Phytophthora kernoviae

An invasive pathogen causing bleeding cankers on beech tree trunks and necrosis on leaves of rhododendrons, pieris and magnolias in the UK.

Discovery of the disease

Whlie undertaking surveys in the southwest of England in November 2003, Phytophthora kernoviae sp. nov. was discovered concurrently by Forest Research and Central Science Laboratory scientists at different woodland sites. This organism, previously unknown to science, has now been described and officially named Phytophthora kernoviae, the name being derived from Kernow - the old name for Cornwall.

Details of the pathogen are given in:

PDF Phytophthora kernoviae sp. nov., an invasive pathogen ^(PDF-258K)

P. kernoviae was isolated initially from the trunk of a large beech tree (>1m diam.) with an aerial bleeding lesion (canker) [Photo 1]. It was also found infecting the leaves and shoots of Rhododendron ponticum at the same site [Photo 2].

Photo 1
First beech tree discovered with P. kernoviae bleeding canker,
Cornwall, UK, 13 Nov 2003

Photo 2
First Rhododendron ponticum leaf positive for P. kernoviae,
Cornwall, UK, 13 Nov 2003

It is now known that P. kernoviae is highly aggressive pathogen which attacks leaves, buds and shoots of understorey woodland rhododendrons and kills the inner bark of beech trees. Two native oak trees (Quercus robur) have also been found with the bark killing bleeding cankers caused by P. kernoviae. In addition a number of popular garden ornamentals such as Magnolia and Pieris species are also affected with a leaf and shoot blight. A full list of hosts found affected in the UK is given below.

Plants found naturally infected with *Phytophthora kernoviae* in outdoor environments in Britain
Common name	Latin name	Family	Symptom expression	Number of affected plants
European beech	Fagus sylvatica	Fagaceae	Bleeding canker	Between 50-100
English oak	Quercus robur	Fagaceae	Bleeding canker	Five or less
Holm oak	Quercus ilex	Fagaceae	Leaf necrosis	Five or less
Tulip tree	Liriodendron tulipifera	Magnoliaceae	Bleeding canker and leaf necrosis	Single plant
Rhododendron	Rhododendron spp.	Ericaceae	Leaf necrosis and stem dieback	More than 1,000
Pieris	Pieris spp.	Ericaceae	Leaf necrosis and stem dieback	More than 100
Bilberry	Vaccinium myrtillus	Ericace	Leaf necrosis	Between 5-10
Magnolia	Magnolia spp.	Magnoliaceae	Leaf spots, bud blast, blossom blight	Between 10-50
Michelia	Michelia doltsopa	Magnoliaceae	Leaf necrosis	Five or less
Drimys	Drimys winterii	Winteraceae	Leaf necrosis	Between 10-50
Chilean hazelnut	Gevuina avellana	Proteaceae	Leaf necrosis	Single plant
Cherry laurel	Prunus laurocerasus	Rosaceae	Leaf necrosis and stem dieback	Five or less
Ivy	Hedera helix	Ariliaceae	Stem necrosis	Single plant
Holly	Ilex aquifolium ‘Variegata’	Aquifoliaceae	Leaf necrosis	Single plant
Podocarpus	Podocarpus salignus	Podocarpaceae	Leaf necrosis and shoot tip dieback	Single plant

Further information about Phytophthora kernoviae

Contact

For further information contact:

Dr Joan Webber
Forest Research
Alice Holt Lodge
Farnham
Surrey GU10 4LH
Tel: +44 (0) 1420 22255
Fax: +44 (0) 1420 23653
Email: joan.webber@forestry.gsi.gov.uk

or:

Dr Sandra Denman
Forest Research
Alice Holt Lodge
Farnham
Surrey GU10 4LH
Tel: +44 (0) 1420 22255
Fax: +44 (0) 1420 23653
Email: sandra.denman@forestry.gsi.gov.uk

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