Impacts of plant-damaging moulds

Phytophthora species are plant-damaging water moulds that are responsible for a number of notorious plant diseases, such as potato blight.  Recently three new species have been identified in the UK, which are causing significant negative impacts to biodiversity.  They are believed to be non-native, and may have been introduced via international horticultural trade.  JNCC is working closely with partners to understand the impacts of Phytophthora on biodiversity.


The new species of Phytophthora can affect a wide range of native and garden plants.  Until recently, ‘wild’ findings were restricted to infections of non-native species such as Rhododendron ponticum, but it has now spread to infect native bilberry.  Laboratory testing undertaken by the Food and Environment Research Agency (FERA) shows that other native species such as heather, cowberry and bearberry may also be highly susceptible.


Once infections occur, they can spread very rapidly, as infected bilberry or Rhododendron produce very high numbers of spores.  Some tree species are also affected and can be killed by the infection.  However, most infected trees do not produce spores, and they will normally only become infected if they are in close contact with other infected plant species.


The biodiversity impact of Phytophthora infection is potentially extremely high.  Infected bilberry suffers very extensive dieback.  Over 60% of 10km grid squares in the UK contain native bilberry, and in many areas bilberry forms a dominant component of the vegetation.  Heathlands, acid woodlands and uplands will be particularly affected.  If other native species, in particular heather, were to become infected then potential impacts could be even more widespread.


Seven of the habitats listed on Annex I Habitats Directive contain bilberry as a major component of the vegetation.  A large number of SSSIs contain heathland types as interest features, and the loss of bilberry would lead these features to be assessed as unfavourable.  A considerable number of species are directly or indirectly dependent on bilberry.  Over 100 insects feed directly on bilberry, and approximately 40 insects are mainly associated with highly susceptible plant species.  Three of these insects are Biodiversity  Action Plan species, including the heath fritillary butterfly.


JNCC is working with Defra, FERA and the country conservation bodies to help assess further the biodiversity impacts of Phytophthora, and to assist in finding appropriate control mechanisms.  As a part of this work, JNCC has produced a leaflet describing the issue that will be available for download on the JNCC website:   



Chris Cheffings

Evidence Manager

Tel: +44 (0)1733 866805