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OAK DISEASE ALERT- GOVERNMENT ACTS TO PROTECT BRITAIN'S TREES

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A ban on imports of plants from parts of the USA and added controls ...
A ban on imports of plants from parts of the USA and added controls

on wood will be imposed by the government to protect native trees and

shrubs from a potential new disease.

Phytophthora ramorum, a fungus which causes a rapid wilting 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

this country.

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

occur

- An extension of current controls on imported oak wood to include

wood derived from all host trees originating in the affected areas of

the USA

- 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.

Notes

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

www.defra.gov.uk/planth

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.

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