Agriculture Reference
In-Depth Information
also occur regularly on glasshouse-grown orna-
mentals such as carnation and chrysanthemum.
The moths sometimes migrate northwards (but
they very rarely reach the British Isles) where, if
conditions are favourable, they may breed; the
pest may also, occasionally, be introduced acci-
dentally into such areas on imported produce.
The larvae (known as Old World bollworms) are
capable of causing considerable defoliation. Also,
on tomato, the young larvae often bore into the
fruits and may then become important contami-
nants in crops sent for processing.
ing the British Isles, where infestations some-
times occur on pot marigold and certain other
cultivated Asteraceae. In southern Europe, the
larvae sometimes cause damage to field crops,
including lucerne, maize, mint and tomato. The
greenish, pale-marked larvae (up to 38 mm long
when fully grown) are often mistaken for those
of the silver y moth,
Autographa gamma
(p. 237)
but are at once distinguished by the greater
number of abdominal prolegs (there are five
pairs) and the characterstic pale spinules that
occur liberally over much of the body surface
(Plate 15a).
Adults (35-40mm wingspan) are
mainly ochreous-yellow, with distinctive darker
olive-brown markings on the forewings (includ-
ing a distinct, blackish reniform stigma); the
hindwings are pale yellowish, with a broad,
blackish border which has a curved inner edge
(cf. scarce bordered straw moth,
Helicoverpa
armigera,
above).
BIOLOGY
In Europe, adults of this migratory, multivoltine
species occur at any time from April to October.
However, the number of generations completed
varies depending on temperature. For example,
the larvae require temperatures above 21°C for
their continued development, with temperatures
in the high 20s being the optimum. In temperate
regions, pupae may be able to overwinter in the
soil but they cannot survive cold conditions.
Hydraecia micacea
(Esper)
Rosy rustic moth
DESCRIPTION
Adult
30-40 mm wingspan;
forewings
mainly
pale ochreous, greenish-grey to reddish-brown,
with slightly darker markings (including a
slightly smoky reniform stigma);
hindwings
creamish-white with a broad blackish border that
is more or less straight along its inner edge
(cf. bordered straw moth,
Heliothis peltigera,
below).
Larva
up to 40mm long;
body
with dis-
tinct humps on the first and eighth abdominal
segments;
body
extremely variable in colour,
ranging from purplish-brown with darker
pinacula and a pale spiracular band to greenish
or yellowish with less conspicuous pinacula;
head
brown and distinctly speckled;
prothoracic plate
brownish or blackish.
Pupa
15-20 mm long,
reddish-brown;
cremaster
very short, with two
long straight spines.
This moth is a minor pest of crops such as barley,
beet, hop, maize, onion, potato, rhubarb, straw-
berry and wheat. Larvae (sometimes known as
'potato stem borers') tunnel singly within the
crowns or stems; attacked plants are weakened
and may wilt and die. Infestations are particu-
larly likely to occur in weedy sites.
BIOLOGY
Moths occur from August to October or Novem-
ber. Eggs are laid on low-growing plants, includ-
ing many weeds, but do not hatch until the
following spring. Larvae feed from spring on-
wards, and then often invade crop plants. Larval
development is usually completed in July or
August. Individuals then pupate in the soil but
without forming cocoons.
Heliothis peltigera
(Denis & Schiffermiiller)
Bordered straw moth
DESCRIPTION
Adult
40-45 mm wingspan;
forewings
reddish-
brown, usually darker centrally;
hindwings
pale brown with a darker median line
(Fig. 322). Larva
up to 45 mm long;
body
This subtropical, migratory, multivoltine species
occurs occasionally in northern Europe, includ-
