Forty per cent of the island’s population of larch trees has been infected by disease, the forestry division has confirmed.
Some 200 hectares (about 500 acres) of larch trees have had to be felled due to phytophthora ramorum – commonly referred to as sudden oak death.
Along with Dutch elm disease, it’s one of two diseases affecting the island’s trees.
In addition, the Department of Environment, Food and Agriculture remains vigilant to the threat of a third, ash dieback.
Head forester John Walmsley said: ‘The main disease problem at the moment is phytophthora ramorum.
‘This is sometimes referred to as sudden oak death although we – the forestry industry – are trying to avoid that title as it is misleading.
‘Although P. ramorum killed thousands of oaks in America, where the disease caused significant damage, it was found that when the disease reached UK shores it switched species and attacked larch.’
He said: ‘The disease is generally spread in moist air currents by infected spores and to date some 40 per cent of the island’s larch population has been infected.
‘As the disease is air borne there is not a lot we can do to stop this disease, but we do ask for the public’s help to minimise the risk of further spread by observing restricted area signage and cleaning of footwear before leaving forest areas to access adjacent heathland and before visiting other forests and sites.’
DEFA is continuing to monitor and fund the dutch elm disease programme.
‘Unfortunately the long hot and dry spell of weather during July was perfect for the elm beetle which carries the spores of the disease and resulted in numerous flying days – the beetle only flies when temperatures reach about 24C,’ he said. ‘The number of new sites of infection has increased by seven with previously infected areas all showing further infected trees
‘ The number of diseased trees felled to date in 2013 has increased by 30 per cent from 2012.’
Meanwhile, the island remains free of ash dieback disease. Mr Walmsley said DEFA was continuing to monitor the situation, with additional surveying work taking place in the spring.
He said that although large scale publicity in the UK press had died down, ‘the potential impact of this disease reaching the island remains significant’.
Legislation is in place preventing the import of all ash trees and ash products.