Pest categorisation of the Ralstonia solanacearum species complex

Abstract

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of the Ralstonia solanacearum species complex (RSSC), a distinguishable cosmopolitan group of bacterial plant pathogens (including R. solanacearum, Ralstonia pseudosolanacearum and two subspecies of Ralstonia syzygii) of the family Burkholderiaceae. The RSSC causes bacterial wilt in solanaceous crops, such as potato, tomato and pepper, but can also cause wilts in other important food crops such as fruit banana, plantain banana and cassava. The pest survives in the soil, and a number of weed species can also be infected by the pest, often asymptomatically. The RSSC is regulated in Council Directive 2000/29/EC (Annex IAII) (indicated by its former name R. solanacearum, as delimited by Yabuuchi et al.) as a harmful organism whose introduction into the EU is banned. In addition, Council Directive 1998/57/EC (amended by Commission Directive 2006/63/CE) concerns the measures to be taken within EU Member States (MS) against the RSSC to (a) detect it and determine its distribution, (b) prevent its occurrence and spread, and (c) control it with the aim of eradication. The pest is present in several EU MS, but in all cases with a restricted distribution and under official control. New phylotypes of the RSSC could enter the EU primarily via host plants for planting (including seed tubers). The pest could establish in the EU, as climatic conditions are favourable, hosts are common and the pathogen has high adaptability. Spread is mainly via plants for planting. Substantial crop losses in the EU would occur in the presence of RSSC epidemics. The RSSC is regarded as one of the world’s most important phytopathogenic bacteria due to its broad geographical distribution, large host range, aggressiveness, genetic diversity and long persistence in soil and water. The list of hosts and commodities for which the pest is regulated is incomplete due to the high diversity of hosts and the lack of knowledge of the complete host range. Moreover, the comparative epidemiology of the different pathogen species has not yet been studied. The criteria assessed by the Panel for consideration of the RSSC as potential quarantine pest are met, while, for regulated non-quarantine pests, the criterion on the widespread presence in the EU is not met.