In 2003 a new, fungus-like pathogen, now formally named Phytophthora kernoviae, was discovered on rhododendron plants and a beech tree (Fagus sylvatica) in the Redruth/Truro area of Cornwall, South West England. Since the initial outbreak was detected, the pathogen has been found in other woodlands in the locality and, in the spring of 2005, in the Penzance area of Cornwall. P. kernoviae was also found in a nursery in Cheshire, although this outbreak has since been eradicated, and it has been found at five locations in South Wales. The Welsh outbreaks have largely been contained at four of the sites, and in the fifth, a private garden, there was one infected plant, which was removed and destroyed. Two outbreaks of have been found in garden sites in Scotland since early 2008.
As for P. ramorum, the principal host of P. kernoviae is rhododendron, mainly R. ponticum, but vaccinium species could also be highly susceptible. P. kernoviae was confirmed on V. myrtillus (bilberry) on a heathland site in Cornwall in December 2007. However, unlike P. ramorum, P. kernoviae appears to be much more virulent at some specific locations in Cornwall, and rhododendron plants can be heavily diseased or killed by it.
The scale of the Truro/Redruth outbreak was of such concern to the Forestry Commission and Defra that a Statutory Instrument was brought into force in December 2004 to help us contain the disease, and a control area is scheduled in the Plant Health (Phytophthora kernovii¹ Management Zone) (England) Order 2004. The purpose of the Order was to supplement the powers available under general plant health legislation and enable inspectors to close footpaths for the purpose of carrying out eradicatory action. The Order also prohibits the removal of all host plants out of the Zone without permission.
In addition, in 2005 a Phytophthora Programme Management Co-ordinator based at the Forestry Commission's office in Silvan House, Edinburgh, as well as a Phytophthora Operations Manager, who oversees the clearance work in Cornwall and is based in Truro, were appointed. A Field Pathologist, also based at Truro, was appointed to liaise between Forest Research and the Operations Manager.
Our Frequently Asked Questions document provides more general and background information about P. kernoviae.
Action to date
Clearance of woodlands in Cornwall with infected Rhododendron ponticum started in August 2005 and is continuing, concentrating on high-risk sites based on a risk matrix. To date (April 2008) clearance of R. ponticum has been undertaken in conjunction with 21 landowners at 25 sites, with 89 hectares of (predominantly) woodland being either cleared or in the process of being cleared. Funding for this work, using the Woodland Improvement Grant Scheme as the payment vehicle, has been provided by the Forestry Commission and Defra's Plant Health Division.
In South Wales, 37ha of native broadleaved woodland in Clyne Country Park has been cleared of rhododendron by the owners, Swansea City Council. This work began in early December 2005 and is 75 per cent funded through the Forestry Commission Woodland Improvement Grant Scheme, which aims to remove non-native invasive weed growth from broadleaved woodland. These ancient, semi-natural woodlands are extensively used for recreation by local people and visitors, and have great amenity value, and therefore qualify for grant aid. There are still about 7-8ha of rhododendron-covered land, also under local authority ownership, to be cleared, and this will be carried out under the new Better Woodlands for Wales Grant Scheme in 2008.
From 2005 to 2007, Defra’s Plant Health & Seeds Inspectorate undertook surveys of woodlands in Cornwall where trees are in mixture with rhododendrons and/or vaccinium. The Forestry Commission complemented this work with surveys in Cornwall in 2005 and in Devon in 2006.
In early 2005, the Interdepartmental Phytophthora Programme Board requested that the high and low-risk sites surveyed in 2004 by the Forestry Commission should be re-surveyed over five years beginning in 2005, with 20 per cent of the woodlands surveyed annually to ascertain whether they remain free of symptoms of P. ramorum and P. kernoviae. This re-survey commenced in 2005 and was to be completed in 2009 (under review).
To view all FC survey reports.
In 2004, when the PHSI found infected rhododendrons in woodlands, the Forestry Commission began inspecting the trees in the woodlands to ascertain whether they, too, had become infected. Any trees suspected of being infected with P. kernoviae were reported to Forest Research for further analysis. This intensive tree survey to assess the incidence of P. ramorum and P. kernoviae in woodland trees in Cornwall took place from 2004 to 2007 on trees in 33 woodlands in Cornwall. Over the four-year period a total of 325 trees were found to have symptoms of the diseases.
Highlights:
To date two English or pedunculate oak (Quercus robur) and 62 beech (Fagus sylvatica) have been confirmed infected.
Other plants known to be susceptible to P. kernoviae are:
Chilean hazelnut (Gevina avellana)
Tulip tree (Liriodendron tulipifera)
Winters bark (Drimys winterii)
Magnolia spp.
Holm oak (Quercus ilex)
Pieris spp.
Michelia doltsopa
Cherry laurel (Prunus laurocerasus)
Ivy (Hedera helix)
Variegated holly (Ilex aquifolium)
In March 2006 Biosecurity New Zealand announced findings of P. kernoviae infecting custard apple (Annona cherimola)in an orchard, and also in a soil sample collected from the Trounson Kauri Park. To view details of these findings.
Images of both of these Phytophthora pathogenss are available in the picture library on the Forestry Commission website.
Who does what?
Defra’s Plant Health Division (PHD) has overall policy and legislative responsibility for P. kernoviae relating to plants and plant produce in England, and also co-ordinates UK plant health policy, liaising with direct stakeholders and interested parties at national level and co-ordinating action across Defra. The Plant Health & Seeds Inspectorate (PHSI) is responsible for enforcing all aspects of the policy: carrying out inspections, surveys, eradication campaigns and liaison with local Government and stakeholders.
The Food & Environment Research Agency (Fera) provides scientific and technical advice/support to PHD/PHSI, and carries out all diagnostic services.
The Forestry Commission’s Plant Health Service (PHS) has overall policy and legislative responsibility for all aspects of P. kernoviae relating to forest trees and wood.
Forest Research (part of the Forestry Commission) is responsible for research, scientific advice and diagnosis of P. kernoviae on trees. Its Technical Services Unit carries out woodland surveys.
The Scottish Government Rural & Environment Directorate's Agricultural Commodities Branch is responsible for policy and legislative matters for P. ramorum relating to non-forestry plants material in Scotland, including liaison with Scottish stakeholders.
The Scottish Government Rural Payments & Inspections Directorate (SG-RPID) is responsible for enforcing policy through inspections, surveys, eradication campaigns and liaison with Scottish local authorities.
Science & Advice for Scottish Agriculture (SASA) provides scientific and technical support to the Scottish Government, along with diagnostic services.
The Welsh Government’s Plant Health and Biotechnology Unit
has policy and legislative responsibility for plant health and P. kernoviae relating to non-forestry plant material in Wales. Under an agreement with Defra, all enforcement and inspection activities are carried out on its behalf by Defra’s PHSI.
Last updated May 2008
