Exotic leaf miners

Primefact number Edition Published Author
1584 First Aug 2017 Plant Biosecurity and Product Integrity

Composite image showing at right black fly with yellow spot on back, yellow marking on head, and long translucent wings with black veins. At left black fly with larger yellow spot on back and brighter yellow marking on head.

Leaves of a bean plant with meandering tunnelling patterns

The exotic leaf miner species Liriomyza bryoniae, L. cicerina, L. huidobrensis, L. sative and L. trifolii are not present in Australia. These pests are a serious threat to Australian agricultural and horticultural industries.

The insect genus Liriomyza has over 300 species of leaf miner flies distributed around the world. Of these 300 species, five are known to attack a wide variety of plants and are considered significant agricultural and horticultural pests in many parts of the world. These five species are currently not present in Australia:

  • Liriomyza bryoniae (tomato leaf miner)
  • Liriomyza cicerina (chickpea leaf miner)
  • Liriomyza huidobrensis (pea leaf miner)
  • Liriomyza sativae (vegetable leaf miner)
  • Liriomyza trifolii (American serpentine leaf miner)

Description

Adults

The adult flies of all five Liriomyza species are very similar in appearance. The flies are small (<3 mm) and grey-black with yellow markings. Usually there is a prominent yellow area at the base of the wings (Figure 1).

Larvae

The larvae of Liriomyza species are yellow to white and usually concealed beneath the leaf surface in tunnels where they feed.

More visible than the larvae themselves are the patterns created in the surface of infested leaves by their tunnelling (Figure 2). The twisting trails appear whitish on the surface of the leaf and become longer and wider as the larva grows. Heavily mined leaves may also show large whitish blotches.

Damage

The larvae of all Liriomyza species ‘mine’ in the leaves of hosts plants. The larvae feed by tunnelling through the leaf tissue.

Extensive tunnelling across leaf surfaces reduces the ability of the plant to photosynthesise and produce energy. Severe damage can result in leaf death or premature leaf drop.

If severe mining occurs early in the fruiting period, defoliation can reduce yield and fruit size and expose fruit to sunburn.

Lifecycle

Female flies use their ovipositor to puncture the leaves of host plants and deposit eggs. The eggs are inserted just below the leaf surface. Many eggs may be laid on a single leaf.

There are three larval stages that feed within the leaves. The larvae usually fall from the plant to the soil to pupate.

The entire life cycle can be completed in as little as two weeks. If conditions are favourable, the flies can reproduce all year round and sustain five to ten generations per year.

Spread

Introduction of exotic Liriomyza flies to Australia is most likely to occur with the transport of plant host material containing eggs or larvae.

The adults are capable of flight but are not very active fliers. They tend to fly within a crop but rarely between crops. Localised spread of the pest is most likely to occur through wind dispersal or on contaminated plant material or equipment.

Hosts

Liriomyza bryoniae, L. huidobrensis, L. sativae and L. trifolii are all significant pests of a number of vegetable crops including beans, cabbage, capsicum, celery, chilli, cucumber, eggplant, lettuce, onions, peas, potatoes and tomatoes.

Melons, cotton and pulses are also known to host both L. trifolii and L. sativae. Liriomyza cicerina is a more specialised species with a narrower pulse host range of chickpeas and faba beans.

A number of ornamental plants including cut flowers are known to host both L. trifolii and L. huidobrensis.

Liriomyza trifolii has also been detected on coffee, barley and oats.

Distribution

Liriomyza trifolii, L. huidobrensis and L. sativae are found worldwide.

Liriomyza bryoniae is present in Europe, Asia and North Africa and L. cicerina is currently restricted to Africa and Europe.

Actions to minimise risk

Put in place biosecurity best practice actions to prevent entry, establishment and spread of pests and diseases:

  • practice “Come clean, Go clean”
  • ensure all staff and visitors are instructed in and adhere to your business management hygiene requirements
  • monitor your crops regularly
  • monitor and control volunteer plants that can harbour the pest
  • source plant material of a known high health status from reputable suppliers
  • keep records