American serpentine leafminer


Have you seen American serpentine leafminer?

American serpentine leafminer has recently been detected on the northern tip of Cape York Peninsula and in Torres Strait.

There are containment measures within the Far Northern Biosecurity Zones that restrict the movement of the pest and any potential carriers out of this area.

Vegetable leafminer is a similar pest which is also found in this area and has been managed successfully through containment measures since 2008.

Be on the lookout and report signs to Biosecurity Queensland on 13 25 23 or contact the Exotic Plant Pest Hotline on 1800 084 881.

Early detection and reporting are key elements in controlling American serpentine leafminer.

American serpentine leafminer (Liriomyza trifolii) is a fly whose larvae feed internally on plant tissue, particularly the leaf.

It poses a significant threat to Australia's agriculture and nursery industry as it is a highly polyphagous species affecting a wide host range of common horticultural crops and ornamental plant species.

Infestation of plants would most likely be detected through the presence of mines in the surface of leaf tissue. Leaf mines are usually white with black and dried brown areas. Leaf mines are typically serpentine or irregular in shape and increase as the larvae mature.


American serpentine leafminer (Liriomyza trifolii) is the larva of small flies belonging to the family Agromyzidae.

The fly larvae tunnel within leaf tissue, which is why they are called leafminers.



  • Small fly-like insects, 1–2mm.
  • Black with yellow head and yellow spots on thorax.
  • Brownish-yellow antennae with dark end segments.


  • Transparent when they first hatch before turning pale yellow-orange then solid yellow-orange as they mature.
  • Develop inside leaf tissue and vary in size but can reach up to 3.2mm.
  • Form irregular serpentine mines, which tend to be restricted by veins.


  • Pupation occurs externally to the leaf usually in the soil below the plant and sometimes on the leaf surface.
  • Adversely affected by high humidity or drought.


  • Slightly translucent and off-white.
  • Tiny, barely visible to the naked eye.
  • Laid under the leaf surface.

Plant stage and plant parts affected

Host plants of any age and stage of growth can be infested but young plants are most susceptible. American serpentine leafminer mainly affects leaf tissue.

Plant damage

Typically, infestation of plants is first noticed by the presence of mines in the surface of leaf tissue. Leaf mines are usually white with black and dried brown areas. Leaf mines are typically serpentine or irregular in shape and increase as the larvae mature.

Mining activity by the larvae causes loss of healthy leaf tissue, affecting the plant's ability to photosynthesize. Disease causing fungi and viruses can also be introduced into the plant through feeding puncture wounds made by the adult flies. In severe infestations leaves can wilt and die, causing defoliation.

May be confused with

Similar damage could be caused by other leaf mining insects that are present in Queensland.

Serpentine leafminer (L. huidobrensis) and vegetable leafminer (L. sativae) produce highly convoluted (squiggly) leaf mines and have a broad host range.

Adult leafminer flies are readily confused with many other flies already present in Australia (incl. other agromyzids). Any flies that resemble American serpentine leafminer need specialist examination, typically with DNA diagnostics analysis, to confirm their identity.

If you suspect an American serpentine leafminer infestation, then you should report it.


The American serpentine leafminer originated in the highlands of South America and is better adapted to cooler climates than vegetable leafminer.

It is established in Africa, Asia, Central America, Europe and North America (in glasshouses in Canada, but not in the United States) and in Indonesia and West Timor.

American serpentine leafminer is not currently widely established in Australia. Since March 2021, there have been multiple detection in Torres Strait, in Far North Queensland (Northern Peninsula Area of Cape York Peninsula), and in Kununurra, northern Western Australia.


American serpentine leafminer affects a wide host range of common horticultural crops and ornamental plant species.

They have been found to seriously affect solanaceous crops (such as potato, tomato and eggplant), as well as crops in the Asteraceae, Cucurbitaceae and Fabaceae families.

Life cycle

Several generations may be produced during a year. Female flies pierce the leaf surface to lay eggs inside. Eggs hatch in 2–5 days depending on temperature and larvae mine the leaf tissue. The larvae of American serpentine leafminer primarily feed on the plant in which the eggs were laid. Larvae leave the plant to pupate.


American serpentine leafminer damage reduces crop marketability and yield, resulting in economic losses to growers.

If the American serpentine leafminer were to become established in Australia without control mechanisms in place, it would have a significant effect on horticultural production.

How it is spread

The greatest risk of pest spread is by people moving infested plant material, soil or packaging.

Adult flies may also hitchhike in vehicles, machinery or aircraft.

The adult flies are not very strong flyers. The flies usually walk quickly over leaves and fly short distances to move between leaves or nearby plants. Strong winds may assist adult flies to fly further afield.

Monitoring and action

Inspect your plants regularly for the presence of leaf mines.

Look for leafminer damage on a variety of plant species or unusual or severe leafminer leaf damage.

If you suspect American serpentine leafminer, report it to Biosecurity Queensland on 13 25 23 immediately

Legal requirements

Under Queensland's Biosecurity Act 2014, there are 2 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 5 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.