Editorial - Has Clavibacter michiganensis ssp. sepodonicus, causal pathogen of potato ring rot, been reported validly in Egypt?

In October 2014 New Disease Reports (NDR) reported Clavibacter michiganensis ssp. sepodonicus as the cause of ring rot of potato (Solanum tuberosum) for the first time in Egypt (and purportedly the first record for Africa) (Seleim et al., 2014). This report was indexed by the EPPO Reporting Service in July 2015 (EPPO, 2015a). However, this finding was dismissed by the Egyptian National Plant Protection Organisation (NPPO), the Ministry of Agriculture and Land Reclamation, in a subsequent entry in the EPPO Reporting Service (EPPO, 2015b) as containing 'serious scientific flaws which rendered this record doubtful, if not erroneous'. For example, the NPPO held that the level of sampling claimed was not feasible and emphasised that the methodological procedures recommended in EC Directive 93/85/EEC were not followed. The pest status conferred by EPPO in this document (EPPO, 2015b) was 'Absent (unconfirmed report only)'. The current pest situation evaluated by EPPO for C. m. ssp. sepodonicus is 'Absent, unreliable record' (https://gd.eppo.int/taxon/CORBSE/distribution/EG).

The Egyptian NPPO subsequently wrote to the Senior Editor of NDR calling for the withdrawal of the report by Seleim et al. (2014). Prior to this the former and present Senior Editors of NDR had already reviewed the editorial processes that led to the approval of Seleim et al. (2014) for publication and the evidence presented by the authors to support their findings.  The results from this review and from dialogue with the authors of Seleim et al. (2014) were as follows:

1. The sampling regime used was feasible given the resources available.

2. It was not necessary to follow European Commission protocols published in Directive 93/85/EC for a scientific report although this would have been desirable.

3. C. m. ssp. sepodonicus has been validly detected but at a very low level, possibly below the threshold used to screen for Ralstonia solanacearum (cause of potato brown rot) that has been Egypt's main concern in its potato trade with the European Union.

4. The prevailing climate might well suppress the development of ring rot symptoms and economic effects in Egyptian potato crops that would be apparent in crops grown in temperate zones.

Overall, it has been concluded that in spite of some remaining methodological issues, Seleim et al. (2014) have validly reported C. m. ssp. sepodonicus, albeit at a very low incidence, and therefore it would not be appropriate to withdraw this report. Clearly it is the responsibility of the NPPO firstly to evaluate the data objectively, following up with its own investigations if considered necessary, then to make a reasoned risk assessment of the impact of the likely occurrence of this bacterial pathogen at a very low level. Finally a decision should be made as to what regulatory action is required, if any.

Readers are reminded that NDR publishes scientific reports on plant diseases; these are not intended to be automatic triggers of regulatory action either by an NPPO or its trading partners. As described in the journal’s disclaimer (http://ndrs.org.uk/legal.php), published reports are provided for information and educational purposes only and in no circumstances should be relied upon as a source of information for legal, regulatory or commercial decisions. The distinction between scientific reports and official reports was emphasised in a previous editorial (Black, 2011).