Biology Reference
In-Depth Information
Stereonychus fraxini
(Degeer) (
355-357
)
syn.
S. rectangulus
(Herbst)
Ash leaf weevil
A southerly-distributed pest of ash (
Fraxinus excelsior
),
including ornamental trees; also associated with certain
other plants, including lilac (
Syringa
) and
Phillyrea
.
Widespread in south-central and southern Europe,
including many parts of France and southern Germany;
also found in Asia Minor and North Africa. Not present
in the British Isles.
LIFE HISTORY
Adults overwinter in debris on the ground, and in other
shelter, emerging in the spring. They then feed on the
buds and, later, on the leaves and leaf stalks. Eggs are
deposited close to the veins on the underside of the
expanded leaves. Following egg hatch, larvae browse
on the surface of the leaves to form a series of window-
like patches. When fully fed they pupate, each in an
oval, yellowish-brown to brownish, parchment-like
cocoon formed on the leaf surface. Young adults appear
about ten days later; they feed on the foliage before
entering hibernation. There is one generation annually.
DESCRIPTION
Adult:
3 mm long; greyish brown to reddish brown,
with a blackish thoracic disc and an elongate,
cylindrical rostrum.
Larva:
up to 4 mm long; greenish
yellow, with a black head.
DAMAGE
Weevils feeding on unopened buds in the early spring
delay the appearance of the new growth. In addition,
adult and larval damage to the expanded foliage is
disfiguring and, if attacks are heavy, will reduce plant
vigour.
Strophosoma melanogrammum
(Förster) (
358
)
syn.
Strophosomus coryli
(Fabricius)
Nut leaf weevil
An often common pest of various trees and shrubs,
including birch (
Betula
), beech (
Fagus sylvatica
),
Rhododendron
and various conifers, but most abundant
on hazel (
Corylus
); sometimes an important pest of
young trees and nursery stock, particularly in wooded
areas. Widely distributed in Europe.
355
DESCRIPTION
Adult female:
4-6 mm long; body bulbous and mainly
black or brown, coated in greyish-brown scales, and
with a distinctive, black longitudinal line down the
thorax and between the elytra; head broad, with
protruding eyes.
355
Ash leaf weevil (
Stereonychus fraxini
).
356
357
356
Ash leaf weevil (
Stereonychus fraxini
) damage to leaf of
Fraxinus
.
357
Pupal cocoon of ash leaf weevil (
Stereonychus fraxini
).
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