HUNT CONTINUES FOR TREE DISEASES (29/06/06)

The Forestry Commission is carrying out three more surveys to determine the current status of two potentially lethal fungal diseases of trees and shrubs that have been found in England and Wales.

These are Phytophthora ramorum, which is the causal agent of a condition known as Sudden Oak Death in the USA, and Phytophthora kernoviae.

P. ramorum first raised alarm bells in the United States, where it has killed significant numbers of trees. A different but related strain has also been found in parts of Europe, including Great Britain, where it has been found in some nurseries and gardens. So far it has been found mostly in non-native shrubs such as viburnum and rhododendron, some beech trees and one non-native oak tree, but the responsible government departments are keeping a close eye on it.

At present P. kernoviae does not appear to affect as many plant species as P. ramorum, but there are indications that it is more virulent, because it appears to be causing more serious damage to its main host, Rhododendron ponticum. Among tree species it is known to have infected are two native English oaks and about 40 beech trees. To date it has been found in 22 locations in Cornwall, five in South Wales, one in a Cheshire nursery, and most recently on a single rhododendron in North West England.

In 2005 the Interdepartmental Phytophthora Programme Board agreed that the high- and low-risk woodlands in England and Wales which are growing in admixture with Rhododendron ponticum, and which had been surveyed by the Forestry Commission in 2004, should be re-surveyed over five years to determine whether they are still disease-free.

The first of these surveys, the National Re-survey of England and Wales, took place during July and August 2005, with no positive findings in the 149 woodlands inspected. This year's survey began in late June and will continue until late August.

The main outbreak of P. ramorum and P. kernoviae has been in Cornwall. Defra's Plant Health & Seeds Inspectorate (PHSI) put in place an extensive programme of new surveys of previously unsurveyed woods, which were supplemented by a further survey by the Forestry Commission of 14 previously unsurveyed woods. These surveys by PHSI and the Forestry Commission resulted in the identification of some further outbreaks.

This combined operation not only extended the woodland area surveyed, but also helped both organisations to determine whether either pathogen is more widespread in Cornwall than was originally envisaged.

An outbreak of P ramorum has been found in Devon near the Cornish border. The Commission is about to survey previously unsurveyed Devon woods, again those in admixture with rhododendrons, to help determine whether P. ramorum is more extensive than the one outbreak so far discovered, and whether P kernoviae is also present in the county.

A third check will be undertaken by the Commission as it carries out a separate Forest Condition survey across Great Britain. As well as checking on the general condition of the woodlands, surveyors will also be looking for symptoms of P. ramorum and P. kernoviae.

Reports on these surveys should be available on the Commission's Plant Health Service website, www.forestry.gov.uk/planthealth, by the end of the year. Anyone who suspects the presence of either disease on plants or shrubs should contact the local offices of Defra in England, the Welsh Assembly Government in Wales or SEERAD in Scotland. If the disease is suspected on trees, they should contact the Forestry Commission's Plant Health Service in Edinburgh on 0131 314 6414. Further information is available from the Plant Health Service website (as above) or the Defra website, www.defra.gov.uk, or by contacting the Commission's Plant Health Service on plant.health@forestry.gsi.gov.uk or telephone 0131 314 6414.