Phytophthora ramorum in the channel islands
T. BROKENSHIRE (1), R. COLLIER (2)
(1) Head of Plant Protection, Commerce & Employment Department, Raymond Falla House, St Martins, Guernsey, GY1 6AF .
(2) Senior Scientific Adviser, States of Jersey Environment Department, Howard Davis Farm, Trinity, JE3 5JP
In 2002 Phytophthora ramorum was confirmed on Rhododendron and Viburnum in the UK. The authorities in Jersey and Guernsey immediately carried out nursery visits and inspections on all imported Rhododendron and Viburnum. The disease was first recorded on the same hosts during May in Guernsey and June in Jersey. In Guernsey the fungus was also confirmed on Pieris (December 02) and Camellia (July 03) - this was the first confirmed natural outbreak on Camellia in the UK.
The islands have followed UK and EU legislation to prevent entry and establishment of the pathogen in order to contain and eradicate outbreaks. Both authorities have undertaken extensive inspections of garden centres, parks and gardens to determine the extent of the problem.
Guernsey took additional action in January/February 2003 and destroyed all known hosts on each infested nursery irrespective of disease status. This was followed by a strict hygiene programme using approved disinfectants and with removal of infested gravel from the standing out areas. Viburnum tinus bait plants were placed out into three of the garden centres to check whether the hygiene programme had worked. These were left in situ for several weeks and assessed for disease development by incubation in conditions suitable for spore germination and development. None of the plants developed symptoms.
There has been a significant reduction in the number of interceptions and outbreaks probably due to plant passporting requirements for the main hosts and the effectiveness of the control strategy. There has also been a significant reaction by the garden centres in both Jersey and Guernsey who now limit importation to less susceptible plant material to reduce the economic risk to their businesses.
The Channel Islands have a favourable climate for the development and spread of P. ramorum but do not have the extensive plantings of R. ponticum, as Cornwall does, to provide the reservoir of inoculum for further spread to trees.
In conclusion the Channel Islands present a low risk for serious P. ramorum outbreaks on established plantings, however, the authorities of both Islands will continue to impose strict import controls and inspections to maintain this situation in order to protect the valuable environment.