Phytophthora Outbreak :
A notifiable plant disease affecting heathland , woodland and rough grassland.

Introduction
There are 19 cases in England and Wales where Phytophthora has been found in Vaccinium (bilberry); 10 on heathland, seven in woodland and two on rough grazing. Other heathland plants are also susceptible. The most northern case so far is North Wales and there is concern in the Lake District about the disease in larch and rhododendron.

Spread of Disease
North Wales and the Lake District represent 'new' outbreaks away from the previously known clusters namely: South West Devon and Cornwall, S.Wales Coast, North West (Liverpool, Chester, Manchester) and the South Coast.

In 2011, cases in Larch (178) and Rhododendron (306) have increased slightly since 2009 but this is in the face of a tripling of surveillance effort. The cases today are much more likely to be connected to previously treated sites rather than new outbreaks which is good news. There are two strains of Phytophthora; ramorum and kernoviae. Out of the heathland sites infected, nine are kernovia and one ramorum. This is good news because ramorum is known to produce spores that can infect the soil in which it grows. Kernoviae produces very few, if any, such soil infecting spores. This means that removing the plant above the surface is enough to remove the infection so no damage to the soil should be necessary. It is thought also that the threat from infected rhizomes (plant roots) is limited.

Severe die-back in bilberry caused by a Phytophthora outbreak.
Crown Copyright Courtesy of The Food and Environment Research Agency (Fera)

The commercial trade in plants susceptible to the disease, often blamed for the outbreak, has tightened biosecurity measures considerably and infection rates have dropped from 3% in 2006 to 0.01% The symptoms of the disease are a blackening of leaves around the midrib in shrubs such as rhododendron, trunk cancers that 'bleed ' black sap in native trees, and wilting or die back of shoots particularly in bilberry. If you or your employees spot a potential infection you should:

• Make a note of the location
• Take a photograph if possible
• Don't touch the plant or take a cutting
• Call The Food and Environment Research Agency (fera) on 01904 465625 or email planthealth.info@fera.gsi.gov.uk

Full biosecurity measures are required. i.e. disinfection of vehicle tyres, footwear and restricted access should the disease be positively identified at a site.

Treatment of Disease
Treatment of disease in Larch and Rhododendron is felling and complete clearance. For bilberry, treatment has trialled with initial burning and followed up with spot spraying with fungicides and/or herbicides. On small scale sites i.e. one or two isolate plants, herbicides alone have been found to be effective. There is a large scale heathland trial being coordinated by NE and Fera with JNCC input due to start this Autumn. It is a site in Cornwall across which a good proportion of the bilberry is infected. Burning is the first line of defence, 'as soon as possible after infection is diagnosed.' In reality this is likely to be within the usual NE licenced burning window. Rather than burn off the whole moor, patches in rotation are more likely to be done ensuring a 10m zone around infected plants as there is some worry that the disease can spread via bilberry's rhizome roots. The burning will be prescribed on a site by site basis. Re-burning may be required if infected bilberry reappears - or follow up with spot lance and herbicide. [Interestingly Tony Laws from NE says that the heathland habitat can cope with re-burning should this be necessary without taking too much harm, so long as burning is done well. This suggests to me that he thinks our burning rotations aren't that bad after all?]

Conclusion for moor owners
Whilst the threat to open heather moorland is still probably quite low, members with adjoining Rhododendron and Larch plants should keep these under surveillance and be prepared for them to be felled if discovered. Those moors in the North West where they are in closest proximity to existing outbreaks and where the weather is most favourable for the disease, (wet), are probably most at risk. Given that the disease has been about for at least 5 years, there is a chance that moor owners may have already burnt off infected, but unidentified bilberry already. Any infected bilberry is more likely to be in areas where it has not been burnt for five years or more and possibly in an area due for burning or possibly even in a no burn zone.