Agriculture Reference
In-Depth Information
contaminate host plants with black excrement.
Heavily infested plants are defoliated, weaken-
ing the crowns and reducing yields.
BIOLOGY
Adults hibernate in sheltered situations, such as
hollow stems or soil crevices, and become active
in the spring. They then disperse to asparagus
plants, where they begin to feed and where mat-
ing takes place. Eggs are deposited on the fronds
in short rows from late June onwards. They
hatch in about a week. The larvae feed for about
3 weeks, passing through three instars. They then
pupate in the soil, each in a parchment-like
cocoon formed a few centimetres below the sur-
face. The next generation of beetles appears 2-3
weeks later. There are usually two overlapping
generations annually.
DESCRIPTION
Adult
6-7 mm long;
head
shiny blue-black;
thorax
reddish, black-edged;
elytra
yellow
and black, the former colour forming six pale
spots and the latter a central band and three
crossbands
(Fig. 216). Egg
1.2-1.6mm long,
elongate-oval with a flat base
(Fig. 217a);
greenish-grey, becoming darker close to
hatching.
Larva
up to 8 mm long;
body
dark,
greenish-grey, distinctly wrinkled and sac-like,
with several short, fleshy abdominal prolegs,
including a well-developed central proleg
(pseudopod) on the anal segment;
head,
prothoracic plate and thoracic legs
shiny black
(Fig. 217b).
Fig. 216
Asparagus beetle,
Crioceris asparagi
(x10).
Crioceris duodecimpunctata
(L.)
Twelve-spotted asparagus beetle
This species is a pest of asparagus in continental
Europe but is not recorded from the British Isles.
In spring, adults of the first generation attack the
emerging asparagus shoots; mating and egg lay-
ing occur at about the flowering stage, the eggs
being deposited at the tips of the fronds. Larvae
feed on the developing asparagus berries for ap-
proximately 10 days and then pupate in the soil,
each in an earthen chamber. There are two
Fig. 217
Asparagus beetle,
Crioceris asparagi:
(a) eggs; (b) larva (x7.5).
generations annually. Adults (5-6 mm long) are
mainly orange-red, with 12 prominent black
spots on the elytra. Larvae (up to 8 mm long) are
yellow, with a black head.
