Agriculture Reference
In-Depth Information
various other protected crops, including cu-
cumber, lettuce and certain ornamentals. Infes-
tations on seedlings and young plants check
growth and will weaken or kill them; mines in
the cotyledons are particularly damaging.
Larvae within cotyledons may also burrow into
the growing points or terminal shoots and fre-
quently cause the death of plants. Attacks on
established plants are less significant, although
hosts may be weakened if outbreaks are severe.
Adult feeding punctures on leaves (see below)
are disfiguring. In Europe, this pest occurs
mainly in the Channel Islands, Denmark,
southern England, France, Germany and the
Netherlands.
Fig. 260
Wing venation: (a)
Liriomyza;
(b)
Phytomyza.
BIOLOGY
At first, adult females feed on exudates from
the foliage, having first formed prominent
punctures in the leaf surface with their oviposi-
tors. Later, eggs are deposited in the upper sur-
face of the leaves. These hatch in 4-8 days.
Larvae then burrow beneath the upper epider-
mis to form long, irregular, whitish mines. Each
mine contains a narrow trail of frass that
may change from one side of the gallery to the
other. The larvae are fully fed in approximately
7-12 days; they then vacate their mines, usually
cutting their way out through the upper epider-
mis, and fall to the ground. They then enter the
soil to pupate. Adults appear 2-3 weeks later,
although emergence will be greatly delayed by
cool conditions. There are normally three or four
generations annually; puparia overwinter in the
soil.
Liriomyza congesta
(Becker)
larva
-
A pea leaf miner
Mines of this widely distributed and polyphagous
species are often found on the upper side of leaves
of labiate crops such as pea and
Vicia
bean (cf.
Liriomyzapisivora,
p. 189). Adults are relatively
small (wings 1.3-1.7 mm long) and mainly
greyish-black to yellow. They appear in the spring
and eventually deposit eggs in the leaves, usually
no more than one per leaf. The larval mines are
linear and narrow, with the black frass dispersed
along either side of a green central band. Each
mine terminates in an expanded blotch, and fully
fed larvae eventually pupate on the ground.
There are two or more generations annually. The
mines cause little or no distortion of the leaves
and are usually insufficiently numerous to have
any adverse effect on the growth of host plants.
Larvae are whitish and up to 3 mm long; they are
distinguished from those of
L. pisivora
(p. 189) by
the 3-pored posterior spiracles.
DESCRIPTION
Adult
mainly pale yellow;
head, thorax and
abdomen
partly shiny black dorsally;
scutellum
bright yellow;
antennae
mainly yellow;
legs
blackish with yellow femora;
wings
1.8-2.1 mm
long, the costal vein extending to vein M
1+
2
(see
Fig. 260a). Egg
0.25 x 0.15 mm, white.
Larva
up to 3 mm long, yellowish-white;
mouth-
hooks
with several prominent teeth;
posterior spiracles
mushroom-like, each with
an arc of 7-12 pores.
Puparium
2mm long,
brownish-yellow.
Liriomyza huidobrensis
(Blanchard)
larva
=
South American leaf miner
Infestations of this polyphagous leaf miner have
occurred recently in various European countries,
including England and the Netherlands, the pest
