I agree that it looks near impossible to limit the airborne spread of Pr in the areas of the UK that are climatically suitable for Pr to thrive (Zone 1 & 2 areas as defined by the FC/FERA etc), BUT there is still a possibility that drier areas can be kept clear of the disease if bio-security measures are adhered to.
This is the current 2013 map:
http://www.forestry.gov.uk/pdf/Pramorum_risk_zones_Oct11.pdf/$FILE/Pramorum_risk_zones_Oct11.pdf
FC Scotland anticipate that 'hot spot' infection will occur in Zone 3 (low risk areas) and this hot spot infection will be due to either airborne spores (moving from distance) OR spores remaining on soil/water being moved by infected round timber/mud.
Yes OnFootForestry is correct that sporolation is via foliage, but where do these spore land? Water-mobile zoospores rain down on stems of infected larch. They then have the potential to survive for at least 3yrs (especially the chlamydospores).
The chance of infection (into a host that can then sporolate Rhodi, larch wounds, foliage) via soil/water contact from larch bark is much, much lower when compared to several hectares of 25m tall larch trees transmitting masses of spores into a damp valley but it is still real risk, hence restrictions on the movement of unprocessed infected logs is controlled.
"yes son, just drop the firewood (larch) down by that rhododendron" - and potentially you have a new infection? Is this not the case???
TimberCutterDartmoor - could you confirm whether movement restrictions have been lifted in England?
If not what are you doing offering infected larch for sale as firewood? Where could this firewood end up? Could it contribute to 'hotspot' infections. I am genuinely interested, would you sell into say Nottingham?
check the link out:
P. ramorum - national update
Phytophthora ramorum in larch trees - Update (July 2012)
Timber movement authorisation system
It is important that we prevent the pathogen being transmitted through the movement of roundwood (logs) from infected stands. We are therefore requiring a number of biosecurity measures to be taken, such as sweeping off vehicles and machinery between movements, and destroying or treating bark, which can harbour infective spores. This means that timber hauliers and timber processing companies must be authorised to handle material from infected stands.
In order to gain movement or processing approval the operator must demonstrate to a Forestry Commission plant health inspector’s satisfaction that they have put in place, and are carrying out, the measures required. Approved hauliers and processing plants will be inspected from time to time to ensure that the measures are working. We will withdraw approval from operators found failing to comply with the terms of their approvals.
Full details and application forms for approvals are available for downloading from the Forestry Commission - Pests and diseases - Phytophthora ramorum area of the Commission’s website.
As for harvesting companies and the FC moving timber under the biosecurity controls - yes it is a real challenge - i speak to a number of those involved in the SW of Scotland where 4 years worth of annual cut has hit the market in less than a year. There is pressure to abandon the movement restrictions to free up processing capacity.
From your location in the SW England and anywhere in Zone 1 or 2 controlling infected larch movements this might appear like pissing in the wind, but from my location, a Zone 3 area, it is a element of control that could allow larch to be grown.
Happy to discuss further.....