Agriculture Reference
In-Depth Information
Family COCCINELLIDAE (ladybirds)
Subcoccinella vigintiquattuorpunctata
(L.)
Twentyfour-spot ladybird
of the young seeds without destroying the germ;
germination of damaged beans kept for seed,
therefore, is often unimpaired. A previously
infested bean (seed) may be recognized by the
presence of a relatively large hole, c. 2 mm in
diameter, through which the new adult beetle
has emerged. One consequence of such damage
in stored beans is contamination, owing to the
frequent lodging of wild oat seeds in these emer-
gence holes. Infestations of this pest are encour-
aged by hot, dry summers. Although infested
beans may be taken into store, this insect is not a
storage pest, as the larvae are unable to invade,
or to survive in, dried beans.
This widely distributed species is associated
mainly with clover and lucerne. Both adults and
larvae scarify leaves and remove the surface tis-
sue to form a series of parallel grooves. Affected
parts of the foliage appear whitish. In addition
to members of the Fabaceae, damage may also
occur on the foliage of other crops, including
potato and tomato.
BIOLOGY
Adults hibernate in various sheltered situations.
They become active in the following May, and
eggs are then laid in batches on the leaves of host
plants. Larvae feed for several weeks before
pupating, and young adults appear about a
week later. There are usually two generations
annually.
BIOLOGY
Adults hibernate amongst leaf litter and in vari-
ous other sheltered situations, emerging in the
late spring. Eggs are laid singly on the outside of
the developing pods of beans during April or
May. The eggs hatch in up to 1-3 weeks, depend-
ing on temperature. The larvae immediately
bore through the pod wall and attack the devel-
oping seeds. Each larva bores within the seed
and becomes fully grown 2-3 months later.
There are four larval instars. Pupation occurs
within the attacked seed, the larva firstly boring
to the bean surface and making a rounded hole
covered only by the opaque outer seed coat.
The adult stage is attained about 2 weeks later,
but individuals usually remain within the pupal
chamber for an extended period and may not
emerge until after the crop has been harvested
and placed in store; some adults may remain
within infested beans until the following spring.
Young adults are often common in the vicinity of
bean crops during the later summer and autumn,
before they enter hibernation. There is just one
generation annually.
DESCRIPTION
Adult
are 3-4 mm long, extremely variable in
appearance;
head and legs
usually reddish-
orange;
pronotum
reddish-orange with a central
black spot;
elytra
range from reddish-orange,
usually with from eight to ten irregular black
marks, to almost entirely black. Egg 0.5-
0.6 mm long, elongate, pale yellow.
Larva
4.4 x
2.0 mm;
body
elongate-oval, yellowish, variably
marked with dark brown;
thorax and abdomen
with numerous tubercles bearing branched setae.
Family BRUCHIDAE (pulse beetles)
Bruchus rufimanus
Boheman
Bean beetle
This generally common beetle is usually a minor
pest of broad bean and field bean; it will also,
occasionally, attack pea. In spring, the adults
feed on the pollen and petals of the flowers but
damage caused is of no significance. The larvae
feed on seeds inside the developing pods. Char-
acteristically, they bore within the cotyledons
DESCRIPTION
Adult
3-5 mm long, mainly black, clothed with
greyish to creamish-white hairs;
elytra
black,
marked with irregular patches of pale hairs, and
noticeably shorter than the abdomen;
antennae
with the basal four segments reddish;
legs
rela-
tively long, with the anterior femora, tibiae and
