HELICOPTERS are being used to survey the spread of disease in larch trees across south Wales, following the announcement that 160,000 trees are to be felled in Cwmcarn Forest Drive.

Initial results from a survey earlier this month found the disease - Phytophthora ramorum- may not have spread as widely as in previous years.

Ten new sites have been identified covering approximately 40 hectares - approximately 40,000 trees - of forestry that warrant further investigation. This is in comparison with results in 2013 which found the disease had spread to approximately 3 million trees.

The rapid spread of the disease could have been the result of the exceptionally wet summer in 2012, which created the ideal conditions for the spores to spread and infect new trees.

Aerial surveys are the best way to spot potential new areas of infection as the larch trees bud or flush during the spring.

Natural Resources Wales announced recently that Cwmcarn Forest Drive will close later this year, as around 160,000 infected larch trees will need to be felled.

Of the 3.4 million trees planted in the last 18 months by Natural Resources Wales, 750,000 of these will replace those felled because of the disease.

Ceri Davies, from Natural Resources Wales, said:“These results are encouraging compared to what we found last year but more trees may show signs of infection as they flush later in the year.

“Unfortunately, those trees that are infected will die or be felled, but we are taking the opportunity this gives us to create better, more resilient forests for the future.”