Biology Reference
In-Depth Information
DESCRIPTION
Female test:
1.0-1.5 mm across; rounded, slightly
convex and whitish, with an eccentric yellow spot.
Male test:
0.5-1.0 mm long; narrow, with a distinct
longitudinal rib; mainly white.
Egg:
oval; pale
yellowish white.
Nymph:
pale greenish yellow.
DAMAGE
Heavy infestations disfigure ornamentals, causing
considerable discoloration of the foliage; affected
shoots and branches look dull and distinctly unthrifty.
Carulaspis minima
(Targioni-Tozzetti)
syn.
C. caerueli
(Signoret)
This more southerly distributed species is virtually
indistinguishable from
Carulaspis juniperi
, but slight
structural differences are apparent in adults. It is
recorded from various parts of Europe; confirmed hosts
include
Cupressus
, Lawson cypress (
Chamaecyparis
lawsoniana
), pencil cedar (
Juniperus virginiana
) and
Thuja
.
LIFE HISTORY
This species infests the foliage, shoots and fruits of
various hosts, and is often present in considerable
numbers. The insects mature in the late autumn or early
winter, when winged males appear and mating takes
place. Tests are readily dislodged from the host plant,
and the overwintering mated females are frequently
taken by insectivorous birds. Eggs are deposited in the
following May, the females then dying. The eggs hatch
in June. First-instar nymphs then swarm over the host
plants before settling down to feed and to complete their
development.
Chionaspis salicis
(Linnaeus) (
199-200
)
syn.
C. alni
Signoret;
C. populi
(Baeunsprung)
Willow scale
Locally common on ash (
Fraxinus excelsior
), common
alder (
Alnus glutinosa
) and willow (
Salix
); infestations
also occur on broom (
Cytisus
),
Ceanothus
, elm
(
Ulmus
), flowering currant (
Ribes sanguineum
), lilac
(
Syringa
), lime (
Tilia
), maple (
Acer
), poplar (
Populus
),
privet (
Ligustrum vulgare
), spindle (
Euonymus
) and
winter jasmine (
Jasminum grandiflorum
). Widely
distributed in Europe; also present in North America.
199
DESCRIPTION
Female test:
1.5-2.3 mm long; whitish to waxy
yellowish white, and irregularly pear-shaped.
Male
test:
0.5-1.0 mm long; white, elongate and very narrow,
with a central and two lateral longitudinal ribs.
Adult
male:
1 mm long; orange to reddish-orange, with a
caudal spine and bright yellow legs and antennae; alate
and apterous forms occur.
Nymph:
rusty-red, oval and
flattened.
199
Nymphs of willow scale (
Chionaspis salicis
) on
Salix
.
LIFE HISTORY
Eggs are laid in August, beneath the body of fertilized
females. The females, each covered by their protective
test, then die. Eggs remain
in situ
throughout the winter
and hatch in May. Newly emerged, red-coloured
nymphs then cluster in large, conspicuous groups on the
bark of host plants. They soon disperse and settle down
to feed, developing to maturity a few weeks later. Adult
males occur from late June to mid-July, wingless forms
considerably outnumbering those with wings.
200
DAMAGE
Heavy encrustations impart a whitish appearance to the
bark of host plants, and the pest has a deleterious effect
on the growth of young trees and shrubs.
200
Colony of willow scale (
Chionaspis salicis
) on
Fraxinus
.
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