Agriculture Reference
In-Depth Information
(a)
(b)
(c)
(d)
Figure 18.16
(a) Cabbage white adult; (b) cabbage white caterpillar; (c) cabbage white pupa; (d) yellow pupae of
Cotesia glomerata
wasp that parasitizes cabbage white caterpillars
18
causing the larva to go grey and die. Birds such as tits
and starlings eat the plump larvae. Private gardeners
often cover brassicas plants with fine-mesh nets to
prevent adults reaching the plants. When damage
becomes severe, spray products containing
lambda-
cyhalothrin
may be used.
hence the species' common name. The male is
a greyish-brown moth, 2.5 cm across its wings,
while the female is
wingless
, looking at first sight
rather like a spider (Figure 18.17b). The female
crawls up the tree and lays 100-200 light green
eggs around a number of buds. The eggs hatch in
spring at bud burst to produce green larvae with faint
white stripes. These larvae move in a characteristic
looping
fashion and when fully grown, descend on
silk threads at the end of May before pupating in the
soil until early winter.
Spread
. This is slow because the females do not have
wings.
Control
. A common control is a
glue band
(see
Figure 16.2b), which is wound around the main trunk
of the tree in October preventing the flightless female
moth's progress up the tree. A spray of
deltamethrin
in spring may be used if necessary.
Winter moth (
Operophthera brumata
)
This pest's timing of life-cycle stages is unusual.
Damage
. These are pests, which may be serious on
top fruit, such as apples, but also attack woody plants
such as currants, roses and beech. The caterpillars
eat away leaves in spring and early summer and
often form other leaves into loose webs, reducing the
plant's photosynthesis. They occasionally scar young
apple fruit.
Life cycle
. The pest emerges as the adult form
from a soil-borne pupa in November and December;
