Phytophthora ramorum - Frequently Asked Questions
What is Phytophthora ramorum? Phytophthora ramorum is a microscopic fungus-like organism which is responsible for a disease known as Sudden Oak Death that has been killing certain tree species on the west coast of North America. It is also responsible for leaf and twig dieback in numerous other species.
When was the disease found in the UK?
The first outbreak was confirmed on a nursery in April 2002. An update of the number of outbreaks in England and Wales can be found on the Plant Health Website http://www.defra.gov.uk/planth/what.htm#sudd. The majority of outbreaks have been Rhododendron, and Viburnum and Camellia plants at nurseries or garden centres with a small number on established plants at historic gardens.
Why are Defra and the Forestry Commission so concerned about this disease?
In the USA the disease has become widespread in coastal California with the loss of thousands of trees of one particular species – Tanoak (Lithocarpus densiflorus). Some American Quercus species, e.g. coast live oak, are also suffering significant mortality. We do not yet fully understand the biology of this organism but it is already apparent that it could have a serious impact on one or more of our native tree species or other native plants, e.g. heathland species. The Government is currently funding research in order to establish which species might be susceptible in the environment and which plants in addition to Rhododendron could act as a source of infection. We believe that a precautionary approach is the correct one. On what plants has the pathogen been found in the UK? Phytophthora ramorum has mainly been found infecting leaves and shoots of Rhododendron, Viburnum and Camellia, but there have also been findings on other species including Pieris, Kalmia, Syringa (lilac), Leucothoe, Taxus (yew), Hamamelis viginiana (witch hazel), Hammamelis mollis (Chinese witch hazel), Laurus nobilis (bay laurel), and Drimys winterii (Winter’s bark); we have also detected the pathogen in rivers and streams near some outbreak sites. The first finding on a tree in the UK was an American southern red oak (Quercus falcata) in November 2003. In this instance, the pathogen had infected the trunk of the tree and was killing the bark with potentially lethal consequences to the tree. Since then, other tree species have been found with similar bark infections including several native beech (Fagus sylvatica), one horse chestnut (Aesculus hippocastanum), a Turkey oak (Quercus cerris) and two southern beech (Nothofagus obliqua). In addition, some other tree species have been found with the infection limited to just leaves and shoots. These include several European holm oaks (Quercus ilex), and sweet chestnut (Castanea sativa). An Exotic Pest Alert is available which has more detail. Is there legislation specifically for Phytophthora ramorum? Emergency measures against the introduction and spread of Phytophthora ramorum were introduced throughout the EU in November 2002, replacing the UK's emergency legislation put in place in May 2002. The EU reviewed these measures in December 2003 and agreed that they should continue and be strengthened in some respects. The Plant Health (Phytophthora ramorum) (England) Order 2004 came into force on 29 October 2004. The Plant Health (Phytophthora ramorum) (Forestry) (Great Britain) Order 2004 will come into force in December. What happens when a nursery is found with the disease? Notice would be served on the landowner requiring: Why destroy plants? Fungicides protect plants from infection but will not cure it. Further research is being done to find treatments but for now the only sure way of eradicating the disease is to destroy the plant which could be the source of further infection. What research are you doing? We have instigated a research and development programme to help us understand how the pathogen spreads and the risk that it poses to our native flora, especially trees and heathland plants such as Vaccinium species. Projects are being carried out at both the Central Science Laboratory and Forest Research. This in turn will help us put in place plans for the future containment and eradication of the disease. Hasn't the disease been present in the UK for a long time? The widespread death of trees in California and problems with dieback in established Rhododendron in Germany and the Netherlands were first recognised in the mid-1990s. The pathogen causing the dieback in Europe was only named in 2001 as a new species and it was only that same year that it was realised that the same organism was causing Sudden Oak Death in the USA. It is not possible to say when the disease first entered the UK or where it came from but experts believe it unlikely that the disease has been present for much more than 5–10 years. The initial introductions into Europe and the USA appear to be separate introductions of unknown origin. The current survey work being undertaken by Defra and the Forestry Commission is aimed at trying to establish whether the disease is present in the natural environment and if so how widespread it might be. It is clear that it is widespread in nursery and garden centre stock across the UK, but there are signs that the eradication campaign is having an impact. Some Growers have claimed the disease is endemic. From surveys so far, the pathogen does not appear to be endemic in the environment. The first survey of woodland areas carried out by the Forestry Commission of over 1300 sites did not find any signs of the disease. A second survey of over 100 woodland sites has been completed and the only evidence of the disease was found in water bait samples close to a known infected site . The number of outbreaks on established plantings and trees remains relatively small. However, in nurseries the pathogen continues to be found but the number of outbreaks is falling. Survey work is continuing and we will understand the position better once our additional survey work is completed. Infection must have come from abroad - why have you not taken steps to ban all imports? We do not know how the pathogen originally arrived in Europe or from where it came. Research and further surveys should give us a better understanding. Our inspectors have found a higher proportion of UK origin plants than continental origin plants to be infected. We believe that banning all imports of host plants would be a disproportionate response. How should the general public respond? There are a number of other diseases and disorders which cause very similar symptoms. The Plant Health website provides information and photographs about the symptoms. However if a member of the public is concerned that the plant may be infected with Phytophthora ramorum then report it immediately. Contact details for Defra and the Forestry Comission can be found on these pages. All enquiries are followed up. People depend on horticulture for their livelihood and this disease could have a major impact on them. How would you reassure them? We are very concerned about the impact that this disease might have on horticulture, biodiversity and on the landscape, where a major epidemic in our native trees could have a substantial effect on other parts of the local economy such as tourism. That is why we are taking this precautionary action in order to ensure that we are able to ascertain whether or not this recently identified pathogen is going to seriously infect any of our native flora. If we were to find that some species were going to die, as they have in the USA, then we would rightly be criticised if the Government had taken no action. Nevertheless, our aim to is to try and minimise the impact of our necessary actions in controlling this disease and our inspectors are working closely with nursery, garden centre and historic garden owners to this end. We welcome the extensive co-operation we have already had in helping us in tackling this disease.
Why give some areas of Cornwall "Disease Management Zone" status? Eradication action at two sites has already been taken in accordance with Government policy. However, clearing these sites of infection is difficult for a number of reasons but mainly the extent of infection and the topography of the area. We have therefore agreed plans with the owners of these sites for a staged approach to eradication and to ensure that biosecurity measures are taken during this time to prevent spread of the disease. Has the action taken to date had any effect? Although it is too soon to say with any certainty that our eradication action is working signs are encouraging with the number of outbreaks falling by 40% during the first six months of 2004 even though the number of inspections have increased by 60%.
|