Defra's Tree Health Management Plan, published this week, includes an update on management of ash dieback, caused by the pathogen Chalara fraxinea, and forecasts of its future spread carried out at the University of Cambridge.
"The latest model outputs indicate that the pathogen is likely to continue to spread in Great Britain, although there is potential regional variation with areas in the South East, East and South West most likely to be affected," it said.
An accompanying map shows Kent forecast to be the worst-affected English county in 2018, with around 75 per cent of ash trees likely to be infected, followed by West Sussex and Norfolk.
The disease is believed to have arrived in the UK in 2012 through a combination of airborne dispersal from the Continent and through the trade in plants, the management plan said.
But it stressed: "As limited information is available on the biology of the disease, spore dispersal and the infection process, the model results are subject to uncertainty."
Ash trees account for just under 5 per cent of UK woodland, though the figure is close to one-fifth in Kent. They have an annual amenity and commercial value to the country of £94-146 million, the management plan said.
- A Chalara workshop organised by the Future Trees Trust will be held in Lawshall, Suffolk on 8 June. Contact Tim Rowland on 01453 884264 or Tim.Rowland@futuretrees.org to book a place.