Insects - Pests of Ornamental Trees, Shrubs and Flowers - page 128

Chrysomela populi Linnaeus ( 267 )
Red poplar leaf beetle
A locally common pest of Populus , including aspen
( P. tremula ); also occurs on willow ( Salix ). Widespread
throughout Europe.

Crioceris duodecimpunctata (Linnaeus) ( 269 )
Twelve-spotted asparagus beetle
A minor pest of asparagus, including ornamental
species such as Asparagus plumosus . Eurasiatic. Widely
distributed in mainland Europe. Also present in North
America.

DESCRIPTION
Adult: 8-12 mm long; thorax bluish black or greenish;
elytra reddish, with a black spot at the extreme tip (cf.
Chrysomela tremula ). Egg: 1.0

DESCRIPTION
Adult: 5-6 mm long; elytra orange-red, spotted with
black; antennae black. Larva: up to 8 mm long; mainly
yellow, with a black head and two blackish plates on the
prothorax.

0.56 mm; elongate-
oval, pale yellow, yellow to brownish. Larva: up to
15 mm long; head black; body creamy white, with a
mainly black prothoracic plate and prominent black
verrucae.

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LIFE HISTORY
Overwintered adults appear in the spring and then
attack the young fronds of asparagus plants. Eggs are
eventually laid at the tips of the fronds and hatch about
10 days later. Larvae feed on developing berries and
eventually pupate in the soil, each in a small chamber.
New adults appear 2-3 weeks later. Larvae of a second
brood feed in late summer and pupate in the autumn.

LIFE HISTORY
Adults occur from May onwards, depositing eggs on the
leaves of host plants. They show a particular liking for
young trees and are sometimes common in poplar stool
beds. Larvae browse on the surface layers of the leaves
but later form holes right through the leaf blade. If
disturbed, larvae are capable of exuding globules of
liquid from a lateral series of tube-like verrucae. Fully
fed individuals pupate in the soil, and adults of the next
generation appear in about July. A second generation of
larvae feed in July and August, and these become adults
in September. These beetles eventually hibernate and
reappear in the spring.

DAMAGE
Young adults sometimes cause extensive damage in
seedbeds where decorative asparagus fronds are being
raised.

Crioceris asparagi (Linnaeus) ( 270-271 )
Asparagus beetle
Although mainly of importance as a pest of edible
asparagus, this generally common and well-known beetle
also attacks ornamental asparagus plants, including
Asparagus plumosus . Adults and larvae browse on the
foliage and, as with the previous species, there are two
generations annually. The mainly grey, black-headed
larvae (up to 7 mm long) are particularly damaging.

DAMAGE
Adults and larvae skeletonize the leaves, and
infestations often result in extensive damage; young
aspen trees are particularly susceptible.

Chrysomela aenea Linnaeus ( 268 )
Widely distributed on alder ( Alnus ) and sometimes
damaging to the foliage of other trees, including willow
( Salix ). There are two generations annually. Adults are
5-8 mm long and coppery blue or metallic green; the
larvae, which often skeletonize the leaves, are up to
10 mm long and blackish to whitish, with prominent
black verrucae and a shiny black head and prothoracic
plate.

Chrysomela tremula Fabricius
syn. C. longicollis (Suffrian)
Adults of this locally distributed beetle are very similar
to those of Chrysomela populi but are smaller (6-9 mm
long) and the body narrower; they also lack the black
mark at the tip of the elytra. The pest occurs on aspen
( Populus tremula ) in various parts of Europe, and
sometimes causes damage to young cultivated trees.