Biology Reference
In-Depth Information
Otiorhynchus ovatus
(Linnaeus) (
338
)
Strawberry weevil
An often common pest of herbaceous plants. Young and
seedling trees, especially Norway spruce (
Picea abies
)
grown as Christmas trees, are also attacked. Eurasiatic.
Present throughout Europe; introduced into Central and
North America.
LIFE HISTORY
Adults occur from April to October, hiding by day in
cracks in the soil, under straw mulches and in other
shelter beneath host plants. At night, they feed on the
foliage, buds and bark, causing most harm from April to
June. Eggs are laid in the soil during the summer. The
emerging larvae then feed on the roots of many kinds of
plant, including various weeds, from late summer
onwards. Fully grown larvae pupate in the early spring,
and adults appear shortly afterwards. Some individuals
survive for two or more seasons, hibernating during the
winter months. Males are very rare and reproduction is
mainly parthenogenetic.
DESCRIPTION
Adult female:
5.0-5.5 mm long; black to reddish
brown, with a slight yellow pubescence; disc of thorax
distinctly furrowed.
Larva:
up to 6 mm long; creamy
white, with a brown head.
LIFE HISTORY
Weevils are active from April or May onwards. They
feed on the foliage and young shoots of various hosts,
especially seedling conifers and strawberry plants. Eggs
are laid in the soil in the spring. Larvae attack the fine
roots, and cause most damage in May and June. They
usually complete their development in the summer.
There is a single generation annually, but details of the
lifecycle vary according to local conditions.
DAMAGE
Larvae attack the roots, sometimes seriously weakening
herbaceous plants in rockeries. Generally, however,
adults are more important pests, the precise type of
injury caused varying from host to host. On young trees,
large irregular areas of bark are removed, stems often
ring-barked and plants killed; the weevils also notch the
leaves and destroy the buds of young grafts. Leaf stalks
on young shoots are sometimes gnawed, causing them
to fold over, wilt and drop off; buds on young bushes are
also attacked, producing misshapen plants with forked
shoots or numerous unwanted laterals; new growth is
often girdled and killed.
DAMAGE
Conifers:
adults destroy the young growth and needles,
affecting the quality and vigour of host plants; the larvae
destroy the smaller roots, weakening and often killing
seedlings.
Otiorhynchus sulcatus
(Fabricius) (
340-343
)
Vine weevil
A major pest of greenhouse and outdoor ornamentals,
including alpines (especially
Saxifraga
,
Sedum
and
Sempervivium
),
Begonia
, busy lizzie (
Impatiens
),
Calceolaria
,
Camellia
,
Cotoneaster
,
Cyclamen
,
Elaeagnus
, ferns (e.g.
Adiantum
), heather (
Erica
), lily-
of-the-valley (
Convallaria majalis
), Michaelmas daisy
(
Aster
), peony (
Paeonia
),
Phlox
,
Polyanthus
, primrose
(
Primula vulgaris
),
Rhododendron
and various tree
seedlings (coniferous and broad-leaved species).
Widely distributed in Europe; an introduced pest in
Australasia and North America.
Otiorhynchus singularis
(Linnaeus) (
339
)
syn.
O. picipes
(Fabricius)
Clay-coloured weevil
An often troublesome pest of ornamentals such as
buddleia (
Buddleja
),
Clematis
, crab-apple (
Malus
),
flowering cherry (
Prunus
),
Hydrangea
, primrose
(
Primula vulgaris
),
Rhododendron
, rose (
Rosa
)
and
Wisteria
; also damaging to conifers, notably western
hemlock (
Tsuga heterophylla
) and yew (
Taxus
).
Widespread in Europe, particularly in grassy lowland
sites; an introduced pest in North America.
DESCRIPTION
Adult:
6-7 mm long; shiny black and strongly
sculptured, but covered with greyish-brown scales that
give the body an irregular pattern and overall matt
appearance; body often encrusted with mud; wingless.
Larva:
up to 8 mm long; head brown; body creamy
white, plump and wrinkled.
DESCRIPTION
Adult:
7-10 mm long; black and shiny, the elytra
parallel-sided and coated with patches of yellowish
hairs; body deeply sculptured; wingless.
Egg:
0.7 mm
across; more or less spherical; white at first, soon
turning brownish.
Larva:
up to 10 mm long; creamy to
brownish white, with a reddish-brown head.
Pupa:
7-10 mm long; white.
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