Agriculture Reference
In-Depth Information
oracic plate
pale brown with blackish-brown
markings
(Plate 13e).
Pyrausta aurata
(Scopoli)
In parts of continental Europe, this moth is con-
sidered a significant pest of cultivated mint. The
larvae web the leaves together with silk and also
cause defoliation. In the British Isles, larvae
sometimes infest mint growing in gardens and
allotments, especially in chalkland areas, but
attacks are not of commercial importance.
Fig. 302
Forewing of
Margaritia sticticalis
(x5).
Ostrinia nubilalis
(Hiibner)
larva =
European corn borer
BIOLOGY
Adults fly in sunshine, and those of the first gen-
eration are active in May and June. First-
generation larvae feed in June and July on wild
and cultivated mint (and related plants),
living amongst spun leaves. Each eventually pu-
pates on the host plant in a tough, brownish co-
coon. Adults of the second generation occur in
July and August, with second-generation larvae
feeding in September and October. When fully
fed, these larvae overwinter in cocoons formed
on plant stems and pupate in the spring.
This migratory species is a major pest of maize
and sweet corn in continental Europe and in
North America but it occurs only rarely in the
British Isles. The larvae bore within the maize
stems, usually causing them to break; the cobs
are also attacked. Infestations can occur on vari-
ous secondary hosts, including barley, beet and
potato; a race of this insect is associated with
Artemisia vulgaris.
BIOLOGY
Adults emerge in June. Eggs are then laid on the
underside of leaves of host plants, typically in
batches of about 20; the eggs hatch about 10 days
later. The larvae at first feed externally but then
bore into the stems where they develop. When
fully fed, the larvae enter diapause inside the
stems or in stubble. In the spring they pupate
in
situ
or in the soil. In northerly parts of its range,
this species has just one generation annually; in
southern districts, it is capable of completing two
or more generations annually. The overwin-
tering stage, although capable of surviving low
temperatures, is very susceptible to excessive
dampness.
DESCRIPTION
Adult
16-18 mm wingspan;
forewings
purplish-
brown marked with yellow
(Plate 13f). Larva
up to 17 mm long;
body
dull green with yellow
longitudinal lines and numerous yellow-edged
black spots;
head and prothoracic plate
light
brown, speckled with black
(Plate 14a).
Family PIERIDAE
Pieris brassicae
(L.)
Large white butterfly
This species is an often common pest of vegeta-
ble brassicas, including broccoli, Brussels sprout,
cabbage and cauliflower, but of significance
mainly in allotments and gardens. Young larvae
graze away the lower epidermis of the leaves but
older ones cause extensive defoliation, and often
reduce plants to a skeleton of stems and major
veins. Plants are also soiled by accumulations of
frass. Although capable of infesting field crops,
DESCRIPTION
Adult
25-32 mm wingspan;
forewings
pale yel-
lowish to olive-brown, with irregular greyish
markings;
hindwings
mainly pale grey, with
darker grey markings.
Larva
up to 25 mm long;
body
pale purplish-brown;
pinacula
brownish
but pale-centred;
head
brownish-black;
proth-
