Biology Reference
In-Depth Information
87
Brachycaudus cardui
(Linnaeus) (
88
)
Thistle aphid
Minor infestations of this generally common aphid
sometimes occur in summer on ornamental plants,
especially silver ragwort (
Senecio cineraria
). The
aphids are similar in appearance to
Brachycaudus
helichrysi
but green to shiny brownish black, with
distinctive black siphunculi.
Cavariella aegopodii
(Scopoli) (
89
)
Willow/carrot aphid
This generally common aphid overwinters on willow
(
Salix
), especially crack willow (
S. fragilis
) and white
willow (
S. alba
). Infestations occur in the early spring
on the young shoots. Winged forms are then produced,
and these migrate in May to various umbelliferous hosts
(Apiaceae). Large colonies often develop on the
summer hosts from late May to early July, before the
production of winged forms and a return migration to
the primary, winter hosts. Apterae (1.0-2.6 mm long)
are green or yellowish green, with swollen siphunculi
and a pair of closely set hairs arising from a prominent
tubercle on the eighth abdominal tergite; alatae
(1.4-2.7 mm long) are green or yellowish green, with
a black patch on the abdomen.
87
Damage on
Prunus
caused by leaf-curling plum aphid
(
Brachycaudus helichrysi
).
Brachycaudus helichrysi
(Kaltenbach) (
87
)
Leaf-curling plum aphid
An often serious pest of damson and plum, including
various ornamental kinds of
Prunus
, and a summer pest
of herbaceous plants such as
Chrysanthemum,
Cineraria
, forget-me-not (
Myosotis
), Michaelmas daisy
(
Aster
) and periwinkle (
Vinca
). Cosmopolitan. Widely
distributed in Europe.
Chaetosiphon tetrarhodum
(Walker)
This small, light green to yellowish-green aphid occurs
on the young shoots and underside of leaves of rose
(
Rosa
) but, unlike many rose-infesting species, the
colonies are not ant-attended. Apterae are 1.0-2.6 mm
long, with capitate body hairs and a short cauda. Alatae
(1.2-2.4 mm long) are greenish, with a blackish head
and thorax, and a black mark on the abdomen. In
favourable conditions, colonies often persist throughout
the year; they are particularly damaging on climbing
roses producing an abundance of new growth.
DESCRIPTION
Apterous female:
0.9-2.0 mm long; brownish to
yellowish green, round and shiny; antennae short;
siphunculi pale, short and flanged; cauda tongue-like.
LIFE HISTORY
Eggs are laid in the autumn on various kinds of
Prunus
and hatch in the early spring before bud-burst; in many
areas the eggs hatch in November and December. At
first, nymphs feed at the base of the buds but,
eventually, as the buds open they move onto the new
blossoms and foliage. Colonies develop throughout the
spring, culminating in the production of winged forms
in May. These aphids migrate to summer herbaceous
hosts, where colonies develop before a return migration
to primary hosts in the autumn. Apterae on secondary
(summer) hosts are distinctly smaller and paler than
those on primary hosts.
Coloradoa rufomaculata
(Wilson)
Small chrysanthemum aphid
This very small, green aphid was introduced from
America into northern Europe where it is now a
widespread, but usually only minor, pest of greenhouse
Chrysanthemum
. The aphids infest the stems and
underside of the leaves, including senescing foliage; they
are also vectors of viruses, including chrysanthemum
virus B. Apterae are 1.0-1.7 mm long, with spatulate
body hairs; the mainly dark siphunculi are very long
(longer than the antennae) and swollen close to their
apex; the cauda is triangular.
DAMAGE
Primary hosts:
infestations cause severe leaf curl, a
yellowing of foliage and distortion of new growth, and
are of particular significance on nursery stock and
young trees.
Secondary hosts:
plants are severely
stunted and distorted; leaves also become mottled with
yellow, affecting the overall appearance and quality of
hosts.
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