P. austrocedrae is a species of Phytophthora that was only recently ‘described’ (in 2007), although it is thought to have been present in Argentina and Chile for at least 50 years. It is a fungus-like plant pathogen which causes an often fatal disease of its host plant. The name ‘austrocedrae’ originates from Austrocedrus, the genus of conifer trees first recorded as a host (i.e. a plant capable of being infected) of this pathogen in Argentina. The recent discoveries of the pathogen are a concern because of the often fatal nature of infection of the host plant, and because the recent findings of P. austrocedrae in the UK are the first confirmed findings of this pathogen in the UK.
The first case of P. austrocedrae to be confirmed in Great Britain occurred in juniper bushes at the Upper Teesdale National Nature Reserve (NNR) in the North Pennines in England in 2011, and in single specimens of Lawson cypress and Nootka cypress trees at garden sites in Scotland. The full list of confirmed cases is now:
Cumbria - 6 sites (5 natural environment, 1 nursery)
County Durham - 1 site (natural environment)
Devon - 1 site (private garden)
Glen Artney, Perth & Kinross - 1 site (natural environment)
Highland - 3 (natural environment)
Western Scotland - 2 (private gardens)
The pathogen has also previously been linked by the Royal Horticultural Society’s Advisory Service at Wisley with symptomatic juniper plants found at a garden in Wales and at other sites during nursery surveys.
Above-ground symptoms on infected trees include dieback of the foliage, stem and collar lesions. The root/collar infection is described as ‘tongue-like’; this can be observed by removal of the outer bark, whereupon the phloem is necrotic, often cinnamon brown, with a distinct margin between diseased and healthy tissue. When roots and collars/stem bases are affected, foliage of infected trees initially appears a slightly lighter colour than that of healthy trees. Later the foliage withers, turns bronze, and finally, light brown, concurrent with drying and darkening of the inner bark.
Disease symptoms caused by P. austrocedrae can be confused with other infections, including those caused by other Phytophthora species, such as P. cinnamomi, a pathogen which is already present on a range of host plants in the UK and around the world. Physical damage caused by heavy snow or drought might result in similar browning of the foliage, but there would be no associated lesions.
Natural England staff on the Moor House-Upper Teesdale reserve are working with the Food & Environment Research Agency (Fera) to survey the area to establish the full extent of infection and implement biosecurity measures for anyone working on site. Removal of all infected plants in certain areas might be tried. However, removal of plants might be of limited value and have the added risk that soil disturbance might promote further spread of the pathogen. This aspect will be monitored. A survey of other areas where juniper is widely distributed is being carried out to determine whether the pathogen is present elsewhere. This will help to determine a longer-term strategy. The devolved administrations in Scotland and Wales have been alerted so that they can consider equivalent surveys.
Plans will also be developed through discussion with landowners, farmers and other stakeholders in the areas affected. A stakeholder meeting will be organised as soon as the three organisations have more information to share and action proposals to discuss. A consultation will be carried out on the basis of a risk assessment that is being undertaken.
This is a significant finding, the first of its type in Europe, and Fera, Natural England, the Forestry Commission and its Forest Research agency are working closely together to tackle the situation in Upper Teesdale and establish the position elsewhere.
Forestry Commission Scotland is taking the lead on juniper health in Scotland, in collaboration with the Scottish Government Plant Health team. An outbreak management team (OMT) has been formed comprising represntatives of the Commission, the Scottish Govenment, Scottish Natural Heritage, Plantlife Scotland, Drummond Estates and the tenant farmer. At its first meeting on 24 May 2012, the OMT agreed that precautionary, containment action (mainly through biosecurity implementation, was reqiuired at Glen Artney pending the outcome of surveys of adjacent juniper sites and, over the coming months, surveys of juniper sites further afield in Scotland.
Pest risk assessment and consultation
A Rapid Assessment of the need for a full Pest Risk Analysis (PRA) on P. austrocedrae has been published, and a formal consultation on its management closed on 21 September 2012. To read the assessment, visit the plant pests and diseases consultation pages of the Fera website.
Imports of Juniperus and Chamaecyparis species from ‘third’ countries (non-EU countries) are banned under EU phytosanitary (plant health) legislation. Other host species are not prohibited, but must be accompanied by a phytosanitary certificate to ensure they are free from harmful organisms.
