Ben Willis on the disease threatening Britain’s horse chestnut population | Environment | The Guardian Annotated

Britain’s horse chestnuts are being attacked by a virulent disease, and half the population could already be affected

Ben Willis

• The Guardian,
• Wednesday April 2 2008

Based on months of detailed fieldwork, the report’s findings show that almost 50% of the UK’s horse chestnut trees could have bleeding canker. In some regions the problem appears especially grave, particularly the south-east, where 76% of the sample trees showed signs of the disease.

Webber says the Forestry Commission reckons there are approximately a million horse chestnuts in Britain. If the research paints an accurate picture of the situation, this therefore means a possible half a million trees may be affected.

the disease is bacterial, rather than fungal. Chestnuts have long been known to suffer from a cankerous infection caused by the fungal-like Phytophthora, though infection rates from this have traditionally been low. Around five years ago, however, a steep increase in the number of reports of bleeding canker prompted researchers to look again, and it was then that they realised a new bacterium had taken hold.

Should the worst happen and the horse chestnut population collapse in the face of disease and other pressures, its absence is likely to be most keenly felt in the historic landscape. Since introduced to the UK in the 1500s – it is a native of the Balkans – the horse chestnut has become a familiar feature in many designed landscapes.

Alan Cathersides, senior landscape manager at the conservation body English Heritage, estimates that of the 1,700 or so registered historic landscapes in Britain, only about 10% are without chestnuts. Consequently, Cathersides describes the Forestry Commission’s research as “really worrying”. He says: “If all those trees died from bleeding canker, it would be a disaster for historic landscapes.”

guardian.co.uk/environment/forests