Biology Reference
In-Depth Information
324
bored through the bark. They often penetrate to the pith
of the branches and trunks of host plants; they also
burrow extensively within the rods and stools. Fully fed
larvae eventually pupate at the end of their galleries
from mid-July onwards. Adults emerge from the pupae
in late July or August but do not vacate the pupal cells
until the following spring.
DAMAGE
Young terminal shoots are partly severed by the adult
weevils, the tips keeling over and eventually turning
black. Shoots may also become riddled with holes; such
damage is of particular importance in willows intended
for basket making; affected rods have to be discarded.
The larvae reduce the production of new shoots from
infested stools, and are sometimes of importance in
nurseries. Heavy attacks cause death of plants.
324
Adult of
Dorytomus taeniatus
.
Dorytomus taeniatus
(Fabricius) (
324
)
Generally common on willow (
Salix
) from May
onwards. The adults browse on the leaves, removing
patches of tissue to expose a network of fine veins; they
often feed in groups, but damage caused is insignificant
(although noticeable and sometimes extensive). Eggs
are laid in the axils of the catkin buds during the autumn
and hatch early in the following spring. The larvae
then mine within the catkins and eventually pupate in
the soil, young weevils appearing in May and June.
The weevils often hide during the day amongst curled
leaves, dropping to the ground if disturbed. Adults are
4-5 mm long, black to brownish black, with elongate,
parallel-sided elytra, an elongate rostrum and toothed
femora; the elytra are also patterned with small patches
of lighter hairs. At least in mainland Europe, the weevils
will also attack alder (
Alnus
), birch (
Betula
) and poplar
(
Populus
).
scales interspersed with irregular patches of darker
ones. The larvae develop beneath the bark, forming
irregular galleries (each up to
c
. 20 mm long) that
extend upwards and downwards from a pair of broad,
more or less horizontal maternal chambers. There is a
single generation annually.
Hypera arator
(Linnaeus)
syn.
H. polygoni
(Linnaeus)
This widely distributed species is associated with
various members of the Caryophyllaceae and is
sometimes a minor pest of carnation (
Dianthus
caryophyllus
) and pink (
D. plumarius
). The yellowish-
grey to greenish larvae (up to 7 mm long) feed within
the flowers, and damage on cultivated plants is
sometimes mistaken for that caused by larvae of the
carnation tortrix moth (
Cacoecimorpha pronubana
,
p. 263). Pupation occurs in oval, yellowish-white
cocoons formed on the foodplant. Young weevils appear
about two weeks later. The adults (5-7 mm long) are
yellowish brown, with pale, dark-edged longitudinal
bands on the thorax and elytra and a black line along the
elytral suture. They may be found from early May to the
end of September.
Hylesinus varius
(Fabricius)
syn.
Leperisinus varius
(Fabricius)
Ash bark beetle
A common but typically secondary pest of ash
(
Fraxinus excelsior
) and lilac (
Syringa
). Other hosts
include common hazel (
Corylus avellana
), false acacia
(
Robinia pseudoacacia
), flowering ash (
Fraxinus
ornus
), hornbeam (
Carpinus betulus
), maple (
Acer
),
olive (
Olea europaea
) and walnut (
Juglans
). Breeding
occurs mainly in felled or fallen trees. However, the
beetles will invade live trees, especially trees previously
weakened or damaged by other factors. Young trees
with thin bark are also favoured hosts. Adults occur
from early March to May, and appear in distinct waves.
Individuals (2.5-3.5 mm long) are blackish brown to
brownish red, with the thorax and elytra covered in grey
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