Agriculture Reference
In-Depth Information
BIOLOGY
This species overwinters in the egg stage on the
shoots of currant. In spring, colonies develop on
the underside of the leaves within the hollows
formed beneath the leaf blisters, and eventually
produce winged forms. These migrate to summer
hosts, especially
Stachys. A
return migration to
currant occurs in the autumn.
BIOLOGY
This species is restricted to apple and over-
winters as eggs secreted under bark or in deep
bark fissures. Colonies develop on the rosette
leaves from early spring onwards, and are well
established by the green-cluster stage. Later, the
aphids also invade the young shoots. Although
producing winged forms during the summer, the
extent of migration is strictly limited and aphids
rarely fly away from the tree upon which they
were reared. Winter eggs are deposited from
mid-Iune onwards, and most colonies will have
completed their development before the end of
My.
DESCRIPTION
Aptera
1.2-2.5 mm long, oval-bodied, either
shiny white or pale ereamish-white to pale
yellowish-green;
body hairs
capitate;
siphunculi
relatively thin, often more than three times as
long as the cauda;
cauda
tongue-like.
DESCRIPTION
Aptera
1.8-2.4mm long, mainly bluish-grey,
coated with white, waxy powder;
antennae
relatively short;
siphunculi
black, short, tapered,
flanged apically;
cauda
black, triangular
(Fig.
191c).
Cryptomyzus galeopsidis
(Kaltenbach)
Black currant aphid
This aphid has two biological races, sometimes
afforded subspecific status: one occurs entirely
on black currant and red currant; the other alter-
nates between
Ribes
(including gooseberry)
and various Labiatae, especially
Galeopsis
and
Lamium
(the labiates are the secondary, summer
hosts). The aphids cause no direct damage.
However, if populations on
Ribes
are large,
honeydew excreted by the aphids will cause no-
ticeable contamination of foliage and fruit. The
aphids are similar in appearance to those of
Cryptomyzus ribis
(above) but readily distin-
guished by the more elongate cauda (usually
more than half the length of the siphunculi); they
are also often greener in appearance and have a
dark dorsal stripe.
Dysaphis plantaginea
(Passerini)
Rosy apple aphid
This aphid (commonly known as 'blue bug') is a
serious pest of apple, causing severe curling and
distortion of leaves; affected tissue (pseudo-
galls) may also become yellowish or brown but
not red (cf.
Dysaphis devecta,
above). Infested
shoots also become distorted and stunted and
fruits remain small and malformed. Heavy infes-
tations also lead to premature leaf-fall and will
reduce cropping potential for the following year.
BIOLOGY
Eggs, overwintering on the bark, hatch in the
early spring. Colonies then develop on the
rosette leaves and, later, on the young shoots.
Winged forms are produced in June or July,
when there is a migration to
Plantago,
es-
pecially
P. lanceolata.
Colonies, however, often
also persist on apple well into the summer. In
early autumn a return migration occurs from
summer hosts to apple, where winter eggs will be
laid.
Dysaphis devecta
(Walker)
Rosy leaf-curling aphid
This aphid is a widespread but local pest of
apple. Infested leaves become curled downwards
and develop a characteristic bright red color-
ation. Attacks tend to occur on mature trees
with roughened bark and are rarely of major
importance.
