Agriculture Reference
In-Depth Information
species of
Prunus,
especially
P. spinosa.
Vast
numbers of aphids often coat the underside of
the expanded leaves; colonies may also spread
along the young shoots. Unlike the leaf-curling
plum aphid,
Brachycaudus helichrysi
(p. 109),
mealy plum aphid does not cause leaf distortion,
but infested foliage often becomes yellow and
may drop prematurely; honeydew excreted by
the aphids is also a problem, enabling sooty
moulds to develop. Attacks sometimes also
occur on almond, apricot and peach trees.
especially common in unheated glasshouses,
and often develop on potato shoots in chitting
houses.
BIOLOGY
In Europe, the potato aphid is mainly
anholocychc, breeding parthenogenetically and
overwintering in protected situations as either
adults or nymphs. Occasionally, however, the
aphid overwinters in the egg stage on Rosaceae,
including cultivated rose. Aphid numbers are
capable of developing rapidly in the spring and,
in May and June, when winged forms are pro-
duced, infestations soon spread to many kinds of
plant.
BIOLOGY
Overwintering eggs, laid on the young shoots
of
Prunus
in the autumn, hatch in the spring.
Colonies then develop on the primary hosts,
numbers at first remaining relatively low but
later increasing rapidly. In June and July, col-
onies are often extremely populous and they
may remain active into August. Winged migrants
are produced from late June or early July
onwards and these fly to various summer hosts,
including
Phragmites communuis.
A return
migration to primary hosts occurs in the autumn.
DESCRIPTION
Aptera
1.7-3.6 mm long;
body
spindle-shaped,
shiny, greyish-green to pink;
antennae and legs
long;
siphunculi
very long and slender, with a
reticulate pattern apically;
cauda
elongate
(Fig. 190c). Nymph
elongate, pale with a dark
central longitudinal stripe and a slight wax
coating.
DESCRIPTION
Aptera
1.5-2.6mm long, elongate, mainly pale
green but dark-mottled and liberally coated with
white, mealy wax;
antennae, legs and siphunculi
dusky-tipped;
siphunculi
short, apically rounded;
cauda
finger-like
(Fig. 191e).
Macrosiphum albifrons
Essig
Essig's lupin aphid
This North American aphid was first reported in
the British Isles in 1981. It has since become a
widespread and important pest of lupin, and is
now also well established in continental Europe.
The aphids are very large (up to 4.5mm long),
and greyish-green, dusted with whitish wax.
They form dense colonies on the leaves and
flower spikes, causing severe damage to lupins
in gardens and nurseries, and also transmitting
viruses. Infestations also occur on agricultural
lupin crops, e.g. white lupin; alkaloid content
and composition of the plant is important in
determining host suitability. On autumn-sown
lupins, infestations often become extensive by
mid-April. On spring-sown crops, aphids usually
occur from July onwards, with largest
populations developing during flowering. In
Europe, this species appears to be anholocychc
and breeds entirely parthenogenetically.
Macrosiphum euphorbiae
(Thomas)
Potato aphid
This polyphagous species, first introduced into
Europe from North America in about 1917, is
often abundant on edible crops such as lettuce,
potato and tomato, and on various other hosts
including borage and many ornamentals. The
aphids often cause stunting and distortion; they
are also vectors of both persistent and non-
persistent viruses, including freesia mosaic,
pea enation mosaic, pea leaf roll and potato leaf
roll; compared with peach/potato aphid
(Myzus
persicae,
p. 116), however, their role in spreading
potato leaf roll virus is minor. Infestations are
