Mites - Pests of Ornamental Trees, Shrubs and Flowers - page 423

Tetranychus cinnabarinus (Boisduval) ( 1137 )
Carmine spider mite
This subtropical species occurs throughout Europe, but
in temperate areas is confined mainly to greenhouses.
Infestations develop on various herbaceous plants,
including cacti, the foliage often becoming coated in
masses of webbing; affected plant tissue also becomes
discoloured. Typically, infested leaves of carnation
( Dianthus caryophyllus ) and pink ( D. plumarius ) tend to
curl downwards. Eggs are laid singly under leaves or on
the webbing, the pattern of development following that
of Tetranychus urticae . There are several overlapping
generations annually but there is no winter diapause; the
rate of development is also less rapid than that of the
previous species, carmine spider mite being adapted to
higher temperatures. Adult females are mainly red, with
dark internal markings visible on either side of the
body; the nymphal stages are green and the eggs whitish
to pink (cf. those of Tetranychus urticae ). This species
crosses regularly with Tetranychus urticae , particularly
in greenhouses, resulting in hybrid populations.

poles. They become active in March or April, and
invade host plants to feed and eventually deposit eggs.
There are several overlapping generations of summer
forms annually, mites passing through egg, larval,
protonymphal and deutonymphal stages before
maturing; males often omit the deutonymphal stage.
Development is completed in less than two weeks at
temperatures above 20ºC, but is greatly protracted
below 12ºC, extending over almost two months at 10ºC;
outdoors, therefore, there tend to be fewer generations
than in protected situations. Colonies occur mainly on
the underside of the expanded leaves, the various mite
stages being sheltered by fine webs of silk. When
populations are large, these webs often become
extensive; they may then cover complete leaves and
parts of shoots and stems. During September, in
response to short days (daylight of less than 14 hours),
orange-coloured winter-female forms are produced;
after mating, these seek shelter for the winter. As plant
vigour also declines, breeding ceases and males and
summer females all die.

DAMAGE
Infested leaves are speckled with yellow and often
become extensively chlorotic. This affects both the
vigour and appearance of plants; hosts may also
be disfigured by webbing. Heavy infestations, which
are most likely to occur in hot, dry conditions, cause
considerable stunting and may result in the eventual
death of plants.

1136 1137

1136 Two-spotted spider mite ( Tetranychus urticae ) damage
to leaves of Impatiens .

1137 Web of carmine spider mite ( Tetranychus cinnabarinus )
on Aporocactus .