Insects - Pests of Ornamental Trees, Shrubs and Flowers - page 144

Family CURCULIONIDAE (true weevils
and bark beetles)

Barypeithes araneiformis (Schrank) ( 316 )
Smooth broad-nosed weevil
Adults of this widely distributed but local weevil are
sometimes damaging during the spring and summer
in conifer nursery beds, when they destroy the
initial shoots and also ring-bark young seedlings. They
also attack young deciduous trees, such as birch
( Betula ), horse chestnut ( Aesculus hippocastanum ) and
oak ( Quercus ), damaging the buds and severing or
forming holes in the expanded leaves. The larvae feed
on the roots of herbaceous plants, including various
weeds. Adults are 3-4 mm long, shiny brownish yellow
to black, with a pointed abdomen.

The main family of weevils, the antennae being
geniculate and with a very long basal segment (scape).
The larvae are apodous, with a distinct head; in repose,
they often adopt a C-shaped posture. Adult weevils
typically feed externally on plant tissue. Larvae may
also feed externally, but those of most weevils mine
within the leaves, stems or roots of host plants.
Bark beetles were formerly separated into the family
Scolytidae but are now included in the Curculionidae.
They are typically small, cylindrical, wood-boring
insects (including some known as ambrosia beetles and
some as shot-hole borers) with relatively short but
distinctly clubbed antennae. The larvae have an
enlarged prothoracic region, giving them a hunch-
backed appearance. Development takes place entirely
within the host, some species being dependent upon the
presence in their galleries of hyphae of ambrosia fungi
upon which the larvae feed. Many species of bark beetle
attack ornamental trees, but infestations occur mainly
on already weakened trees and those growing under
stress. Examples cited below are restricted to the genera
Hylesinus , Phloeosinus and Scolytus .

Barypeithes pellucidus (Boheman) ( 317 )
Hairy broad-nosed weevil
This locally distributed weevil is sometimes damaging
to young or seedling trees. Adults are distinguished
from those of Barypeithes araneiformis by the longer,
denser and more distinct pubescence.

Cionus scrophulariae (Linnaeus) ( 318-320 )
Figwort weevil
A generally common pest of cape figwort ( Phygelius
capensis ), mullein ( Verbascum ) and orange ball buddleia
( Buddleja globosa ); also abundant on wild figwort
( Scrophularia nodosa ). Widely distributed in Europe.

Anthonomus brunnipennis (Curtis) ( 314 )
syn. A. comari Crotch
A generally common and widely distributed species,
associated with wild and cultivated cinquefoil
( Potentilla ). The weevils feed on the foliage and flower
petals, producing numerous small holes. Individuals are
about 2 mm long and mainly black, with the thorax and
elytra covered extensively in fine punctures.
Infestations have no significant effect on plant growth.
However, damage is unsightly, particularly on petals of
opened blossoms.

DESCRIPTION
Adult: 4.0-4.5 mm long; thorax small, elytra square;
body black but largely coated with a purplish-grey
pubescence; elytra with a regular pattern of black
markings, including two large circular patches;
antennae dark red. Larva: up to 6 mm long; yellowish,
with a black head and prothoracic plate; body coated
with greenish-yellow slime.

LIFE HISTORY
Adults occur on host plants from May or June onwards,
feeding on the leaves, leaf stalks and flowers. Larvae
feed during the summer on the leaves, removing tissue
from one surface, the other remaining intact. Fully
grown larvae construct more or less spherical,
brownish to yellowish-brown, parchment-like cocoons
on the stems and leaves, and then pupate. Adults emerge
2-3 weeks later and eventually produce a further brood
of larvae. Adults of the final generation enter
hibernation to reappear in the spring.

Barynotus obscurus (Fabricius) ( 315 )
Adults of this widely distributed and locally common
weevil feed on the flowers of various plants, including
ornamentals such as primrose ( Primula vulgaris ), rose
( Rosa ) and violet ( Viola ). Damage occurs from spring to
mid-summer, most serious attacks having been reported
on rose bushes in England. The weevils are 8-10 mm
long and black or brownish, with a coating of round,
close-set, yellow (sometimes greenish or coppery)
scales; they are superficially similar in appearance to
otiorhynchid weevils (pp. 159-63) but the thoracic
region is relatively broad, with only a slight constriction
between thorax and abdomen; the femora are untoothed.

DAMAGE
Attacked plants are disfigured, and leaf tissue infested
by larvae may eventually split; flower buds are also
destroyed.