Insects of Southern Australian Broadacre Farming Systems - Grains ...

Eggs are laid just below the leaf surface and larvae feed
internally on the plant in which the eggs were laid. The
number of eggs laid varies according to the host plant
and temperature.
Larvae (maggots) are legless, typically cylindrical in
shape and tapering at the head region. There are three
larval stages that feed within the leaves (beneath the
surface) creating a winding tunnel or ‘mine’. They
occasionally feed on the outer surface of young pods.
The larvae of Liriomyza spp. leave the plant to pupate,
so pupae may be found in crop debris, in the soil or
sometimes on the leaf surface. In contrast, pea leafminer
(C. horticola) larvae pupate inside the leaf at the
end of the larval mine.
These closely-related species are difficult to tell apart
and identification requires specialist knowledge.
These biosecurity threats can be confused with native
leaf-miner species. Most of these are host-specific but
they are not well known, and as many species remain
undescribed, they should be sent for identification.
The occurrence of leaf mining (tunnelling) can be easily
recognised in the field.
Crops attacked/host range
L. trifolii: beans, peanuts, soybeans, lentils, lupins, faba
beans and chickpeas.
L. huidobrensis: beans, lupins, field peas and faba beans.
C. horticola: sunflower, field peas, canola, lentils,
lupins, chickpeas and other Brassicaceae, Fabaceae and
Asteraceae plants.
L. cicerina: chickpea, sweet clovers, disk trefoil and
Ononis species.
Damage symptoms
Typical leaf miner damage includes leaf destruction (leaf
wilt, desiccation and premature fall) and retarded plant
growth. Plant damage in the form of stippling can also
be caused by females puncturing leaves for sap-feeding
and egg-laying (oviposition). Plants can also suffer from
secondary attack when pathogenic fungi enter the leaf
through puncture wounds. Mechanical transmission of
plant viruses can also occur. Severe infestations can lead
to total crop loss due to both larval-mining and leafpuncturing.
Most leaf mines are greenish in colour at first, turning
whitish over time. Leaf mines wind irregularly through
the leaf and increase in width as larvae mature.
Distribution and potential spread
L. trifolii is present in Europe, Asia, Africa, Central
America and the Caribbean, North and South America
and Oceania.
L. huidobrensis is widespread through Africa, Asia,
Central America, Europe, Canada and the USA.
C. horticola is widespread in Africa, Asia and Europe.
L. cicerina is found in Africa and Europe.
Agromyzid flies are not very active flyers and tend to
remain close to their target crops, often only moving
very short distances between host plants within a crop.
They can move longer distances if carried by wind.
Entry of these invasive agromyzids (apart from L. cicerina)
is likely to be via imported plant material containing
leaves, particularly seedlings or propagation material
where eggs have been deposited.
If eggs have not yet hatched and no signs of mining
are visible, the eggs may survive treatment at port
of entry. Initial incursions are likely to arise from
horticultural areas, and grains industries will face
secondary attack from these horticultural incursions
if eradication is not achieved.
Mine shapes in the leaf tissue can vary depending on
the species and can be narrow and linear with anterior
spiracles (e.g. C. horticola), linear and shallow on the
upper leaf surface (e.g. L. trifolii), serpentine in shape
(e.g. L. cicerina) serpentine or irregular in shape (e.g. L.
huidobrensis) or have distinctive trails of frass deposited
in black strips on the sides of the mine (e.g. L. trifolii).
Surveillance
While fully-formed leaf mines should be readily visible to
quarantine officials, signs of early infestations are much
less obvious and can be easily overlooked.
Any leaf-mining damage or insect that resembles these
flies must be sent to a specialist for identification.
Early detection of plant pests can greatly increase
the chance of successful eradication and reduce the
cost and social impact of an incursion.
Incorporate surveillance for exotic pests when
undertaking routine crop monitoring and other crop
detection and measurement activities.
SECTION 4 COMMON Pest, Beneficial AND EXOTIC Species
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Insects of Southern Australian Broadacre Farming Systems Identification Manual and Education Resource © 2012