Agriculture Reference
In-Depth Information
BIOLOGY
Adults are active mainly in May and June, and
often swarm in sunny weather. They feed on the
flowers, fruits and leaves of various herbaceous
and other plants. Eggs are laid in the soil, usually
deposited singly but close together, each in a
small earthen chamber. Larvae feed from June
or July onwards. They attack plant roots and
typically rest with the head adpressed to the anal
segment
(Plate 3d).
Individuals are fully grown
by the autumn but they do not pupate until the
following spring.
are usually most numerous in permanent grass-
land, where populations may reach or exceed
several million per hectare. After destruction of
infested grassland (e.g. by ploughing), surviving
wireworms readily transfer their attention to fol-
lowing crops. Damage is most severe in spring
and early summer, especially on potato tubers
and on vegetable crops such as celery, leek, let-
tuce and onion; infestations may also be of sig-
nificance on beet, hops, mangold, oats, spinach,
strawberry, wheat (especially in the second year
following grass), and on many other crops. Some
plants, including barley, beans, clover, fodder
brassicas, linseed, lucerne, mustard, oilseed rape,
peas and rye, are resistant to attack. Wireworms
browse on the roots or bite through the stems at
about soil level; they also produce ragged holes
in the basal parts of stems or bore into planted
seeds, swollen tap roots or tubers, producing dis-
tinctive, small, rounded entry holes.
DESCRIPTION
Adult
7-11 mm long, distinctly hairy;
head and
thorax
metallic bluish-green;
elytra
reddish-
brown;
legs
black.
Larva
up to 15 mm long;
body
mainly white;
head
pale yellowish-brown;
anal segment
translucent, the anal slit transverse
and surmounted by two parallel rows of spines
(Fig. 203d).
BIOLOGY
Adult click beetles are active from April to June.
Eggs are then laid in the soil in batches of up to
100, usually amongst grass or other vegetation.
The eggs hatch 5-6 weeks later. Wireworms
(larvae) develop slowly, especially in their later
instars, development usually extending over 4 or
5 years. They cause most damage in early spring,
especially from March to May, with a second
period of activity in the late summer or early
autumn. Pupation takes place in August of the
final year of larval development, each larva first
forming an earthen cell 10 cm or more below the
surface. The adult stage is reached 3-4 weeks
later; however, the beetle does not emerge but
remains within the pupal cell until the following
spring.
Serica brunnea
(L.)
Brown chafer
Minor infestations of this locally common chafer
sometimes occur on crops, such as potato, grow-
ing in fields adjacent to forests or woodlands.
Root damage is also reported in wooded areas
on young spruces grown as Christmas trees.
Adults are 7-11 mm long and mainly reddish-
brown; they occur throughout the summer
months. The larvae, which usually take 2 years
to complete their development, reach 18mm
in length and are creamish-white with a pale
yellowish-brown head; the body bears reddish-
brown hairs and the anal slit is surmounted by an
arc of spines
(Fig. 203e).
DESCRIPTION
Adult
7-10 mm long and mainly dark yellowish-
brown, with a darker head;
elytra
with alter-
nating dark and pale longitudinal striations;
pronotum
relatively long, with a moderately dis-
tinct median longitudinal cleft
(Fig. 204). Egg
0.6 mm long, more or less oval, whitish.
Larva
up to 25 mm long, shiny yellowish-brown, with a
darker head, powerful jaws and small thoracic
Family ELATERIDAE (click beetles)
Agriotes lineatus
(L.)
A common click beetle
The larvae of click beetles (commonly known as
'wireworms') are important, polyphagous pests.
They attack the subterranean parts of plants, and
