Main Insect Orders - Agricultural Entomology - page 161

damage to the root system often loosens the turf
and infested areas often develop into brownish,
unthrifty patches; larval damage to the roots of
cereals is also reported.

NOTE Adults of various other species of Phyllobius,
and members of the related genus Polydrusus, also
cause damage to fruit trees and ornamental plants;
most of these weevils are clothed in coppery-brown
or metallic-green scales. Larvae of one species
(Phyllobius pomaceus Gyllenhal) sometimes cause
significant damage to the roots of strawberry plants
(see also Otiorhynchus spp., p. 159 et seq.).

BIOLOGY
Adults appear in the spring, from late April on-
wards. They often congregate in large numbers
on trees and shrubs (Rosaceae), and on other
plants, where they feed on the foliage and flow-
ers. Eggs are laid in the soil during the early
summer, usually in association with grasses, each
female depositing up to 200 over a period of
a few weeks. The eggs hatch in 2-3 weeks. The
larvae feed on the roots of grasses and other
plants, and usually become fully grown by the
onset of winter. They then overwinter and pu-
pate in the spring, shortly before the emergence
of the adults.

Plinthus caliginosus (F.)
Hop root weevil

This generally uncommon weevil is most often
found in hop gardens and vineyards but will also
attack crops such as raspberry and strawberry.
Most damage is done by the larvae; these attack
the roots and are especially damaging to newly
planted stock and in young plantations.

BIOLOGY
The adult weevils may be found throughout the
year but are most common in the late summer
and autumn. They are rather inactive and usually
shelter during the daytime beneath moss, stones
or pieces of wood. Eggs are laid mainly from
September to November, each placed singly in a
small puncture made in the rootstock or subter-
ranean part of a newly planted set. The larvae
feed within the host plants for up to 18 months;
they then pupate within the feeding gallery and
adults emerge 2-3 weeks later, usually in the late
summer.

DESCRIPTION
Adult 5-7 mm long, black, clothed in coppery,
golden-brown or greenish-bronze scales; rostrum
very short (Fig. 235). Larva up to 7 mm long;
body creamish-white and translucent; head
yellowish-brown (Plate 6b).

DESCRIPTION
Adult 5.5-9.0mm long, dark brown to black;
body elongate, strongly punctured (Fig. 236) and
often coated in mud; rostrum stout and finger-
like. Larva up to 10mm long; creamish-white;
head brown; frons with a characteristic median
line (Fig. 237).

Sitona lineatus (L.)
Pea & bean weevil

This generally abundant weevil is a pest of vari-
ous members of the Fabaceae, including broad
bean, field bean and pea. Adults form character-

Fig. 235 Common leaf weevil, Phyllobius pyri (xlO).