Agriculture Reference
In-Depth Information
mouth-hooks
with their main axis more or less
in line with the rest of the mouthparts (cf.
asparagus
in about a week. The larvae then attack the fi-
brous roots and also graze on the surface of the
tap root. Some second-instar larvae mine within
the tap root but most internal feeding occurs
during the third (= final) instar. When fully
grown, the larvae return to the soil to pupate,
and adults of the second generation emerge from
late July or early August onwards. Second-
generation larvae usually complete their devel-
opment in the autumn, but many will continue to
feed well into the winter before eventually pu-
pating. Under favourable conditions a third or
partial third generation of adults appears in the
autumn; thus, adults may occur at any time from
May to October or November. Depending on
temperature, the precise timing of adult appear-
ance and the duration of the immature stages
vary considerably from site to site and from year
to year.
miner,
Ophiomyia
simplex,
p.
191).
Puparium
6-8mm long, light brown.
Family PSILIDAE
Psila rosae
(F.)
Carrot fly
The carrot fly is a widespread and important pest
of carrot, celeriac, celery, parsley and parsnip;
several wild species of Umbelliferae (but not all)
are also hosts.
Carrot:
roots of plants of all ages
are affected. Seedlings are often killed; this
causes noticeable gaps in crop rows and in-
creases the likely severity of attacks on surviving
plants later in the season. Infestations on young
plants cause the foliage to turn reddish, wilt and
die; superficial damage by larvae can cause root
fanging and stunting of plants. On older plants,
larvae mine the outer tissue of the tap root; the
cortex then becomes riddled with brown or
rusty-red tunnels (cf. damage caused by carrot
miner,
Napomyza carotae,
p. 189); the extent of
damage increases throughout the late summer
and autumn, and will also continue in clamps
throughout the winter. Mined roots are suscep-
tible to canker and subsequent rotting.
Celery:
damage to fibrous roots causes the outer leaves
to wilt; more seriously, mining in the base of leaf
stalks, crown and main roots results in poor
top growth and yellowing of the foliage. Early-
season transplants are particularly liable to be
attacked, and damage affects the size and overall
quality of plants.
Parsley:
larvae mine the outer
tissue of the tap root and also destroy the fibrous
roots; this affects plant vigour and quality.
Pars-
nip:
the main roots of young plants are often
severed, and the larvae also burrow within the
petioles; on older plants, mining is restricted
mainly to the region of the tap root in the top
15 cm of soil.
DESCRIPTION
Adult
5-7 mm long, shiny black;
head
reddish-
brown;
legs
yellowish
(Fig. 252);
antennae
with
the bulbous third segment half yellow and half
black
(Fig. 253a)
(cf.
Psila nigricornis,
182);
wings
5.5 mm long, large and iridescent.
Egg
1.0 x 0.4 mm, white, ribbed longitudi-
nally.
Larva
up to 10 mm long, shiny creamish-
white, slender-bodied
(Plate 7b);
mouth-hooks
with their long axis more or less continuous with
the rest of the mouthparts, and each with one
BIOLOGY
Adults of the first generation appear in May or
June, and eggs are deposited singly or in small
groups in the soil close to host plants. They hatch
Fig.
252
Carrot fly,
Psila rosae
(xl0).
