A DECISION to remove nurseries infected with Chalara ash dieback from an official outbreak map could undermine attempts to understand and limit the disease, experts have warned.

Forestry Commission officials have said allowing anonymity encourages nursery owners, who have complained that being identified could damage trade, to report cases of the condition that threatens Britain’s 80 million ash trees.

But critics claim the act of concealing the identity of affected nurseries means scientists and the public – who have played an important role in mapping the spread of the fungus by reporting and photographing symptoms – will not have a complete picture.

Suffolk Wildlife Trust (SWT) chief executive Julian Roughton, said the move appeared to be a “retrograde step”. He added: “It does seem odd because I would have thought where Chalara has been identified in a nursery, it highlights the need for vigilance in the wider countryside.

“I would have hoped the whole purpose of the map was to raise awareness and in a way to target people’s efforts in terms of where to look.

“I think it undermines citizen science. It seems a retrograde step in terms of keeping an open and close view of the progress of this disease.” Currently there are 61 sites in Suffolk that are displayed on the Forestry Commission’s map, including five of SWT’s ancient woodlands.

Bradfield Woods, near Bury St Edmunds; Bull’s Wood in Cockfield; Arger Fen, near Assington; Bonny Wood, near Needham Market; and Comb’s Wood, near Stowmarket, all have confirmed cases of the disease. Groton Wood, near Hadleigh, so far remains clear.

Official data from the Forestry Commission lists 339 infected UK sites but does not map the 17 nursery sites. It is not known if any Suffolk sites have been excluded.

A Forestry Commission spokesman said: “We responded to concerns from nurseries that the information on the maps could be used to identify them and had the potential to harm the business of those who have done the responsible thing and reported cases of the disease at those nurseries.

“The risks posed to the wider environment by infections on commercial premises are very low because of the swift control action taken.”