Symptoms, description and lifecycle

Larvae feed singly, forming an upper surface linear-blotch mine. Pupation either internal or external, with the puparium loosely glued to the leaf. Oviposition near the leaf margin, at some distance from the lead tip. From there develops an upper surface corridor-blotch. At first the mine ascends as a narrow corridor towards the leaf tip, then the direction turns and the mine, steadily widening, descends in the direction of the leaf base. Frass irregular, in rather coarse grains. Larva solitary. Pupation mostly outside the mine; in that case the puparium often sticks to the leaf.

Liriomyza trifolii (American serpentine leaf miner) Liriomyza trifolii feeding punctures appear as white speckles between 0.13 and 0.15 mm in diameter. Oviposition punctures are usually smaller (0.05 mm) and are more uniformly round. Liriomyza trifolii leaf mines can vary in form with the host plant, but when adequate leaf area is available they are usually long, linear, narrow and not greatly widening towards the end. They are usually greenish white. In very small leaves the limited area for feeding results in the formation of a secondary blotch at the end of the mine, before pupariation. The frass is distinctive in being deposited in black strips alternatively at either side of the mine, but becomes more granular towards the end of the mine. Fungal destruction of the leaf may also occur as a result of infection introduced by L. trifolii from other sources during breeding.

Organism

Liriomyza trifolii (American serpentine leaf miner), Phytomyza rufipes (Cabbage leaf miner), Chromatomyia horticola (Pea leaf miner), Agromyza albipennis (Black wheat leaf miner)

Conditions favouring pest

Pupa of Leaf miners are unable to cope with high humidity or drought. Areas with sub-tropical/tropical zones are at highest risk for this insect.

Host range

Phytomyza rufipes (Cabbage leaf miner) = canola
Chromatomyia horticola (Pea leaf miner) = pulses, canola and sunflowers
Agromyza albipennis (Black wheat leaf miner) = cereals

Method of spread

Insects are able to move small distances, while further distances can be traversed with wind, human, soil, plant or packaging.

Confused with?

There are shared features within the leaf miner group and expert diagnosis is required.

Where?

Pea leaf miner = Africa, Asia and Europe.
American serpentine leaf miner = Africa, Asia, Europe, North America, South America, Samoa, Guam and Tonga.

Image 30. Liriomyza trifolii.
Source: Agriculture Victoria.

Image 31. Liriomyza huidobrensis. Papa Santiago, 1987, R. Muuoz.
Source: Sarah McCaffrey, Museum Victoria.