Phytophthora kernoviae

In the course of surveys in 2003 for P. ramorum another species of Phytophthora, now named as Phytophthora kernoviae, was found in Cornwall causing similar damage to beech trees and rhododendrons. This pathogen is taxonomically a distant cousin of P. ramorum. It appears to behave in a similar fashion, sporulating on rhododendrons and causing lethal stem cankers on trees. However, there is some evidence that it may kill rhododendron more rapidly under UK conditions than P. ramorum.

As P. kernoviae is a recently described species our understanding and knowledge about its development, spread and survival is still relatively limited. Unlike P. ramorum it seems to have spread mostly by natural dispersal through woodland (spores may be carried locally by rain splash, wind-driven rain, irrigation or groundwater) rather than by movement on nursery stock. It has not been reported from any other country, although expert speculation is that it, too may have been introduced from the areas from which rhododendrons have been collected by plant hunters. Outside Cornwall, where around 40 beech trees and two oak trees have been found affected, the only findings have been on rhododendrons at a nursery in Cheshire (from which it has now been eradicated) and three parks on the outskirts of Swansea.

In December 2007 P. kernoviae was confirmed on bilberry (Vaccinium myrtillus) at a woodland site in Cornwall and in February 2008 in open heathland in Cornwall.

Since the first confirmations in 2003 there has been a coordinated approach to disease control within GB aimed at containment and eradication whilst evidence was gathered to make a decision on future policy. During that time the disease has continued to spread, albeit slowly and mainly in the southern and western parts of GB. Following a review of the historic and current situation, available scientific and economic evidence and public consultation on options for management of the pathogen in the future, Ministers concluded that more needs to be done to contain and eradicate P. kernoviae and another fungus-like pathogen, Phytophthora ramorum.

A new 5 year programme, which began on 1 April 2009, includes research and development, an awareness programme and disease control through funding clearance of host plants in high risk areas. This will involve an increased level of activity, aimed at reducing the level of inoculum to epidemiologically insignificant levels; by removal of infected sporulating hosts in woodlands and the wider environment and proactive clearance of uninfected areas to protect high risk sites; combined with enhanced containment and eradication measures in infected gardens and nursery sites, as well as the identification and control of any new outbreaks.