Agriculture Reference
In-Depth Information
with a paler stripe along the back, edged by
irregular black bars, and an interrupted black
spiracular line;
head
black;
prothoracic plate
black with whitish lines.
Autographa gamma
(L.)
Silver y moth
Fig. 319
Forewing of silver y moth,
Autographa
gamma
(x3).
This moth is a notorious migrant, and popula-
tions spread northwards and westwards each
year from Mediterranean areas, where the pest is
endemic. The larvae attack various glasshouse
and outdoor plants, including brassicas, celery,
field bean, lettuce, linseed, pea, potato and
strawberry. Defoliation is usually the main prob-
lem but frass pellets accumulating between the
leaves of infested lettuce plants are also often an
important problem.
BIOLOGY
The first immigrants usually arrive in northern
Europe in May, but can sometimes occur much
earlier. Eggs are laid singly or in small groups on
various foodplants and they hatch 1-2 weeks
later. Larvae feed for about a month before pu-
pating, each in a flimsy silken cocoon between
leaves. Adults appear within about 2 weeks and
often fly during sunny weather, to feed on nectar
from various flowers. A second, and sometimes a
third,
generation may be completed during the
summer and autumn. However, although capa-
ble of breeding continuously in heated glass-
houses, outdoor populations in the British Isles
are unable to survive the winter and autumn-
reared adults usually migrate southwards, back
to more favourable breeding grounds.
Fig. 320
Larva of silver y moth,
Autographa gamma
(x2): (a) abdominal proleg and crochets (further
enlarged).
head
mainly green, marked with black on each
'cheek
-
(Fig. 320).
Cerapteryx graminis
(L.)
Antler moth
The antler moth is a sporadic pest of grasses,
especially hard-textured species. Although
present in various lowland sites, most damage is
caused in upland areas. The larvae, sometimes
known as 'armyworms', damage the roots and
shoots; they occasionally migrate in large num-
bers, devouring grasses as they advance, and can
then cause death of plants over a wide area.
DESCRIPTION
Adult
35-45 mm wingspan;
forewings
greyish-
brown to velvet-black, suffused with whitish-
grey, often tinged with purplish, and bearing a
silver, y-shaped mark
(Fig. 319);
hindwings
light
brown with a darker border.
Larva
up to 45 mm
long;
body
varying from green to blackish-green,
with a whitish or yellowish spiracular line, an
often dark dorsal stripe and pale wavy lines
along the back; three pairs of abdominal prolegs;
BIOLOGY
The moths are usually most abundant in August
and early September. They fly both at night and
during the daytime, often in considerable num-
bers. Eggs, usually about 200 per female, are
dropped at random as the moths fly over grass-
