Phytophthoras are soil or water-borne fungus like pathogens which can cause widespread death in a variety of trees and shrubs. Evidence from California and Chile have shown Phytophthora can have a devastating effect on the environment and landscape. The evidence is that two non native species of Phytophthora (ramorum and kernoviae) and one native species (pseudosyringue) are spreading rapidly through the South West and parts of Staffordshire causing death to tree and shrub vegetation.
The discovery of Phytophthora kernoviae on bilberry (Vaccinium myrtyllus) and Phytophthora ramorum on various species of tree have raised particular concern for the potential risk to our native biodiversity interest and ultimately the condition of heathland and woodland landscapes. In the UK two species, P. ramorum and P. kernoviae, are the subject of containment and eradication action by the UK Government.
P. ramorum was first found in the UK on viburnum in a nursery in Sussex in February 2002, and on American southern red oak (Q. falcata) in November 2003. Other trees which have since been affected include Japanese larch, horse chestnut, sweet chestnut, several oak species, silver birch, sycamore and southern beech.
More recently, P. kernoviae has been found in the UK on bilberry (Vaccinium myrtillus), and appears to behave in a very similar way to P. ramorum. The spores of both species can survive in plant debris and soil for many years, and contaminated soil, water, equipment and footwear may harbour the pathogen.
In the UK, the majority of nursery hosts are species of rhododendron, viburnum and camellia. Laboratory experiments have shown that native wild plant species are also vulnerable, including heather (Calluna vugaris), bilberry (V. myrtillus), cowberry (V. vitis-idaea), bearberry (Arctostaphylos uva-ursi) and crowberry (Empetrum nigrum).
The disease causes bleeding bark cankers which may girdle and kill trees. Other symptoms, which occur on a range of shrub hosts and also some trees, include leaf blight, wilting, discolouration of foliage and dieback.
Currently there are no known mechanisms for controlling Phytophthora. Once the plant is infected with the disease, death happens quickly. No chemicals appear to kill the disease, most simply suppress it. Control of the disease is normally by destructive measures, i.e. by removing all infected plants. Whilst there could be positive impacts for biodiversity if Rhododendron is removed from wild sites, removal of native infected species could be devastating.
An interdepartmental Programme Board, with representatives from Defra, the Forestry Commission and the Devolved Administrations oversee a programme aimed at containing and eradicating this disease. Natural England has a seat on the Board.
If you suspect the presence of this disease on your premises, you should immediately contact your local Fera Plant Health and Seeds Inspector or Tel: 01904 465625, Email: firstname.lastname@example.org, Web: Contact PHSI
If you suspect the presence of the disease on trees you should contact the Forestry Commission Plant Health Service, Edinburgh: Tel: 0131 314 6414, Web: Plant Health Service contacts
Information about the disease, including images which will help identify it, is available on the FERA and Forestry Commission web sites.
Food and Environment Research Agency