Very early symptom showing a brown lesion developing around the
leaf node
What is it and where is it found?
Phytophthorais a devastating fungus-like organism that causes damage to a wide
range of trees and plants. Recently two species of Phytophthora– Phytophthora
ramorumand Phytophthora kernoviae – have been causing damage to our
environment.
Why the concern?
Initial findings of the disease were predominantly confined to ornamental plants in
nurseries. Since then, findings in the wider environment have continued to spread
across the UK after initially being concentrated in the South West. With a large and
varied host range, if left unchecked they may change our landscape with the loss of
many trees, shrubs and heathland plants. PLANT DISEASE FACTSHEET
Phytophthora ramorum and
Phytophthora kernoviae
diseases on bilberry
(Vaccinium myrtillus)
A threat to our woodlands,
heathlands and historic gardens
Very early symptom showing a brown lesion
developing around the leaf nodeVery early symptom development showing a dark
brown/black, lesion. Lesions can develop at any
point along the stem, not just at leaf nodes or
buds
Where is it found?
P. ramorumwas first identified in 1995 causing the death of oak and tanoak trees in the coastal
counties of California in the USA. It was first detected in the UK in 2002 in the nursery trade and has
since spread to the wider environment including historic gardens, parks, woodlands and heathlands.
The first finding of P. ramorumon the heathland plant Vaccinium myrtillus(bilberry/blaeberry) in the
wild was confirmed in January 2009. More recently, in August 2009, the pathogen was identified on
Japanese larch trees at sites in South West England.
P. kernoviaewas first discovered in 2003 causing severe damage to rhododendron and beech trees in
Cornwall. The disease has been found in woodlands, gardens and a small number of nurseries with
outbreaks mainly confined to the South West. In December 2007 P. kernoviaewas confirmed on
bilberry at a woodland site in Cornwall and in February 2008 in open heathland.
Current situation
There are currently 22 discrete outbreaks of P. ramorumor P. kernoviaeon bilberry in England and
Wales (as of 30/04/2012). Of these, there are 10 outbreaks of P. ramorumon bilberry nationally
compared to 13 outbreaks of P. kernoviae(one site affected by both pathogens). P. ramorumis
occurring predominantly on bilberry in woodland whereas P. kernoviaeis more prevalent on bilberry in
open heathland. Approximately 70% of the outbreaks on bilberry are in Cornwall, the majority of which
are outbreaks of P. kernoviaein open heathland. Although the number of sites affected nationally is
small, there is an upward trend since the first findings in 2007/08.
Disease spread has been shown to be predominantly via localised splash dispersal but also in wind-
driven rain, via run off or on footwear and vehicles. Evidence for long distance dispersal in the
absence of rain is limited. Inoculum can also survive in soil, litter and in watercourses.
Bilberry is highly susceptible to P. ramorumand P. kernoviaeand symptoms can develop within 2 days
of infection under warm conditions. In tests on susceptibility of a range of hosts to P. ramorumand
P. kernoviaethe orders of susceptibility were as follows:
P. ramorum: viburnum > rhododendron > bilberry>pieris > camellia > magnolia
P. kernoviae: pieris > bilberry> rhododendron > magnolia
Monitoring work using bilberry bait plants to detect peak periods for sporulation and infection shows
that bilberry is susceptible all year round and that infections will take place whenever there are
prolonged conditions of high humidity. Temperature does not appear to be a limiting factor for
Table 1. Summary of options for disease management of outbreaks on bilberry*
*Sourced from defra Research Project PH0601 (http://randd.defra)
P. ramorumbut laboratory studies indicate that P. kernoviaemay be more environmentally sensitive.
Monitoring has shown that vaccinium plants are capable of supporting high levels of sporulation by P.
kernoviaeof over 1600 spores per cm
2of stem and that peaks in sporulation occur in the late autumn
(November). This means that bilberry could be a primary source of spores and therefore further
spread of the disease in the environment.
Latest work at Fera on modelling local epidemics can describe current epidemic development and
could be used for future prediction at a range of spatial scales from local to national. Latest outputs
are based on measurements of when conducive weather has taken place and are being used to target
when surveillance work should be undertaken.
Disease management
Timely management action is proven to limit disease spread and following evaluation in small scale
trials, recommendations are now available for disease containment strategies for infected bilberry in
both woodland and heathland environments. These strategies are supported by the availability of
standard operating procedures for biosecurity and waste disposal (including composting), all backed
up by extensive research.
Recommended management actions are not available as full documents due to the need for some
further work on logistics, but the options can be summarised as follows:
Outbreak type Outbreak extent Disease management options
Infected heathland Limited Spot treatment with an approved herbicide
Infected heathland Widespread Burn and then spot treat with an approved
herbicide
Cut and remove material and then
spot treat with an approved herbicide
Infected woodland Limited Spot treatment with an approved herbicide
Spot burn
Cut and remove material
Infected woodland Widespread Treatment with an approved herbicide
Cut and remove material and then
spot treat with an approved herbicide
Advisory Information
Phytophthora ramorumand Phytophthora kernoviaeare quarantine diseases and Defra needs to be
notified of any findings so action can be taken against them. If you suspect that such a pest or disease
is present, you should report it immediately to your local Plant Health and Seeds Inspector (contact
details below).
Regional teams are working to identify and eradicate outbreaks of the diseases as part of a wide-
reaching programme to manage the impact of Phytophthora ramorumand Phytophthora kernoviaein
the UK. This programme is being run by the Food and Environment Research Agency (Fera), on
behalf of the Department for Environment, Food and Rural Affairs (Defra).
If you discover any plants showing the symptoms illustrated in this leaflet:
Make a note of the location
Take a photograph if possible
Don’t touch the plant or take a cutting
Use the contact information below
Telephone: 01904 465625
Email: planthealth.info@fera.gsi.gov.uk
The Food and Environment Research Agency (Fera). October 2012
© Crown copyright 2012.
The Food and Environment Research Agency Sand Hutton, York
YO41 1LZ, UKTel +44 (0)1904 462 000
Fax +44 (0)1904 462 111E-mail info@fera.gsi.gov.uk
www.defra.gov.uk/fera
