Agriculture Reference
In-Depth Information
over the dorsal part of the abdomen; siphunculi
strongly and abruptly swollen, shiny black (Fig.
190f); cauda bluntly triangular; head smooth (i.e.
not spinose: cf. the following species); antennae
noticeably hairy. Nymph green; siphunculi
black.
summer on maize and sweet corn. The aphids
often then occur beneath leaves shielding the
developing cobs, and affected tissue becomes
soiled by sticky honeydew and blackened by
sooty moulds.
BIOLOGY
This often abundant species occurs on grasses
and cereals. Under mild conditions, it over-
winters parthenogenetically on these secondary
hosts. Overwintering aphids on autumn-sown
cereals and grasses usually occur on the shoots,
just below the soil surface. Other populations
overwinter in the egg stage on Prunus padus, the
primary host, these eggs being deposited from
September to November. Spring colonies on
Prunus occur from April onwards, and culminate
in the production of winged forms which migrate
to cereals and grasses in May and early June.
Aphids on Poaceae in summer occur mainly on
the lower leaves but, if numerous, may become
established on other aerial parts of the plants.
On oats, and also on maize and sweet corn, the
aphids often feed within the shelter of the leaf
sheaths.
Rhopalosiphoninus staphyleae tulipaellus
(Theobald)
Mangold aphid
The mangold aphid has a wide host range. It
breeds on plant roots during the summer but is of
most significance as a pest in mangold clamps.
where large populations often develop; the
aphids also overwinter on stored bulbs and
corms (including crocus, lily and tulip). Direct
feeding damage is of minor consequence but the
aphids are vectors of viruses, including beet yel-
lows. Apterae are very similar in appearance to
those of Rhopalosiphoninus latysiphon (above),
from which they may be distinguished by the
spinose head, the less noticeably hairy antennae,
the interrupted dark pattern of plates on the ab-
domen and the less-abruptly swollen siphunculi;
the swollen middle section of each siphunculus
is also noticeably paler than either the basal or
the apical sections (Fig. 190g). This subspecies,
which is sometimes treated as a separate species,
was restricted to Europe, but appears also now
to have been introduced into North America.
DESCRIPTION
Aptera 2mm long; body rather plump, brownish-
green to olive-green, with a conspicuous rusty-
red patch around the base of each siphunculus
and near the base of the cauda; antennae short;
siphunculi pale, flanged apically and slightly ta-
pered; cauda elongate and tapered (Fig. 193b);
front of head with lateral prominences slightly
higher than the median bulge (Fig. 189h).
Rhopalosiphum padi (L.)
Bird-cherry aphid
The bird-cherry aphid is an often common pest
of cereals, including barley, oats and wheat. In
mild regions (including southwest England),
where populations survive the winter on these
secondary hosts, the aphids are particularly im-
portant as vectors of barley yellow dwarf virus
(BYDV). Early-sown winter cereals are most at
risk from aphids migrating into them in Septem-
ber and October from grasses and cereal stubble.
Direct damage to crops in summer is rarely of
significance, although the aphids may cause
stunting and discoloration of foliage. In some
years, heavy infestations develop during the late
Rhopalosiphum insertum (Walker)
Apple/grass aphid
The apple/grass aphid overwinters as eggs on
apple, pear and certain other Rosaceae. During
the summer, the aphids occur on cereals and
grasses, their secondary hosts. Heavy popula-
tions on primary hosts in early spring can be
damaging but usually occur only if the previous
summer was wet and, therefore, conducive to the
growth of grasses. Summer populations on cere-
als and grasses are of little or no importance,
Search WWH ::




Custom Search