Phytophthora kernoviae on ornamentals in the UK 1

The newly described Phytophthora kernoviae (previously known as P. taxon C) was first found in the UK in October 2003 and has been subject to emergency European Community phytosanitary legislation since 2004. Since the first finding, P. kernoviae has been found on a limited number of shrub hosts in the UK. The majority of observations have been on Rhododendron ponticum where both leaves and stems may be affected. Symptoms range from slight necrosis of leaf tips through to extensive leaf lesions, stem cankers, defoliation and apparent death of the bush. Diagnosis of P. kernoviae begins in the field with the use of generic lateral flow test kits and is completed in the laboratory using cultural and molecular techniques. To date, the organism has been detected at 29 UK sites, mainly in the South West of England. DNA profiling has shown that isolates are related with no distinct groups or clusters based on host, geographical distribution or place of origin.