on wood will be imposed by the government to protect native trees and
shrubs from a potential new disease.
known as 'sudden oak death', is killing native oak trees and other
plants in California and Oregon. Once diseased, plants can die within
a few months.
It is not known whether or to what extent the disease might affect
trees and plants here, and Phytophthora ramorum is not established in
However, plant health and seeds inspectors here have found evidence
of the disease in viburnum plants at a small number of nurseries. The
organism's identity was determined at the Central Science Laboratory
and confirmed by Forestry Commission experts.
The affected plants were destroyed and possible sources of infection
are being investigated to determine whether there has been any spread
and whether there are any links to imported plants.
In order to reduce further risk of the disease spreading to and
within the UK, Ministers are announcing a number of new measures:
- A ban on the import of rhododendron, viburnum, vaccinium and oak
planting material from areas of the USA where the disease is known to
- An extension of current controls on imported oak wood to include
wood derived from all host trees originating in the affected areas of
- A requirement to notify DEFRA of commercial deliveries of host
plants, of any origin, into and within England and Wales
Imports of oak wood from North America are already subject to
measures such as removal of bark to reduce other risks.
The government has urged the European Commission to require Member
States to carry out surveys of potential host material this summer
and to report their findings later this year. The commission has now
agreed to draft measures for consideration at the next meeting of its
plant health committee.
The fungus has been found infecting rhododendrons and viburnums in
the Netherlands and Germany. However, preliminary Forestry Commission
research suggests that European species of oak may be more resistant
to the fungus than North American species. DEFRA and the Forestry
Commission are undertaking further research.
Sudden oak death is a notifiable disease.
Anyone who suspects the presence of this disease on their premises
should contact DEFRA Plant Health and Seeds Inspectorate (for
rhododendrons and viburnums) on 01904 455174 or the Forestry
Commission Plant Health Service (for trees) on 0131 314 6414.
The legislation in respect of plants would be implemented in England
and Wales by DEFRA. The legislation in respect of oaks and timber
would be implemented in Great Britain by an order of the Forestry
Commissioners, with the agreement of the forestry ministers in
Scotland and Wales.
The Forestry Commission has published an Exotic Pest Alert on this
disease and a copy can be viewed at www.forestry.gov.uk/planthealth.
DEFRA are preparing a poster and information note, copies are
available from Plant Health Division, with details on the website
Since July 2001, DEFRA Plant Health and Seeds Inspectors have carried
out 659 inspections of host plants on 320 premises in England and
Wales, taking 35 samples of suspect material for laboratory
diagnosis. Surveys have also been carried out in Scotland and
Northern Ireland. Forestry Commission experts have monitored a
number of sites in Great Britain with known problems of oak dieback,
and have circulated information and advice to arboriculturists, tree
officers and foresters.
Forestry Commission scientists realised there could be a connection
between the tree disease outbreaks in California and a new species of
fungus, since named Phytophthora ramorum, affecting rhododendrons and
vibernums on continental Europe. It has since been confirmed that the
same fungus is involved.
The identity of the organism at a small number of nurseries here was
determined at DEFRA's Central Science Laboratory and confirmed by the
Forestry Commission's Alice Holt Research Station.
Preliminary Forestry Commission research suggests that, although
European species of oak may be more resistant to the disease than
North American species, other broadleaves such as European beech may
be vulnerable. Further tests are planned. The pathogen in Europe is a
different sexual mating type to the one present in the USA. If
isolates of Phytophthora ramorum from the USA were to establish in
Europe then the genetic variability of the pathogen may increase
through sexual recombination.