Phytophthora kernoviae

 

In 2003 a new fungus-like pathogen, now formally named Phytophthora kernoviae, (after the old name for Cornwall, ‘Kernow’), was discovered on rhododendron plants and a beech tree (Fagus sylvatica) in the Redruth/Truro area of Cornwall. Since the initial outbreak was detected, the pathogen has been found in other woodlands within the locality, and in the spring of 2005, the disease was also found in the Penzance area of Cornwall. P. kernoviae has also been found in a nursery in Cheshire, although this outbreak has now been eradicated. In South Wales, there are five locations where P. kernoviae has been found. At four of these locations the outbreaks have largely been contained, and in the fifth, a private garden, there was one infected plant which was removed and destroyed. Since early 2008, two outbreaks of P. kernoviae have been found in Scotland in garden sites. 

Like P. ramorum, the principal host of P. kernoviae is rhododendron, mainly
R. ponticum, but vaccinium could also be highly susceptible and  P. kernoviae has been confirmed on V. myrtillus on a heathland site in Cornwall (December 2007. However unlike P. ramorum, this new pathogen appears to be much more virulent at some specific locations in Cornwall and rhododendron plants can be heavily diseased or killed by P. kernoviae. The scale of the Truro/Redruth outbreak was of such significant concern to the Forestry Commission and Defra that in December 2004, a Statutory Instrument was brought in to force 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.

Prior to formal naming, Phytophthora kernoviae was referred to both as P. kernoivii and P. Taxon C

In addition, in 2005 a Phytophthora Programme Management Co-ordinator based at Silvan House, Edinburgh as well as a Phytophthora Operations Manager, who oversees the clearance work in Cornwall and based in Truro, were appointed. A Field Pathologist, also based at Truro, was appointed to liaise between Forest Research and the Operations Manager.

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 Ha 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 Plant Health Division

In South Wales, 37ha. of native broadleaved woodland containing rhododendron has been cleared in Clyne Country Park, by the owners, Swansea City Council. This work  commenced in early December 2005 and is 75% 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 both locals and visitors alike,  are of great amenity value and therefore qualify for grant aid. There are still c7-8ha 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 have undertaken 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 a five year period, commencing in 2005, with 20% of the woodlands surveyed annually to ascertain whether these woods remain free of symptoms of both P. ramorum and P. kernoviae.  This re-survey commenced in 2005 and will be completed in 2009 (under review)

To view all FC survey reports.

In 2004 when PHSI found infected rhododendrons in woodlands, the Forestry Commission have inspected the trees to ascertain if 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 Phytophthora ramorum and Phytophthora kernoviae in woodland trees in Cornwall has taken place since 2004 until 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 oak (Quercus robur) and 62 beech (Fagus sylvatica) have been confirmed infected.
 
Other plants known as being 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 in an orchard infecting custard apple (Annona cherimola), and also from a soil sample collected from the Trounson Kauri Park. To view details of these findings.

Images of both the Phytophthoras are available 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; liaison with direct stakeholders and interested parties at national level and for co-ordination of action across Defra. The Plant Health and 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 Central Science Laboratory (CSL) 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 (an agency of the Forestry Commission) is responsible for research, scientific advice and diagnosis of P. kernoviae on trees. Its Technical Support Unit carries out woodland surveys.

The Scottish Government Rural Directorate - 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.

SASA (Science and Advice for Scottish Agriculture) provides scientific and technical support to the Scottish Government, along with diagnostic services.

The Welsh Assembly 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)