Agriculture Reference
In-Depth Information
most damage to late-sown spring cereals; af-
fected plants remain stunted and gouty. Where
eggs are laid on more advanced plants, the ear
may fail to emerge from its sheath; in such situa-
tions grain yields are reduced. In the British
Isles, this pest is most abundant in southern and
southwestern England.
Puparium
5-7 mm long, yellowish-brown, elon-
gate, flattened
(Plate 9b);
posterior spiracles
in-
conspicuous
(Fig. 264).
Oscinella frit
(L.)
Frit fly
Frit fly is a major pest of oats but will also cause
significant damage to barley, maize (including
sweet corn), rye, wheat and various cultivated
grasses, especially Italian and perennial
rye-grass. Damage in the British Isles is most
significant on grassland and oats, although eco-
nomically important attacks on sweet corn are
also frequent. Infestations are usually most
severe on lowland pastures and on crops direct-
drilled into grass swards or on crops following a
grass ley, as the larvae transfer readily from the
old sward or the ploughed grass to recently ger-
minated crops.
First-generation (spring) and
third-generation (autumn/winter) larvae:
these
attack young plants to feed on the growing points
of the central shoots, which then wither and die
('dead-heart' symptom); each larva is capable of
attacking several shoots and damage is particu-
larly severe if crops have not begun to tiller. The
most important damage to cereals occurs in
plants up to the fourth-leaf stage, with 'dead-
heart' symptoms on winter wheat evident from
BIOLOGY
Adults of the first generation occur in May and
June. Eggs are then deposited singly on the up-
per surface of cereal leaves, usually no more than
one per plant. The eggs hatch in approximately
10 days. The larvae bore into the centre of the
main shoot to feed, and individuals become fully
grown in about a month. Each then pupates
in
situ,
and the adult fly emerges from the puparium
a month or so later. Adults of the autumn gen-
eration occur from late July to early October.
Their eggs are deposited on early-sown winter
cereals, cereal volunteers and grasses, but usu-
ally not until September at the earliest. Larvae of
the autumn generation feed slowly throughout
the winter months and usually complete their
development in March or April.
DESCRIPTION
Adult
4-5 mm long, mainly yellow, marked with
dark brown dorsally;
thorax
with three dark,
broad, longitudinal bars;
scutellum
bright yellow
(Plate 8f). Egg
1 mm long, elongate-oval, white
(Fig. 263);
chorion
with a distinctive hexagonal
sculpturing.
Larva
up to 8 mm long, translu-
cent, hyaline-whitish to creamish-white, broadly
sausage-shaped
(Plate 9a);
sternal spatula
black,
clearly visible;
posterior spiracles
inconspicuous.
Fig. 264
Puparium of gout fly,
Chlorops pumilionis
(xfO).
Fig. 263
Egg of gout fly,
Chlorops pumilionis
(x40).
