The disease known as Sudden Oak Death in the western USA and as Ramorum Dieback in northern Europe was identified in the early 1990s. It arrived recently in these areas from an unknown country of origin. In Europe it was first recorded in Germany and the Netherlands. It has since been found in Belgium, Finland, Denmark, France, Ireland, Italy, Norway, Poland, Spain, Switzerland, and Sweden.

The disease produces different symptoms in a range of unrelated species, including viburnums and rhododendrons in Europe and native Californian oaks in California and Oregon, USA, where the disease has become widespread, and thousands of Tanoak trees (Lithocarpus densiflorus) have been killed.

It was discovered in the UK in imported Viburnum shrubs in 2002. It has since been identified at 625 sites in England and Wales as well as some sites in Scotland, Northern Ireland and the Channel Islands. Viburnums, rhododendrons and camellia are most commonly infected. Also Syringa and Kalmia.

The first case of infection of an established tree outside of the USA was confirmed in November 2003 on a mature southern red oak (Quercus falcata). Other species since infected include European Holm oak (Quercus ilex), Turkey oak (Q.cerris), native Beech (Fagus sylvatica), Southern beech (Nothafagus oblique), Horse Chestnut (Aesculus hippocastanum), Sweet Chestnut (Castanea sativa) and Winter�s Bark (Drimys winterii). All these findings are associated with nearby diseased rhododendron - the main source of P. ramorum leading to tree infection.

The name Ramorum Dieback is preferred in the UK, as so far our native oaks (Q. robur and Q. petraea) seem relatively resistant.

In 2003, a new, potentially more virulent form, Phytophthora kernoviae, was identified in Cornwall. It was also found (but contained) at 5 sites in South Wales. Concern was such that areas of Cornwall are now designated as a 'Disease Management Zone' under Statutory Instrument.

Emergency measures to prevent the introduction and spread of P. ramorum were introduced by the UK Government, and then by the EU, in 2002 - and strengthened in 2003. They include the restriction of exports from the USA of susceptible species, 'plant passports' for Viburnum, Rhododendron & Camellia plants, and compulsory eradication and containment measures where the pathogen is found to exist.

The establishment of the 'Disease Management Zone' in Cornwall, under the Plant Health (Phytophthora kernovii Management Zone) (England) Order 2004, allowed the compulsory clearance of infected woodlands, the temporary closure of footpaths, the confiscation and destruction of suspect plant material and prohibition of host plant movement out of the zones. Woodlands have also been cleared in areas of South Wales.

Both P. ramorum and the new species P. 'kernoviae' are notifiable pathogens and the Forestry Commission should be informed if symptoms are detected on these hosts. If you suspect the disease you must check the symptoms with the photographs in the Defra leaflet above. If still suspicious, you are required by law to notify the relevant authority:

Symptoms in shrubs: ring the Plant Health & Seeds Inspectorate on 01904 455174 (HQ in York).

Symptoms in trees: ring the Forestry Commission Plant Health Service on 0131 314 6414.

Defra records indicate that both the total number of outbreaks, and the number of confirmed infection on nurseries, fell each year from 2003 to 2005, despite the number of inspections carried out having significantly increased.

Further Information and References:

Forest Research - The research agency of the Forestry Commission: Detailed latest information, diagnostic photo gallery and advice on disease management. Overall policy and legislative responsibility for all aspects of P. ramorum relating to forest trees and wood.

Defra - Department for Farming and Rural Affairs: overall policy and legislative responsibility for P. ramorum relating to plants and plant produce in GB.

Additional information was taken from the Royal Horticultural Society.