Scientific Opinion on the Pest Risk Analysis onPhytophthora ramorumprepared by the FP6 project RAPRA

Abstract

The Panel on Plant Health was asked to deliver a scientific opinion on the Pest Risk Analysis on Phytophthora ramorum prepared by the FP6 project RAPRA, taking into account comments by Member States and additional information since RAPRA. P. ramorum is the oomycete causing sudden oak death in the USA and leaf and twig blight/dieback on a range of ornamental species in North America and Europe. Currently P. ramorum is not listed as a harmful organism in Council Directive 2000/29/EC, but the Commission adopted in 2002 provisional emergency measures to prevent introduction into and spread within the EU. Recent large-scale outbreaks in Japanese larch (Larix kaempferi) plantations in the UK and Ireland have worsened the potential consequences in the risk assessment area. However, the Panel concludes that the broad narrative in the RAPRA report stands and supports its conclusion that "There is a risk of further entry (of known or new lineages and/or mating types), establishment and […] impact". It is advisable to avoid introductions of different lineages because of inherent phenotypic differences and the potential for sexual recombination. The Panel supports the management options proposed in the RAPRA report and adds further measures for consideration. Uncertainty remains over the extent to which the association between control measures and gradual reduction in the number of cases in nurseries is causal. The emergency measures have not prevented outbreaks occurring in the natural environment. The many other remaining uncertainties (fitness of progeny, hybridisation with other Phytophthora species, host range and epidemiological role of new hosts, early detection of new outbreaks, understanding of long-range dispersal, structure of plant trade networks, origin of the pathogen) call for further research on P. ramorum across Europe. 4 Editorial changes have been made on pages 51 (acronym PRA removed as it was not in line with the Panel's dictionary as discussed in Appendix 2 of the Guidance on a harmonised framework for pest risk assessment and the identification and evaluation of pest risk management options by EFSA) and 89 (statement which referred to the Panel agreeing with the RAPRA conclusion that "P. ramorum fulfils the criteria of a quarantine pest" was removed as requested by the Panel during adoption of the draft opinion). The changes do not affect the overall conclusions of the opinion. To avoid confusion the original version has been removed from the website. The scope of this Scientific Opinion is the evaluation of the RAPRA report, taking into consideration the comments of Member States as well as additional information published after finalisation of the RAPRA report, or not cited in the RAPRA report. A systematic literature search until March 2011 was carried out. It should be noted that the scientific community is concerned by the shift of P. ramorum to new hosts (with a special focus on the Japanese larch) and its further spread, and therefore new results of ongoing research are constantly be...

Sudden Oak Death: Interactions of the Exotic Oomycete Phytophthora ramorum with Naïve North American Hosts

“…A study on A1-A2 progeny revealed a high incidence of non-Mendelian inheritance and of aneuploidy suggestive of significant differences in synteny (gene arrangements), and possibly in chromosomal number, between lineages (119). Nonetheless, two studies have determined that a percentage of oospores generated from laboratory crosses may be viable (5,35), highlighting the importance of avoiding intermixing of lineages carrying different mating types (Fig. 1).…”

“…ramorum highlights the indirect effects of human commercial and industrial activities on natural ecosystems: in this case, a pandemic affecting forest trees has been clearly driven by the longdistance trade of infected ornamental plants used not for reforestation but for landscaping in the urban-wild interface. Given this scenario, it should be no surprise that in less than a decade, P. ramorum has driven a significant policy shift in how plant pathogens are diagnosed by the regulatory agencies of many countries, moving from a diagnosis exclusively dependent on morphological identification of cultures to a more articulated process in which culturing, immunological, and nucleotide sequence-based detection assays must be utilized (2,35).…”

Commodity risk assessment of maple veneer sheets from Canada

“…One possible pathway of entry for P. ramorum according to Sundheim et al. ( 2009 ), EFSA PLH Panel ( 2011 ) and Thomsen et al. ( 2023 ) is susceptible wood.…”

Commodity risk assessment of Quercus petraea plants from the UK

“…Possible pathways of entry for Phytophthora ramorum are plants for planting (excluding seed and fruit) of known susceptible hosts; plants for planting (excluding seed and fruit) of non-host plant species accompanied by contaminated attached growing media; soil/growing medium (with organic matter) as a commodity; soil as a contaminant; foliage or cut branches; susceptible (isolated) bark and susceptible wood (EFSA PLH Panel, 2011).…”