American serpentine leafminer

There have been multiple detections of American serpentine leafminer (Liriomyza trifolii) in Torres Strait, in Far North Queensland, and in Kununurra, Western Australia. Further detections of American serpentine leafminer have also occurred in the Northern Peninsula Area of Cape York Peninsula which are still undergoing confirmatory identification.

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 a National Priority Plant Pest.

Routine plant health surveys undertaken by the North Australian Quarantine Strategy (NAQS) collected suspected leafminer samples in the Kununurra area of northern WA in March 2021. These samples were collected by sweep netting a cotton crop and associated weeds, and some larvae within leaf mines on coatbuttons and wild gooseberry weeds.

On 17 May 2021, the NAQS officers collected larval specimens of suspect leafminer on Thursday Island, QLD from the common Cinderella weed as part of a 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.

Surveillance is still being conducted to determine the distribution of this pest.

The Consultative Committee on Emergency Plant Pests (CCEPP) met on 19 July 2021 to discuss the detections. CCEPP agreed that American serpentine leafminer is considered an emergency plant pest under the Emergency Plant Pest Deed, but further information was needed to determine whether it was technically feasible to eradicate.

More detailed surveillance and diagnostic data was thought to be valuable to inform the committee’s consideration of technical feasibility of eradication and the appropriate course of action. This information will be provided by WA for the committee’s consideration.

Once the committee has considered this information it will make a recommendation to the National Management Group regarding emergency plant pest status and the technical feasibility of eradication.

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 Heathwood 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.

There have been no previous detections of American serpentine leafminer in Australia.

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.

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


International - Exports

Although L. trifolii impacts a significant range of host plants and species, it is present across large areas of Africa, Asia, Europe and the Americas, which suggests trade issues are likely to be limited if the pest establishes in Australia. However, there are several certification requirements, mainly for seeds, for this pest in the Manual of Importing Country Requirements (MICoR) which may cause some trade implications. Countries with certification requirements include China, Japan, Georgia, the UK and France, however the pest is present in China and France.  

Other importing countries do not have certification requirements for L. trifolii for Australia currently, however we cannot discount the possibility that they may impose new regulations based on the presence of this pest in Australia.

Australian exporters will be notified by the Department of Agriculture, Water and the Environment should importing countries change 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

Domestic trade restrictions will be considered further once work to delimit the extent of the outbreaks in QLD and WA is undertaken, and a final decision is made on technical feasibility of eradication.

There are restrictions already in place in QLD, on the movement of carriers of American serpentine leafminer from Torres Strait and Cape York Peninsula. WA is also considering restrictions to prevent the movement American serpentine leafminer within the state.