Exotic leafminers

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

Figure 1 Mining damage caused by L. huidobrensis  larvae on leafy vegetables

Figure 2 Mining damage caused by L. huidobrensis larvae on tomato leaf

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

Exotic serpentine leafminer (Liriomyza huidobrensis) is an insect pest that has been detected in NSW.

Serpentine leaf miner poses a serious threat to Australian agriculture and horticultural industries. Severe infestations of serpentine leaf miner may result in premature leaf drop, poor growth, and reduced crop yields.

Current situation

Updated: 18 November 2020

NSW DPI and Local Land Services are responding to a confirmed report of exotic serpentine leafminer (Liriomyza huidobrensis).  The infestation was reported to the Exotic Plant Pest Hotline from a market garden situated in the peri-uban area of western Sydney on 22 October 2020.

Samples were collected and diagnosed as the exotic serpentine leafminer (Liriomyza huidobrensis) (SLM) on 28 October. Surveillance is being undertaken by NSW DPI and Local Land Services in the Sydney Basin and more broadly across NSW to determine the extent of the spread. Currently there are 8 infested premises in the Sydney Basin.

Surveillance

  • Surveillance and tracing is being conducted around the Sydney Basin and Central Coast to determine the extent of the spread of this pest.
  • Since the confirmed detection, a further 100 samples have been collected from nearby properties with diagnostic test results pending.
  • The NSW Department of Primary Industries has established an Incident Management Team and Forward Command Postto coordinate the response.
  • Infested sites are being assessed to inform further actions.

Notifiable status

Exotic leafminers must be reported immediately to NSW DPI by one of the following methods:

A full list of notifiable plant pests and diseases can be found in Schedule 2 of the NSW Biosecurity Act 2015.

About serpentine leafminer

  • Serpentine leafminer (Liriomyza huidobrensis) is an exotic leafminer species that poses a significant economic threat to Australia’s horticulture and nursery production plant industries.
  • Serpentine leafminer is a plant pest that has a wide host range of plant species which includes broccoli, beet, spinach, zucchini, chilli, peas, beans, potatoes and cut flowers. It also infests a number of common weed species.
  • The pest is wind borne and eggs, larvae and pupae can be spread through the movement of plant material, soil and equipment.
  • Serpentine leafminer damage is primarily caused by larvae feeding inside the leaves. Typically, this feeding causes long, narrow, serpentine-shaped 'mines' which appear as white or grey lines on leaves.
  • High levels of infestation affect the plant’s ability to photosynthesise, reducing plant growth and crop yields.

Reporting

If you suspect an exotic leafminer infestation, you should report it immediately to the Exotic Plant Pest Hotline on 1800 084 881.

Exotic leafminers

Exotic serpentine leafminer (Liriomyza huidobrensis) has been detected in NSW.

The exotic leafminer species Liriomyza bryoniae, L. cicerina and L. trifolii are not present in Australia.

The exotic vegetable leafminer, L. sativae is present on mainland Australia at the tip of Cape York peninsula but has not made it to agricultural production areas and is contained within northern biosecurity zoning.

These pests are a serious threat to Australian agricultural and horticultural industries.

The insect genus Liriomyza has over 300 species of leafminer 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. Three of these species are not currently present in Australia

  • Liriomyza bryoniae (tomato leafminer)
  • Liriomyza cicerina (chickpea leafminer)
  • Liriomyza trifolii (American serpentine leafminer)

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 3).

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 (refer to images). 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 host 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 is found worldwide except for Australia. Liriomyza bryoniae is present in Europe, Asia and North Africa and L. cicerina is present in Africa, Europe and the Middle East.

Liriomyza sativae was found on Cape York, Queensland in 2015 and is under management to prevent further spread.

Liriomyza huidobrensis was found in western Sydney in 2020 and is currently being responded to.

Actions to minimise risk

Production nurseries and growers should check their crops regularly for signs of plant pests and disease.

Good on-farm biosecurity practices are vital to preventing incursions of plant pests and diseases.  The farmbiosecurity.com.au website has helpful information that can be tailored to your property.

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

  • practise “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

If you suspect an exotic leaf miner infestation, you should report it immediately to the Exotic Plant Pest Hotline on 1800 084 881.

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