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 and will not become a pest in its own right.
Spider Mite Description
Small yellow/olive mites which have dark patches on either side of the body, red spider mite are less than 1mm long. Also known as "two-spotted mite" they can be found in large numbers on the underside of leaves.
In bad infestations they can produce fine webs. As day lengths reduce in the autumn, they become deep red in colour.
Spider Mite Damage
The mites suck sap from cells on the underside of plant leaves, in the early stages, characteristic white speckles can be seen from the upper leaf surface.
As mite numbers increase these white speckles will increase in number, the leaf will take on a bleached appearance and die.
The mites are found in highest numbers on the underside of leaves although you may need a magnifying glass to see them!
As the population builds you will start to see webs and aggregations of mites at certain sites, usually the growing points of the plant.
Spider Mite Life cycle
The mites go through 5 development stages. Egg to adult takes about 14 days at 21ºC, or less than a week at 30ºC. Eggs are laid on the underside of leaves. Each adult female can produce more than 100 eggs in 3 weeks. They reproduce at alarming rates - 10 spider mite in May are capable of becoming 1,000 by June & 100,000 by July!
High humidities can reduce the egg laying rate of the mites.
During the autumn, when day lengths shorten the mites turn deep red in colour and migrate from the plants to hibernate in crevices within the glasshouse structure.
Red spider mite can overwinter without feeding and re-emerge in the spring and summer to re-infest plants.
NB. Artificial lighting may stop the mites from hibernating.