Serpentine leafminer

Primefact number Edition Published Author
PUB20/934 First Nov 2020 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

NSW DPI liaison team: Serpentine leafminer

NSW Department of Primary Industries has established a serpentine leafminer primary industries liaison team to help primary producers navigate the challenges and impacts of serpentine leafminer on their business and industry.

You can contact the team by emailing leaf-miner.info@dpi.nsw.gov.au to discuss your individual business or industry circumstances.

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: 2 December 2020

NSW DPI and Local Land Services are responding to a confirmed report of serpentine leafminer (Liriomyza huidobrensis).

The infestation was reported to the Exotic Plant Pest Hotline from a market garden situated in the peri-urban area of western Sydney on 22 October 2020. Samples were collected and diagnosed as serpentine leafminer (Liriomyza huidobrensis) on 28 October.

NSW DPI and Local Land Services launched an emergency response that involved surveillance and tracing to determine the extent of the infestation. Identified infected premises included wholesale nurseries, market gardens and a retail nursery.

The Consultative Committee on Emergency Plant Pests is Australia’s key technical body for coordinating national responses to emergency plant pest incursions and assessing the technical feasibility for their eradication. The committee recommended that serpentine leafminer (SLM) is not technically feasible to eradicate due to the extent of the infestation. Based on this recommendation, NSW DPI will transition to management. This will focus on managing pathways of spread, abating domestic trade issues to retain market access, ensure control options are available and that industry is supported through the changes in required pest management to ensure business continuity.

General Biosecurity Duty

Part 3 of the Biosecurity Act (2015) describes how people have a General Biosecurity Duty to prevent, eliminate or minimise the risk of SLM in NSW. People dealing with SLM host plants which have visible signs of leaf miner damage must act to ensure they are meeting this General Biosecurity Duty. Put simply, you must always act to prevent further spread of SLM in NSW, eliminate heavy infestations of the pest and minimise the impacts of SLM in plant production systems. This duty may be met by any number of means that are considered Best Management Practice for SLM including by not selling heavily infested SLM host plants, through the use of integrated pest management to minimise the impact of SLM in the production system, adhering to industry standards such as BiosecureHACCP or market access arrangements like ICA29, or treating host plants with approved insecticides, fumigation or irradiation to prevent spread in host produce.

The General Biosecurity Duty for SLM is a legislative mechanism due to the risk of an adverse effect on the economy and the community that arises from the presence, spread or increase of serpentine leafminer within New South Wales.

Reporting

Immediately report suspected serpentine leafminer to NSW DPI by one of the following methods:

Reports will need to be confirmed by NSW DPI entomologists. Courier or express post samples early in the week, avoid sending on Thursday or Friday so samples don’t spend the weekend in transit. Samples deteriorate quickly in the heat.

For situations where there is leafmining damage on multiple host species, submit a leaf sample following this method

  1. Collect small leaves or parts of large leaves that have obvious, recent leafminer tunnels in them
  2. If you find small brown pupae (1-2mm long) on the underside of leaves collect these as well
  3. Place the samples in a zip lock sandwich bag. Press the air out and securely zip the lock fully closed
  4. Write on the front of the bag in permanent black marker the name of the host plant, date and location address collected and the name of the person who collected it
  5. Collect each host plant in a different zip lock bag
  6. Place all of the sample bags inside one larger zip lock bag (to ensure all insects are contained) and place inside a padded envelope with a completed Plant Health Diagnostic Service Specimen Advice form
  7. Post to:

Attn: SLM
Plant Health Diagnostic Service
EMAI, Woodbridge Rd
Menangle NSW 2568

If you suspect an exotic leafminer infestation and you can submit a sticky trap for identification:

  1. Place a yellow sticky trap in the crop/garden so that the bottom of the trap is level with the top of the plants
  2. Leave it out for 5 days
  3. Take a plastic A4 sleeve and in black permanent marker write the trap collection date, property address and a contact name and phone number on the front
  4. With scissors cut open the sealed outer edges of the plastic sleeve so that it opens like a book
  5. Place the sticky trap carefully on one side of the plastic sleeve and close the plastic sleeve gently over the trap so you don’t squash any insects on the trap
  6. Place inside a padded envelope with a completed Insect Identification Request form
  7. Post to:

Attn: SLM
Biosecurity Collections
Orange Agricultural Institute
1447 Forest Rd, Orange NSW 2800

Webinar

This webinar was held in response to the detection of Serpentine leafminer in Western Sydney in late 2020, providing information on pest biology and chemistry, integrated pest management and regulatory requirements.

Description

Adults

The adult flies are small (<3 mm) and grey-black with yellow markings. Usually there is a prominent yellow area at the base of the wings.

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. Damaged leafy vegetables are unmarketable to supermarkets.

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

Serpentine leafminer is a significant pest of a number of vegetable crops including beans, cabbage, capsicum, celery, chilli, cucumber, eggplant, lettuce, onions, peas, potatoes and tomatoes. Ornamental plants including cut flowers are also hosts. See the full host list

Distribution

SLM was found in western Sydney in October 2020 and is currently being responded to. Surveillance found it was also present in regional NSW.

Queensland reported a detection in the Fassifern Valley in November 2020.

Globally, SLM is found in Africa, Asia, Europe, North and South America.

Actions to minimise risk

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

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

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.

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