Insects - Pests of Ornamental Trees, Shrubs and Flowers - page 194

Liriomyza congesta (Becker) ( 450 )
larva

Liriomyza sativae Blanchard
A mainly American species but sometimes introduced
into Europe on imported plants, especially
Chrysanthemum cuttings. The larval mines are sinuous
but relatively small; however, large numbers can occur
in the same leaf, so that damage becomes extensive and
host plants severely weakened or killed. Fully fed larvae
pupate externally in pale orange-yellow puparia; the
posterior spiracles each bear three stout bulbs. In
common with other alien species, infestations may
occur on various ornamentals and protected vegetables;
larvae also invade weeds such as bittersweet ( Solanum
dulcamara ), common ragwort ( Senecio jacobaea ) and
groundsel ( Senecio vulgaris ). Breeding is continuous
under suitable conditions and host plant availability.

pea leaf miner
A generally common, polyphagous leaf miner;
sometimes a minor pest of sweet pea ( Lathyrus
odoratus ). The larvae (up to 2 mm long) are greenish
white. They form narrow linear mines on the upper side
of the leaves, with black frass dispersed characteristically
along either side of a green central band; the mines,
usually no more than one per infested leaf, terminate in
an expanded blotch. Fully fed larvae pupate externally on
the ground (cf. Chromatomyia horticola , p. 199). There
are two or more generations annually, populations often
building up throughout the season; however, the mines
cause little or no distortion and are usually insufficiently
numerous to affect plant growth. Adults (wings
1.3-1.8 mm long) are greyish black, with the frons,
scutellum and sides of both thorax and abdomen,
antennae and legs yellow.

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Liriomyza strigata (Meigen) ( 452 )
syn. L. pumila (Meigen); L. violae Curtis
This common and widespread species attacks a wide
variety of herbaceous plants, including ornamentals, but
is usually present in only small numbers. The leaf
mines, which usually occur only on older plants, tend to
follow the midrib, with distinctive lateral branches
extending into the leaf blade. Although the presence of
mines on ornamentals may be disfiguring, they rarely, if
ever, cause actual harm to host plants.

Liriomyza huidobrensis (Blanchard) ( 451 )
larva

South American leaf miner
A very polyphagous, mainly South American species
found occasionally in Europe on imported plants,
especially Chrysanthemum ; also well established in
California. The yellowish-white larvae (up to 3.25 mm
long) feed in distinctive linear leaf mines that often
commence their development in association with the
midrib and other major veins. Later, the mines
frequently turn back upon themselves to give the
appearance of a broad, blotch-like gallery; the larvae
may also burrow alongside mines formed in the same
leaf by other individuals. Fully grown larvae pupate in
the soil or within the feeding gallery, each forming
a yellowish-brown or reddish-brown puparium;
characteristically, each posterior spiracle has about
6-9 small pores arranged in an arc. Adults are similar in
appearance to those of Liriomyza trifolii but larger
(wings 1.7-2.2 mm long) and slightly darker.

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Nemorimyza posticata (Meigen)
Widely distributed and locally common on golden-rod
( Solidago virgaurea ), the larvae forming characteristic
blotch mines on the leaves; the mines are extensive and
adorned by wavy lines of frass. Pupation takes place
externally. Although usually an unimportant species,
significant damage to cultivated hosts has occurred in
southern England. Adults (wings 3.0-3.3 mm long) are
mainly black, with the knees of the fore legs and (in
males) the anterior abdominal tergites yellow.

Phytomyza ilicis Curtis ( 453 )
larva holly leaf miner

An often abundant pest of holly ( Ilex ), occurring on
wild and cultivated plants. Widely distributed in
Europe; also now well established in parts of North
America, having been introduced from Europe along
with its foodplant.

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DESCRIPTION
Adult: wings 2.5-3.0 mm long; body mainly dark
brown or black; legs black. Egg: 0.4

0.2 mm; white.
Larva: up to 3 mm long; whitish to yellowish white.
Puparium: 2.5 mm long; brown.

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