Action in woodlands and gardens (P. ramorum and P. kernoviae)
DISCUSSION SESSION
Facilitator: Karen Pugh (Defra Plant Health & Seeds
Inspectorate)
Short talks by: Ian Wright (National Trust) Dr Judith
Turner (Central Science Laboratory)
Rapporteur: Philip McMillan Browse (Lost Gardens of Heligan)
Bio-Security, Disease Biology, the Destruction of Rhododendron
ponticum and the issue of Costs
The issue of public access to areas where the disease is/has been present was a matter of concern. However it was acknowledged that each site has its own unique problems and there was no situation in which the possible spread of the disease could be prevented without denying access to the public and this was not an economically viable option for Gardens or a practical option for other areas open to the Public.
In ‘historic’ gardens it was possible to engage the public’s interest with notices but this was not feasible in an extensive area such as a Countryside Park in which the use is principally recreational.
Although it is circumstantially evident that the disease can be transmitted by people on their clothes and footwear, the degree to which this occurs is not known and does not appear to be a prime cause. If the disease is moved by humans the same could be applied to mammals and the movement of these is not readily controlled. It was agreed that it was not effective or reasonable to introduce the use of disinfectant footbaths as a control measure except for cosmetic use to increase awareness. It would appear that water courses and drainage systems are an important agent of movement.
The destruction of infected plants is also an issue - as the movement of infected material, tools and staff through a garden is potentially more of a problem than the public. It is possibly best to burn at the immediate site where this is feasible.
It was acknowledged that the major host of the disease in its foliar phase was Rhododendron ponticum and that the foliar infection of other species (except perhaps Pieris) largely occurred as a result of the build up of pathogen pressure from the Rhododendron (indeed infection of other Rhododendrons was generally, largely a function of pathogen pressure rather than significant susceptibility). The foliar phase is the significant threat as the infection of trees on the trunk and causing death does not present a threat in terms of spread.
The crucial issue for owners of land is therefore the presence of the Rhododendron as a potential source of infection. The elimination of it will thus reduce the potential for spread. A very real problem for garden owners is the presence of Rhododendron on adjacent land, which is not in their ownership and where the elimination (unless infected) is not necessarily in that landowners interests (eg cover for game).
The destruction of Rhododendron presented further problems in relation to the vegetative regrowth of stumps which it was not possible to remove; as these were apparently easily re-infected. The use of Glyphosate for the destruction of regrowth was acknowledged as the only material currently approved but this would only be effective on young soft growth. It was important to cut back as low as possible for this activity.
There was comment on the presence of R. ponticum in unmanaged woodland and the threat it potentially created to managed woodland.
The biology of the viability and longevity of the various spores was also unclear in the spread and re-infection situation.
Financial assistance for the destruction/elimination of host plants
The compensation issue resolved into two segments:-
a) the cost of destruction of infected plants as a result of the imposition
of a Defra order.
b) the cost of the wholesale (large scale) elimination of potential host
plants (foliar phase) to reduce risk of infection.
The latter issue elicited comment on the basis that should infection
occur on a particular site and this then moves into another ownership,
why should the second owner be penalised? A further comment asked why
a landowner would undertake the very significant cost of destroying plants
philanthropically in order to curtail the spread?
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Page last modified:
6 Nov 2006
Page published: 25 Nov 2005