Agriculture Reference
In-Depth Information
colour and by their unswollen, slightly tapered
siphunculi.
Chaetosiphon fragaefolii
(Cockerell)
Strawberry aphid
This species is a well-known pest of cultivated
strawberry. Although causing little direct dam-
age, the aphids contaminate plants with sticky
honeydew and are particularly important as po-
tential vectors of persistent and non-persistent
viruses.
BIOLOGY
The aphids breed parthenogenetically on straw-
berry throughout the year, and tend to be most
numerous on the underside of young leaves.
Colonies are usually most populous in early
summer (established plants) or autumn (first-
year plantings); although excreting considerable
quantities of honeydew, the aphids are not at-
tended by ants. Winged females are produced
in May and June, and sometimes also in late
autumn or early winter, but there is usually no
sexual phase in the life-cycle; males and egg-
laying females (oviparae) are, however, reported
to occur under artificial conditions.
Fig. 192
Tip of abdomen of willow/carrot aphid,
Cavariella aegopodii.
to umbelliferous summer hosts. Colonies on
these secondary hosts occur mainly from late
May to early July. There is then a return
migration to primary hosts where oviparae
are produced and eggs laid. Although usually
overwintering on primary hosts in the egg stage,
viviparous aphids may survive the winter on
overwintering umbelliferous plants or in carrot
clamps.
DESCRIPTION
Aptera
0.9-1.8mm long, elongate-oval, pale
greenish-yellow to translucent whitish;
eyes
reddish;
body hairs
capitate;
siphunculi
rela-
tively long, tapered;
head and basal segments
of antennae
with prominent, capitate hairs
(Fig. 189d).
DESCRIPTION
Aptera
1.0-2.6 mm long, mainly green to
yellowish-green or reddish, elongate-oval,
dorsoventrally flattened;
siphunculi
relatively
long and distinctly swollen apically;
body
with an
elongated tubercle (the supracaudal process) on
the eighth abdominal tergite
(Fig. 192).
Cryptomyzus ribis
(L.)
Red currant blister aphid
Cavariella theobaldi
(Gillette
&
Bragg)
Willow/parsnip aphid
This species is a generally common pest of red
currant, causing noticeable reddish or purplish-
red blisters (pseudo-galls) on the foliage; in-
fested tissue also becomes distorted, and foliage
and fruits contaminated by sticky honeydew and
sooty moulds. Colonies occur occasionally on
other kinds of
Ribes,
causing less obvious, usu-
ally yellowish-green, blisters.
This species, which also overwinters on
Salix,
occurs in summer on various umbelliferous
plants, including cultivated parsnip. The aphids
cause direct damage and are also capable of
spreading viruses such as parsnip yellow fleck.
They are distinguishable from
Cavariella
aegopodii
(above) by their brighter green body
