Agriculture Reference
In-Depth Information
Fig. 193 Siphuculi and caudas of three common species of cereal aphid: (a) rose/grain aphid,
Metopolophium
dirhodum;
(b) bird-cherry aphid,
Rhopalosiphum padi;
(c) grain aphid,
Sitobion avenae.
either in the egg stage or, more frequently, as
adults. There are no non-poaceous hosts and,
hence, no alternation of generations in the life-
cycle. The aphids are similar in appearance to
Metopolophium dirhodum
(p. 115) but slightly
smaller (up to 2.2mm long), yellower in colour
and without the dark longitudinal dorsal stripe; a
reddish form also occurs.
on stored bulbs, corms and root vegetables, and
on various glasshouse plants. Under mild condi-
tions, colonies can also survive the winter out-of-
doors (e.g. on strawberry). Winged migrants
appear in the spring, and these spread infesta-
tions to various herbaceous plants; colonies on
winter hosts often then die out.
DESCRIPTION
Aptera
1.1-2.2 mm long, pale shiny brown,
greenish-brown or yellowish-brown, distinctly
convex;
siphunculi
pale, moderately long (but
shorter than the third antennal segment) and the
apical half distinctly swollen;
cauda
triangular,
hardly visible from above (at least in live speci-
mens)
(Fig. 190d);
head
with lateral tubercles
slightly convergent.
Myzus ascalonicus
Doncaster
Shallot aphid
The shallot aphid is an often common pest of
herbaceous plants, including beet, lettuce, onion
(Plate 2d),
potato, shallot, strawberry and vari-
ous ornamentals. Infestations lead to consider-
able stunting, distortion and malformation of
the foliage or flower trusses of host plants; subse-
quent growth from previously infested bulbs or
corms in store may also be affected when these
are planted out, the new shoots often being weak
and noticeably distorted. Damage to strawberry
crops (a winter host) tends to be patchy and
sporadic, typically occurring in the early spring
but usually only if the late winter has been mild.
Shallot aphid is also a virus vector.
Myzus persicae
(Sulzer)
Peach/potato aphid
The peach/potato aphid is a polyphagous pest of
herbaceous plants, often attacking beet, cucum-
ber (it is the main aphid pest of glasshouse-
grown cucumber in northern areas of Britain),
lettuce, mangold, oilseed rape, potato and veg-
etable brassicas; various ornamentals are also
affected. This species is a notorious vector of
plant viruses, including beet western yellows,
cabbage black ringspot, carnation latent and
BIOLOGY
This species breeds parthenogenetically
throughout the year, often surviving the winter
