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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.
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.
Biological
Control of Red Spider Mite
Red
spider mite can be controlled biologically indoors or outside by
using their natural enemy, the predatory mite Phytoseiulus persimilis.
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