Agriculture Reference
In-Depth Information
males, deposit the winter eggs. In favourable
situations, especially in glasshouses, aphids may
survive on lettuce throughout the winter.
are produced from mid-May onwards, and these
aphids then migrate to wild and cultivated hop,
the main secondary hosts. This migration usually
reaches a peak in mid- to late June and then
declines but, exceptionally, may extend into
August. Colonies of wingless aphids develop
rapidly on the leaves and cones throughout the
summer, ending with the production of winged
aphids that fly to winter hosts where, eventually,
winter eggs are laid.
DESCRIPTION
Aptera 1.3-2.7 mm long, shiny dark green (sum-
mer form: often shiny pale yellow to green or
reddish, with dark brown abdominal markings);
antennae and legs long, with dusky tips;
siphunculi moderately long, flanged, dark-tipped
(in summer form: dark green or blackish); cauda
elongate (Fig. 188f).
DESCRIPTION
Aptera 2.0-2.5 mm long, elongate-oval, pale
shiny green to yellowish-green with three longi-
tudinal stripes on the abdomen; head with long
lateral tubercles (Fig. 189g).
Ovatus crataegarius (Walker)
Mint aphid
This aphid forms small colonies in spring on
young shoots of Crataegus and, sometimes, cer-
tain other Rosaceae, but does not cause damage.
However, in summer, the aphids infest wild and
cultivated mint, and may then be troublesome in
kitchen gardens. Apterae are small (1.1-1.9mm
long), oval and yellowish-green to green, with
moderately long, tapered siphunculi and a pair of
prominent, convergent antennal tubercles. In fa-
vourable situations, the aphids continue to breed
parthenogenetically throughout the year. Else-
where, the winter is passed in the egg stage on
Crataegus.
Rhopalosiphoninus latysiphon (Davidson)
Bulb & potato aphid
This aphid is a generally common pest of
glasshouse-grown bulbs or corms, and of pota-
toes in store or in chittting houses; heavy infesta-
tions cause discoloration and death of sprouting
shoots. The aphids will also damage such crops in
the field, infested potato haulm turning yellow
and wilting, significantly reducing yields. Heavily
infested plants may be killed, especially in hot,
dry summers when crops are under particular
stress. Although known to transmit viruses, in-
cluding potato leaf roll, this species is not an
important virus vector.
Phorodon humuli (Schrank)
Damson/hop aphid
BIOLOGY
Subterranean field infestations occur throughout
the summer on potatoes, tulips and other hosts,
colonies (which often include winged forms)
typically becoming established several centi-
metres below the soil surface. The aphids are
entirely parthenogenetic and breed without a
sexual phase. Unlike many other species, their
colonies are not attended by ants. The aphids
usually survive the winter in store on host bulbs,
corms or tubers.
On damson and plum, this notorious pest is of
little direct importance; however, infestations on
hop are of considerable significance, reducing
plant vigour and potentially limiting crop pro-
duction; foliage and developing cones also
become contaminated with sticky honeydew,
upon which sooty moulds develop. The aphids
transmit various plant viruses, including hop
mosaic, hop slit-leaf blotch and plum pox
('Sharka disease').
BIOLOGY
Colonies develop in spring on the underside of
the leaves of damson, plum and certain wild
Prunus hosts, such as P. spinosa. Winged forms
DESCRIPTION
Aptera 1.5-2.5 mm long; body plump, shiny dark
olive-green, with a distinct shiny blackish shield
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