Ramorum disease of larch trees has been found in two new areas of Great Britain.
Outbreaks have been confirmed in larch woodlands in Lancashire, England, and on the island of Mull in western Scotland.
The Lancashire outbreak, in woodland managed by Lancashire County Council at Churn Clough Reservoir between Burnley and Clitheroe, is the second confirmed finding on larch in England outside the South West.
Although the site is about 60 miles from the next nearest confirmed outbreak on larch, in the Peak District, there have been findings on other plants, such as rhododendron, nearby. Investigations are continuing into other suspected sites in north-west England, and the Forestry Commission believes there is a high probability that more outbreaks will be confirmed in the region.
The Mull outbreak is only the second larch site in Scotland confirmed with the disease, following an outbreak in a small woodland on the Craignish peninsula in Argyll found in 2010. Suspected host plants near the Mull outbreak, such as rhododendron, are being investigated.
Ramorum disease is caused by Phytophthora ramorum, a fungus-like pathogen that is particularly serious in Japanese larch trees and rhododendron. It can kill larch within one growing season after symptoms are first observable and, given the right conditions, they produce huge numbers of the spores that can spread the disease. The only effective control measure is to fell the trees as quickly as possible before the next time spores are released. Current knowledge indicates that this occurs in the autumn.
These cases were first suspected in aerial surveys by the Forestry Commission, in conjunction with the Food & Environment Research Agency (Fera), which are continuing over large parts of Britain. Experts follow up with ground checks at the suspect sites and other larch woodland in the surrounding areas to confirm the cause and discover whether the disease is more widely present. Local woodland owners are being informed and given information about the disease and the measures for containing it.
Dr John Morgan, Head of the Forestry Commission’s Plant Health Service, said,
"’These new cases are cause for concern because they represent further evidence of the disease spreading to larch. Our surveillance is picking up individual trees with symptoms at a very early stage of infection, and although the new findings are disappointing, they are not altogether surprising, given the proximity of other infections.
"We cannot be sure of the full implications of these outbreaks yet.
Overall, the number and area of outbreaks on larch that we are finding this year are down on the previous two years, and most are close to or contiguous with previously infected sites.
"However, these outbreaks in new regions demonstrate that the threat posed by this disease is still serious. I therefore continue to encourage everyone involved with tree and forest management to remain vigilant for signs of the disease, not just in larch trees, but also in other susceptible plants, particularly rhododendron and bilberry. Anyone who suspects they have seen its symptoms should report it to us without delay." (Bilberry is known as blaeberry in Scotland.)
Councillor Tim Ashton, Lancashire County Council cabinet member for highways and transport, said:
"This is an important piece of work, and we will be co-operating fully with the Forestry Commission’s efforts to bring this disease under control. Unfortunately, this means we are going to have to fell all the larch trees at Churn Clough.
"We fully understand that a felling operation on this scale will cause concern to local people and many visitors to Sabden and Pendle Hill.
"We will let people know when the work is due to start, and keep them informed of progress through the media and public notices. We will erect signs explaining why the work has to take place and how visitors can help to prevent the spread by following some simple guidelines to reduce the possibility of carrying the disease to other sites or gardens on their boots, bicycle wheels or dogs’ paws.
"Anyone who has any questions can phone the council’s countryside team on 01772 533919."
