Agriculture Reference
In-Depth Information
following year, usually in June, and then seek
host plants on which to feed. In areas where the
pest is well established and routine insecticidal
sprays are applied to potato crops, infestations
are usually most readily detected on volunteer
potato plants that have emerged in crops such as
cereals. Eggs are laid in batches of 20-80 on the
underside of the leaves, each female being ca-
pable of depositing many hundreds of eggs over
a month or more. The eggs hatch in about a week
and the larvae then feed for about 3-5 weeks,
passing through four instars. Fully grown larvae
enter the soil to pupate in earthen cells. New
adults emerge 2-3 weeks later. These beetles
feed on potato foliage during the summer, and
some may lay eggs to produce a second brood
of larvae, before eventually overwintering. Any
second-brood larvae that successfully complete
their development before the potato haulm dies
down in the autumn, pupate in the soil to pro-
duce new adults in the following year. Adults
have a life span of up to 2 years. As a result of
this and the protracted period of egg laying, the
generations often overlap so that, during the
summer months, all stages of the pest may be
found together.
H / elongated basal
lH
/
segment of tarsus
Fig.
218
Hindleg of flax flea beetle,
Longitarsus
parvulus.
of
Longitarsus parvulus
tend to emerge from
hibernation slightly earlier in the spring. Adults
are 1.2-1.6 mm long and black or brown, with a
slightly metallic lustre; the elytra are finely punc-
tured and, characteristically, the basal segment
of each hind tarsus is elongated
(Fig. 218).
Oulema lichenis
Voet
Infestations of this beetle occur mainly on wheat,
especially on less-hairy-leaved cultivars. Various
other cereals (but not oats), and grasses such as
cocksfoot, are also attacked. Adults and larvae
cause direct damage to the foliage of host plants.
They graze away longitudinal strips of epidermis
from the upper surface of the leaves, between
the veins, the damaged tissue appearing pale
brown to whitish. Infestations on flag leaves are
especially important and the loss of photosyn-
thetic tissue can have an adverse effect on plant
development; spring cereals are more suscep-
tible than winter crops. The beetles are also
capable of transmitting viruses, notably
cocksfoot mottle virus. Although often of con-
siderable significance in continental Europe, in
the British Isles this pest is unimportant and far
less abundant than the following species.
DESCRIPTION
Adult
10 mm long, distinctly hemispherical;
head, thorax, legs and antennae
orange, marked
with black;
elytra
longitudinally striped alter-
nately black and yellow
(Plate 3f). Egg
1.2 mm
long, yellowish-orange.
Larva
up to 12mm
long;
body
sac-like, at first reddish-brown, later
reddish-orange, with two rows of prominent
black spots along either side;
head, prothoracic
plate and anal plate
black;
abdomen
with several
short, fleshy prolegs, including a well-developed
pseudopod on the anal segment (see Fig. 75).
Longitarsus parvulus
(Paykull)
Flax flea beetle
BIOLOGY
Adults of this univoltine species hibernate
amongst plant debris and in various other situa-
tions, reappearing in April. They then invade
wheat crops to feed on the leaves. Eggs are laid
This widely distributed pest occurs most com-
monly on flax and linseed. Damage is similar
to that caused by
Aphthona euphorbiae
(p. 138);
both pests have a similar life history but adults
