Biology Reference
In-Depth Information
Myzus cerasi
(Fabricius) and
M. pruniavium
Börner (
114
)
Cherry blackflies
Generally common pests of cherry, the former (as the
sour cherry blackfly) on
Prunus cerasus
and the latter
(as the sweet cherry blackfly, which is a more damaging
species) on
P. avium
. Eurasiatic; also found in
Australasia and North America. Widely distributed in
Europe. The two species are morphologically identical,
and often considered merely subspecies.
DESCRIPTION
Apterous female:
1.2-1.5 mm long; shiny yellow to
yellowish green; antennae long and green; siphunculi
long, yellow to green, with dusky tips, and slightly
swollen just beyond the mid-region; cauda yellowish
and tapered.
Alate:
1.5-1.8 mm long; yellowish to
yellowish green, with a brown head, brown thoracic
lobes and brown abdominal crossbars, the last-
mentioned often forming a distinct patch between the
dark, moderately long, slightly swollen siphunculi.
DESCRIPTION
Apterous female:
1.5-2.6 mm long; dark brown to
black, and very shiny; front of head emarginate;
siphunculi black, moderately long and tapered.
Alate:
1.4-2.1 mm long; blackish, but abdomen yellowish
brown and with a large black dorsal patch.
Nymph:
purplish to blackish.
LIFE HISTORY
Eggs are deposited on the shoots of privet in early
winter and hatch in the spring. Colonies of aphids then
develop on the foliage in slightly rolled leaves on the
new shoots, reaching the peak of their development
from June or July onwards. Males are produced late in
the season, and these mate with females (oviparae)
which eventually deposit the overwintering eggs.
LIFE HISTORY
Eggs, overwintering on the spurs and young shoots of
cherry, hatch in March or April, before the white-bud
stage. Colonies of wingless aphids then develop on the
underside of the young leaves, and populations build up
very rapidly. Winged forms are produced in June, at the
climax of colony development, and these fly away to
establish colonies on summer hosts such as bedstraw
(
Galium
) and speedwell (
Veronica
). Colonies on cherry
then decline and eventually die out, although breeding
on the primary host often continues throughout July.
A return migration to cherry takes place in the autumn,
where sexual reproduction takes place and winter eggs
are eventually laid.
DAMAGE
Infestations are most common on regularly clipped
hedges with an abundance of new growth. Individual
leaves become discoloured and curl longitudinally to
produce noticeable distortion on the young shoots.
Persistent attacks affect the appearance and vigour of
hosts, and may lead to leaf death and premature
defoliation.
Myzus ornatus
Laing (
116
)
Violet aphid
A generally common, polyphagous pest of herbaceous
ornamentals such as African violet (
Saintpaulia
hybrida
), azalea (
Rhododendron
),
Begonia
, busy lizzie
(
Impatiens
),
Veronica
and violet (
Viola
). Cosmopolitan.
Widely distributed in Europe.
DAMAGE
On susceptible hosts, colonies of the sweet cherry
blackfly cause severe distortion of young shoots and
leaves, and affected foliage later turns brown or black;
heavy infestations distort growth and may kill shoots.
Attacks are most serious on young trees and nursery
stock.
DESCRIPTION
Apterous female:
1.0-1.7 mm long; pale brownish
yellow or dull green, with paired, blackish markings on
the thorax and abdomen; antennal tubercles distinctly
convergent; siphunculi pale, cylindrical and moderately
long.
Nymph:
light green, with dark red eyes.
Myzus ligustri
(Mosley) (
115
)
syn.
Myzodes ligustri
(Kaltenbach)
Privet aphid
A locally common pest of privet (
Ligustrum vulgare
),
and sometimes of importance on garden hedges in
suburban areas. Widespread in mainland Europe; in the
British Isles most numerous in southern England. Also
present in North America.
LIFE HISTORY
This species is entirely parthenogenetic, and occurs in
small numbers on the leaves of various ornamental
plants. Under favourable conditions, including
greenhouses in northern Europe, breeding continues
throughout the year. The aphids produce considerable
quantities of honeydew, which coats the foliage and
upon which white, cast nymphal skins accumulate.
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