What is Phytophthora kernoviae?
Phytophthora kernoviae is a fungus-like pathogen that affects the aerial parts of the trees and shrubs that it infects.
How did it get its name and when was it found?
Phytophthora kernoviae is the formal name given to the pathogen. It was initially given the working title Phytophthora Taxon C, but the pathologist who discovered it, Professor Clive Brasier, Emeritus Mycologist at the Forestry Commission’s Forest Research agency, named it Phytophthora kernoviae after Kernow, the ancient name for Cornwall. It was also referred to as P. kernovii for a while.
It was first found in October 2003 when, during the course of surveys for Phytophthora ramorum, Forestry Commission scientists isolated and characterised a Phytophthora that was different from P. ramorum from a large bleeding canker on a mature beech from the south-west of England. At the same time scientists from the Central Science Laboratory (now called Fera, the Food & Environment Research Agency) isolated an identical new organism from established rhododendrons, also from south-west England. Both were confirmed as being the same organism, now formally named as P. kernoviae. Since then it has also been found mainly in south-west England sites, but occasionally in other locations in England, as well as at a site in Wales and a few others in Scotland. All samples submitted are now routinely analysed for P. ramorum and P. kernoviae.
What action have the FC and DEFRA taken?
Information on the action taken can be viewed here.
Is P. kernoviae established in the UK?
P. kernoviae is not established widely in the UK, but occurs mainly in Cornwall. It does not appear to affect as many plant species as P. ramorum, but there are indications that it is more virulent, because it can cause more-serious damage to rhododendron. It has also been found causing potentially lethal infections on two pedunculate ('English') oaks and more than 60 beech trees, as well as infecting other ornamental trees and shrubs. It has also proved to be highly damaging to Vaccinium myrtillus (bilberry), a native healthland species, and has now been found affecting bilberry at several locations in England's West Country. All this has increased our concern about the potential impact of this pathogen
What are its host plants?
So far the organism has been found most commonly on rhododendron (mainly Rhododendron ponticum) and bilberry, and also occasionally on infected beech trees that are in close proximity to infected rhododendron. Ornamental shrub and tree species such as Pieris, magnolia and Winters bark (Drimys winterii) growing in gardens have also been affected. Other much less common hosts include Chilean hazelnut (Gevuina avellana), tulip tree (Liriodendron tulipifera), and two individuals of pedunculate oak (Quercus robur). A few Holm oak (Q. ilex) have also been found with foliar infections. A regularly updated list of all known hosts of P. kernoviae can be found on the Fera website.
What research is being undertaken into P. kernoviae?
Research is one of the main priorities under the Defra and Forestry Commission Phytophthora Programme. Research has already helped us understand how the organism spreads, and the process of infection, so that disease-management strategies can be developed. Some of the known infected sites in south-west England are designated as experimental sites so that we can learn more about the impact and management of this pathogen in different environments.
If you do not understand the disease, should plants be destroyed?
It is precisely because we know very little about the organism that, as a precautionary measure to prvent or limit its spread, we are taking action to destroy infected plants in the same way that we have for P. ramorum. However, our evidence suggests that trees which become infected do not themselves become a source of infection, and might even recover from disease caused by P. kernoviae, and this is being investigated at the research site in south-west England.
Are we trying to trace it in other countries?
Information about P. kernoviae has been given to the EU Plant Health Committee, and all Member States received notification that there was a new Phytophthora affecting beech and rhododendron. We also supplied descriptions (morphological and molecular profiles) to enable scientists to identify it. Similar information has been made available to scientists world-wide. EU Member States now routinely look for P. kernoviae as part of obligatory surveys for P. ramorum, but so far outside the UK it has only been recorded in Ireland and New Zealand. We will continue to be on the look-out for this new Phytophthora species outside the locations where it has been found already.
What impact will it have?
It is too early to say what the long-term impact will be, but we know that P. kernoviae is capable of causing the same degree of damage to beech as we have previously found for P. ramorum. However, the impact that it could have will also depend on whether P. kernoviae is widely distributed, or is confined only to the locations found so far.
Last updated 5 August 2011