The Forestry Commission Plant Health Service:
Sightings north of the Humber/Mersey line:
Tree Health Diagnostic & Advisory Service, Forest Research, Northern Research Station, Roslin, Midlothian EH25 9SY;
Tel: 0131 445 2176
Fax: 0131 445 5124
Sightings south of the Humber/Mersey line:
Tree Health Diagnostic & Advisory Service, Forest Research, Alice Holt Lodge, Wrecclesham, Farnham, Surrey GU10 4LH;
Tel: 01420 23000
Fax: 01420 23653
1. What plant species are at risk?
The natural host of P. austrocedrae in South America is the Chilean cedar (Austrocedrus chilensis). In the UK, Lawson cypress (Chamaecyparis lawsoniana), Nootka cypress (Chamaecyparis nootkatensis) and the common juniper (Juniperus communis) have now been confirmed as hosts.
2. What countries is it present in?
The current reported distribution of P. austrocedrae is limited to Argentina, Chile and the recent findings in the UK.
3. How did it get to the UK?
At present it is not known how the pathogen entered the UK. The pathogen has the potential to be moved in soil from infected sites to other at-risk areas, and on plants for planting of known natural hosts (i.e. Chilean cedar) from countries where P. austrocedrae is known to occur. However, it has not been reported from countries other than Argentina and Chile.
4. Where has it been found in the UK?
See "Distribution" above.
5. How were the findings in England and Scotland detected?
Forest Research had been researching for some time the dieback in juniper trees in Natural England’s Upper Teesdale NNR and at the Glen Artney SSSI. These studies recently revealed the presence of P. austrocedrae, which causes dieback and eventual plant death.
6. What caused it?
The source of infection is unknown and only limited information is available about the disease. Additionally, this particular phytophthora species is difficult to identify. However, scientists believe it is spread by water, infected plant material and contaminated soil, making it also very difficult to control.
7. What are the implications?
The impact of the pathogen is currently limited in the UK as a whole. However, it is potentially serious for the Upper Teesdale juniper, because these are rare plants and this site has the second largest population of the species in the UK. There are only about 400 hectares (1000 acres) of juniper woodland in Great Britain, most of it in Scotland. At Upper Teesdale it is protected as part of a Special Area of Conservation (SAC). Common juniper is already recognised as important and vulnerable, because over the past 25 years its extent and condition have declined considerably, especially on upland sites, where its importance is tied in with nature conservation and game management. Juniper is also a key food plant for a wide range of invertebrates and birds, and it has a unique and specialised group of associated insects, fungi and lichens. Its decline has already been attributed to overgrazing, burning, afforestation and other land use changes. The establishment of P. austrocedrae in the UK could further contribute to the decline of this ecologically important species.
14. What is the situation elsewhere in the EU?
At present P. austrocedrae has not been recorded elsewhere in the EU.
15. What is the European Union doing about it?
There are no immediate plans for the EU to regulate P. austrocedrae. There are many harmful organisms awaiting review, and P. austrocedrae has not been considered as a priority to date. Any consideration of EU regulation would need to take into account the current distribution of the organism and its potential for establishment and to cause economic damage. The hosts which have been found to be infected with P. austrocedrae in the UK -juniper and Chamaecyparis species - are already prohibited from third countries, but there are no specific requirements in relation to other potential hosts. In the absence of EU requirements, Member States can decide on their own action.
16. Is the action the same, wherever it is found?
Decisions are taken on a case-by-case basis according to the specific circumstances of the findings. Eradication is the objective where feasible, but in the case of Upper Teesdale this will not be practicable, so containment is likely to be the goal. The position will be re-assessed in light of further work, in this area and elsewhere.
17. Can pesticides be used to remove infection instead of destroying trees?
Treating the aerial parts of plants with pesticides is unlikely to be effective because of the nature of infection.
18. Is compensation available if plants are destroyed?
The long-standing policy of successive Governments is that compensation is not paid when plants have had to be destroyed to eradicate or contain outbreaks of plant disease. It is felt that the limited resources of the Plant Health Services are better employed in the detection and identification of outbreaks, and research into the risks and risk-management measures.