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Red
spider mite
(last
updated 24 June 2008
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Small mites (Acarina
Tetranychidae) up to 1mm long. Colonies develop on leaves, stems
and flowers, usually containing all stages from egg to adults. They
feed by extracting sap and cell contents, producing characteristic
mottling and other discolorations.
Red spider mites
traditionally are not a serious pest of chrysanthemums, however
since the weather has become dryer and warmer they have become a
problem in dryer areas. Greenhouse
Red Spider (Tetranychus urticae) is more of a problem because
of the dry conditions under glass which they like. There is also the
Carmine spider mite (Tetranychus cinnabarinus) which is also
troublesome under glass. |
Red spider mite |
Symptoms.
They first show as fine light speckling, or pale yellow spots on the
upper surface of the leaves. Examination with a hand lens will reveal
colonies of mites. As the colony increases severe damage to plants
occur. June to September is the worse time for severe infestations.
Hibernating females of Tetranychus urticae turn red in the
autumn and stop feeding.
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Biology.
Female red spider mites live for about a month and lay about 100 eggs
on the undersides of leaves. Eggs hatch in 3 days in hot weather and
up to 30 days in cooler weather. There are 3 nymphal stages
before they become adults, during this time the nymphs feed
continually, this can take 8 days to 2 months depending on
temperature. The carmine
spider mite continue feeding through the winter whereas the greenhouse
spider mite hibernates, only to reappear next spring.
Left: attack by Red Spider mite
showing characteristic webbing
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Controls
Misting twice a day will control the pest, however this is not always
possible because of fungal attack to the plants.
Unfortunately
most amateur products give very little control.
Some of
the newer insecticides for the professional grower give quite good
control. These include:-
Tebufenpyrad.
Abamectin.
Petroleum oils.
Fatty acids.
Spiromesifen
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Other information
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