Science in relation to risk
DISCUSSION SESSION
Facilitator: Dr Alan Inman, Defra Plant Health Division
Short talks by: Dr Claire Sansford, Central Science Laboratory
Dr Joan Webber, Forest Research
Rapporteur: Dr Martin McPherson, Stockbridge Technology
Centre Ltd
Following short introductory presentations from Dr Sansford on the Principles of Plant Health Risk Analysis’ and Dr Webber on ‘Science in relation to P. ramorum & P. kernoviae’ to fill some of the knowledge gaps (both presentations are available – see left hand menu), Dr. Alan Inman led a discussion session to explore what the key questions & issues relating to these pathogens were and to identify areas where additional research may be needed.
It was highlighted that Key Research Findings (pdf) were summarised in a document available on the Defra Plant Health website. Final research project reports were also available on the Defra website at: http://www.defra.gov.uk/planth/pramorum6.htm. The EU RAPRA project website was also a good source of information, especially the host database: http://rapra.csl.gov.uk/
Discussion was fairly wide ranging and can be outlined in four broad areas:-
1. Epidemiology
It was evident from discussion that there remain many unanswered questions,
though some may be covered with existing R&D programmes. Areas of
specific interest included:-
a. Soil persistence – it’s not clear how long the pathogens
survive in the soil in proximity to and in the absent of host roots, though
there was data from Defra-funded research projects for survival in soil/debris.
b. Systemic infection – does this occur and what is the potential
significance?
c. Dispersal in water – data available for P. ramorum though
less known about P. kernoviae in this respect.
d. Root infection – can the anecdotal information from the US be
substantiated; the EU RAPRA project has some work in progress.
e. Dispersal by animals, birds or invertebrates. What is the risk, if
any. Data was available from the USA and some observations from the UK.
f. Risk assessment for wood products e.g. bark mulch, green-waste compost
etc.
g. Disposal of infected material needs reconsideration with respect to
the option of burial…at least until more information is available
on both soil survival and dispersal in water. There was concern that deep
burial on site might result in contamination of water courses.
h. The issue of inoculum potential was raised though it was pointed out
that a considerable amount of R&D had already been undertaken in this
regard and it was not clear that more was needed. To review perhaps?
i. Wind dispersal…is this possible long distance via dust, leaf
litter etc? Scientists flagged up research in the USA (California and
Oregon) and in the UK.
2. Environmental Influences
A claim was made that we need more information relating to potential for
various environmental impacts on host susceptibility e.g. soil acidity
impacting on both pathogen and host. No scientific support currently available
for such hypotheses, though equally no strong evidence to refute either.
In the USA, there was some evidence that ‘healthier’ trees
were often more at risk, i.e those with higher stem water potentials.
Scientists were urged to keep an open mind to possibilities and all parties
to gather evidence where available. This issue was perhaps the most controversial
of all discussions in the session.
Also, comment about potential impact on use of glyphosate around nursery
sites and effect on host susceptibility and symptom expression in pathogen.
3. Host Taxonomy
Brief discussion regarding relative susceptibility of hosts and cultivars
in susceptible species. A specific area of concern was the taxonomy of
Rhododendron spp. (“It’s a mess” someone quoted) and
additional research requested in this area. It was suggested that data
from existing surveys might be useful in highlighting very susceptible
cultivars of certain species.
4. Pathogen Taxonomy
The two different A1 & A2 mating types and the risk of recombinants
were seen as a potential threat to the industry and environment. It was
noted that the EU populations of P. ramorum appeared to be more
uniform and pathogenic than those from the USA though it was also noted
that they don’t reproduce readily, presumably under artificial conditions
in the laboratory, and therefore the risk of novel variants is lower than
in P. infestans. The general consensus of this brief discussion
was that it warranted ongoing concern. Regular monitoring of the populations
dynamics was deemed appropriate so that the industry can react should
any new situation arise.
Click here if you need free pdf software
Page last modified:
6 Nov 2006
Page published: 25 Nov 2005