Insects - Pests of Ornamental Trees, Shrubs and Flowers - page 154

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344 Privet weevil ( Otiorhynchus crataegi ). 345 Female of Otiorhynchus niger .

young plants. Most important damage, however, is
caused by the larvae which destroy the finer roots, or
burrow into the fleshy parts of corms and rhizomes;
affected plants lack vigour and may suddenly wilt, or
collapse and die. Damage is particularly important on
outdoor containerized plants growing in peat composts
and on greenhouse pot plants, but may also be extensive
in nursery beds and rock gardens.

LIFE HISTORY
In outdoor situations, adult females of this
parthenogenetic weevil emerge in May and June. They
are active at night, feeding on the foliage of various
plants. During the daytime, they tend to hide away
beneath debris, in crevices in walls or in other shelter.
The weevils mature a few weeks after commencing
feeding, each being capable of depositing several
hundred eggs. The eggs are laid in soil near the host
plants from late July onwards. They hatch in 2-3 weeks
and the larvae then attack plant roots, corms or
rhizomes. Larval feeding extends over several months.
Development is completed in the following spring, fully
grown individuals pupating in oval subterranean cells
formed in the soil; transformation to the adult stage
occurs from mid-April to June. Most weevils die before
the onset of winter. However, some survive for two
seasons or longer, overwintering in sheltered situations
and reappearing in the spring. Young adults are
distinguished from older individuals by the presence of
a thick spine on each mandible; this usually breaks off
soon after emergence. In heated greenhouses, adults
often emerge in large numbers in the autumn; also, eggs
are laid over a more extended period, and all stages of
the pest may occur at one and the same time.

Otiorhynchus crataegi Germar ( 344 )
Privet weevil
This small species is a pest of various ornamentals in
eastern and certain other parts of mainland Europe. The
weevils browse on foliage and the larvae feed on the
roots of various plants, including lilac ( Syringa ) and
privet ( Ligustrum vulgare ). In 1985, following an
accidental introduction, extensive but localized damage
was reported on privet hedges, ornamental shrubs and
certain other plants, in south-central England. Adults are
5 mm long and mainly dark brown, marked irregularly
with golden brown; the narrow, rounded thorax, bulbous
abdomen and relatively narrow waist are characteristic.

Otiorhynchus niger (Fabricius) ( 345 )
A common forestry pest in mainland Europe,
particularly in mountainous areas; sometimes found on
amenity trees but not an important pest of ornamentals.
Adults are 9-11 mm long and mainly black, with dark
orange legs and deeply sculptured elytra.

DAMAGE
Adults notch the leaves of host plants, and often cause
extensive damage to ornamentals such as camellia, lily-
of-the-valley and rhododendron. They also ring-bark