Agriculture Reference
In-Depth Information
(a)
(b)
Figure 18.22
(a) Flea beetle damage on radish leaves; (b) Lily beetle
Piercing
and
sucking
mouthparts
Black
spots
Fused
body
segment
Four
pairs of
legs
Glasshouse red spider mite (
100)
Figure 18.24
Two-spotted mite. Note that this
pest is very small (0.8 mm) and can easily escape a
gardener's attention
Figure 18.23
Gooseberry sawfl y damage
normally help in the breakdown of soil
organic
matter
. They may cause damage in greenhouses on
cucumber roots.
serious pests on plants. The life cycle is composed of
egg, larva, nymph and adult stages.
Two-spotted mite or glasshouse red
spider mite (
Tetranychus urticae
)
Mite pests
The mites (
Acarina
) are grouped with ticks, spiders
and scorpions in the
Arachnida
. Although similar to
insects in many respects, they are distinguished from
them by the possession of
four pairs of legs
, a
fused
body
structure (no clear abdomen or thorax) and the
absence of wings
(Figure 18.24). Many of the tiny
soil-inhabiting mites serve a useful purpose in breaking
down plant debris. Several above-ground species are
Damage
. The piercing mouthparts of the mites inject
poisonous juices which cause localized death of
leaf cells. This results in a
fine mottling
symptom
on the leaf. In large numbers, the mites can kill off
leaves and eventually whole plants. Numerous fine
silk strands are produced in severe infestations
(FigureĀ 18.25b)