Agriculture Reference
In-Depth Information
minor importance. Apterae on blackberry
are broadly spindle-shaped, 2-3 mm long, shiny
yellowish-green with dark or mainly dark
siphunculi (cf. bramble aphid, Amphorophora
rubi, p. 105). Those on cereals and grasses are
smaller and mainly dirty greenish; they are dis-
tinguished from Sitobion avenae (above) by the
longer siphunculi (about twice as long as
the cauda) and by the pale basal segments of the
antennae.
Eriosoma lanigerum (Hausmann)
Woolly aphid
Infestations of this notorious pest occur mainly
on apple but may also develop on other trees and
shrubs (Rosaceae), including various orna-
mentals. The aphids produce considerable quan-
tities of waxen 'wool', which often contaminates
shoots, leaves and fruits. The aphids also cause
significant galling of infested wood and heavy
infestations lead to considerable disfigurement
and disruption of growth; damage is of particular
importance on young trees. The often walnut-
like galls may split open, allowing canker and
other diseases to gain entry.
Family PEMPHIGIDAE
Aploneura lentisci (Passerini)
Colonies of this species occur on the roots of
grasses throughout the year, and are most obvi-
ous from May to October, but damage caused is
of little or no significance. The aphids produce
considerable quantities of whitish wax that accu-
mulates around the aphids in cottonwool-like
masses. Winged forms occur in large numbers in
the summer; in Mediterranean areas, these are
able to locate Pistacia lentiscus, the primary host,
upon which the species then overwinters.
Apterae are 1-3 mm long, spindle-shaped and
mainly pale to ochreous yellow, with dark, very
short legs and antennae (Fig. 194).
BIOLOGY
This aphid remains on apple throughout the
year. The winter is passed as bare (wax-less)
nymphs that shelter in cracks or crannies in the
bark of host trees. Activity is resumed in the
spring and colonies soon develop beneath con-
spicuous masses of whitish, waxen 'wool', espe-
cially on the shoots, spurs and branches. There
are several generations throughout the summer
months, and colonies at this time often develop
on sucker growth and water shoots. Small num-
bers of winged aphids may be produced in
July but they are of only minor importance in
spreading infestations. Egg-laying females
(oviparae) appear in September but any eggs
they deposit fail to hatch, aborting the sexual
phase. Wax-covered colonies of parthenogenetic
females persist well into the autumn and finally
die out as the nymphs that will overwinter enter
hibernation. 8
DESCRIPTION
Aptera 1.2-2.6 mm long, soft-bodied, purplish-
brown, covered with masses of white, mealy wax;
antennae short, with the third segment elongated
(Fig. 195a); siphunculi pore-like.
8 It is thought that colonies persist throughout the
winter on the roots of host trees but accounts from
authors differ as to whether there is a regular seasonal
migration from the aerial parts of host plants to the
roots and back.
Fig. 194 Anterior part of body of Aploneura
Search WWH ::




Custom Search