Biosecurity Alert: American Serpentine Leaf Miner

Dept of Primary Industries and Regional Development WA

Type: biosecurity alert

2021 detection in Western Australia

American serpentine leafminer (Liriomyza trifolii) is a tiny fly whose larvae damages plants by tunneling (mining) through leaf tissue. It poses a serious threat to Australia’s horticulture, nursery production, and agriculture plant industries. It is known to feed on more than 400 plant species, including most vegetable and legume crops, as well as ornamental plants.

This species of leafminer was detected in northern Western Australia in July 2021. This was the first time it had been detected on the Australian mainland.


American serpentine leafminer adult flies are 1-2mm in size, grey-black in colour, and distinguished by a prominent yellow area at the base of the wings. Larvae are white-yellow.

What to look for

  • 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.
2021 - Dept of Primary Industries and Regional Development WA
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