Pest categorisation of Citrus tristeza virus (non‐European isolates)

Abstract

The Panel on Plant Health performed a pest categorisation of non-European isolates of Citrus tristeza virus (CTV) for the EU territory. CTV is a well characterised virus for which efficient detection assays are available. It is transmitted by vegetative multiplication of infected hosts and by aphid vectors. The most efficient one, Toxoptera citricida, has limited EU presence but another one, Aphis gossypii, is broadly distributed. CTV is reported from a range of countries outside the EU and EU isolates are present in seven of the eight citrus-growing member states. Non-EU isolates are not known to occur in the EU and therefore do not meet one of the criteria for being a Union regulated non-quarantine pest. The natural host range of CTV is restricted to Citrus, Fortunella and Poncirus species. CTV non-EU isolates are listed in Annex IIAI of Directive 2000/29/EC and the main pathway for entry, plants for planting, is closed by the existing legislation. CTV isolates may therefore only enter through minor alternative pathways. They have the potential to subsequently spread through plants for planting and through the action of aphid vectors. CTV non-EU isolates are able to cause severe symptoms on a range of citrus crops that EU isolates do not induce. Overall, non-EU CTV isolates meet all the criteria evaluated by EFSA to qualify as Union quarantine pests. The main knowledge gaps and uncertainties concern (1) the status of Rutaceae species other than Citrus, Fortunella and Poncirus as natural hosts for CTV; (2) the potential undetected presence of non-EU CTV isolates in the EU and in particular the prevalence and biological properties of CTV isolates that may be present in ornamental citrus; and (3) the inability of EU CTV isolates apparently related to non-European stem pitting (SP) isolates to cause SP in sweet orange.

PM 7/31 (2) Citrus tristeza virus

“…Note on the phytosanitary categorization: CTV non‐EU isolates are able to cause severe symptoms on a range of citrus crops that EU isolates do not induce. For this reason, non‐EU CTV isolates have been evaluated as Union quarantine pests (EFSA, 2017). Throughout this document, CTV isolates that can cause severe symptoms are referred to as ‘severe isolates’.…”

“…It should also be noted that the term ‘strain’ has been used in literature both as a synonym for ‘isolate’ and to group isolates on their molecular and/or biological properties (EFSA, 2017). Therefore, in this protocol the Panel on Diagnostics in Virology and Phytoplasmology decided to use the concept of phylogenetic group in relation to genetic characteristics and strain in relation to pathogenic characteristics.…”

“…Biological indexing of these isolates resulted in rare occurrence of inconspicuous symptoms on indicator plants. Outside of Europe, in the main citrus producing countries of the world, CTV isolates causing stem pitting appear to be present (EFSA, 2017).…”

Pest survey card on non‐European isolates of citrus tristeza virus

“…An extensive range of techniques, methods and tools are available for the detection and discrimination of CTV isolates (EPPO, 2004;EFSA PLH Panel, 2014a,2017Jackson, 2019). Due to the fact that, CTV is present in the EU, detection methods are required to discriminate between the EU isolates of CTV and the resistance-breaking and aggressive non-EU isolates.…”

“…The information presented in this pest survey card is summarised from the EFSA pest categorisations (EFSA PLH Panel, 2014a, 2017, the European and Mediterranean Plant Protection Organisation (EPPO) Diagnostic Protocol (EPPO, 2004), the Centre for Agriculture and Bioscience International (CABI) datasheet on citrus tristeza virus (CABI, 2018), the EPPO Global Database, and other documents.…”