American serpentine leafminer
American serpentine leafminer only occurs in some parts of WA and must be reported if detected outside its known distribution.
About the American serpentine leafminer
American serpentine leafminer (Liriomyza trifolii) is a tiny fly whose larvae damages plants by tunnelling (mining) through leaf tissue. American serpentine leafminer is one of a number of well-known leafminers from the Agromyzidae family, whose larvae feed internally on plants, often as leaf and stem miners.
Most other leafminer species in Australia are very host specific and do not impact on horticultural production. American serpentine leafminer is considered a National Priority Plant Pest as it has a wide host range and can cause significant yield losses and quality reductions.
Current situation
- DPIRD confirmed the presence of American serpentine leafminer in WA in July 2021 from a sample collected near Kununurra, as part of the Commonwealth’s Northern Australia Quarantine Strategy surveillance program.
- American serpentine leafminer has also been detected in Torres Straight and the Northern Territory, and it is considered a National Priority Plant
DPIRD is working with industry stakeholders, the Commonwealth Department of Agriculture, Fisheries and Forestry, and other states and territories to minimise the impact of the pest fly and its larvae on Western Australia's primary industries.
This includes liaising with the horticulture industry in the Ord River, Broome, Carnarvon and Geraldton to undertake surveillance, to determine the presence and spread of the pest.
The national technical committee, the Consultative Committee on Emergency Plant Pests, concluded that eradication is not technically feasible, due to the pest’s biology, current distribution and wide range of host plants.
The committee agreed that there may be measures that could be undertaken to limit the spread of American serpentine leafminer to other areas of Australia.
Producers, agronomists and homeowners can help by monitoring plants and reporting any tunnelling leaf damage and suspect flies to DPIRD. Reporting both absence and presence of the pest will support DPIRD’s surveillance efforts.
Frequently asked questions
American serpentine leafminer is known to feed on more than 400 plant species, including many economically important vegetables, cut flowers and legume crops.
Hosts can include beans, celery, chrysanthemum, cucumber, gerbera, gypsophila, lettuce, onion, potato, tomato, peanuts, soybeans, lentils, lupins, faba beans and chickpeas.
- Trails or 'mines' (light green to white squiggles) on leaf surfaces.
- Trails get wider as the larvae grow.
- Fungal and bacterial infection may occur, as the feeding damage increases susceptibility to secondary infections.
- Leaf surfaces with necrotic (brown) patches.
- Trails may be indistinguishable from the damage of other leafminers – so report any damage, even if unsure.
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Lettuce leaves with necrotic patches. Photo – © 2024 Department of Agriculture, Water and the Environment - Northern Australia Quarantine Strategy team |
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Sunflower plant with damaged leaves. Photo – © 2024 Department of Agriculture, Water and the Environment - Northern Australia Quarantine Strategy team |
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American serpentine leafminer larvae damage can be identified by twisting white patterns on the leaf surface, caused by the tunnelling or 'mining' activity. Photo – © 2024 DPIRD |
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- American serpentine leafminer adult flies are 1-2 mm in size, grey-black in colour and distinguished by a prominent yellow area at the base of the wings. Larvae are white-yellow.
- Although female adults are larger and more robust than males, their small size still limits field identification. Adult flies of Liriomyza species are very similar in appearance, difficult to distinguish by eye and require molecular diagnostic tests to confirm species.
- The larval stages are not usually seen as they remain inside the leaf tissue. An infestation would most likely be detected through the presence of the mines on leaf surfaces.
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Adult flies are difficult to distinguish by eye and require molecular diagnostic tests. Photo – © 2024 Department of Agriculture, Water and the Environment - Northern Australia Quarantine Strategy team |
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Larvae are not usually seen as they remain inside the leaf tissue. Photo – © 2024 Department of Agriculture, Water and the Environment - Northern Australia Quarantine Strategy team |
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Adult American serpentine leafminer. Photo – © 2021 Pia Scanlon, DPIRD |
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American serpentine leafminer larvae are white-yellow. Photo – © 2024 DPIRD |
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American serpentine leafminer poses a serious threat to Australia’s horticulture, nursery production, and agriculture plant industries.
- Damage is caused primarily by larvae feeding under the surface of leaves, and tunnelling (mining) within the leaf tissue. Leaf damage also occurs through puncture wounds from the adult feeding and depositing eggs.
- As the damage (mines) age, the leaf surface becomes necrotic (brown patches).
- Tunnelling can impede plant photosynthesis, causing leaf death or premature leaf drop, resulting in yield losses, sunburn and reduced quality.
The American serpentine leafminer is widespread overseas, being present in North and South America, Asia, Africa, Europe and some Pacific islands.
- The fly’s eggs, larvae and pupae can spread through the movement of plant material, soil clothing and equipment.
- The adults are capable of flight but are not very active fliers. They tend to fly within a crop but rarely between crops.
- Check crops regularly.
- Make reports to DPIRD on both absence and presence of leafminer damage or suspect flies.
- Arrive clean, leave clean – good on-farm biosecurity practices are vital to preventing incursions of plant pests and diseases.
- Permits are in place that cover the treatment of a number of exotic leafminer fly species, including American serpentine leafminer. More information is available from the Australian Pesticides and Veterinary Medicines Authority.
- This pest is known to develop resistance, so insecticide treatments should be used that incorporate resistance management strategies.
- Overseas, management of leafminers like the American serpentine leafminer include the use of natural enemies, such as parasitoids that attack larvae, so good management practices should consider the use of pesticides that favour beneficial insects.
Legal duty to report
American serpentine leafminer only occurs in some parts of WA.
Liriomyza trifolii (Burgess, 1880) is a declared pest under section 22 of the Biosecurity and Agriculture Management Act 2007.
This means that any person who finds or suspects the presence of American serpentine leafminer outside of its known distribution must report it to the department.
WA's official control of American serpentine leafminer is supported by general and specific surveillance and specific import requirements to prevent its entry.