contained in the document wallet on the package.

Remember! Biological controls are living creatures and can be effected by chemical usage. If you've used any pesticides recently, check with us before ordering Phytoseiulus as it may not be possible to use them. For heavy infestations of two spotted (red) spider mites, to spot treat a small outbreak, or if it is too cold, you can use SB Plant Invigorator, an organic spray. This will target colonies and reduce the population. The beneficials can be released as soon as the SB treated leaves are dry but it should not be used after their release.