American serpentine leafminer

There have been multiple detections of American serpentine leafminer (Liriomyza trifolii).

Leaf miners are small flies whose larvae feed internally on plants. American serpentine leafminer poses a serious threat to Australia’s horticulture, nursery production, and agricultural plant industries. Severe infestations of American serpentine leafminer may result in premature leaf drop, poor growth, and reduced crop yields. Australia considers it to be a National Priority Plant Pest.


The pest was first detected from samples taken by North Australian Quarantine Strategy (NAQS) officers in Torres Strait, in Far North Queensland, and in northern Western Australia.

The WA samples were collected in March 2021 by sweep netting a cotton crop and associated weeds, and some larvae within leaf mines on coatbuttons and wild gooseberry weeds.  In May 2021, the NAQS officers collected larval specimens of suspect leafminer on Thursday Island, Torres Strait from the common Cinderella weed as part of their routine Torres Strait plant health survey.

The samples of suspected leafminer species in WA and QLD were identified as American serpentine leafminer (Liriomyza trifolii) with a 99%+ genetic match between the Kununurra and Torres strait specimens. This identification was confirmed during the week of 9 July 2021 using genetic testing and morphological identification techniques.

In August 2021, further detections of American serpentine leafminer occurred near Bamaga in the Northern Peninsula Area of Cape York, and in Darwin and Katherine in the Northern Territory following broader surveillance activities.

Response by industry and governments

The Consultative Committee on Emergency Plant Pests (CCEPP) has met in response to these detections. Members agreed that American serpentine leafminer is considered an emergency plant pest under the Emergency Plant Pest Response Deed.  However, following additional surveys, it was also agreed that American serpentine leafminer is not technically feasible to eradicate. It cannot be eradicated because:

  • it is widespread
  • has a wide host range which includes weed species
  • has a rapid reproduction rate with populations likely to propagate faster than they can be removed
  • treatment options have limited effectiveness with the potential for pesticide resistance to develop
  • there is the potential for reintroduction due to an unknown entry pathway.

The CCEEPP’s recommendation will be put to the National Management Group for endorsement.

Read more on how we respond to outbreaks.

Movement restrictions for produce

Restrictions to contain American serpentine leafminer within Western Australian and the two far northern biosecurity zones in Queensland will remain unchanged.

Under Queensland’s Biosecurity Act 2014, there are two far northern biosecurity zones covering Torres Strait and the northern Cape York Peninsula. The Far Northern Biosecurity Zone 2 begins north of Coen and ends in a line between Mapoon and Heathlands in the northern Cape. The Far Northern Pest Biosecurity Zone 1 continues above Zone 2 and spans the five townships of the Northern Peninsula Area as well as Torres Strait. Plant material cannot move out of Zone 1 or south out of Zone 2 without a permit.

Movement between Torres Strait and mainland Australia is also controlled under the Commonwealth’s Biosecurity Act 2015. Federal legislation specifies that plant material cannot move from the Torres Strait Permanent Biosecurity Monitoring Zone into mainland Australia without a permit.

Public advice and reporting

Production nurseries and growers should always check their crops regularly for signs of plant pests and disease. If you suspect an American serpentine leafminer infestation, report it to the department of primary industries or agriculture in your state or territory. You can do this by phoning the Exotic Plant Pest Hotline on 1800 084 881.

Good on-farm biosecurity practices are vital to preventing incursions of plants the pests and diseases. The website has helpful information that can be tailored to your property.

About American serpentine leafminer

American serpentine leafminer top view
Photo courtesy of WA DPIRD
American serpentine leafminer side view
Photo courtesy of WA DPIRD
Damage caused by American serpentine leafminer
Photo courtesy of WA DPIRD

American serpentine leafminer is an exotic leafminer species that poses a significant economic threat to Australia’s horticulture, nursery production, and agricultural plant industries.

It is a plant pest that has a wide host range of plant species which includes beans, celery, chrysanthemum, cucumber, gerbera, gypsophila, lettuce, onion, potato, tomato, peanuts, soybeans, lentils, lupins, faba beans, chickpeas and many more. 

American serpentine leafminer can be confused with other Australian native and introduced Liriomyza species.

The pest can be spread through the movement of plant material, soil, clothing and equipment. The adult can spread short distances either unaided or assisted by the wind.

Leaf damage occurs through puncture wounds from the adult feeding and depositing eggs, as well as the larvae tunnel, or mine, within the leaf tissue.

High levels of infestation affect the plant’s ability to photosynthesise, reducing plant growth and crop yields. For leafy vegetables and ornamental crops, visible damage from the pest may render the product unsuitable for sale.

There is further information about leaf miners on the Plant Health Australia website.


International - Exports

It isn’t expected that there will be significant trade impacts for the majority of our export markets if American serpentine leafminer establishes in Australia.

Although American serpentine leafminer has a broad host plant range, it is already widely distributed across large areas of Africa, Asia, Europe and the Americas. There is the potential that some importing countries that are currently free of American serpentine leafminer, such as New Zealand, may consider new regulations based on the presence of the pest in Australia. 

The Department of Agriculture, Water and the Environment will work with industry and exporters should there be any changes to their requirements.

International - Imports

The American serpentine leafminer incursion is not expected to change import conditions for the import of plant material into Australia. There are currently no import requirements specifically for Liriomyza trifolii on imported plant-based goods. General pre-export conditions that are applied offshore and manage the risk of Liriomyza trifolii on fresh plant-based goods and nursery stock imports will remain unchanged.

Domestic trade

There are no current interstate trade restrictions on the movement of plant material for the American serpentine leafminer. However, the WA Department of Primary Industries and Regional Development is currently reviewing their restrictions as well as other restrictions in place for the serpentine leafminer (Liriomyza huidobrensis), covered under a separate incident, to ensure consistency.