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BAA 2010/26 - Draft PRA report for candidatus liberibacter

​Biosecurity Australia Advice 2010/26 - Draft Pest Risk Analysis Report for ‘Candidatus Liberibacter species’ and their vectors associated with Rutaceae

30 August 2010

Biosecurity Australia Advice 2010/26

This Biosecurity Australia Advice (BAA) invites stakeholders to provide comments on the Draft pest risk analysis report for ‘Candidatus Liberibacter species’ and their vectors associated with Rutaceae by 29 October 2010 (60 days consultation).

‘Candidatus Liberibacter species’ cause Huanglongbing (HLB) disease in citrus which is considered one of the most destructive diseases of citrus worldwide. The pathogens and their vectors occur on all species and cultivars of citrus and on some non-citrus members of the Rutaceae. Australia is currently free from ‘Ca. L. species’ and their known vectors, Diaphorina citri and Trioza erytreae.

The pest risk analysis (PRA) considers all potential host plants and import pathways of ‘Candidatus Liberibacter species’ and their insect vectors, Diaphorina citri and Trioza erytreae, from all countries.

The draft report proposes quarantine measures for importation to Australia of ‘Candidatus Liberibacter species’ host plant material from countries where these pathogens and/or their vectors are present.

Currently, imports of fresh citrus fruit are only permitted from Egypt, Israel, Italy, New Zealand, Spain and the USA (Arizona, California and Texas). In recent years, ‘Ca. L. species’ and their vectors have extended their range around the world. The continued expansion in range of ‘Ca. L. species’ and their vectors, particularly towards countries and regions that are approved to export fresh fruit to Australia, and the identification of new pathways for their entry has resulted in a renewed interest in these pathogens. Plant Biosecurity initiated this PRA to assess the quarantine risks associated with these pests and the importation of host plant material into Australia.

This draft pest risk analysis identified nursery stock (live plants), budwood, seed for sowing and psyllid vectors infected with ‘Ca. L. species’ as potential pathways for the introduction of ‘Ca. L. species’ into Australia. Fruit, nursery stock, budwood and fresh leaves were identified as potential pathways for the introduction of D. citri and T. erytreae. These potential pathways have an unrestricted risk that exceeds Australia’s appropriate level of protection (ALOP), therefore risk management measures are required. Plant Biosecurity considers that the risk management measures proposed in this draft PRA report will achieve Australia’s ALOP against ‘Ca. L. species’ and their psyllid vectors. Specifically, the proposed risk management measures are:

For budwood (potentially carrying ‘Ca. L. species’ and psyllid vectors):

  • existing policy for citrus budwood applies to all hosts of ‘Ca. L. species’ (on arrival inspection, mandatory fumigation and mandatory growth in closed government post-entry quarantine (PEQ) facilities until the required pathogen screening/testing is completed); and
  • additionally, plants grafted with imported budwood must be grown at 22–24 °C to promote symptom expression for ‘Ca. L. species’ and polymerase chain reaction (PCR) testing for ‘Ca. L. species’ prior to release.

 For seed for sowing (potentially carrying ‘Ca. L. species’):

  • hot water treatment of seed at 50 °C for 20 minutes from all sources; or
  • if seed is sensitive to heat treatment, mandatory surface sterilization and growth at 22–24 °C in closed government PEQ facilities for 24 months with pathogen screening including PCR testing for ‘Ca. L. species’ prior to release.

 For fruit (potentially carrying psyllid vectors):

  • area freedom from citrus psyllids; or
  • a systems approach using pre- and post-harvest measures to ensure that fruit is not infested with psyllids; or
  • an application of a treatment to fruit known to be effective against all life stages of the psyllid (including but not limited to methyl bromide fumigation).

 For fresh leaves (potentially carrying psyllid vectors):

  • area freedom; or
  • hot air treatment at 85 °C for 8 hours; or
  • mandatory methyl bromide fumigation 

Comments on the draft report should be submitted by 29 October 2010 to:

Plant Biosecurity
Biosecurity Australia
GPO Box 858

Telephone:  +61 2 6272 3933
Facsimile:  +61 2 6272 3307
E-mail: Plant Biosecurity 

Dr Colin J Grant
Chief Executive